The PROHITECH project seeks the intervention strategies for historical buildings
taking .... During the preliminary investigation, the nature and general degree of ...
CHAPTER 5 INTERVENTION STRATEGIES
Dan LUNGU, Cristian ARION Structural Safety for Natural Hazard Research Centre, Technical University of Civil Engineering Bucharest, Romania
5.1 GENERAL & TERMINOLOGY The value of heritage cannot be measured simply in terms of price. Conservation professionals and decision-makers increasingly must confront economic realities. Policy makers decisions are many times outside the domain of conservation practice for the cultural heritage. The PROHITECH project seeks the intervention strategies for historical buildings taking into accounts the economic and cultural background of the specific countries. The following web sites contains criteria and methodology for seismic rehabilitation of historical heritage buildings: www.unep-wcmc.org, www.wmf.org, www.worldbank.com www.iccrom.org, www.getty.edu, www.international.icomos.org. Who is implementing the “project”? The project strategy should contain informations that can be used by building owners, public clerks, architects, engineers and policy makers in order to decide on the adequate solutions for necessary rehabilitation interventions on constructions. Implementing the concept of a target performance, the rehabilitation should allow a comprehensive understanding of the parameters essential in the analysis that can ultimately provide the optimal intervention solutions. Who is responsible? The responsibility of safeguarding the existent individual building falls on the owners, while in the case of public constructions that exhibit a high level of vulnerability the responsibility extends to the authorities. Planning the retrofit of historical buildings before an earthquake strikes is a process that requires teamwork of engineers, architects, code officials, NGO, administrators and authorities. Policy development should also include consideration of other urban and environmental factors affecting the future of a place/location of building. What is the target? 1
The two major goals of the seismic rehabilitation/strengthening in historic buildings are life safety and the protection of historical value of the building. Because rehabilitation should be sensitive to historic materials and the building's historic character, it is important to put together a team experienced in both seismic requirements and historic preservation. Team members should be selected for their experience with similar projects, and may include historians, architects, engineers, code specialists, contractors, and preservation consultants. Because the typical seismic codes are written for new construction, it is important that both the historians & architect and structural engineer be knowledgeable about historic buildings and about meeting building code equivalencies and using alternative solutions. The rehabilitation programs might be active i.e. directly intended for strengthening of the building and passive i.e. due to the change of occupancy of the buildings. The reinforcement of the historical buildings to meet new construction requirements often, can destroy much of the historical building's appearance integrity and value. Important preservation principles Three important preservation principles should be kept in mind when undertaking seismic retrofit projects: • Historical materials should be preserved at the largest extent possible and not replaced wholesale with other new materials in the process of seismic strengthening; • New seismic retrofit systems, whether hidden or exposed, should respect and should be compatible to the architectural and structural integrity of the historical building; • Seismic work should be "reversible" to the largest extent possible to allow future removal for the use of future improved systems. While seismic upgrading work is often more permanent than reversible, care must be taken to preserve historical materials to the historical appearance of the building. In addition to the above principles, the general aim of building conservation is to preserve the cultural significance of the place where the building is culturally aggregated. Places of cultural significance should be safeguarded and not left at risk in a vulnerable state. The different intervention works are defined in various manners documents from various countries, as well as in general literature, TABLE 5.1. TABLE 5.1 Terminology for seismic rehabilitation of historical buildings Oxford popular English FEMA 2004, and dictionary The Australia ICOMOS charter for the conservation of places of cultural significance modifying a place to suit the existing use or a suitable for new use or Adaptation proposed use conditions the operations which maintain the building as it is Conservation today, even if limited interventions are accepted to improve the safety levels the rebuilding or renewal of any parts of the Make or become secure and Consolidation construction (of some elements or an assembly of strong elements) with the purpose of obtaining an enhanced structural capacity; for example, highresistance capacity, enhanced stiffness, better 2
Examination
Intervention Maintenance Preservation Repair
Reshaping Rehabilitation
Restoration
Reconstruction Strengthening
FEMA 2004, and The Australia ICOMOS charter for the conservation of places of cultural significance ductility the visual part of an investigation that excludes material testing, structural analysis, structural testing, and other more sophisticated investigative techniques a concept that involves standards/norms regarding consolidation, repair and reshaping of structural and/or non-structural elements continuous protective care of the fabric/aggregate and setting of a place, and is to be distinguished from repair maintaining the fabric/aggregate of a place in its existing state and retarding deterioration rebuilding or renewal of any damaged or faulty part of the construction to obtain the same level of resistance, stiffness and/or ductility with the those previous to its degradation Repair involves restoration or reconstruction. the rebuilding or renewal of any parts of the construction resulting in the change in function or in the occupancy rebuilding or renewal of a damaged construction in order to ensure the same level of functioning, similar to the that previous to the degradation of the building returning the existing fabric/aggregate of a place to a known earlier state, by reassembling existing components without the introduction of new material
Oxford popular English dictionary
enter a situation to change its course or resolve it process of something
maintaining
keep safe, unchanged, or in existence put into good condition after damage; make amends
redevelop condition
into
restore to a normal life or good condition bring back to its original state
returning a place to a known earlier state and it is reconstruct; restore distinguished from restoration by the introduction original form of new material into the work. judicious modification of the strength and/or stiffness of structural members or structural systems to improve their performance in future earthquakes. Strengthening generally includes increasing the strength or ductility of individual members or introducing new structural elements to significantly increase the lateral force resistance of the structure. On occasion, strengthening can also involve making selected structural members weaker to improve the interaction of the structural members and prevent premature failure of a weaker adjacent member.
The diagram of used terminology is presented in FIGURE 5.1. 3
certain
to
its
value strengthening
100
requirements maintenance ageing without maintenace damage
repair
restoration
ageing with maintenace
time t
FIGURE 5.1. Value alteration diagram of a building
5.2 INTERVENTION SOLUTIONS AND CRITERIA FOR SEISMIC UPGRADING & REHABILITATION OF CONSTRUCTIONS The intervention solutions must rely on cost-benefit analyses and take into account their socioeconomic impact on society. An obvious requirement is to minimize as much as possible the disturbance of the owners of the building during the building rehabilitation. The financial resources available decisively influence the intervention solutions for the particular purposes, including labor work capacity, equipments, materials, duration of the work etc. It is also compulsory to have alternative strategies for intervention and to evaluate the decrease in building vulnerability with various strategies. The following excerpts from various international organizations should be considered for intervention decisions. Examples of international organizations are given in TABLE 5.2. Traditional techniques and materials are preferred for the conservation of old building aggregates. However, modern techniques and materials, which offer substantial conservation benefits, may sometimes be also appropriate. Restoration and reconstruction should reveal significant cultural aspects of the place. Restoration is appropriate if there is sufficient evidence of an earlier state of the fabric. Reconstruction is appropriate only a place is incomplete through damage or alteration, and where there is sufficient evidence to reproduce an earlier state of the fabric. In rare cases, reconstruction may also be appropriate as part of a use or practice that retains the cultural significance of the place.
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Demolition of significant fabric of a place is generally not acceptable. In some cases minor demolition may be appropriate as part of conservation. Removed significant fabric should be reinstated when circumstances permit. TABLE 5.2. International organizations related to historical heritage preservation http://www.international.icomos.org
ICOMOS is an international non-governmental organization of professionals, dedicated to the conservation of the world's historic monuments and sites. World Heritage
http://www.unep-wcmc.org
ICCROM Via di San Michele 13, Rome, Italy Tel: +39 06 585531 www.iccrom.org
International Centre for the Study of the Preservation and Restoration of Cultural Property
http://www.getty.edu The Getty Conservation Institute http://www.wmf.org
World Monuments Fund is the foremost private, non-profit organization dedicated to the preservation of historic art and architecture worldwide through fieldwork, advocacy, grant making, education, and training
The intervention strategy and the intervention techniques must take into account the following criteria:
(i) (ii) (iii) (iv) (v) (vi)
Seismic hazard level at the construction site; Characteristics of the building intended use (architectural constrains, original occupancy of the building, building structure, technical equipments within the building, etc); Building safety as a response to daily activities, mainly related to the seismic safety (structural vulnerability, vulnerability of non-structural elements, appliances or/and equipments, building exposure or value, etc.; Required level for building performance (life safeguarding, immediate occupancy after earthquake, preventing building-collapse, etc); Economical criteria, including insured & reinsured value of the building; Technological capability available at the site.
5.2.1 The Repair and Strengthening Design Process Even though the main aim of this workpackage is the reviewing of intervention strategies, some basic principles on current approaches to damage assessment and definition of vulnerabilities of structural types will be cited for completeness.
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5.2.1.1 Criteria of Repair and Strengthening A post earthquake evaluation of the seismic parameters of the region and the individual sites is required for the earthquake affected region and structures. The definition of the seismic parameters for the region is a prerequisite for successful accomplishment of the repair and strengthening of damaged/undamaged structures. The study should include the expected maximum acceleration of bedrock for different return periods, amplification factors and to propose adequate time histories and average spectra for design of repaired structures. For more important structures, group or typical structures it is necessary to determine the seismic parameters for the considered sites and to perform field, soil investigations and geophysical studies to be used as input design parameters. The definition of seismic criteria comprises the correlation of the seismic force design parameters with the structural characteristics in terms of strength, deformability, ductility, etc. Each country or governmental area should establish its own criteria based on specific conditions related to the seismology and probable seismic events of the region. The criteria for repair and strengthening should preferably not be fully encompassed by the current building code for new construction, although showing respect to its provisions. The designer must use established criteria or Codes and Regulations of the area as the minimum standard for repair and strengthening projects. For selected projects such as historical structures, the designer may have to use criteria in excess of the established ones, based on the particular circumstances regarding the project. The designer may also have to establish criteria or methods to assign strength values to traditional materials whish are not covered by modern Building Codes or Regulations.
5.2.1.2 Structural investigations During the preliminary investigation, the nature and general degree of damage is determined. In order to design repair and/or strengthening measures, it is necessary to perform additional investigations and gather supplemental data while fully utilizing the preliminary investigation ones. Documents regarding the original construction should be compiled to the extent that they are available. This includes the designs, drawings, specifications, construction details, data on original construction material strengths, foundation and soil condition data, previous repairs or alterations, coeds under which the original design was prepared, etc. The information gathered should be compared with the actual structure to confirm that it was built in conformance with that information. Deviations should be noted and recorded. If information is not available or considered untrustworthy, field measurements and observations must be taken into account to verify the characteristics of the original construction. More specifically, the problems that arise while treating rehabilitation tasks of historical buildings concern the laborious work demanded for evaluating material characteristics and structure of bearing elements, as well as the lack of relevant written material. It is often required studying specific structures under loading conditions which are considered probable to have occurred, instead of designing on purpose of fulfilling safety demands under well-defined loading cases. In addition, interpretation of the actual structural performance is expected to be based on existing damage, the full record of which is non achievable. Completion of the detailed site inspection, which begun in the preliminary investigation, must be accomplished. This operation is an essential and important phase in the process of designing repair and strengthening measures. Damage due to seismic forces most often appear in structural elements as 6
columns, shear and infill walls, beams, beam-column joints, staircase towers, floor slabs and the connection between floors and walls and foundations. Each structural member must be inspected and the damage or lack of damage must be recorded, sketched and photographed. Damage and location of non-structural elements should also be recorded and present status, characteristics and strength of original construction materials should be estimated during the additional investigation.
5.2.1.3 Damage evaluation and selection of a repair and strengthening solution Utilizing the investigation data which has been documented and the criteria for repair and strengthening, the designer must typically evaluate the damage, perform analysis to determine why the damage occurred, and develop alternative schemes to repair and/or strengthen the structure. These alternative schemes must be evaluated and the most appropriate solution should be selected. The engineer must first analyze the damaged structure and thoroughly understand the causes of damage occurrence. The force resistant paths in the building must be determined, explaining why certain members sustained damage while others were practically untouched. It must be determined whether the structure suffered due to discontinuities in strength or stiffness, due to torsional moments within the structure, due to hammering with adjacent structures or due to improper connections or details. The effects of non-structural elements such as infilled walls and appendages on the structural performance must be considered. It must be determined if members failed due to shear, compression, tension, flexure, bar anchorage, etc. This analysis is essential before any repairs can be assigned. Calculations and analysis must be performed in order to evaluate the existing strength and stiffness of the damaged structure. The decision of the need to strengthen the structure will generally follow these analyses. If the repaired structure without strengthening conforms to the design criteria, then strengthening will generally not be required. If the repaired strength is less than the requirements of the criteria, the strengthening will generally be desirable in addition to repairing the damage. Based on results obtained by this analysis, alternative solutions for repair and/or strengthening can be determined for evaluation of their feasibility. Imagination and ingenuity should be exercised by the designer utilizing professional experience, as the best and most economical solution is seldom the first one conceived. Analysis for every alternative scheme must be performed to evaluate the effects of the strengthening measures and provide a reasonable basis for comparison among them. It must be recognized that despite the specific design criteria used, possible “weak links” in the structure can be detected during the analytical procedure. A future earthquake strong enough to cause damage will result in some elements of the repaired structure exceeding their yield strength and sustaining inelastic response. With a thorough understanding of the potential “weak links” in the structure, the designer can propose repair and strengthening measures whish will improve the response of the structure in future earthquakes. The repair and strengthening measures should establish an improved structure for seismic performance by avoiding irregularities in plan, abrupt changes in stiffness between floors and elements subjected to shear or brittle failure. The effects of strengthening elements added to the structure must be carefully evaluated to insure that they will not cause increased damage in a future earthquake. Conclusively, in order to select one solution for implementation, apart from the factors discussed above, the feasibility evaluation of alternative solutions must include the following aspects: • Compatibility with the functional requirements of the structure • Feasibility of construction, including availability of materials, construction equipment and personnel with specialized training and the ability to implement the solution 7
• • •
Economical considerations Sociological considerations Aesthetics
5.3 OPTIONS FOR INTERVENTION STRATEGY The strategy of interventions for improvement of the seismic performance of a structure or for the reduction of seismic risk might contain technical or/and managing approach. The technical strategies approach use the interventions on the bearing structure for the repair of possible deficiencies, on the increase of strength and stiffness of the structure, on the increase of the deformation assumption capacity, on the increase of the energy dissipation capacity and the reduction of seismic requirements. The basic intervention selection criterion is the limitation of damages caused to the primary and the secondary structural elements to acceptable levels for a given performance level. There are also managing strategies that can be taken into consideration during the design of interventions. Managing strategies comprise: (a) the decision of realizing interventions while the building remains in use or of evacuating it until the end of the strengthening works, (b) the acceptance of the existing seismic risk of the building and the omission of interventions or the alteration of its use in a way that renders the seismic risk acceptable, (c) the demolition of the existing building and its substitution with another, (d) the realization of the proposed interventions progressively in a very large time margin or the taking of temporary strengthening measures until the replacement of the structure, (e) the accomplishment of interventions on the external of the building in order to minimize the negative consequences for the inhabitants or in the internal in order not to change the characteristics of its external aspect. Managing strategies should be co-assessed by engineers and owners in order to select the suitable intervention strategy. Generally, the best solution for a building is related to the taking of decisions of a managing and technical nature.
5.3.1 Technical Strategies The technical strategies might apply when the structure should dispose a complete system for seismic load assumption, able to limit deformation in extents that correspond to acceptable damage levels for the targeted structural performance level. The main parameters which define the efficiency of the seismic loading bearing system are: (a) the mass, stiffness, damping and configuration of bearing and not bearing structural elements, (b) the deformation capacity of bearing and not bearing structural elements and (c) the energy and character of the seismic excitation imposed to the structure.
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Deciding the intervention strategy on building in terms of structure resistance, deformation and ductility performance, as well as in terms of non-structural elements performance should be made explicit through the following relation: SEISMIC REQUIREMENT~ ≤ CAPACITY
The measures of intervention for the accomplishment of the above relation are: (i) Reducing seismic requirements; (ii) Improving the mechanical characteristics of the construction; (iii) Combining modalities: (i) and (ii). In other words, the options the designer has are either to ensure an elastic behavior of the structure or to increase the hysteretic energy through plastic behaviour which involves the degradation of the structural elements. The strategy of improving a structure through local interventions is applied to structures which, although dispose the basic elements of an adequate seismic loading bearing system, lack of some constructional details which are necessary for the system optimization and the ensuring of the required functionality. The deformation capacity of such a structure may be adequate in comparison with the given seismic requirements, all the same before reaching this deformation it is probable that local damages in different locations of the structure occur. The most usual defects which are to blame for such local damages are the inadequate seating length at abutment locations of precast elements and the inadequate anchoring or connection between structural elements, either primary or secondary. Local interventions aiming at reforming these defects would allow a satisfactory structural behavior. Very often the strategy of local interventions is used in combination with other strategies in order to reach an adequate structural behavior.
5.3.1.1 Reducing seismic requirements Reducing seismic requirements can be achieved by the following methods:
(i) Reducing resistance requirements. The modalities of reducing seismic inertia forces developed in the structure can be identified by analysis of the structural elastic response acceleration spectrum. The objective is to stay away, as much as possible, from the maximum amplification of the spectrum by altering the characteristics of the structure. Reduction of resistance requirements may also be achieved through a reduction of building mass. This can be obtained by eliminating unnecessary weights: getting out one or several storeys, reducing the weight of partition walls, replacing a heavy roof with a light one etc. (ii) Reducing drift requirements. The reduction of drift requirements may be generally achieved by reducing the natural period of building, either by increasing the stiffness or by decreasing the mass of the construction. 5.3.1.2 Improving the mechanical characteristics of the construction Improving the mechanical characteristics of the construction can be done by, FIGURE 5.2.:
a) Increasing the stiffness to lateral forces. Increasing stiffness certainly reduces the effective drifts under values given by the lateral forces; b) Increasing of the plastic deformation capacity, i.e. increasing of ductility; 9
c) Increasing the resistance capacity. In many situations of insufficient ductility increasing the ductility is difficult to be achieved in practice and seems to be much easier increasing the building resistance; d) Increasing the dissipation/damping capacity. In several cases increasing the dissipation capacity can be achieved by elements that may be sacrificed on purpose. The infilled walls (partitions) may be specially designed to fit this purpose. In most cases the intervention on a structural characteristic will inevitably modify other properties that the structure has. The increase in stiffness, for example, may enhance the resistance of the structure as well as the decrease in drift and ductility requirements.
FIGURE 5.2. Concept of seismic retrofit and seismic performance upgrading of existing building
5.3.1.3 Choice of intervention systems The seismic strengthening methods can be classified as follows, as far as their target is concerned: 1. In case the target is the increase of stiffness and structural strength, the most effective method is the addition of walls in the existing frames. What follows is the method of adding truss bracings, the method of adding walls as an extension of existing columns and the use of composite materials. 2. In case the target is the increase of plasticity, the method that is recommended is the application of jacketing on a number of selected columns, as well as the use of composite materials. 3. In case the target is the simultaneous increase of strength, stiffness and plasticity of the structure, any seismic strengthening method can be used taking into consideration the required degree of increasing each of the above mentioned characteristics. In case that the necessary increases are very high for all three characteristic, it is generally inevitable the addition of new vertical elements.
5.3.2 Repair & Strengthening of Existing Buildings As the general awareness of the earthquake risk increases, and standards of protection for new buildings become higher, the safety of the older, less earthquake-resistant construction becomes an increasingly important concern. In many earthquakes, damage is concentrated in the older building stock, while recently constructed buildings stiller comparatively lightly. The problem can be expected to diminish over time if improved standards of new construction can be achieved, because the 10
proportion of unsafe buildings in the total building stock will diminish. This is true particularly where there is a high rate of turnover of the building stock. But such cases are rare; in many industrialized countries the rate of new building construction is only about 1% per annum, and even in more rapidly developing areas with sustained growth rates of 8% and more, the total number of older buildings does not diminish very rapidly. Indeed, rather than being taken out of use, the older building stock is increasingly being modified and adapted, sometimes in ways which significantly increase the loading or reduce its inherent resistance to earthquake ground shaking. And where old buildings are not being modified, lack of maintenance may lead to decay of already weak and poorly integrated structures, resulting in a continual decline in earthquake resistance possibly made worse by the cumulative effect of low levels of damage in previous earthquakes. For all these reasons, strengthening existing buildings is assuming increasing importance in earthquake regions. For most types of buildings, strengthening is a cheaper way of bringing earthquake resistance up to acceptable levels than rebuilding; depending on the situation and construction type, costs of strengthening typically range from 5% to 40% of the cost of a new building. Careful consideration needs to be given to the type of strengthening best suited to achieve the desired safety level. Factors which need to be taken into consideration in deciding whether to strengthen, and which method to use, will include: • The required level of structural resistance; • The general structural form and any changes needed; • The materials and degree of connection in the existing structure; • Foundation conditions and the effect of strengthening on them; • The effect of strengthening on the appearance and functioning of the building; • Required strengthening of non-structure and services; • The time during which the building will be unusable; • The cost of the work. The main objective in strengthening is to achieve a structure, which satisfies the principles of good earthquake-resistant design. The actual methods used are different for different types of structure.
5.3.2.1 Strengthening unreinforced masonry buildings Many cities, towns and villages in earthquake zones consist primarily of unreinforced masonry buildings of a great variety of types and ages which experience has shown to have poor resistance against earthquakes. Damage to masonry structures usually takes the form of tension and/or shear cracks caused by imposed deformations e.g. differential settlement, excessive lateral forces e.g. from arch thrusts or incipient bursting due to buckling of ashlars or expansion of rubble fill in structures which consist of relatively thin ashlars faces with a core of rubble and mortar. The principal sources of the weakness of these buildings are: • Low-strength masonry units and mortar inadequately bonded together. • Insufficient interconnection between inner and outer leaves of external walls, insufficient connection at the junctions of perpendicular walls. • Insufficient rigidity of floor and roof slabs in their own plane, and inadequate connection between these slabs and the bearing walls. 11
These weaknesses are frequently compounded by the deterioration of the structure due to weathering and rot, and to extensive structural modification during the lifetime of the building. According to the weaknesses identified in particular cases, strengthening may involve any or all of the following interventions: • Modifying the plan form of the building to improve symmetry, improving the connections between perpendicular walls; • Strengthening or replacing floor and roof structures, and improving their connection with the load-bearing walls; • Strengthening the walls themselves; • Strengthening the foundations. The range of techniques available is wide, and details depend on the type of masonry involved. Common strengthening techniques include: • Stiffening existing wooden floors and roofs by covering them with a thin layer of reinforced concrete; • Insertion of reinforced concrete ring beams into the inner face of external walls at floor and caves level to tie vertical and horizontal elements together; • Extensive strapping of masonry walls to each other and to slabs using both horizontal and vertical steel straps; • Strengthening of walls (mainly when cracked) by cement injection or by adding a thin layer of cement render reinforced with steel mesh on either side of the wall; • Adding plywood sheathing; • Strapping parapets. Where repair and strengthening by these means is not considered feasible, an alternative is to introduce a new independent concrete frame to carry the earthquake loads, and attach the masonry to it. Methods of evaluating the earthquake resistance of existing unreinforced masonry building have been developed both in California and New Zealand. These methods can also be used to assess the effectiveness of proposed strengthening interventions, and so to consider the cost-effectiveness of strengthening as against alternative mitigation measures such as reconstruction or change of use.
5.3.2.2 Strengthening reinforced concrete buildings The need for strengthening reinforced concrete buildings has become more urgent in recent years in countries where recent earthquake damage has indicated that the resistance requirements in previous codes were inadequate or where buildings have been found to be below code standard. The principal causes of weakness in reinforced concrete buildings are: • Insufficient lateral load resistance, as a result of designing for too small lateral loads. • Inadequate ductility, caused by insufficient confinement of longitudinal reinforcement, especially at beam-column or slab-column junctions. • A tendency to local overstressing due to complex, and irregular geometry in plan and elevation. • Interaction between structure and non-structural walls resulting in unintended torsional forces and stress concentrations. • Weak ground floor due to lack of shear walls or asymmetrical arrangement of walls. • High flexibility combined with insufficient spacing between buildings resulting in risk of neighboring structures pounding each other during shaking. • Poor-quality materials or work in the construction. Unrepaired damage from previous earthquakes may also be a reason for requiring strengthening.
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The principal objective in most strengthening interventions is to increase the lateral load resistance of the building; usually increasing the ductility of the structure will be an additional objective. The strengthening may also involve removing or redesigning non-structural walls which may affect the performance of the building, and sometimes the strengthening effect may be achieved by removing load from a structure (by, for example, reducing the number of stories). For tall buildings on soft soil deposits, an increase in stiffness may also help to improve a building's performance by reducing its natural period to a value below that of the subsoil. Often the intervention may require simultaneous strengthening of the foundations. The principal technical options for improving the lateral loadcarrying ability of existing reinforced concrete structures include: • Adding concrete shear walls, • Buttressing, • Jacketing, • Adding cross-bracing or external frames. Adding Shear Walls The most common method of strengthening of reinforced concrete frame structures is the addition of shear walls. These are normally of reinforced concrete, or may exceptionally be of reinforced masonry. In either case, they are reinforced in such a way as to act together with the existing structure, and careful detailing and materials selection are required to ensure that bonding between the new and existing structure is effective. The addition of shear walls substantially alters the force distribution in the structure under lateral load, and thus normally requires strengthening of the foundations. Buttressing Buttresses are braced frames or shear walls installed perpendicular to an exterior wall of the structure to provide supplemental stiffness and strength. This system is often a convenient one to use when a building must remain occupied during construction, as most of the construction work can be performed on the building exterior. Sometimes a building addition intended to provide additional floor space may be used to buttress the original structure for added seismic resistance. Buttresses typically require the construction of foundations to provide the necessary overturning resistance. Even considering the extra foundation costs, the cost of buttressing an occupied building may be substantially lower than that for interior shear walls or braced frames. The aesthetic impact and the availability of building space adjacent to the existing building are obvious factors affecting choice of this solution. Jacketing An alternative technique is to increase the dimensions of the principal frame members by encasing the existing members in new reinforced concrete. The technique is known as jacketing. Adequate reinforcement of the new encasing concrete can increase both strength and ductility, and concrete damaged in a previous earthquake can be replaced at the same time. Again careful consideration needs to be given to achieving an adequate bond between the existing and new concrete. Jacketing of beams is much harder than columns; jacketing the beams and columns may be ineffective if the beam/column joint is inadequate, and retrofitting joints is also difficult. Jacketing may be a viable option where a significant improvement is available from increasing the strengthening and ductility of some or all of the columns, without substantial intervention to the beams and joints. It may be attractive where there are architectural difficulties in adding shear wails. Jacketing is a valuable technique when complex or deep foundations make the change in the lateral load-bearing system required by a shear wall system impossible or very costly. Addition of Cross-bracing Both of the above techniques involve major interventions to the structure. An alternative technique, involving a less drastic intervention and smaller increase in foundation loads, is the addition of steel 13
cross-bracing to increase lateral load resistance. Tin's generally also involves the strengthening of adjacent columns, which will have to carry increased axial loads, although this is offset by a reduction in column moments and ductility demand. Strengthening of columns may be achieved by the addition of an external steel cage surrounding each of these columns. The addition of steel bracing considerably alters the appearance of a building, but is particularly suitable for comparatively low-cost strengthening of buildings which have not been damaged in a previous earthquake. Other Methods Other methods sometimes adopted to improve the performance of reinforced concrete buildings in earthquakes include the addition of separate external frames (ATC-40), or the removal of one or more storeys to reduce the lateral load. New techniques such as bonding of steel plates to the concrete frame have been proposed but are as yet little tested. In rare instances, base isolation has been used to protect the superstructure from the ground shaking, but this is very expensive. The addition of supplemental damping devices is becoming increasingly used as a retrofit measure for concrete frame buildings. This is generally suitable for special cases; it would not be recommended unless a high level of the relevant engineering expertise is available. In a few cases strengthening through the use of advanced fiber-reinforced plastic (FRP) has been used. While this method has the drawback of cost, it offers the advantage of quick installation, minimum disruption, and no weight increase in the structure.
5.3.2.3 Repair and strengthening of historical buildings In what way do monumental buildings differ from other buildings that constitute the world’s architectural heritage? The international framework of principles for the protection and restitution of historical buildings is known as the “International Charter of Venice”. The International Charter of Venice was drafted in May 1966 on the occasion of the second international conference of architects and building technicians involved in the restoration and maintenance of monuments that was held in Venice. It consisted of a re-examination of a similar Charter of 1931 and summarized the experiences and lessons of almost twenty years of intense postwar restoration activity. For obvious reasons the creators of the Charter were almost entirely concerned with medieval and later buildings that were in use immediately before the war and not with the special case of monumental buildings of Greco-Roman civilization. Nevertheless, the Charter of Venice has become widely accepted because of its concise, uncomplicated character. Speaking about structural restoration, from all the 16 articles included in the Charter, the followings have a significant meaning: Article 2: The conservation and restoration of monuments must have recourse to all sciences and techniques, which can contribute to the study and safeguarding of the architectural heritage. The involvement of structural engineering faculty in the restoration practice is fully justified from this article. Article 9: The process of restoration is a highly specialized operation. Its aim is to preserve and reveal the aesthetic and historic value of the monument and is based on respect for original material and authentic documents. It must stop at the point where conjecture begins, and in this case moreover any extra work, which is indispensable, must be distinct from the architectural composition and must bear a contemporary stamp. The restoration in any case must be preceded and followed by an archaeological and historical study of the monument. Article10: Where traditional techniques prove inadequate, the consolidation of a monument can be achieved by the use of any modern technique for conservation and construction, the efficacy of which has been shown by scientific data and proved by experience.
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Another principle, deriving indirectly from the Charter of Venice, is the reversibility that is the acceptance of the possibility of the restitution of a monument to the condition it was in prior to the intervention. This principle stems from the view that a monument is a source of scientific evidence and from the premise that mistakes may occur during the execution of the work. It takes as its starting point the intention to preserve the monument as a source of evidence after the work is completed and also to ensure that any mistake is rectifiable. Historical buildings constitute a case of special importance. A distinction has to be made between: (1) Historical monuments and (2) Historical urban centers. Each is valued for different reasons and the strengthening techniques necessary to retain those values arc different, and have different costs and constraints. It is important in planning the repair of older buildings to consider which approach and level of budgeting suits each building. Usually strengthening of historical structures will be done as a result of minor damage from an earthquake, or they may have been damaged in other ways. In either case, the techniques for repair and strengthening are the same.
Historical Monuments Historical buildings are valued for their cultural associations and interesting physical construction. In restoration and strengthening, the physical fabric of the structure must remain essentially the same as before the earthquake. Strengthening elements that are added should be unobtrusive and. where possible, reversible, i.e. removable by future renovators. This type of restoration work requires specialist skills and is expensive. There may be only a few buildings for which this sort of expense can be justified. Restoration and strengthening techniques used on historical monuments include: • Dismantling damaged masonry and reassembling it with improved mortar and concealed reinforcement (e.g. metal cramps, reinforcing bars, mesh, etc.). • Addition of concealed tension bars, as anchor bolts, ring beams, corner ties, splay members, arch chords, and other structural connections. These maybe drilled through masonry using extended bit drills, capped and grouted into place. • Internal grout or chemical injection into wall cores where poor-quality rubble has to be stabilized and bonded without altering the external wall finish. • Strengthening or stiffening foundations. There may often, however, be some conflict between the desire for reversibility and the effectiveness of the intervention. Grouting can be gravity fed or pressure injected, but is irreversible and often unpopular with renovators. Historical Urban Centers The historical centers of many earthquake-prone cities consist of dense residential and commercial districts whose buildings are usually of unreinforced stone or brick masonry, much altered in unrecorded ways over the centuries and often in poor condition. Although they represent a valuable and irreplaceable part of the urban heritage, they are often under threat from general decay and deterioration and from the pressure for redevelopment in addition to the earthquake risks they face. To date little has been done to protect any of such buildings from future earthquake damage, and upgrading strategies are needed which will fulfill the sometimes conflicting criteria of life safety for occupants and functional upgrading, limitation of damage from future earthquake, and limitation of alteration to the fabric and appearance of the buildings. Criteria governing the choice of upgrading strategy for historical centers are: first, that interventions should make a significant improvement to the earthquake resistance of the buildings in a way which is both identifiable and measurable; secondly, that interventions should cause only very limited alteration to the external appearance of the building; and thirdly, that interventions should be consistent with existing programs of upgrading for the 15
buildings in terms of cost, appropriate techniques and the process of design and management. Repair and strengthening techniques suitable for use in these situations include: • Use of steel tie rods passing through the floors and external walls with external anchorage plates or bars to connect the walls and the floors together. • Improving the stiffness of floors in their own plane by adding new timber members - for instance, two layers of floorboards laid perpendicular to each other or by cross-bracing with steel straps. The monolithic floors can themselves be made into strengthening diaphragms for their supporting walls by chasing in and casting skirting beams around the edge of the floor. • Jacketing the walls by application of layers of wire mesh on each face, tied together through the wall at intervals and covered with a layer of dense plaster. Where upper storeys are badly cracked and lower floors are relatively sound, the upper storey may be demolished, a reinforced concrete ring beam cast on top of the remaining wall, and a new identical upper storey constructed. New masonry should be reinforced and may be in solid brick, high-quality concrete block work, or cut stone. Original wall thicknesses should be retained, and a reinforced concrete ring beam at roof level should top all walls. In reconstruction, the plan of some buildings - for example, 'L'-shaped plans - may be compartmented into interlocking rectangular structural units, by means of ring beams and cross-ties, for greater seismic rigidity. In cases of moderately damaged walls with elaborate stucco decoration work, it may be possible to save the wall and its original decoration by using cement injection grout injected into the core of the wall. This should only be used in conjunction with extensive 'stapling', i.e. drilling and grouting steel reinforcing bars as connector reinforcements between walls and from walls to floors. The skills needed for repair and restoration of the buildings of historical urban centers are general building skills. Techniques of grouting, stapling and mesh reinforcement are relatively straightforward to learn and can be carried out by almost any building professional. Skilled craftwork is needed for repair and for renovation of any original interiors that owners wish to preserve.
5.3.2.4 Materials and construction techniques Repair materials should be compatible with the original construction. This applies to the stone, as well as the mortar. Repair and strengthening techniques are conveniently considered under the headings of the defects they are intended to remedy. The selection of a suitable solution for repair or strengthening of a structure presupposes that the engineers involved have a satisfactory knowledge on materials and techniques available for such interventions. Conventional materials of construction are often insufficient at providing solutions, even though they still play a major role in the procedure. The need of using new materials and innovative technologies combined with modified traditional ones arises very often. As a result, there would be established a system of quality control and cooperation insuring between traditional and new materials.
Replacement and Strengthening of wall Intersections: Wall intersections are particularly vulnerable to earthquake damage, resulting frequently in large vertical cracks or separations as the walls are insufficiently interconnected and lack adequate strength to allow proper interaction. Considering the basic weakness of masonry construction under earthquake conditions, repair procedures are most often combined with a local strengthening of the wall intersection.
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Stone stitching, or adding stones across the crack is a method, which can be used. A reinforced concrete corner column properly tied into the intersecting walls could be added to strengthen the wall intersection.
Strengthening Walls by Confinement with steel sections: structural steel sections can also be used to strengthen masonry walls. Steel sections can be quickly installed and are often used when urgency of repair and strengthening is necessary. Depending on conditions, light steel sections may also be more readily available than shotcreting equipment or other suitable alternatives. The steel sections must be attached to tie beams or belts and the horizontal diaphragms at both top and bottom. Strengthening Rubble Core Stone Walls with Injection: Strengthening of rubble core stone masonry structures can be summarized as connecting the walls of the building at the level of the floor and roof by steel ties on both sides of the wall, anchored at their ends, and by grouting the walls with cement emulsion or other adhesives. This method of strengthening stone structures can be used in combination with other procedures such as adding shear walls or strengthening shear walls by jacketing of some wall parts within the structure. In this case, when new elements are introduced into the structure, the foundation structure should be checked and strengthened, if necessary. Steel profile jacketing: steel profile skeleton jacketing consists of four longitudinal angle profiles placed one at each corner of the existing reinforced concrete column and connected together in a skeleton with transverse steel straps. Jacketing with steel profiles (angles and straps) is used at the strengthening of separate members, mainly columns. The joint beam-to column is difficult to strengthen by this technique. Jacketing by steel encasement is implemented by gluing of steel plates on the external surfaces of the original members. This technique does not require any demolition, it is considerably easy for implementation and there is a negligible increase in the cross section size of the strengthened members. Steel encasement: Steel encasement is the complete covering of the existing column with thin steel plates. Special measures must be provided for fire and corrosion protection. Steelwork for structural restoration Steelwork can be conveniently used for the consolidation of all kind of structures, both old and new, made of all common constructional materials, i.e. masonry, timber, reinforced concrete and also steel itself. In the case of consolidation of historical structures, the use of steel gives further advantages to the designer who has undertaken this delicate operation. The use of steelwork is widely used in many consolidation operations which are framed in restructuring. Comparing to the use of metal sheets for structural reinforcement, the alternative application of FRPs introduces some significant advantages, such as the excellent weight to strength properties, the material availability in an unlimited length, the comparatively easier installation and the strength against corrosion. These advantages render composite materials to be a very attractive alternative proposal.
Glued Metal or Fiber Reinforced Polymer straps The use of glued straps of steel or Fiber Reinforced Polymers, for strengthening of reinforced concrete elements, is nowadays a very popular technique due to the ease of its implementation. The traditional way of practice suggests the use of steel plates but the implementation of FRP straps has been growing competitively.
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Shear connectors – anchors Metal connectors which are anchored on existing concrete elements can act either as studs or as anchors, depending on the type of load applied. Studs are subjected to shear stress while anchors are stressed by axial load. There is a variety of industrialized connectors which are anchored on concrete elements in a mechanical or chemical way. Chemical fixing of connectors, constituting the most popular choice in practice, is almost always performed by epoxy resins. Anchorage and welding of new reinforcement bars Anchorage of reinforcement bars on hardened concrete is accomplished in chemical way, by the use of an epoxy resin. FIGURE 5.3 indicates that by adding wing wall increases strength and ductility, ductility is increased remarkably by RC jacketing, steel jacketing, FRP wrapping and installing seismic slit.
FIGURE 5.3. Strengthening effect in the case of columns observed in structural test
Repairing Gravity Load Capacity of Beams: Steel rods can be used for improving the shear resistance of damaged or undamaged beams. If load reversals are anticipated, four-sided jacketing is the preferred method of strengthening. Steel plate reinforcement is a new technique which can be used for beams subject primarily to static loading to improve their shear strength or midspan flexural strength. This procedure is not recommended for beams subject to cyclic loading due to earthquakes. FRP jacketing: The implementation of this kind of materials results in the increase or, even better, the alteration of bending, shear and axial strength of the member on which they are applied. The use of FRPs should generally be avoided when the bedding conditions are unknown or poor, there is in progress a significant corrosion of the reinforcement bars or there is no reinforcement ensuring the plastic behavior of the member to be strengthened. Among the most important advantages of the use of composite materials for structural repair and strengthening, in comparison to relevant traditional methods, the following ones can be stated: • Insignificant repair is required in the work site. The evacuation of the area is not necessary and the annoyance to the users is minimal. The preparation of the elements to be strengthened is small and brief. • The application of composite materials is simple. 18
• • • • • •
The dimensions of the strengthened structural element remain practically unaltered, due to the small thickness of the composite material. The placing of composite materials is feasible even when there are working space restraints. The weight of composite materials is small and for their placing no heavy or specific equipment is required. Composite materials can be coated and colored according to the aesthetical needs of the work. The architectural characteristics of the structures remain practically unaltered. The application cost of composite materials is analogous to that of the traditional repair/strengthening methods.
In FIGURE 5.4 is presented a comparison study based on structural tests regarding the strengthening methods applied to the RC frames. It is indicated an 3.5 to 5.5 times increase in strength in case of infilling wall. 0.6 to 1.0 times in strength and a little bit increased ductility can be seen in case of infilling wall compared with monolithic RC wall.
FIGURE 5.4. Strengthening effect observed in structural test
Introduction of new structural elements/systems: New vertical trusses can be constructed with steel members, cast-in-situ reinforced concrete members or a combination of the two. If reinforced concrete members are used, all members should be confined with closely spaced ties for their full length to provide adequate member ductility. Concentrically braced frames: This traditional form of bracing is, of course, widely used for all kinds of construction such as towers, bridges, and buildings, creating stiffness with great economy of materials in two-dimensional trusses or three-dimensional space frames. Concentrically braced frames are constructed from steel, timber, and concrete and composite forms are frequently met such as timber beams and columns with steel diagonals. Eccentrically braced frames: This system conforms in part to the requirement for good earthquake design of failure mode control, insofar as post-elastic behavior of the frame is largely confined to selected portions of the beams and sudden failure modes are suppressed. Hybrid structural systems: The most common of these hybrid systems are those in which momentresisting frames are combined with either structural walls or diagonally braced frames. While hybrid systems are often unavoidable and can provide good seismic resistance, care must be taken to ensure that the structural behavior is correctly modeled in the analysis. 19
FIGURE 5.5. Strengthening effect observed in structural test
5.3.2.5 Foundations It may be desired that the strengthening of the foundation is not required in seismic retrofit pf buildings. In general, strengthening of foundation shall be performed only when the retrofit scheme is simple, practical, cost effective, and reliable for drastic improvement of seismic performance. Also, when adverse effects to the structural performance of building concerned is expected in future due to settlement of ground, negative friction of pile, and liquefaction of sandy soil at the time of earthquake, we have to improve the soil performance appropriately.
FIGURE 5.6.Seismic strengthening method of pile foundation 20
FIGURE 5.7. Construction methods as measures against liquefaction
5.3.3 Passive Control of Structures—Energy Isolating and Dissipating Devices 5.3.3.1 Introductory remarks Earthquake ground motions impart kinetic energy into structures, and the principles of specific structural forms for earthquake resistance control the location and extent of the damage caused by this energy. This philosophy can be extended beyond specific structural forms to any means which may further protect the structure by reducing the amount of energy which enters it. The family of earthquake protective systems has grown to include passive, active and hybrid (semiactive) systems as shown in FIGURE 5.8. Passive systems are the best known and these include seismic (base) isolation and passive (mechanical) energy dissipation. Isolation is the most developed member of the family at the present time with continuing developments in hardware, applications, and design codes. Passive seismic control strategies are based on the reduction of energy, which may affect a structure in case of earthquake events. Some well known approaches make use of frictional, plastic or other energy dissipating behavior of special devices. Modern structural protective systems can be divided into three major groups: - Seismic Isolation Elastomeric Bearings Lead Rubber Bearings Combined Elastomeric and Sliding Bearings Sliding Friction Pendulum Systems Sliding Bearings with Restoring Force - Passive Energy Dissipation 21
Metallic Dampers Friction Dampers Viscoelastic Solid Dampers Viscoelastic or Viscous Fluid Dampers Tuned Mass Dampers Tuned Liquid Dampers - Semi-active and Active Systems Active Bracing Systems Active Mass Dampers Variable Stiffness and Damping Systems Smart Materials By considering the actual dynamic nature of environmental disturbances, more dramatic improvements can be realized. New and innovative concepts of structural protection have been advanced and are at various stages of development. Consequently, some new engineering techniques for modifying the structure to achieve better earthquake resistance are available, and can be expected to become more widely used in the future. The most important of these techniques are base isolation and the use of energy absorbers.
FIGURE 5.8. Family of earthquake protective systems
5.3.2.2 Isolation from seismic motion The principle of isolation is simply to provide a discontinuity between two bodies in contact so that the motion of either body, in the direction of the discontinuity, cannot be fully transmitted. The discontinuity consists of a layer between the bodies which has low resistance to shear compared with the bodies themselves. Such discontinuities may be used for isolation from horizontal seismic motions of whole structures, parts of structures, or items of equipment mounted on structures. Because they are generally located at or near the base of the item concerned, such systems are often referred to as base isolation, although the generic term seismic isolation is preferable. The layer providing the discontinuity may take various forms, ranging from very thin sliding surfaces (e.g. PTFE bearings), through rubber bearings a few centimeters thick, to flexible or lifting structural members of any height. To control the seismic deformations which occur at the discontinuity, and to provide a reasonable minimum level of damping to the structure as a whole, the discontinuity must be associated with energy-dissipating devices. The latter are also usually used for providing the required 22
rigidity under serviceability loads, such as wind or minor earthquakes. Because substantial vertical stiffness is generally required for gravity loads, seismic isolation is only appropriate for horizontal motions. The soft layer providing discontinuity against horizontal motions cannot completely isolate a structure. Its effect is to increase the natural periods of vibration of the structure, and to be effective the periods must be shifted so as to reduce substantially the response of the structure. Clearly, the shape of the design spectrum, the fixed base period, and the period shift are the three factors which determine whether base isolation has any force-reducing effect (or. indeed, the opposite!). The location of the isolating devices should obviously be as low as possible to protect as much of the structure as possible. However, cost and practical considerations influence the choice of location. On bridges it is generally appropriate (to isolate only the deck where isolation from thermal movements is required anyway. In buildings the choice may lie between isolating at ground level, or below the basement, or at some point up a column. Each of these locations has its advantages and disadvantages relating to accessibility and to the very important design considerations of dealing with the effects of the shear displacements on building services, partitions, and cladding, TABLE 5.3. TABLE 5.3. Advantages and disadvantages of base isolation function of the location in buildings Location Advantages Disadvantages - May require cantilever elevator - Minimal added structural costs Bearings located at - Separation at level of base isolation is pit bottom of first story simple to incorporate columns - Base of columns may be connected by diaphragm - Easy to incorporate back-up system for vertical loads - May require cantilevered - No sub-basement requirement Bearings located at elevator shaft below first floor - Minimal added structural costs top of basement level - Base of columns connected by columns - Special treatment required for diaphragm at isolation level internal stairways below first - Back-up system for vertical loads floor level provided by columns - Special consideration required - No sub-basement requirement Bearings located at for elevators and stairways to - Basement columns flex in double mid-height of accommodate displacements at curvature and therefore may not be basement columns mid story required to be as stiff as for bearings - No diaphragm provided at located at the top or bottom isolation level - Difficult to incorporate backup system for vertical loads Bearings located at - No special detailing required for - Added structural costs unless sub-basement required for sub- basement separation of internal services such as other purposes elevators and stairways a separate - No special cladding separation details - Required (independent) retaining wall - Base of columns connected by diaphragm at isolation level - Simple to incorporate back-up system for vertical loads
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5.3.3.3 Analysis concepts of damage controlled structures Two design concepts: - The old aseismic design has been based upon a combination of strength and ductility. For small, frequent seismic disturbances, the structure is expected to remain in the elastic range, with all stresses well below yield levels. In the case of major earthquake a traditional structure is expect to respond non-elastically. Total deformation of the structure: ∆ ≡ ∆f ≡ ∆d
∆f - Elastic deformation of beam and columns. These structural system could deform elastically until 1/100 inter story deformation angle. ∆d = Elastic and plastic deformation of dampers
Building structure
Primary structure To support vertical loads
Seismic members To absorb earthquake energy
Beam
Damper
Column
FIGURE 5.9. Idealized structure
24
- The design engineer relies upon the inherent ductility of buildings to prevent catastrophic failure, while accepting a certain level of structural and nonstructural damage. This philosophy has led to the development of aseismic design codes featuring lateral force methods and, more recently, inelastic design response spectra. With these approaches, the structure is designed to resist an “equivalent” static load. Small/medium earthquake
Large earthquake
Q Frame
Old concept
Q Frame
δ
δ
Elastic Q
Q New concept
Frame
Inelastic
Damper
δ Elastic
δ Inelastic
Q Frame
Q
Damper
δ
δ
Elastic
Inelastic
5.3.3.4 Seismic isolation using flexible bearings The most commonly used method of introducing the added flexibility for seismic isolation is to seat the item concerned on either rubber or sliding bearings. The energy dissipators (dampers) that must be provided may come in various forms. In addition, all-in-one devices, incorporating both isolation and damping, are used, namely lead-rubber and high damping rubber bearings. The most effective device, the lead-rubber bearing, is discussed below. The lead-rubber bearing (Robinson and Tucker, 1977) is conceptually and practically a very attractive device for seismic isolation, as it combines all of the required design features of flexibility and deflection control into a single component. It is similar to the laminated steel and rubber bearings used for temperature effects on bridges, but with the addition of a lead plug energy dissipator. Under cyclic shear loading the lead plug causes the bearing to have high hysteretic damping behaviour, of almost pure bilinear form. The high initial stiffness is likely to satisfy the deflection criteria for serviceability limit state loadings, while the low post-elastic stiffness gives the potential for a large increase in period of vibration desired for the ultimate limit state design earthquake. Further developments in seismic isolation are going on. One such development is an improvement to both the Rubber Isolation Bearing and to the Lead Rubber Bearing, consisting of a centre-drive to the top and bottom of the bearings. The “centre drive” approach has two advantages; first it allows a greater displacement to height ratio and second it provides increased damping capacity at large displacements, thus providing some of the additional damping needed for resisting “near fault fling”.
5.3.3.5 Rocking structures As well as the methods described in the preceding sections, the flexibility required to reduce seismic response may be obtained by allowing part of the structure to lift during large horizontal motions. This mechanism is referred to variously as uplift, rocking, or stepping, and involves a discontinuity of contact between part of the foundations and the soil beneath, or between a vertical member and its 25
base. The good performance of many ordinary structures in very strong ground shaking can only be explained by rocking having beneficially occurred during the earthquake. However, despite apparently favorable results, such structures have not yet been enthusiastically adopted in practice. This is probably due to continuing design uncertainties regarding factors such as soil behavior under rocking foundations in the design earthquake, the possible overturning of slender structures in survivability events, or possible impact effects when the separated interfaces slam back together. With the addition of energy absorbers the above hazards are lessened, and utilization of the advantageous flexibility of uplift has been put to practical effect in completed constructions.
5.3.3.6 Energy dissipators for seismically-isolated structures In the preceding sections on isolation methods, a number of energy dissipators (dampers) were presented having been used with seismically-isolated structures, namely: (1) Lead plugs, in lead-rubber bearings. (2) Tapered steel plate cantilevers. (3) Steel torsion-beam. A variety of other devices have been investigated which are also suitable in this situation: (4) Lead extrusion devices. (5) Flexural beam dampers.
5.3.3.7 Energy dissipators for non-isolated structures As discussed above, energy-dissipating devices are an essential component of seismic isolation systems, and they also may be used to reduce seismic stresses in non-isolated structures. Various forms of energy-dissipating devices have been developed for such structures. Energy dissipators in diagonal bracing Diagonal bracings incorporating energy dissipators control the horizontal deflections of the frame and also the locations of damage, thus protecting both the main structure and non-structure. A number of devices to be connected to diagonal steel bracing show high energy-absorbing capabilities, such as the lead extrusion damper also used in base isolated structures. Energy dissipation in bolted beam-column joints If bolted joint interfaces are designed to permit controlled sliding rotations in earthquake motion, not only is energy dissipated, but damage is limited or eliminated.
Element for earthquake protection (used at NPP in Romania) made by GERB The system is effective against forces in both the orizontal and vertical directions. These elements are maintenance free. Spring elements may provide local elasticity and attract a great extent of the seismic 26
energy. In many cases they represent the most flexible part of the structure. Viscodampers, installed beside the spring elements, have the task to absorb the kinetic energy. They serve as a displacement limitation of the structure and the devices As passive structural control systems begin to see an increased acceptance within the earthquake engineering community, strong research efforts have been shifted towards the development of semiactive structural control systems. For the sake of completeness, it is worth mentioning that a semiactive control system may be defined as a system which typically requires a small external power source for operation and utilizes the motion of the structure to develop the control forces, the magnitude of which can be adjusted by the external power source. Control forces are developed based on feedback from sensors that measure the excitation and/or the response of the structure. The feedback from the structural response may be measured at locations remote from the location of the semi-active control system. Semi-active control systems maintain the reliability of passive control systems while taking advantage of the adjustable parameter characteristics of an active control system (requiring a large power source for operation of electrohydraulic or electromechanical actuators which supply control forces to the structure). Semi-active systems which are currently under research worldwide include stiffness control devices, electrorheological dampers, magnetorheological dampers, friction control devices, fluid viscous dampers, tuned mass dampers and tuned liquid dampers. It has to be noted that usually it is meaningful to apply a combination of methods or particular techniques in order to achieve the best solution, economically and technically. It is also worth mentioning that many times, the intervention method which is selected as the most suitable is not technically feasible, in terms for example of creating enormous demands for foundation alterations or functionality problems when the structure returns in use. The legislative framework which is set by the state tries to combine the “desirable” with the “feasible” and constitutes an issue of a wide political decision. In recent years new technologies have been used. Passive control and/or base-isolation methods are now widely used for earthquake protection of buildings and their contents. A state of the art example report on new technologies is that of Japan Society of Seismic Isolation, JSSI, K.Kasai 2004.
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Devices of Passive control systems
Viscous 粘性ダンパー
Oil オイルダンパー
Viscoelastic 粘弾性ダンパー
せん断，流動抵抗 Shear/Flow Resist. Panel, Box, Cylinder 面型， 箱型， 筒型
流れ絞り抵抗 Flow Resist. Cylinder 筒型
せん断抵抗 Shear Resist. Cylinder, Panel, etc. 筒型，面型， その他
F = C ⋅ u& α
F = C1 ⋅ u& or C 2 ⋅ u&
F = K (ω ) ⋅ u + C (ω ) ⋅ u&
F
F
u
Steel 鋼材ダンパー
塑性履歴抵抗 Axial/Shear Yielding Cylinder, Panel, etc. 筒型，面型， その他
F = K ⋅ f (u )
F
F
u
u
u
Framing types of passive control systems
FIGURE 5.10. Passive Control Scheme for Mitigating Seismic Damage to Buildings and Equipments (From K. Kasai, Tokyo Institute of Technology, Japan, 2004)
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FIGURE 5.11. Examples of configuration of passive control systems (From K. Kasai, Tokyo Institute of Technology, Japan, 2004)
29
FIGURE 5.12. Examples of configuration of passive control systems (From K. Kasai, Tokyo Institute of Technology, Japan, 2004)
30
5.3.4 Conclusive Remarks It is very well known, especially from recent evidence, that historical constructions are by far the most vulnerable form the seismic point of view, demanding the definition of urgent strategies for the protection of the cultural heritage from seismic hazard. Within the current practice in the field of seismic rehabilitation, the methodologies for seismic upgrading of constructions can be based on either strengthening of structural elements or control of seismic response. Strengthening systems described in details previously, most commonly adopted, are based on traditional approaches but adopt the concept of Reversible Mixed Technologies (RMT). As already known, the concept of RMT can be exploited through the use of both innovative materials and special devices purposely conceived for the enhancement of seismic performance. Concerning innovative materials, most suitable are metal materials. New metal-based technologies, indeed, ensure an increased safety level under any load condition, with an overall cost comparable with or lower than the one required by traditional options. At the same time, they allow the existing configuration of the construction to be preserved as much as possible, and this turns to be very important in applications in the monumental field. Eventually, the use of metals is also environmentally friendly, as such materials can be easily removed and recycled at the end of their operational life-time. Ultimately, the application of more advanced and sophisticated solutions, including active, semi-active or passive systems, has been proposed for the reduction of seismic vulnerability of existing buildings.
5.4 COUNTRY SEISMIC LEGISLATION & ACTIONS FOR SEISMIC INTERVENTION ON CONSTRUCTIONS 5.4.1 Seismic Risk Management Legislation and Actions 5.4.1.1 Algeria Algeria has always been subjected to an intense seismic activity, which has resulted in many losses in human lives and caused significant material damages that has each time, disturbed if not blocked, the development activities of the country for a number of years. The recent major earthquake of 2003 with about 5 Billions of US dollars damages and 2300 losses of lives and the one that stroke the region in 1980 inducing more than 2600 deaths and damaging 70% of the region are clear examples of the seismic vulnerability of the country which, in a period of 20 years, has witnessed more than 9 earthquakes of magnitudes exceeding 5.4 on the Richter scale. Yet, the country has not developed clear intervention strategies and has not developed a seismic culture for the population to live with. Education syllabuses do not contain much about the nature of earthquakes, their consequences, and how should the population behave when these geological phenomena occur. It is thus important that Governments set up intervention strategies according to their abilities and means at their disposal in the aim of managing the disaster when the seismic hazard strikes. Intervention strategies at a wider scale consist of making people aware of the risk well in advance. Such awareness is best transmitted to the population through education. These intervention strategies should be guided by laws and regulations based on the work of technicians and experts. Prevention and mitigation measures are very important intervention strategies that should be considered before the disaster strikes in order to alleviate the risk consequences. 31
The construction act should be carried out according to specific engineering requirements set up by expert engineers and architects in a planned land for use. Indeed, land use planning is as important as the technical engineering requirements for buildings that are expected to absorb the seismic shock without great damages and losses of lives. Disaster preparedness is a very important intervention strategy, which makes the population aware of the risk by learning from past disasters or from probable scenarios of seismic hazards. Governments and political authorities have a great role in inculcating the seismic risk education to the population and making them prepared at any time. The same governments and political authorities should be able to implement the planned measures put in place in the preparedness phase in a short time. This disaster response includes emergency relief measures such as health, food, water, sanitation, shelter, logistics and supply, security, etc.This response should be ensured for a maximum number of people affected before re-establishing gradually the services. The rehabilitation and reconstruction stage should start immediately in order to get the population to normal life with the promotion of social and economical aspects.
1980 Chlef earthquake The 1980 earthquake that hit the region of Chlef had a magnitude of 7.3 on the Richter scale and came after a period 26 years from a previous less stronger one which hit the same region in 1954 with a magnitude of 6.7. The devastating nature of this 1980 earthquake, which is classified amongst the major earthquake disasters of the 20th century had slashed away 70% of the region and made evident the lack of preparedness of the country to cope with natural disasters of this kind. This earthquake was however the occasion for the Algerian authorities and the population as a whole to learn lessons from what has happened. An open seismic training center was there for everybody to get trained and know about these natural hazards. The technical bodies and civil engineering research institutions from all over the world precipitated to the accidental site to learn from the catastrophe. Among the recommendations that were retained to be implemented, the following points deserve to be recalled: - Sustained effort for training and information - Setting up of procedures for normalisation and homologation of building materials - Tightening up of the procedures for granting agreements for intervention in the building sector - Tightening up of the control in the building sector (at the design office and at the construction site) - Generalisation of the seismic hazards and microzoning studies - Installation of networks of seismic equipment to record seismic characteristics when they strike - Elaboration of a code for repair and strengthening of damaged constructions - Elaboration of a seismic code for the building sector - Creation of a research center for para-seismic studies However, the seismic code that has come out after the 1980 earthquake was considered as must only for official and collective buildings and the private and individual houses continued to be designed without taking into considerations the seismic regulations, which were not vulgarised in design offices and insufficiently taught at universities. The control was not in anyway tight and the para-seismic construction could not succeed in the absence of a follow-up body specially designated by the political authorities with a full decision power at his disposal. This laxity in considering seriously the seismic design regulations and improving the quality of workmanship on sites is greatly responsible for what has happened in the 2003 earthquake that hit Boumerdes and Algiers; the lessons was not learned from the 1980 earthquake; let’s hope that it is after what has happened in the 2003 earthquake and the similar type of collapses that were recorded for constructions built after the 1980 earthquake. 32
5.4.1.2 Belgium In case of a seismic event, the “Crisis Centre” of Belgium and the “Royal Meteorologic Institute” has to deal with the occurring problems. Nevertheless, Belgium doesn’t possess a general strategy to be used in case of seismic event. The local authorities are responsible for the rescue interventions and expertises after a natural disaster. So, after the earthquake of Liège 1983, it is the security service of Liège who was in charge to expertise all the damaged buildings. For each damaged buildings, quick checks were done as: - Verification of the building stability; - Verification of the electric equipments; - Verification of the gas pips; - Check for cracks in the chimney (to avoid problems with the CO2 gas). These checks were done directly after the earthquakes and took about 20 days. After this first verification, more detailed investigations were performed for more damaged buildings. The damages caused to the buildings needed reparations for a total amount of 75 million euro. So, the Belgium authorities decided to subsidize investigations to estimate the seismic risk in Belgium and to find solutions, which could decrease the amount of damages in case of a seismic event. Here below are mentioned two of the conducted investigations: - A first project dedicated to the estimation of the seismic risk in a 4km² area in Liège and conducted by the University of Liège. - A second project aiming at investigating the behaviour of “non-designed” family houses under seismic loading. This project conducted to the publication of a technical document proposing simple and low cost solutions for improving the behaviour of such buildings under seismic loading.
5.4.1.3 Egypt 'Le Service des Antiquites d’Egypte’, was set up in 1859 to control and to organize the activities related to Egyptian Antiquities. In 1971, it was replaced, by the "Egyptian Antiquities Organization (EAO), which more recently, in 1994, was replaced by the "Supreme Council of Antiquities' (SCA). In 1985, the EAO published the program of its policy (National Heritage: Challenge and Response: 1982-1985). The program focused mostly on restoration of (Islamic) historical buildings noting that more than 1000 Islamic monuments have perished since 1882 and that the budget for restoration and conservation was minimal. It reported that more than 500 Islamic monuments are in ruins and noted that the situation was worsening. Deterioration problems were defined related to: rising of subsurface water, changes in loads affecting the foundations, pollution, increasing population density and lack of maintenance, expansion of housing and lack of public awareness. Recently earthquakes are considered.
Current Institutional Organization and Functions of SCA The SCA is a department of the Ministry of Culture. The current organizational chart of the SCA reveals a highly centralized authority headed by the Minister of Culture. The everyday operations of the SCA are entrusted to a secretary general. 33
The main divisions of the SCA Include, the secretariat, two main divisions are heading to Egyptian/Greco-Roman monuments, and with Islamic/Coptic monuments, and three other divisions concerned with museums, projects, and funding. In addition, the council supervises the Nubia Fund (which administers the funds remaining from the UNESCO Nubia Campaign). These divisions are all based in Cairo, presiding over smaller regional divisions. These regional units subdivided as follows: · Upper Egypt and the Oases · Middle Egypt · The Delta, Sinai and the Mediterranean coast · Cairo and Giza Each of these regional units administered from capital centers in turn oversees local inspectorates. The regional units include specialized group concerned with ownership and properties, documentation, and excavations. By law, SCA is the main public institution concerned with monument conservation and controlling all restoration projects in Egypt. However, other conservation efforts may be carried out by other government organizations such as the Ministry of Waqfs, involved in restoring mosques and Islamic monuments. Restoration may also be carried out through private initiatives or by municipalities and governorates. During last ten years, other establishments are emerging under the auspices of different ministries to deal with documentation and conservation studies of historic districts, particularly, Historic and Islamic Cairo project, among others. The Ministry of Planning, the Ministry of Communications, Information and Technology (MCIT), and even the Information and Decision Support Center (IDSC) are involved.
5.4.1.4 Italy In the past years, after the occurrence of a seismic event, a series of legislative actions useful for the clearing of the emergency and for the reconstruction works has been carried out in Italy. The used policy strategies were not the same for every earthquake, because of both the differences of situations and the absence of a comprehensive system of rules to be applied in a seismic emergency. A collection of the policy strategies adopted in the past can be useful to try to define an unique strategy for seismic protection. In order to thread a path among the policy strategies undertaken in Italy in the past, three major earthquakes occurred in the second half of 20th century have been considered. The referred earthquakes are the following: • Friuli, 6th May 1976; • Irpinia, 23rd November 1980; • Umbria-Marche, 26th September 1997. The choice of these earthquakes makes it possible to understand the post-seismic approach in Northern (Friuli), Central (Umbria-Marche) and Southern (Irpinia) Italy. For each seismic event a synoptic table is provided. Such tables present, in a chronological order, the main policy measures undertaken. For each measure, the competent Authority and the main tasks and/or contents are also indicated.
34
TABLE 5.4. Friuli earthquake, 6th May 1976 DATE 10/05/1976
AUTHORITY Friuli – Venezia Giulia Region
MEASURE Regional Law no.15
18/05/1976 and 20/05/1976
Government and Friuli – Venezia Giulia Region Parliament
D.P.C.M. and D.P.G.R.
Friuli – Venezia Giulia Region Friuli – Venezia Giulia Region Government
Regional Law no. 17
29/05/1976
07/06/1976 1976 30/10/1976 08/09/1976 19/11/1976 27/04/1977 1977 20/06/1977
Government
Parliament Friuli – Venezia Giulia Region
Law no. 336
Regional Law no. 28 Law no. 730 D.P.C.M.
Law no. 30 Regional Law no. 30
08/08/1977
Parliament
Law no. 546
1982 01/12/1986
Parliament Parliament
Law no. 828 Law no. 879
MAIN TASKS / CONTENTS -Establishment of a solidarity fund for the intervention after 1976 earthquake; -Ordering for the demarcation of the damaged areas (after the first series of seismic shocks, occurred in May). -Demarcation of the damaged areas (after the first series of seismic shocks, occurred in May). -Ordering for the demarcation of the damaged areas (after the first series of seismic shocks, occurred in May); -Allocation, on the whole, of 2118 million Euro, for the emergency (310 million Euro, before the demarcation of the damaged areas; 1808 million Euro, after the completion of the demarcation), by considering specific criteria for industry, commerce, craft, tourism, agriculture, public works and housing. -Benefits for small structural repairs. -Recovery of productive activities (with consequent allocation of 23.6 million Euro). -Ordering for further demarcation of the damaged areas (after the series of seismic shocks occurred in September). -Further demarcation of the damaged areas (after the series of seismic shocks occurred in September). -Allocation, on the whole, of 1782 million Euro. -Recommendations for structural repair of masonry structures; -Intervention on minor cultural heritage (with consequent allocation of 274 million Euro). -Further economical contribution for reconstruction, socialeconomical development, cultural heritage safeguard; -The rules for the realization of the previously mentioned tasks are defined by Friuli-Venezia Giulia Region. -Allocation, on the whole, of 904 million Euro. -Grant aid for buildings interested by state of seismic readiness; -Allocation, on the whole, of 607 million Euro.
35
TABLE 5.5. Irpinia earthquake, 23rd November 1980 DATE 24/11/1980
AUTHORITY Government
1980
Parliament
December ’80 December ’80
Government
MEASURE D.P.C.M.: -Declaration of the state of particularly deep natural calamity; -Establishment of the Extraordinary Commissioner of the Government for the Campania and Basilicata Regions Law no. 874
-
Extraordinary Commissioner
Order: Delegation to the Public Works Authorities, which delegate the Cities
December ’80
Government
Delegation to the Budget Ministry, which delegates the CNR
January ’81 1981
Extraordinary Commissioner Parliament
22/05/1981 and 13/11/1981 14/10/1981
Government
30/03/1990
Interdepartmental Committee for the Economical Planning Government
Order n. 80 Law no. 219
MAIN TASKS / CONTENTS (ex art. 5 L 996, 8/12/1980; D.L. 776, 26/11/1980) -The Commissioner coordinates the assistance and realizes the emergency services, he provides for aid and assistance, creating operative centres, temporary lodgings, field military hospitals
-Confirmation to the Extraordinary Commissioner of the powers (given to him by the Government) to lead towards the crossing of the emergency state (with the exception of the reconstruction plans); -Establishment of a fund for pressing needs of the earthquake-stricken people; -Grant aid for the reparation of the housing; -Norms of fiscal facilitation and extensions; -Detection of 2 tasks for the Government: 1) together with earthquake-stricken Regions and Local Administrations, damage assessment, within 6 months, in order to take legislative measures for the reconstruction; 2) by Ministry of Public Works, together with Superior Council of Public Works and C.N.R., seismic reclassification of the earthquake-stricken towns (already stated by Law no. 64/74) -First temporary demarcation of the damaged areas -Coordination of the damage assessment, which is based on forms relating to single buildings, making an essentially “qualitative” evaluation. This kind of study was performed for provincial capitals. -Coordination of the damage assessment, which is based of forms similar to those used after 1977 Friuli earthquake, making an analytical evaluation. This kind of study was performed for the other cities (only for housing) -Reorganization of the local scopes for the reconstruction -System to provide organic reconstruction works and the economical development of the earthquake-stricken people (for instance, facilitations for agricultural activities, repair and reconstruction of industrial settlements, etc.). -The local authorities provides for housing reconstruction and to local public works. -The State provides for the facilities and the economic development plan for the earthquake-stricken people. -Demarcation of the damaged areas
D.P.C.M. Establishment of the C.R.E.D. (Centre of Data Collection and Elaboration)
-Drafting of annual reports about reconstruction.
Order in Council BE no. 76: Unified code of the l f i i i
-Reorganization of the series of laws issued after 1981 relating to the post-seismic intervention.
36
laws for intervention in earthquake-stricken Campania, Basilicata, Puglia and Calabria Regions.
TABLE 5.6. Umbria-Marche earthquake, 26th September 1997 DATE 27/09/1997
AUTHORITY Government
28/09/1997
Ministry of the Interior (delegated for civil defence by D.P.C.M. 24/05/1996)
30/03/1998
Parliament
MEASURE D.P.C.M.: -Declaration of the state of emergency Order no.2668: -The Presidents of Umbria and Marche Regions are nominated Delegated Commissioners
Law no. 61
MAIN TASKS / CONTENTS -
-Communication, within 7 days, of the list of towns situated within the heavily damaged area; -Implementation of the interventions for private and public safety; -Restarting of the ordinary life conditions -Realization of a plan for emergency measures (together with G.N.D.T) -Establishment of a fund for damaged subjects -Norms for fiscal facilitation -Planning of urban interventions; -The damaged Cities must prepare their “Recovery Programs” (to be carried by the Regions) useful for: -Reconstruction / recovery with seismic improvement of destroyed / damaged buildings (by picking out the damages; summarizing the proposed measures; calculating the costs; choosing the actuator subjects) -Demarcation of the damaged areas; -Financing for the re-establishment of productive activities -Grant aid for preventive interventions for reduction of urban seismic vulnerability (through the so called Unitary Interventions, referred to entire buildings or to building complexes) -Interventions against hydrogeological instability conditions
The funds for reconstruction allocated as a consequence of the series of mentioned post-seismic policy measures have been subdivided between the different involved subjects, according to their particular scope. All the subjects involved in the post-seismic activities are listed in the following. The specific scopes of each subject are reported. • Extraordinary Commissioner, for the implementation of the emergency interventions; • Heavily Damaged Cities, for the grant aid to private citizens to realize the reconstruction, for the realization of cheap housing, for the realization of local public works ; • Naples, for the realization of the extraordinary plan for the metropolitan area of Naples; • Campania and Basilicata Regions, for the reconstruction and repairing in the agricultural, tourist, craft and entertainment fields; • Ministry of: Agriculture, Cultural heritage and environmental conservation, Defence, Finance, Justice, Public works, Postal and telecommunications, Education and Transport, for reconstruction, repairing and improving of the public works within their references; • Special Office for Industrial Development, for grant aid to the companies etc. 37
The following diagram shows the subdivision of the total fund (22.850 million Euro) between the mentioned subjects. 5% 4% 11% 35%
Cities Neaples Industrial Development Extraordinary Commissioner
16%
Ministries Regions 29%
In the following some data referring to the Unitary Interventions are presented, in order to show the “answer” given by the Cities to the innovative tools introduced by law no. 61/98. • Total settlement number: 95 • Total number of Unitary Interventions present in the Recovery Programs: 458 • Total number of buildings listed in Unitary Interventions: 1539 • Average number of buildings for each Unitary Interventions: 3,36 • Number of buildings in U.I. out of the total number of damaged buildings: 35,96 % • Cost for U.I. buildings repairing: 249 million Euro • Percentage of the U.I. buildings repairing costs on the total cost for buildings repairing: 37,87 %
5.4.1.4 Maroc Decree n°2-02-177 dated 9Hija 1422 (22February 2002) approving the Paraseismic Construction Code, with the acronym referred to by “R.P.S2000”, applicable to the buildings and establishing the paraseismic regulation and the creation of the National Committee of the Paraseismic Engineering THE PRIME MINISTER DECREE HEADLINE I The Parasismique Construction Code ART. 1: - approved as was annexed to the original version of this decree, the Paraseismic Construction Code, abbreviated as "R.P.S.2000", is intended to enforce the paraseismic construction regulation to insure the building safety. ART.2- For the application of paraseismic Construction code, R.P.S.2000, to the buildings: 1- the territory is divided into different seismic zones according to their degree of seismic activitiy, 2- buildings are assigned to different classes according to the degree of protection they must satisfy. The repartition of seismic zones in districts and communities is fixed by joint decree emanating from the government authorities in charge of the housing, urban planning, infrastructures and interior affaires. Before issuing the decree, the opinion of the National Committee of the Paraseismic Engineering must be considered in accord with the articles 4 and 5 hereafter. - The classification of buildings is pronounced by a joint decree of the aforesaid authorities mentioned. The modification of the so-called classification is also made public under the forms and conditions referred to above. - The buildings designed according to traditional local techniques and the bearing structure of which utilizes primarily the ground, straw, wood, palm trees, reeds or similar materials. 38
- The one storey buildings aimed at dwelling or professional uses, with a total area equal or less than 50 m². HEADLINE II The National Committee of the Paraseismic Engineering ART.4 : A committee was set up under the name of "National Committee of the Paraseismic Engineering" whose tasks are: - to propose and issue its opinions with respect to the classification and seismic zoning as well as their eventual modification per district, as envisaged in article 2 of the code. - to examine the modifications and to propose improvements to RPS 2000, taking into account, ART. 5: This committee is composed, under the presidency of the authority responsible for the Housing policy, of the representatives of the governmental authorities hereafter: governmental authority in charge of Urbanism, governmental authority in charge of interior affaires, governmental authority in charge of infrastructures, governmental authority in charge of Mine Exploration and Management, governmental authority in charge of Scientific Research, the representatives of the university departments, of the scientific and technical institutes, the schools of higher education and of professional organizations, the list of which is ratified by a decree of the governmental authority in charge of the Housing responsibility. the secretariat of the National Committee of the Paraseismic Engineering is ensured by the authority in charge of the Housing Policy. HEADLINE III Various Provisions ART.6: - is declared null the decree n° 2.60.893 of the Rajeb 3, 1380 (December 21, 1960) enforcing the application of some paraseismic provisions to the Agadir urban perimeter and to the small island of management belonging to the south-eastern part of the peripheral zone of the city of Agadir. ART.7: - the Minister in charge of Urbanism, Housing and Environment, the Minister of the Interior and the Minister of Infrastructures are charged, each one in his field of responsibility, of the execution of this Decree which will come into effect six (6) months after its publication in the Official Bulletin. Issued in Rabat on Hija 20, 1422 (February 22, 2002) The PRIME MINISTER
5.4.1.5 Romania The Ministry of Transport, Construction and Tourism (MTCT) is in charge with the National Program for Reduction of Seismic Risk in Romania. MTCT has the responsibility for contracting and financing standard building laws and technical regulations for earthquake resistant constructions in Romania. It also represents the National authority for approval of building codes and other technical regulation/norms for constructions. The present (2005) organization of the MTCT has a Minister Delegate for Public Works and Territorial Planning and a Technical Direction for Regulations/Norms for Constructions coordinating seismic risk reduction policy in Romania. 39
Technical activities related to seismic safety of existing and new important buildings are in the responsibility of the Technical Commission for Seismic Risk Reduction established at MTCT by Decision of the Minister. Important documents related to the management and national policies of reduction of seismic risk in Romania are: (i) Governmental Ordinance No.20/1994 concerning measures for seismic risk reduction of existing buildings, revised 1999; published in Official Gazette of Romania No.36/29.01.1999 (Ordinance) and No.516bis/25.10.1999 (Methodology for Ordinance application); (ii) Order No.6173/NN/1997 of the Minister of Public Works claiming to Municipalities to prepare: (i) the classification of existing building stock with respect to period of construction, structure type, class of seismic risk (I-IV) and (ii) the priorities for building identification and retrofitting. (iii) Governmental Ordinance No. 578/1998 on the Program of actions of seismic risk reduction for buildings expertised as having seismic risk class I and for financing the retrofitting works for tall RC buildings (ground-floor plus more than 4 storeys) built before 1940 in Bucharest. (iv) A new Government Ordinance in 2001,stated that the Government will 100% advance the necessary payment, for strengthening of the buildings, to the private owners of apartments classified as in “seismic risk class 1” buildings (more than 95%of housing units are private in Romania!). If the owner salary is less than national average, he have to pay back (to the state) nothing. If it is not, he has to pay the money back in 25 years, with 5% interest. Anyway, the owner has to agree on the strengthening of its apartment, since he has to leave the housing unit during the construction work. Of course, the owners do not like leaving and the necessity buildings for temporary housing during strengthening are not yet implemented. Moreover, if one apartment owner does not agree on strengthening of its apartment, the strengthening of the whole building cannot start. During the last years, the Municipality of Bucharest prepared several thousands of detailed engineering reports for buildings having significant cumulative seismic damage and high risk of collapse in case of a strong earthquake (comparable to 1977 event). However, the total number of vulnerable buildings in Bucharest is probably two times larger than the present number of identified as severely damaged buildings. In May 2005, from the list of 123 tall residential buildings in Bucharest: - 5 buildings are fully retrofitted; - 10 buildings are under retrofitting works; - 14 buildings have to participate at the bid for construction works; - 16 buildings have to participate at the bid for design of retrofitting intervention. The joint effort of the engineers, authorities and building owners for building strengthening in Bucharest is justified by the certitude that for a 50 –100 years recurrence interval Romanian subcrustal earthquake, several dozens of pre-war tall RC buildings in Bucharest will collapse(about 60-100 pers/bldg!). Unfortunately, in Bucharest, there are still more than 50 residential buildings built in the 60’ which were identified in seismic risk class 1 buildings. Bucharest is recognized by the World Bank reports as well as by professionals as the most seismically dangerous capital of Europe due to the combination of (i) fragile tall RC buildings built before WWII and (ii) long predominant period of ground vibration during strong subcrustal Romanian earthquakes. 40
The list of cultural heritage buildings in Bucharest prepared by National Institute of Historical Monuments Bucharest, 2004, contains: - 87 churches, half of them built in the XVIIIth century; - 27 palaces, 20 schools, 15 hotels, 23 malls and shops, half of them built in the XIXth century; - other buildings. The present state of the retrofitting works for the most Bucharest are as follows: Multistory steel structures Ministry of Transport and Constructions Palace Telephone Palace Multistory reinforced Government Palace concrete structures City Hall Sector 1 Athene Palace hotel Ambasador hotel La Fayette Mall Masonry and reinforced Palace of Justice concrete buildings: Royal Palace i.e. National Museum of Art
important historical palaces and hotels in to be retrofitted within WB project Retrofitted by Romtelecom to be retrofitted to be retrofitted within WB project Retrofitted to be retrofitted to be retrofitted under retrofitting partially retrofitted
In the case of seismic upgrading of cultural heritage buildings, the Government has decided that the central role of the state has to be replaced by new partnership models with private sector, international donors, organized community groups and civil society at large. The Ministry of Culture has initiated an examination of the state role in parallel with a search for international assistance and private sector partnerships in order to build financing for the nation's patrimony. The current Government goal is to seek finance for the sector, using it for improved longterm national cultural heritage partnership and mobilize additional financing from other international donors such as the World Monuments Fund, UNESCO, Council of Europe, bilateral donors and others. One major issue is the deterioration and/or loss of a number of historic sites and cultural assets and the lack of financial resources to prevent further deterioration. A closely related issue is the lack of local capacity to manage, in a cost effective and sustainable manner the cultural legacy at a time of transition from state control. For seismic upgrading/strengthening of historical building in terms of priority of intervention, seismic risk matrix similar to that used for the general building stock should be implemented, TABLE 5.6. TABLE 5.6 Priorities for buildings retrofitting Building importance & exposure (value) class Seismic vulnerability /fragility class
Essential facilities
1 2
I
II
III
Buildings that represent substantial hazard to human life in the case of collapse2)
All buildings except those listed at I and II
Highest priority for retrofitting
Highest priority for retrofitting
Priority for retrofitting
Priority for Retrofitting
Retrofitting
-
1)
1)
Hospitals and facilities having emergency treatment facilities, Fire, rescue and Police stations, Communications centers, Buildings and others structures having critical national defence functions; 2) Schools with capacity greater than 250, buildings with capacity greater than several hundreds of persons, health care facilities with capacity of 50 or more resident patients but not having surgery facilities.
41
Proposed risk matrices for prioritisation of intervention on cultural heritage buildings, TABLE 5.7. Seismic vulnerability/ fragility class i ii iii
TABLE 5.7. Seismic risk matrix Combined class: Importance & value I II III
IV
1 1
3 3
1 2
2 3 3
March 4, 1977: Collapse of the two fragile high-rise RC buildings built before 1940 in the Center of Bucharest
5.4.1.6 Slovenia Regarding the intervention strategies at the moment in Slovenia there is no corresponding legislative available. In practice, a technical commission of experts, established by the government, estimates the damage and gives the recommendations for the buildings retrofitting. The repair is financed partly by the state and partly by the owners. The technical commission decisions are based mostly on the following codes (and past experience): • Technical regulations for repair, strengthening and reconstruction of buildings damaged in earthquakes, Slovenia (Yugoslavia), 1985. • Eurocode ENV 8-1-4: Strengthening and repair of buildings.
5.4.1.7 Turkey The Ministry of Reconstruction and Settlement, the predecessor organisation of the current Ministry of Public Works and Settlements, was established in 1958 to reduce the risk of death and injury to the population, and to reduce the scale of the economic risks involved from earthquake and other natural disasters. The single and most important mandate was to implement two laws, the so-called “Development Law” and “Disaster Law,” which were created by the Ministry of Reconstruction and Settlement in 1959. 42
The current Development Law (No.3194, termed the “Reconstruction Act” as literally translated from Turkish) was enacted in 1985, and it is the fourth generation in a tradition of such legislation in Turkey. The Development Law is the principal legal instrument governing how buildings are constructed. This law was devised to ensure the establishment of settlement areas and structures in compliance with planning, health and environmental conditions. This law has a few articles in Part 4 that regulate the supervision of building construction. The law holds municipalities (or governorates for buildings outside of urban areas) responsible for design supervision. Construction supervision is entrusted to the inspector, so-called “engineers of record.” For certain classes of buildings to be built in nonmunicipality areas, non-engineering degree holders have also been enabled to serve in this capacity. There are other exceptions granted for rural settlements. Plans for areas remaining inside or located outside of municipal and residential areas, and all structures to be constructed are subject to provisions of this law. In Turkey, the legal system functions by chartering by-laws, regulations, or statutes that regulate how a given law is enforced. Numerous regulations complement the Development Law as follows: - Standard building regulations for non-metropolitan municipalities - Land and property sharing with renewed alignments according to Article 18 - Standards and procedures for preparing and revising plans - Building regulations for areas without a plan
Illegal Housing Construction Laws In Turkey, the informal settlement sector plays an important role in housing construction. Illegal housing, or so-called “gecekondu”, a Turkish word meaning “overnight construction”, began to appear in the 1940’s. At first, the government tried to remove gecekondu. However, rapid increase of gecekondu and massive political power of its inhabitants forced the governmental policy to take more feasible measures (Hirayama, 2001; Kobayashi et al., 2001). In 1953, a law was issued to prohibit new gecekondu but permit existing illegal housing. In the late 1950’s, construction of illegal housing became industrialized. Planned but illegal housing development, and its selling and renting were established as a commercialized system. In 1963, the Republic’s five-year national development plan was institutionalized, and housing provision was included under the plan. In 1966, a major shift in the housing policy was made when a gecekondu law was issued. The law designated gecekondu areas that satisfied certain conditions as “improvement areas,” and their improvement and infrastructure were promoted. Gecekondu areas that did not satisfy certain conditions were designated as “prohibited areas,” and the removal of housing from these areas along with provisions of alternative housing were promoted. Illegal occupants in public areas were requested to buy the land in short period of time as sub-division, and then they become subject to property taxation. Gained revenue was to be used for the improvement of the gecekondu areas. In Istanbul in the 1950’s, the informal sector consisted of 45% of its housing construction. In the 1970’s, the informal sector accounted for over two thirds of housing construction. Gecekondu law was revised later in 1976 and in 1983, maintaining basic principles from its first version. In 1985, financial assistance systems for acquisition of housing such as the Mass Housing Law, and the Mass Housing Fund were outlined under the 5th National Development Plan. In the same year, a 43
new reconstruction law penalized illegal development covering areas over 1000 m2, but small illegal housing developments covering areas less than 1000 m2 were legalized.
Recent Decrees related to Safe Construction Following two earthquakes in 1999, new decrees were developed to ensure safe construction (Gulkan, 2001). a. Building Construction Supervision (Decree No. 595, April 10, 2000) Decree No. 595 was issued to ensure that nominal quality standards are abided within the building construction continuum. Institutional buildings are excluded. The individuals deemed responsible for a given building are the design engineer, contractor, site engineer and building supervision firm. Design engineers are required to have the title of “expert engineer,” similar to a professional engineer. In essence, the building supervision firm exercises the duties of the municipal or governor offices in ensuring both the correctness of the designs and conformance of the actual construction to the design. In each provincial capital and town with populations numbering more than 50,000 inhabitants, a building supervision oversight commission is established under the general coordination of the field office of the Ministry of Public Works and Settlements. Ankara’s “Building Supervision Supreme Council” is embedded in the same ministry and manages this hierarchical structure. Fees for design and construction supervision range from 4 to 8 percent of the estimated cost of the building and are disbursed by the owner through the municipality. Unless there exists a confirmation that the building has been completed in conformance with the actual design, municipalities are not able to grant occupation permits for people to move into the premises. The building construction supervision firm is the party primarily responsible for offsetting any losses incurred by the owner that may arise during the first ten years after the occupation permit is issued, including those caused by natural disasters. To ensure this compensatory liability, firms must purchase insurance for each job they supervise. All firms engaged in this type of activity have this coverage. The enforcement of this decree was initiated in 27 pilot provinces, including all that were impacted by the 1999 earthquakes. An omission in the text of the decree is the detailed construction inspection procedures that are required for effective quality assurance. Architects have been left out of the inspection procedures, with the civil engineering profession having received prime responsibility there. A number of regulations have also been issued to facilitate the implementation of the decree.
b. Regulation for Implementation of Construction Supervision (May 26, 2000) Construction supervision firms are classified into three groups in order of reduced responsibility and manpower requirements. These firms must be owned by a majority of engineers or architects. Their chief mission is to ensure that the designs conform to the appropriate building code as well as the seismic code. Local site evaluations are specifically mentioned because of past experiences with liquefaction and loss of soil strength. This regulation also contains clarifications regarding the manner in which different-level supervision councils are to function, and how their records are to be kept. c. Revision of the Law on Engineering and Architecture No. 3458 and Law on the Union of Chambers of Turkish Engineers and Architects No. 6235 (Decree No. 601, June 28, 2000) The practice of engineering and architecture, and the empowerment of engineers and architects to organize themselves into chambers and a union comprising the different chambers are regulated by these two laws. With the introduction of “expert” engineers or architects in the process of construction supervision, corresponding amendments to the parent laws were required. This decree achieves that 44
objective. The chambers are enabled to set the guidelines for conferral of the expert title, but generous transition (grandfather) clauses have also been admitted. General Conditions for Mandatory Financial Liability Insurance for Construction Supervision Firms (July 10, 2000). This directive issued by the Under secretariat of the Treasury sets the rules and procedures for the purchase of the mandatory financial liability insurance all supervision firms must have for each construction they undertake to oversee. Coverage articles refer to “unreasonable” damages caused by the disaster as being excluded from the intent of the underwriting, but no specific guidelines are mentioned. In successive articles, the obligations of the insurer and the insured are spelled out when events leading to physical damages have occurred because causes of damage are often not easily ascribed to only one party in the building delivery process. The insurance premium is 1.3 percent of the insured value.
d. Testing Laboratory Requirements for Decree No. 595 (July 30, 2000) Independent testing laboratories must certify that minimum requirements are met for building materials used in construction. This directive and a companion set out the requirements for these laboratories. Disaster Laws The 1982 Constitution The 1982 Constitution outlines the rules and procedures for the declaration of a state of emergency and the suspension of fundamental rights. Article 15 describes the suspension of the “Exercise of Fundamental Rights and Freedoms” as follows: “In times of war, mobilization, martial law, or state of emergency, the exercise of fundamental rights and freedoms can be partially or entirely suspended, or measures may be taken, to the extent required by the exigencies of the situation, which derogate the guarantees embodied in the Constitution, provided that obligations under international law are not violated.” Article 119, "Declaration of a State of Emergency on Account of Natural Disaster or Serious Economic Crisis," in the constitution defines the activation of a state of emergency. The article states that "in the event of natural disaster, dangerous epidemic diseases or a serious economic crisis, the Council of Ministers, meeting under the chairmanship of the President of the Republic may declare a state of emergency in one or more regions or throughout the country for a period not exceeding six months." Article 121 states the "Rules Relating to the State of Emergency" as follows: "In the event of a declaration of a state of emergency under the provisions of Articles 119 and 120 of the Constitution, this decision shall be published in the Official Gazette and shall be submitted immediately to the Turkish Grand National Assembly for approval. If the Turkish Grand National Assembly is in recess, it shall be assembled immediately. The assembly may alter the duration of the state of emergency, extend the period, for a maximum of four months only, each time at the request of the Council of Ministers, or may lift the state of emergency. The financial, material and labor obligations which are to be imposed on citizens in the event of the declaration of state of emergency under Article 119 and, applicable according to the nature of each kind of state of emergency, the procedure as to how fundamental rights and freedoms shall be restricted or suspended in line with the principles of Article 15, how and by what means the measures necessitated by the situation shall be taken, what sort of powers shall be conferred on public servants, 45
what kind of changes shall be made in the status of officials, and the procedure governing emergency rule, shall be regulated by the Law on State of Emergency. During the state of emergency, the Council of Ministers meeting under the chairmanship of the President of the Republic, may issue decrees having the force of law on matters necessitated by the state of emergency. These decrees shall be published in the Official Gazette, and shall be submitted to the Turkish Grand National Assembly on the same day for approval; the time limit and procedure for their approval by the assembly shall be indicated in the Rules of Procedure."
National Development Plan Unlike former plans, the 8th National Development Plan fully addresses natural disasters in section seven, “Natural Disasters,” and in chapter nine, “Enhancement of Efficiency in Public Services.” The plan describes objectives and principles as follows: “The main objective is to establish the social, legal, institutional and technical structure for reducing the damages of disaster to the minimum through measures to be taken. Central coordination in the establishment of this structure is the main principle. Through continuous and systematic training efforts, measures shall be taken against earthquakes and other disasters, and it shall be ensured that these disasters shall be perceived as common natural events. Training efforts for people shall be continued to include the social ethical rules. Necessary efforts shall be made to guarantee sufficient security for all the existing or future infra and superstructures. A small part of the large resources, which were utilized after the disasters but proved not to be efficient, shall be utilized under a plan before the disaster to take measures for reducing the damages of a possible disaster. Since design of the disaster-proof buildings requires specialization, emphasis shall be given to earthquakes and other issues on disasters in engineering graduate programs. Furthermore, programs improving the sense of responsibility of the engineers and laying down a professional ethic shall be emphasized. Earthquake engineering postgraduate programs shall be introduced by the technically eligible universities and existing programs shall be improved. Efforts shall be made to reduce deficiencies of engineering in practice. Since most of the building stock is not secure against earthquakes, these buildings shall be examined and strengthened systematically against earthquakes, starting, first of all, from the places where earthquake occurrence possibility is high. Establishment of Building Assessment Centers where competent engineers shall work for assessment and strengthening of the existing buildings against earthquakes shall be supported. With a view to making the principles and methods of the field use and construction plans sensitive against disasters, related legislation shall be reviewed and effective mechanisms shall be introduced for strict implementation. Liabilities and relevant sanctions of those who will act against the rules shall be revised. A disaster management system, in harmony with the existing legal and institutional structure and including the studies for National Extraordinary Situation Plan shall be made. This system shall cover a fast, effective and comprehensive rescue and first aid operation in order to reduce the damages of the disasters before and during the disaster and accomplish the functions towards eliminating the economic, social and psychological damages of the disaster.” 46
The plan describes legal and institutional arrangements as follows: “Necessary arrangements shall be made in the legislation to make the Turkish Emergency Management Institution operative. The Law on Engineers and Architectures laying down the duties, authorities and responsibilities of the engineers and the Law concerning the Turkish Engineers and Architectures Chamber Union setting out the duties and authorities of the professional chambers shall be revised to introduce a concept of Competent Engineering. Construction Law shall be amended to introduce a sound construction control system and revised to include the liabilities of those acting against the rules and the sanctions to be applied to them. The Law on Municipalities and the Metropolitan Municipalities Law shall be amended to bring about a sound construction control system and revised to arrange the duties, authorities and responsibilities of the local administrations on the determination of natural disaster threats and risks and reduction of their likely damages. Full and accurate implementation of the provisions of the Natural Disaster Regulation is considered adequate for ensuring earthquake-proof building design in the future. Legislation for other disasters needs to be updated and accurately implemented. Related provisions of the Civil Code, Law of Obligations and Trade Law shall be reviewed as regards construction controls, responsibilities and insurances, and necessary legal arrangements shall be made to this end. The Law on the Measures and Assistance in Natural Disasters Affecting Life which considers the state as a natural insurer covering all damages incurred shall be amended to cover only the cases which are impossible to be insured, thus public liability shall be limited. A national disaster information system shall be established through which cooperation with institutions in the other countries and international bodies shall be possible. A national disaster communication system that would provide continuous service during the disaster shall be established.”
Disaster Law (Law No. 7269) A “law on the measures to be taken and assistance to be directed due to disaster having influence on social life,” or so called “Disaster Law,” was issued in 1959 as a fundamental law in dealing with disasters, and was later amended in 1968. The main scope of this law is to provide public intervention capacity and to improve the efficiency of relief operations after disasters such as earthquakes, fires, floods, erosions, rockslides, avalanches, etc. For this purpose, the law entitles extraordinary powers for provincial and district governors, making them the sole authority with powers commanding all public, private, and even military resources to manage response activities. Each governor is responsible for drawing a relief operation plan to become effective immediately after a disaster. The relevant ministries, provincial administrations, and subdistricts are required to draw up their own emergency preparedness plans. A disaster fund is allocated annually from the national budget for all recovery expenses.
Regulations Concerning the Fundamentals of Emergency Aid Organisation and Planning Associated with Disasters (Decree No. 88-12777) As one of the by-laws pursuant to Article 4 of the Disaster Law, this regulation was established in 1988 by the Ministry of Public Works and Settlements. The object of these regulations is to define the formation and duties of emergency aid organizations by effectively planning the facilities and 47
resources of the State before natural disasters occur to ensure that, in case of a natural disaster, the State gets fastest access to natural disaster areas and survivors get efficient first aid. Provincial and district governors are entitled with the most responsibility and given extraordinary power to seize men, vehicles, land, and properties in the event of a disaster. These regulations stipulate that the Provincial Emergency Aid Committee be formed under the governor and that the Permanent Provincial Disaster Office be established under the Provincial Directorates of the Ministry of Public Works and Settlements. The Provincial Disaster Office is composed of nine service groups and associated subservice groups, formed by various public organizations. The service groups will work for the victims from the beginning of the disaster up to 15 days, though the termination date of the services may be extended. The regulation also stipulates that district governments set up district emergency aid committees including the district mayor and formed under the district governor, and to form district emergency aid service groups and provide services which are similar to or reduced in scale to the provincial ones.
Civil Defense Act (No. 7126) Civil Defense Act (No. 7126) was issued in 1959 and serves as a legal basis of present civil defense. This act entitles civil defense with rescue work authority. Organizations that operate rescue activities must have a protocol with civil defense. Laws Related to Fire Brigade Services of the fire department and control of hazardous facilities are defined as duties of municipality, as defined in the Municipality Act, and in Metropolitan Municipality Act. In addition, there are 30 laws, rules and regulations in total that are concerned with fire, though special fire laws do not exist. Laws Related to Compulsory Earthquake Insurance Following are a set of decrees related to earthquake insurance that were issued after the 1999 Marmara Earthquake (Gulkan, 2001): a. Compulsory Earthquake Insurance (Decree No. 587) Compulsory earthquake insurance was issued as an act on December 27, 1999. All existing and future privately owned property is required to contribute to the Turkish Catastrophe Insurance Pool (TCIP). Non-engineered rural housing and fully commercial buildings are excluded. The intention of this decree is to create a fund contributed to by homeowners’ annual payments for use in disasters so that no one will be left homeless, with a nominal sum, currently capped at US$28,000, being disbursed immediately to homeowners who are left homeless. An important feature of this decree is its denial of assistance in accordance with the Disasters Law No. 7269 when homeowners have not participated in the TCIP. This article became operational in March 2001. A number of penalty clauses, missing from the original text, have been added when the draft law was forwarded by the Undersecretariat of the Treasury to parliament.
b. General Conditions for Compulsory Earthquake Insurance (September 8, 2000) Issued by the Under-secretariat of the Treasury, this directive regulates the manner in which insured parties shall make claims for losses against the Natural Disasters Insurance Council (“DASK” is the Turkish abbreviation). The amount payable by DASK essentially covers the minimum amount required for a modest new accommodation. Homeowners can, of course, purchase additional voluntary insurance if their property is worth more. However, for additional coverage to be purchased, the 48
compulsory insurance policy must be presented to the insurer. TCIP coverage is for property only and does not extend to contents or life. TCIP is insurance, not compensation. This means that payments will be proportional to actual losses, i.e. an indemnification will occur. TCIP is a policy that specifically covers the earthquake peril. Damage due to fires, explosions and/or landslides triggered by an earthquake is also automatically covered. Homeowners may purchase additional voluntary insurance for their property if they so wish.
c. Tariff and Instructions for Compulsory Earthquake Insurance (September 8, 2000) While, for 2000, the limiting compensation equals 20 billion TL (approximately US$28,000), premiums are differentiated based on location with respect to the earthquake zone map and on type of construction. The premium for the highest risk buildings such as non-reinforced masonry is rated at 0.5 percent of the assessed value, which cannot exceed 20 billion TL. Disaster Management Organization With the experience of two earthquakes in Turkey in 1999, many disaster management organizations were established at various levels, from prime ministry to municipality. The following describes the foundation, organization and function of these organizations:
Central Government a. Prime Ministry Disaster Crisis Management Centre The Prime Ministry Crisis Management Centre was established at the time of 1999 Marmara Earthquake to integrate the disaster response of the government. Later, the General Directorate of Emergency Management under the Prime Ministry was established as a permanent organization to ensure efficiency in emergency management. The activities of the general directorate are as follows: - To establish emergency management centers within local governments, determine their principles and carry out inter-institutional coordination - To carry out preliminary actions, make short- and long-term plans, monitor and evaluate databases in order to prevent and mitigate disasters - To coordinate the utilization of public and civilian vehicles and facilities in case of emergencies - To promote volunteer efforts by organizations and individuals in emergencies - To coordinate the procurement, warehousing and distribution of relief materials
b. Ministry of Public Works and Settlements Motivated by frequent earthquakes in Turkey, the Ministry of Reconstruction and Resettlement was established in 1958. Its aims were to reduce the risk of death and injury to the population, and to reduce the scale of the economic risks. The name of the ministry has been changed to the current name through organizational restructuring. General Directorate of Disaster Affairs: In the ministry, the General Directorate of Disaster Affairs is the organization responsible is for disaster management. In the directorate, the Earthquake Research Department has three subdepartments focusing on earthquake research.
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- The Earthquake Engineering Department is responsible for providing the necessary measures for constructing earthquake-resistant structures and for providing and developing basic principles for the rehabilitation of structures damaged by earthquakes. - The Seismology Division is responsible for the establishment, operation and development of the National Seismological Observation Network and for the monitoring of micro seismic activity to aid in earthquake prediction and to study aftershock activities. - The Laboratory Division is in charge of carrying out international joint projects and is responsible for building and updating a GIS, which covers earthquakes and other data for the whole country. It also sets up and operates the strong motion recording stations covering the whole country.
Central Disaster Coordination Council: The Central Disaster Coordination Council is formed in case of a disaster as shown in FIGURE 5.10. However, since the prime ministry has established a crisis management centre that deals with administrative aspects, this ministry now mainly deals with technical aspects.
FIGURE 5.10. Organization of the Central Disasters Coordination Council (Oktay, 1999)
c. Civil Defense The Civil Defense was organized as apart of military in 1928. The current Civil Defense became an independent organization with the “Civil Defense Act” of 1959. With the experience of major earthquakes, the Civil Defense has reinforced its rescue teams. The Civil Defense is unarmed, protective, and involved in the development of rescue measures and activities. The General Directorate of Civil Defense has been carrying out these services under the auspices of the Ministry of Interior. The organization consists of both central and provincial bodies. The central organization includes the General Directorate, Civil Defense College, and the Warning and Alarm Centers. Provincial organizations have been set up as Province and Town Civil Defense Directorates, Civil Defense Local Forces, and Civil Defense Search and Rescue Units Directorates. In addition, every governmental organization must have a civil defense section, for firefighting, rescue, first aid, and the security of 50
each organization. The head of the civil defense section in each organization is appointed by the central government. The goal and purpose of the Civil Defense Organization is to minimize life loss and other types of losses during warfare or any natural disaster.
d. Turkish Red Crescent The International Federation of Red Cross and Red Crescent Societies was founded in 1919, and it comprises 176 members (making up the world's largest humanitarian organization). The international federation provides assistance without discrimination as to nationality, race, religious beliefs, class or political opinions. The federation's mission is to improve the lives of vulnerable people by mobilizing the power of humanity. Vulnerable people are those who are at greatest risk from situations that threaten their survival, or their capacity to live with an acceptable level of social and economic security and human dignity. The federation carries out relief operations to assist victims of disasters, and combines this with development work to strengthen the capacities of its member National Societies. The federation's work focuses on four core areas: promoting humanitarian values, disaster response, disaster preparedness, and health and community care. The Turkish Red Crescent has a fund source independent of the government. Planning of the Turkish Red Crescent is centralized under the Ankara Planning Directorate, which plans the distribution of food and tents. There are 600 branches in Turkey covering every province. The Turkish Red Crescent Society’s services are relief services, youth services, blood services and health services.
e. Natural Disasters Insurance Council As earthquake insurance became obligatory for building owners in urban areas on March 27, 2001, management of the insurance pool is entrusted to a new entity called the “Natural Disasters Insurance Council” (DASK), under the General Directorate of Insurance in the Ministry of the Treasury. (2) Provincial Government Provincial Rescue and Relief Committee: On February 1999, before the Marmara Earthquake, the Istanbul Governorship had established a provincial disaster relief committee and execution groups, according to regulation, as shown in FIGURE 5.11. The committee is the decision-making body chaired by the governor. Nine provincial emergency service groups were formed for the execution of emergency response efforts in different categories of service. Governorship Disaster Management Centre (AYM): The Istanbul provincial governorship established the Disaster Management Centre (AYM in Turkish abbreviation) as the organization for integrated disaster management, by the order of president just after the 1999 Marmara Earthquake. The Disaster Management Centre consists of the council, the scientific consultancy committee, the administrative board, and the management office as shown in FIGURE 5.12. Under normal conditions, it aims to promote and coordinate disaster preparedness of concerned organizations, and it will be shifted to the Provincial Disaster Management Centre in case of crises. In addition, in case of a major disaster that affecting several provinces, a Regional Disaster Management Centre is established under the MPWH. 51
FIGURE 5.11. Organization of the Provincial Rescue and Relief Committee (Oktay, 1999)
FIGURE 5.12. Organisation of Governorship Disaster Management Centre 52
(3) Metropolitan Municipality Government Istanbul Metropolitan Municipality Disaster Coordination Centre (AKOM in Turkish abbreviation) was established in 2000 due to the necessity to establish a communication channel within IBB, by the order from mayor and authorization by the Municipal Assembly. The initial members of the centre were the fire department, health department, ISKI and IGDAS. Planning, mapping, and other departments joined later on to form the current organization. The object of AKOM is to coordinate tasks among organizations within Istanbul Metropolitan Municipality. The organization structure of AKOM is shown in FIGURE 5.13.
FIGURE 5.13.Organization of Disaster Coordination Centre in IMM
(4) District Disaster Management Centre The district disaster regulation requires establishing a permanent district disaster management centre in every district, with the district head serving as the head of the centre. Mayors in each municipality will work with district heads under the governorship. Each disaster management centre is connected to AYM, but it does not have a direct relationship with AKOM. ISKI and IGDAS have subsidiary offices in each district, and they are designated to work with each district management centre. The real situations of the district disaster management centers vary from district to district. In some municipalities, the municipalities have built their own disaster management centre, and it provides office space for a district head. In this way, the municipality disaster management centre practically works as a district disaster management centre. In other municipalities, existing buildings are used as a district disaster management centre, and district head and related service group organization are included. 53
5.4.2 Building Codes and Codes Inter-Benchmark Periods 5.4.2.1 Algeria The Algerian seismic regulation has gone through several stages, depending on the different seismic events that have marked the seismic activity of the north of Algeria. Indeed, already in 1716, following the seism which devastated Algiers and made approximately 20000 victims, then Dey of Algiers promulgated an edict under the term of which he prescribed constructive recommendations. Among these recommendations, the arching system, with its flexibility, was found to absorb lateral forces without damages and transmitting them to the floors. Floors were made in wooden joists fixed to the walls or supported on wooden beams. Following the earthquake of Orléanville in 1954 (later on El Asnam and then Chlef after the 1980 earthquake), the French colonial authorities at that period edited and published the AS55, which became, after various corrections and updating, the PS69 (1969). The first draft of the Algerian seismic regulations was started in 1976 in collaboration with the University of Stanford (USA). Stanford University was more precisely charged of studying the seismic risk in Algeria in the aim of providing a chart for the seismic risk on the basis of the seismic history of the country. This study was finished in 1978 and has been used for the development of the first Algerian seismic regulations code published in 1981 after the fatal earthquake of 1980 which devastated the region of Chlef. It is to be noted that the relatively rapid publication of the Code (in 1981) after the earthquake obeyed to the recommendations that were made after the disastrous event.
FIGURE 5.14. History of Algerian seismic regulations As can be seen from the chart, the Algerian seismic design regulations have been updated after each earthquake that has caused damages and losses of lives. 54
Indeed, it is more about implementation than updating the seismic guidelines that were never fully respect by the construction industry and the supervising bodies were never strict enough. The 2003 earthquake showed it very clearly that where the RPA guidelines were respected, buildings did not collapse and lives were saved even though in the previous version of the code, the region hit was considered as a medium risk zone.
5.4.2.2 Egypt 5.4.2.2.1 Development of building codes The following is a brief summary on development of codes for computing seismic loading and design of structural elements to resist earthquakes. It is to be noted that – to date – none of these codes address historical construction: • The first seismic loading provisions were published by the Egyptian Society of Earthquake Engineering 1988. However, due to lack of official backing, it had minimal impact. • The first code to include seismic loading was the Egyptian Code for Reinforced Concrete Construction, 1989 which included an equivalent static method with a minimum lateral load of 1%. • A similar equation was defined in the Egyptian Load for Foundations, 1990, but with different seismic coefficients. • In order to avoid the discrepancy between the two codes, reference to seismic loading in both codes was superseded by the Egyptian Code for Loads and Forces, 1993. This code followed UBC 85-type equation for the equivalent static method. It states that dynamic analysis is required for certain types of buildings. However, it does not provide a response spectrum or criteria for time history records. The seismic zoning map divided Egypt into three zones, FIGURE 5.15. The effect of soil was included by dividing the soil into three categories. Based on the soil type, the factor S was chosen and included in computing the equivalent static force. The value of S ranged from 1.0 to 1.3, depending on the type of soil. The Code stated that dynamic analysis is required for certain types of buildings. However, it does not provide a response spectrum or criteria for time history records.
FIGURE 5.15. Seismic zoning map of the Egyptian Code for Loads and Forces, 1993. 55
• This why the code for loads has recently been updated (2003). The new code follows a Euro-code format, and minimizes the use of the equivalent static method. It included a zoning map that divided Egypt into five zones, and provided peak ground acceleration for each zone (ranging from 0.1 to 0.25 g), FIGURE 5.16. The effect of soil is taken into consideration in the new code by dividing the soil into 4 types. The code recognizes two types of response spectrum, one for the north coastal area (Type 2) and one of the remaining areas of the country (Type 1). Type 2 has an extended plateau to cater for long-period components. Loads in the new code vary substantially from the older version, and are generally higher. Soil characteristics in different localities in Egypt and their impact on seismic wave attenuation and modification are important parameters that control earthquake risk.
FIGURE 5.16. Seismic zoning map of the Egyptian Code for Loads and Forces, 2003. 5.4.2.2.2 Building stock The building stock in Egypt may be divided into engineered and non-engineered structures. Nonengineered structures may be either old buildings, such as most buildings in the old Cairo neighborhoods, as well as historical monuments, or more modern construction, in semi-rural areas. Construction material often used in these buildings is stone masonry laid in lime mortar. Engineered structures include a mixture of reinforced concrete skeletal structures (slabs, beams, and columns are reinforced concrete), concrete slabs poured on top of masonry walls, wooden slabs on top of masonry walls, prefabricated concrete construction, and adobe construction. A survey of the building stock in greater Cairo two decades ago indicated the percentage of each construction type as follows: Type %
R.C. skeleton 25.2%
Prefab. 0.3%
R.C. slab
Other slab
36%
22%
Adobe
Other
13.1%
3.4%
The same survey classified the buildings by year of construction as follows: Date
Before 1940 %
14.2%
1940-59 16.2%
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1960-79 38.8%
After 1980 30.8%
5.4.2.3 Greece Laws – Regulations In 1928, after the destruction of Corinth, the first Code containing seismic provisions for structures was brought out in Greece. The Code had a local character, as it was valid only for structures in Corinth and the neighboring town of Loutraki. In 1959 the first seismic Code for the whole country was published. It was the result of the work of Prof. A. Roussopoulos, “father” of earthquake engineering in Greece and Europe. According to the code provisions, horizontal earthquake forces on the structure should be defined as H = εV , where ε = seismic coefficient and V = sum of vertical loads. The distribution of earthquake forces along the height of the structure was considered to be uniform. Static 3Dimensional structural analysis was proposed according to a pioneering for the time being method, by Prof. Roussopoulos and Japanese scientists. For every floor, the mass center and stiffness center (under assumption of rigid structure) were determined. The influence of overturning moments due to distress was not taken into account. The control process was accomplished according to the theory of allowed stresses, the values of which were increased up to 20%. For Athens, the ε coefficients were defined as 0.04, 0.06 and 0.08, depending on the soil conditions (rock, medium, soft). As a consequence, the buildings of the city, whose largest part is built on rock, were analyzed with seismic coefficient value at 0.04. In an effort of comparison with current provisions for control of reinforced concrete buildings by the method of partial safety coefficients, the above mentioned values need re-examination. For reasons of equivalence, they are multiplied by the global safety factor 1.75 and the partial one 1.15 for steel reinforcement, and divided by the increasing factor 1.20 of allowed stresses. As a result, the values of coefficients turn up to be 0.065, 0.10 and 0.13. After the earthquakes of 1978 and 1981, the two biggest Greek cities Thessaloniki and Athens, faced the short-term need of revising the existing Code. This was really imperative as knowledge on the field had progressed and construction types and methods had changed. Assumptions concerning the stiffness of structures and the negligibility of overturning moments had to be re-assessed. The challenge of urgent solutions didn’t permit a radical revision and finally in 1984, “supplementary provisions” on the existing Code were released. They introduced a triangular shaped distribution of earthquake induced forces along the height of the structure, a more specific 3D structural analysis and special constructive detailing measures (strong columns-weaker beams, increased steel reinforcement in junction areas etc.) In 1995, the New Greek seismic Code was published (NEAK), having much in common with Eurocode 8. The country is divided in 4 zones with appropriate values of Peak Ground Acceleration (PGA) defined at 0.12g, 0.16g, 0.24g, 0.35g. Athens is classified in the second zone, meaning PGA=0.16g. The design spectrum for frame structures can be derived from the elastic spectrum after applying a behavior factor of maximum value q=4.0. Comparing this design spectrum to the elastic response spectrum actually produced by the Athens earthquake (1999), a significant difference (of factor 20) for stiff structures is observed. The difference is also considerable between the elastic spectra of the Code and of the real earthquake which in the area of small fundamental periods is of factor 3 ( 0.16 g ⋅ 2.5 = 0.4 g instead of the actual 1.2 g ).
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On April 2001, the currently used edition of the Greek seismic Code (EAK2000) was released, as a revision of NEAK after 4 years of implementation. It comprises revisions and completions which were considered necessary based on experience acquired through NEAK and recent seismic events, as well as adaptive paragraphs in respect to EC8 and EC7. As far as ancient and historical buildings before Codes’ existence are concerned, there have been some relevant legal provisions such as in law 5351-art.52 /1932 on antiquities, law 1469/1950 on preservation of exceptional structures and artistic achievements after 1830 and law 1337/1983 on urban planning and evolution. Nowadays, there is an effort in process aiming at covering the existing gaps on current practice in retrofit methods by creating a National Code for Repair and Strengthening, at least for common structures. Still, current practice is the result of gathered experience, international standards and published scientific wok, assisted by national pre-standards and supplemental publications such as the “Recommendations for pre-seismic and post-seismic interventions in buildings” by the Greek Earthquake Planning and Protection Organization.
Percentage of Greek buildings after code applied
9% 13% 46% New codes "Supplementary" provisions 32%
Without seismic code Seismic code 1959
FIGURE 5.17. Buildings assignment according to the Greek Technical Chamber 5.4.2.4 Italy
5.4.2.4.1 Current codes’ orientations According to the Italian seismic legislation (Order of the President of the Council of Ministers 20th March 2003 no. 3274, Annex 2, Section 11.1), the interventions on existing buildings can be divided into two groups: •
Seismic improvement, i.e. the realization of interventions faced to obtain a higher safety degree; • Seismic upgrading, i.e. the realization of a series of structural interventions to make the structure able to withstand the new earthquake design actions This distinction was introduced for the first time in Italian seismic legislation by the Ministerial Decree (DM) 24th January 1986. 5.4.2.3.2 Rules referring to existing important buildings The OPCM 3274/2003 establishes that the owners of: • buildings of strategic importance and facilities relevant for civil defence, 58
•
buildings and facilities that can be relevant if related to the consequences of their possible collapse must check their buildings from the seismic point of view, within 5 years (OPCM 3274/2003, article 2, paragraph 3), considering a priority for buildings and facilities present in seismic zones 1 and 2. On the basis of the available financial resources, it must be realized a temporal plan of structural checks and the individuation of the buildings and facilities previously mentioned. The Department of Civil Defence (DPC) makes it referring to the works of state reference, while the Regions make it referring to the works of regional reference (OPCM 3274/2003, article 2, paragraph 3). The Decree 21st October 2003 of the Chief of DPC (Official Journal, 29th October 2003) establishes a list of the buildings and facilities of state reference and includes the historical buildings among the ones of relevant importance in case of collapse. The lists of regional reference must be prepared by each Region. The financial resources necessary for the mentioned structural checks derive from: • those deriving from article 80, paragraph 21 of the Law 289/2002 (OPCM 3274/2003, article 3, paragraph 2); • further financial resources found by the DPC, according to the Regions (OPCM 3274/2003, article 3, paragraph 3). 5.4.2.3.3 Fund for extraordinary interventions for the reduction of seismic risk A Fund of the President of the Council of Ministers (PCM) useful for the extraordinary interventions to reduce the seismic risk is established by the Law 24th November 2003 no. 326. It allocates Euro 73.487.000,00 for the year 2003. The OPCM 8th July 2004 no. 3362 regulates the procedures of activation of the previously mentioned Fund (OPCM 3362/2004, article 1, paragraph 1). It allocates Euro 100.000.000,00 for the year 2004 and Euro 100.000.000,00 for the year 2005. For each of these two years, Euro 67.500.000,00 are allocated for interventions of regional reference, and Euro 32.500.000,00 are allocated for interventions of state reference (OPCM 3362/2004, article 1, paragraph 2). Moreover, the intervention typologies that can be referred to the Fund financing are defined (OPCM 3362/2004, article 1, paragraph 4). In particular, they are • technical checks; • upgrading or improvement. The rate of the financing that are allocated for the technical checks is established by each Region (OPCM 3362/2004, article 1, paragraph 5). The Fund financing is referred to the interventions in zones 1, 2 and 3, on structures built before 1984 and on important buildings, as indicated at § 1.2.1 (OPCM 3362/2004, article 1, paragraph 7). The subdivision of the first part of financing (Euro 100.000.000,00 for the year 2004) is established on the basis of the seismic risk (OPCM 3362/2004, article 2, paragraph 1). The subdivision is reported in the TABLE 5.8. TABLE 5.8. Subdivision of the Fund financing for the year 2004 REGION Piemonte Valle d’Aosta Lombardia
PERCENTAGE 0,86 % 0,01 % 3,02 %
59
AMOUNT (Euro) 580.317,00 7.237,00 2.040.303,00
Prov. Autonoma of Bolzano Prov. Autonoma of Trento Veneto Friuli-Venezia Giulia Liguria Emilia-Romagna Toscana Umbria Marche Lazio Abruzzo Molise Campania Puglia Basilicata Calabria Sicilia Sardegna TOTAL
0,00 % 0,63 % 5,96 % 2,43 % 1,27 % 8,26 % 8,95 % 2,49 % 4,32 % 11,03 % 3,39 % 0,93 % 17,22 % 5,45 % 1,91 % 7,53 % 14,32 % 0,00 % 100,00 %
0,00 425.969,00 4.026.129,00 1.642.901,00 860.160,00 5.578.731,00 6.040.875,00 1.680.831,00 2.916.281,00 7.446.927,00 2.287.573,00 629.237,00 11.624.262,00 3.676.077,00 1.291.937,00 5.080.090,00 9.664.163,00 0,00 67.500.000,00
Within 120 days from the publication of the OPCM 3362/2004 the Region had to communicate to the DPC a temporal plan for the structural checks and a plan of upgrading and improvement, with the indication of the rate that could be financed by the implementing subject and the one by the beneficial owner (OPCM 3362/2004, article 2, paragraph 2). The Regions can to use a quantity of resources exceeding the amount fixed by the Government, if deeper analyses are needed. The amount can’t exceed 20% over the value established by the Government. In presence of “serious and present” seismic risk, the limit can be exceeded, and the Region can use financial resources taken by its own budget (OPCM 3362/2004, article 3, paragraph 1). Referring to the buildings, the financial resources are allocated through the definition of a conventional cost (OPCM 3362/2004, Annex 2). Then, only the Government, on the basis of the seismic zone where the building is located, assigns a fraction of this conventional cost. The remaining rate is chargeable to the beneficial owner. Buildings checks The conventional costs for buildings checks is defined on the basis of the total volume (V) of the building, according to the TABLE 5.9. TABLE 5.9. Unit conventional cost for building check according to OPCM 3362/2004 VOLUME (mc) < 10.000 10.000 – 30.000 30.000 – 60.000 60.000 – 100.000 > 100.000
UNIT CONVENTIONAL COST (Euro / mc) 2,50 (min 3.000,00 Euro / building) 1,80 for the volume exceeding 10.000 mc 1,20 for the volume exceeding 30.000 mc 0,60 for the volume exceeding 60.000 mc 0,30 for the volume exceeding 100.000 mc
The Government provides the 50% of the intervention conventional cost if the buildings are in seismic zones 1 or 2, while it provides the 30% of the intervention conventional cost if the buildings are in seismic zone 3. Buildings upgrading It is considered a conventional cost equal to 150,00 Euro/mc. The Government provides only a fraction of the cost of the intervention. This fraction is calculated on the basis of the parameter α (to be chosen 60
among the values αu and αe, depending on probabilistic considerations related to the seismic hazard). The Government provides financing in the measure of: • 100% of the whole conventional cost if α < 0,2; • 0% of the whole conventional cost if α> 0,8; 380 − 400α • % of the whole conventional cost if 0,2 < α < 0,8. 3 Buildings improvement The conventional cost for buildings improvement is equal to 150,00 Euro/mc. The Government provides the 60% of the whole conventional cost of the intervention in seismic zone 1, the 50% in seismic zone 2, the 30% in seismic zone 3. A synthesis of the Italian rules is shown by FIGURES 5.18 and 5.19. Within 5 years (since 2003) the owners of strategic and relevant buildings must check them from the seismic point o f view Department of Civil Defence (DPC)
Regions
Buildings of state reference
Buildings of regional reference
•
Temporal plan of the necessary seismic checks
•
List of buildings to be checked
•
Plan of upgrading and improvement interventions Financial resources
Fund of the President of the Council of Ministers for extraordinary interventions
•
•
Owners
YEAR 2004: 67,5 million Euro for buildings of regional reference; 32,5 million Euro for buildings of state reference (total 100 million Euro for the year 2004) YEAR 2005: 67,5 million Euro for buildings of regional reference; 32,5 million Euro for buildings of state reference (total 100 million Euro for the year 2005)
FIGURE 5.18. Intervention framework according to OPCM 3274/2003 and 3362/2004
61
REGIONS: -Temporal plan of the necessary structural checks -Plan of upgrading and improvement interventions with the indication of the conventional cost of the interventions, calculated on the basis of the Annex 2 of the OPCM 3362/2004 to Department of Civil Defence
Special Orders of the President of the Council of Ministers for the individuation of the interventions to be realized
Structural checks
FINANCING Fund / Owners
30%
50%
50%
50%
70%
Upgrading
Seismic zone 1
Improvement
50%
Seismic zone 3
Seismic zone 2
The rate of state financing is depending on the collapse risk
30% 40% 50%
50%
60%
70%
Seismic zone 1
Seismic zone 2
Seismic zone 3
FIGURE 5.19. Intervention framework on buildings of regional reference
62
5.4.2.5 Maroc
Following the 1960 Agadir earthquake, Morocco adopted a first seismic buiding code "Normes Agadir 1960”, through the royal law n° 2-60-893 of the 2nd Rajeb 1380 (December 21, 1960). The application of this code was limited geographically to the Agadir region. Between 1960 and 2002 (42 years), no official nationwide seismic code “RPS-2000” was applied. In the year 2002, a new seismic code was approved through the law n° 2-02-177 of 9 Hija 1422 (February 22, 2002). Thus, the application of this code became effective in september 2002. This code is based on two major axes: a- building classes & b- seismic zoning (FIGURE 5.20).
A = 0.01g A = 0.08g A = 0.16g
FIGURE 5.20. Seismic zones in Morocco as defined in the seismic building code “RPS-2000”. The RPS-2000 main seismic zones and the corresponding acceleration coefficients with a 10% exceedance probability in 50 years are shown on FIGURE 5.20. Thus, three zones are identified with accelerations that vary between 1%g and 16%g. Following the February 24, 2004, Al Hoceima earthquake, this code is presently under revision. 5.4.2.6 Romania
The following building codes are presently related to the design of earthquake resistance of the new buildings in Romania: P100-92 Code for seismic design of civil and industrial buildings. Ministry of Transport, Construction and Tourism, MTCT, Bucharest, 1992, 152p (English version 1993, 151p). Chapters 11, 12 were modified in 1996, 50p; P100-04 Code for earthquake resistance of buildings. Draft which follows EUROCODE 8 format and requirements for the new buildings, 2004. A tentative code for earthquake resistance of existing buildings is under preparation at UTCB and should be matter of concern for the World Bank Project on Risk Mitigation in Romania, Earthquake Risk Reduction Component (2004-2009). The evolution of the seismic codes and zonation map standards in the last 65years in Romania is summarized in TABLE 5.10. 63
TABLE 5.10. Classification of codes for design of earthquake resistance of buildings and standards for seismic zonation of Romania (1940-2005) Period Code for earthquake Seismic resistance of structures zonation standard* Pre-code, Prior to the 1940 earthquake P.I. - 1941 P.I. – 1941 before 1963 and I - 1945 I – 1945 Prior to the 1963 code STAS 2923 - 52 Low-code, Inspired by the Russian P 13 - 63 STAS 2923 - 63 1963-1977 seismic practice P 13 - 70 Moderate-code, After the great 1977 P 100 - 78 STAS 11100/1 - 77 1977–1990 earthquake P 100 - 81 Moderate to After the 1986 and the 1990 P 100 - 90 STAS 11100/1 - 91 high-code, earthquakes P 100 – 92 SR 11100/1 - 93 after 1990 P 100 – 04 (draft) * The intensity scale used in Romania is MSK - 64 scale (STAS 3684 - 63, STAS 3684 - 71)
Classification of building age as function of seismic codes inter-benchmark periods provides immediate information about the level of seismic knowledge incorporated into the building design. The RISK-UE project, WP1 gives the classification in TABLE 5.11. of building stock age in 7 European towns, as well as the classification of codes inter-benchmark periods in TABLE 5.12. TABLE 5.11. Building stock age versus seismic codes inter-benchmark periods Town Barcelona Bitola Bucharest Catania Nice Sofia Thessaloniki
Seismic codes inter-benchmark periods Pre-code Low-code Moderate code 79% 21% -48% 29% 23% 30% 30% 40% 92% 8% 75% 25% Data not available 20% 50% 30%
TABLE 5.12. Code for earthquake resistance of structures Country Spain FYR Macedonia Romania Italy France Bulgaria Greece
Pre-code < 1968 ≤1948 and PTP-2 ≤1964 ≤1941 and ≤1963 P13-63 < 1981 ≤ 1955 ≤1964 < 1959
Level of knowledge incorporated into seismic design Moderate-advanced Low-code Moderate code code 1968.... 1964-1981
1981-1990
1990 Æ present
1963-1977
1977-1992
1992 Æ present
1956-1969 1964-1972 1959- 1984
1970-1992 1972-1987 1984- 1995
1981 Æ present 1993 Æ present 1987 Æ present 1995 Æ present
One might observe the precode buildings might represent even more than 90% of total stock in Catania and maybe less than 20% of total stock in Thessaloniki; but moderate/advanced code buildings are generally less than 25% of total stock in many countries in spite the Bucharest new buildings represent about 40 % of total number of buildings in the city TABLE 5.13. and TABLE 5.14. 64
TABLE 5.13. Housing units in Bucharest according to the periods of validity of various seismic codes Seismic code benchmark periods before 1941 1941-1963 1963-1970 1970-1978 1978-1992 1992-2000 Total
(Bucharest Report for UN Radius Project, 1999) inter- Housing units built during inter- % housing units built during benchmark periods inter-benchmark periods 168,556 21.5 ~22% 69,702 8.9 ~38% 110,669 14.2 119,625 15.3 292,594 37.4 ~ 40% 21,282 2.7 782,428 100%
TABLE 5.14. Distribution of tall buildings in Bucharest by period of construction and number of storeys (Bucharest Report for UN Radius Project, 1999) < 1945 1946 - 1963 1964 -1970 1971-1977 1978 - 1990 Storeys 1) 9 89 104 45 88 1550 10 17 77 137 51 177 11 63 70 447 830 1063 >11 9 34 7 87 72 Total 486 434 657 1091 2970 1) Including the ground floor
1990 -1992 21 4 5 1 36
5.4.2.6 Turkey
Seismic regulations in Turkey are developed in conjunction with a nation-wide zone map and associated codes. The first seismic regulation in Turkey was developed in 1944 with two zones, motivated by severe damage due to the 1939 Erzincan earthquake that killed more than 30,000 people. The national zone map has been revised three times since then. Changes are associated with increment of zones, increment in fundamental base shear coefficient, and inclusion of more coefficients such as structural type, ground type, spectral, and importance, as shown in TABLE 5.15. The current seismic building code, “Regulations for Structures to Be Built in Disaster Areas,” was established by the Ministry of Public Works and Settlements as another by-law in pursuant to the Disaster Law. The latest revision of the seismic zone map was made in 1996. In the previous 1972 map, the boundary of each zone was made based on observed ground motions. However, in the new map, the boundary of each zone is based on calculations of the maximum effective acceleration for a return period of 475 years. FIGURE 5.21 shows the latest 1996 revision of the national seismic zone map. Because of the existence of North Anatolian fault, the highest risk area (zone I) extends in the east-west direction in Turkey. According to the map, the southeastern part of the Istanbul Province on the Asian side is located in one I, while most of the European side of the province is located from zone II to zone IV.
65
TABLE 5.15. Development of Seismic Regulation in Turkey (Kobayashi, K et al., 2001)
FIGURE 5.21. National Seismic Zone Map as Revised in 1996 (Ministry of Public Works and Settlements)
66
5.5. SUCCESSFUL INTERVENTION FOR CULTURAL HERITAGE CONSTRUCTIONS 5.5.1 Strengthening of a Church Using Steel Members 5.5.1.1 Description of measures
The Church of the Ascension of Christ is the Metropolitan Church of Koropi town, located 30 km out of Athens at the area of Messogeia. The construction of the Church started in 1858 and lasted six years and ten months. The Church belongs to the category of cruciform basilicas' with dome. It is made of limestone masonry walls, of 0.8-1.0 m thickness, on a shallow foundation and masonry arches made from light sandstone. The quality of masonry is moderate, characterized by the small size of stones. The Church was built with a defect at the NE main column having a vertical eccentricity of about 0.15 m. Moreover, in 1973 they added a second taller reinforced concrete dome to the church, so as to be seeing from the remote edges of the expanding town. In its lifetime the Church has suffered several strong earthquakes, the most recent ones being the one in 1981 [www.itsak.gr] and recently in September 1999 the Athens earthquake [www.itsak.gr/report.htm] originated from a nearby fault at the mountain Parnes. The accumulated damage from all these events and mainly from the last earthquake were major cracks in the walls, cracks almost in all arches, major cracks at the marble column capitals and extensive smaller cracks at the tipper part of the church, indicating a uniform tendency of disorganization of the masonry. Based on this evidence, the authorities closed the Church and asked for repair and strengthening measures for the structure. An analysis of the structure, modeling all main structural components, was performed on the basis of Finite Element Method using Nastran Code for the existing structure and the strengthened one (Figures 5.22., 5.23.).
FIGURE 5.22. Finite Element model of the exterior masonry
67
FIGURE 5.23. Finite element model of the interior arches with the added line steel members The aim was first to correlate the areas of critical stresses in the model, with the damaged areas in the structure and obtain confidence on the model and then to identify ways to improve the performance of the structure in future seismic events. The properties of the materials were determined by appropriate testing. Plate and membrane elements were used for the masonry walls and arches, whereas beam elements for the main columns. An equivalent linear static analysis with earthquake forces based on the design spectrum of the Greek code was performed. This pointed out areas of excessive stresses in close agreement with the observed damage. This was specifically true for the east part of the sanctuary. The dynamic characteristics of the existing structure, apart from the different sway modes, revealed the importance of vertical modes of vibration in the area of the double dome at relatively low frequencies. The spectral analysis that followed accounted also for these vertical mode shapes, so as to understand and estimate the influence of the added second dome to the entire structure. The fundamental frequency is 3.77 Hz and the mode shape is along the lateral direction (FIGURE 5.24.). The fourth mode that contributes mainly in the area of the side entrances and the dome is presented in FIGURE 5.25.
FIGURE 5.24. Fundamental mode at 3.77 Hz
FIGURE 5.25. Fourth Mode, with localized motion at Side Entrances
The analysis of the existing structure was followed by a series of different scenarios aiming to control the dynamic behavior of the structure and to redistribute the stresses so as to avoid potential premature failure modes, as for example collapse of the domes and/or side entrances. All these alternatives were based on adding steel members. The decided layout is presented in FIGURES 5.26. and 5.27. 68
FIGURE 5.26. Plan View of the Church with strengthening steel members
FIGURE 5.27. Section A-A of the Church
The aim is to control the action of arches by constructing a grid of hollow sections SITS 120/120/7.1 at the level of the base of the arches together with the inclined struts at the side aisles (FIGURES 5.28.5.30.). The steel members controlled the horizontal movement of the central columns without destructing the greatness of the area underneath the dome. A lighter system with only tensile members didn't offer adequate restrain on the rotations at the base of the arches, which was needed for the protection of the marble capitals. All steel members were welded in situ and anchored in areas of the masonry that were previously strengthened locally. After the completion of the steelwork the Church opened before the Easier of 2000. The design of all the additional steel members was based on Eurocode 3, where the diagonal members are designed both in tension and compression. These members are connected to the arches with rectangular strips made of 300x30 mm steel plates anchored to the masonry with epoxy resin dowels (FIGURE 5.31), while the gaps were filled with non-shrinking cement mortar. Moreover, the motion of the domes was controlled effectively by the inclined struts, which transfer part of the load to the external piers and prevent overloading of the central columns that carry the loads safely without any major strengthening. Although this Church officially is not a monument, all suggested measures considered the Church as such. Additional strengthening measures were decided and applied that consist of a) strengthening of the masonry walls and arches by injection of grout of particular composition, so as to assure penetration as well as adequate bonding, b) repair and strengthening of the marble column capitals with epoxy resins and mortars and bronze hoop ties and c) strengthening of the main piers of the axes 1 and 2 of FIGURE 5.32 at the north and south side with carbon fibber composites.
69
FIGURE 5.28. Steel strengthening at the arch base
FIGURE 5.29. Steel members at the right aisle
FIGURE 5.30. Steel members at the SE Column 70
FIGURE 5.31. Epoxy resin anchor bolts at column capital base
FIGURE 5.32. Bronze hoop ties at column
The injection of grout at low pressure was performed in zones that were elevated gradually. The grid of injection points was dense from the outside (0.2 to 0.5 m) and more sparse from the inside not to damage the hagiography. The cracks in the monolithic marble column capitals were investigated with endoscopic photographs to measure their extent and width. The cracks were sealed with epoxy mortar and epoxy resin, mixed with marble powder of different grain size in relation to the crack width, injected from a dense net of injection points. To increase the load carrying capacity of the column capitals slightly prestressed bronze hoop strips were place at appropriate positions. To secure further the piers of the north and south entrance strengthening with carbon fibber composites was applied in two vertical and two horizontal strips at each side.
FIGURE 5.33. South view after completion of grout injection Repair and strengthening of the Church of the Ascension of Christ using mainly steel members turned out to be very effective, practical and relatively fast in increasing the load carrying capacity and enhancing the dynamic behavior of the structure. 71
5.5.2 The Cases of Toscana and Campania Regions (Italy) Toscana and Campania Regions are here considered as examples of application of the measures adopted by the Government for the reduction of seismic risk. 5.5.2.1 The case of Toscana Region
Toscana Region assigned the 100% of the financing of 2003 and the 30% of the financing for 2004 (financing deriving on the basis of the Law 23/96) for the realization of preventive interventions against the seismic actions. A Regional plan for the seismic checks on strategic and relevant buildings (VVSESeR) has been defined as a consequence of the Resolution of Toscana Regional Council (GRT) 27th October 2003, no. 1114. In particular, the considered buildings are the ones, belonging to local authorities, used for: • instruction; • institutions; • local authorities; • strategic centres for civil defence; • hospitals. Referring to the Fund for extraordinary interventions, presented in the previous paragraph, Toscana Region presented to the DPC (on 16th November 2004) its “Temporal plan for technical checks” and its “Plan of upgrading and improvement interventions”. 5.5.2.2 The case of Campania Region
Campania Region received by the Government a total of Euro 11.624.262,00. The Resolution of Campania Regional Council (GRC) 30th December 2004 no. 2535 established that Euro 10.000.000,00 had to be allocated for the improvement of strategic public buildings and Euro 1.624.262,00 had to be allocated for structural checks. In the Annex of the mentioned Resolution, a list of all the buildings interested by improvement or check interventions is presented. For each building the following information are presented: • seismic zone • address • name • structural system • usage • total volume • intervention cost • state contribution (according to OPCM 3362/2004) • cost chargeable to the beneficial owner The total number of improvement interventions on strategic buildings is equal to 27. The considered masonry buildings are 22, while the remaining 5 buildings are r.c. structures. 15 of the considered buildings have a civil function, 5 have a health function, 7 have a schooling function. The total cost of the improvement interventions is equal to 17.884.950,00 Euro. The Government must provide 9.692.535,00 Euro, while the beneficial owners must provide the remaining 8.011.466,00 Euro. The total number of structural checks on strategic buildings is equal to 98. Among them, the masonry structures are 87, while r.c. structures are 11. 24 of the considered buildings have a civil function, 7 have a health function, 67 have a schooling function. The total cost of the structural checks is equal to Euro 1.613.108,00. 72
5.5.3 Reinforcement Techniques by the Addition of a New Structure For historical monuments, in Morocco, the procedure of restoration is generally the following: Structural works: • infrastructure intervention: o intervention on foundations, o renewal of the sewer and the electric networks, and Branching • works in superstructure; o Repairing masonry, o Scouring of the existing coatings (plaster, lime or cement) o Surfaces flattening and traditional sealer (rendering), o Shape of slopes, o Watertightness and struggle against humidity: multilayered tightness and protection of the tightness in Zellige (tiles), Secondary Works: • Restoration of sculpted plasters; • Revetment in Zellige (coating with tiles) of walls and floors, • Restoration of the structural wood, • Plumbing and sanitary, • Electricity restoration, • Painting and windows-glasses; • Cover of the patio in Plexiglas In structural problem cases, backing techniques consist generally either by the setting up of a new reinforcement structure made of steel, or out of wood (FIGURE 5.34).
FIGURE 5.34.Setting up of reinforcement structure in wood to avoid the collapse of walls for neighbouring houses in the street in the old Medina of Fez (Morocco); a reversible intervention. 73
5.5.4 Brancusi Endless Column in Romania
Targu Jiu in Romania
FIGURE 5.35. Brancusi Endless Column at Targu Jiu, Romania The reversible restoration of Constantin Brancusi’s monumental Endless Column in Romania, has been completed on-site on December 17th, 2000. The 29.8m steel column cast-iron 1.8m-high modules was originally installed in Targu Jiu in 1938. The Government, the World Bank, the World Monuments Fund and other institutions have supported the restoration.
Târgu-Jiu, spine with Romanian financially
"It is, for Romania, for the Ministry of Culture, for the inhabitants of Târgu-Jiu, and also for our partners — The World Bank and World Monuments Fund — a great event," said Mr. Caramitru, the Romanian Minister of Culture in December 2000. "We are happy to state that this important project, aimed at the restoration and preservation of one of the most outstanding open-air works of art of the 20th century, has been implemented by respecting Brancusi's original work i.e. keeping the original steel spine and original cast-iron modules as they were designed by the artist and by the engineer. In 1998, the Romanian Government and WMF successfully established a partnership with the World Bank to finance the restoration of the entire ensemble. The World Bank committed $2.6 million to the overall project in Tg. Jiu in the form of a loan to the Romanian government. WMF was able to raise over $600,000 from many sources including companies and private individuals. The Romanian Government provided the rest of the cost of restoration. "While physically the Endless Column is the simplest structure WMF has ever dealt with," said John Stubbs WMF Vice President for Programs, "Its restoration was one of the most complex, especially from a theoretical standpoint." The Technical University of Construction Bucharest report entitled “Wind action on Brâncusi Endless Column at Tg. Jiu, Romania, according to the wind loading codes from European Union, USA and Romania” in 2000, was the technical and theoretical justification for the structural rehabilitation of the Endless Column spine by keeping the original steel core. 74
The adverse alternative –which has been defeated - was the substitution of the original steel core by a new stainless steel solution. The Endless Column consists of three components: i)
Foundation, made of two concrete blocks (4.50x4.50x2.00m and 3.50x3.50x5.00m) with metallic anchorage fixed with bolts;
ii)
Central steel spine 28.90 m high, with a square cross-section made up of angle irons and steel plates connected with rivets and screws; at the base of the spine 5.50 m from 28.9 are filled up with concrete;
iii)
17 modules, shaped as double pyramid with curved surface made of cast iron and, measuring 180 cm height and 45–90 cm width.
FIGURE 5.36. The lower part of the spine, before and after the tanning
75
+28.90
CI 4-4
+19.70
CI 3-3
+11.70
CI 2-2
+0.56 ~
~
CI 1-1
Weight of the structure 14947 daN; Weight of the modules 14226 daN; Weight of interior concrete 1408 daN; Total weight of the column 30581 daN; FIGURE 5.37. Characteristics of the OL 37 steel Endless Column structure (central spine, inside Column)
76
The structural model consists of 32 FRAME elements evenly distributed on the height of the column. Each frame element has 90 cm in length. The results of the modal analysis performed with SAP90 computer code are given TABLE 5.16. Other results provided by former analytical studies or on site measurements are also presented. TABLE 5.16. Fundamental period of vibration for Endless Column, in seconds
Steel spine, without modules Endless Column with modules
Measured on site after strengthening, UTCB, Dec. 2000
Modal analysis, UTCB, 2000
Measured on site, INCERC, 1985
Modal analysis, INCERC, 1984
1.28
1.43
-
-
1.95
1.99
1.80
1.90
The largest fundamental period of vibration (1.99s) has been selected for Endless Column dynamic response to wind, in order to get the most severe response.
FIGURE 5.38. Vibration measurements at Endless Column site, December 2000 Y
Y
X
X
Case 1
X Case 2
Y X
Y
Y X
Case 3
FIGURE 5.39. Arrangement of the sensors Dec. 3rd, 2000
FIGURE 5.40. Arrangement of the sensors Dec. 14th, 2000
77
The value of the aerodynamical coefficient is confirmed by the wind tunnel tests at University of Florence led by Prof. Giovanni Solari, University of Genoa which gives cf = 1.1 for wind normal to face (average slenderness of the model about 8); According to American and European codes the tests value needs an increase of about 25-30% to take into account the actual slenderness of the Column.
CD 1.6 1.5 1.4 1.3 1.2 1.1 1 0.9 0.8 -60
-55
-50
-45
-4 0
-35
- 30
-2 5
-20
- 15
-10
-5
0
5
10
15
20
25
30
35
40
45
50
55
60
ang o lo [g rad i]
FIGURE 5.41. Wind tunnel test model for Endless Column at Florence University, Italy
Vibration measurements of the Endless Column in Targu Jiu, December 2000 78
5.5.5 Rehabilitation and Conservation of Historic Cairo: Managerial Strategies Historic Cairo, proclaimed as a world heritage site by UNESCO, is receiving national attention. In 1995, UNDP financed a study for the rehabilitation of Historic Cairo. Consequently, a Presidential Committee with representatives of all concerned authorities has established. The committee dealt with the occupation of 274 squatters for 105 heritage sites, with instituting a plan to preserve 146 monuments in stages; the first includes 43 buildings in Gamaliya, Ghouryia, AJ-Azhar, AI-Darb Al-Ahmar( Al- Saliba, and Ibn Tulun districts at a cost of 350 million Egyptian pounds. Preservation is to be conducted under the authority of the Ministry of Culture. The Ministry of Housing is completing two tunnels at a cost of one billion Egyptian pounds that will allow traffic to flow underground freeing the AI-Azhar area to become a pedestrian zone. An administrative unit, Historical Preservation Administrative Unit (HCPAU) and the Center of Studies and Development of Historic Cairo, attached to the Office of the Minister of Culture, control the project progress. It has charged with updating the map of Cairo Islamic monuments and creating a computerized database related to each historic structure. The preservation and restoration adapted methodology includes specifications for documentation, architectural drawings, studies of soil properties and subsurface water movement, material analyses, deterioration evaluation and finally, urban rehabilitation. Historical records are studied to provide information on the original layout, construction, and uses of the building as well as its conservation and restoration life history. With this framework, actually, 90 historical building are under restoration and preservation. Assessment of the seismic vulnerability of monuments, as a complex multi-disciplinary task, is initiated as one step of stability analysis & conservation project of historical buildings that includes the following steps: • Immediate measures to maintain stability and prevent total or partial collapse. • Comprehensive study to identify critical elements and define numerical parameters (historical Studies, Surveying & architectural detailing, geotechnical, materials evaluation, infrastructure/utilities, site observations and monitoring) • Structural assessment and studying various retrofitting schemes 79
•
Seismic issues, modal analysis vs. time-history analysis: historical events and their effect on the monument, current seismic code provisions and its applicability to historical buildings. Assessing alternatives for strengthening of structure (traditional methods, new technology, and reversibility of intervention). Special features in monument studies should be evaluated, these include as bonding of structural materials, statical system, load-bearing slender walls (multi-leaf), stone arches and ties, domes, minarets. Number of intervention modes may be considered: Soil strengthening – Soil injection Soil reinforcement by micropiles – – Soil stabilization by cement or lime components Foundation strengthening – Increasing the bearing area – Injecting foundations – Utilize deep foundations (micropiles) Material strengthening – Injection. – Replace bonding material. – Replace stone/brick System strengthening – Introduce new walls – Strengthen existing walls
–
Improve or introduce confinement.
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REFERENCES Reference Literature ASCE 7-93, 1993, ASCE7-95, 1995 and ASCE7-98, 2000. Minimum design loads for buildings and other structures. American Society of Civil Engineers, New York European Prestandard ENV 1991-2-4, 1994. EUROCODE 1: Basis of design and actions on structures, Part 2.4 : Wind actions, CEN Eurocode 8 - Design provisions for earthquake resistance of structures, 1994. Part 1-1: General rules - Seismic actions and general requirements for structures. CEN, European Committee for Standardization, Oct. Guidelines for Seismic Retrofit of Existing Reinforced Concrete Buildings, 2001. Published by The Japan Building Disaster Prevention Association, Translated by BRI. 91 pages Ministry of Environment, Land Use and Public Works - Greek Earthquake Planning and Protection Organization, Greek Seismic Code (EAK2000 – modifications 2003) Standard for Seismic Evaluation of existing Reinforced Concrete Buildings, 2001. Published by The Japan Building Disaster Prevention Association, Translated by BRI. 76 pages. Technical Manual for Seismic Evaluation and Eeismic Retrofit of Existing Reinforced Concrete Buildings, 2001. Published by The Japan Building Disaster Prevention Association, Translated by BRI. 85 pages. The Burra Charter The Australia ICOMOS charter for the conservation of places of cultural significance, 1999. The Getty Conservation Institute, Incentives for the Preservation and Rehabilitation of Historic Homes in the City of Los Angeles, A Guidebook for Homeowners, 2004 2001 California Historical Building Code, California Code of Regulations, Title 24, Part 8 published by International Conference of Building Officials 5360 workman mill road whittier. ICOMOS, 2003 Recommendations for the analysis, conservation and structural restoration of architectural heritage Aldea, A., Arion, C., Demetriu, S., Saito, T. (2001), Ambient vibration measurements for Brancusi Endless Column, Internal Reports, Technical University of Civil Engineering of Bucharest Avrami Erica, Randall Mason, Marta de la Torre, Values and Heritage Conservation Research Report for The Getty Conservation Institute, Los Angeles, 2002 Coburn, A., Spence, R., (1992), "Earthquake protection", John Wiley & Sons., New York, 355p. Kasai, K., 2004. Current status of Japanese passive control scheme for mitigating seismic damage to building and equipments, Modern Urban Seismic Network in Bucharest, Romania, Proceedings of the First International Conference on Urban Earthquake Engineering, March 8-9, 2004, Tokyo Institute of Technology, Yokohama, Japan, 12p., p.121-133 Kasai, K., 2004. Lecture note at the IISEE, Tsukuba, Japan Lungu, D., Aldea, A., Arion, C., Cornea, T., 2001. City of Bucharest Seismic Profile: from Hazard Estimation to Risk Management, Earthquake Hazard and Countermeasures for Existing Fragile Buildings, Contributions from JICA International Seminar: Bucharest, November 23-24, 2000, Lungu, D., Saito, T. (editors), Independent Film, Bucharest, p. 43-66 Lungu, D., Aldea, A., Arion, C., 2000. "Engineering, state & insurance efforts for reduction of seismic risk in Romania" In: Proceedings of the 12th World Conference on Earthquake Engineering, Auckland, New Zealand, Jan/Feb. Lungu, D., Văcăreanu, R. - Wind Action on Brancusi Endless Column at Tg. Jiu, Romania according to the wind loading code from European Union, Technical Report for the World Bank Project - Cultural Heritage, Rehabilitation of Endless Column by Constantin Brancusi, 25 p, 2001. Nawrotzki, P., 2005. Visco-elastic devices for the seismic control of machinery, equipments and buildings. 9th World seminar on Seismic Isolation, Energy Dissipation and active Vibration Control of structures, Kobe, Japan, June 13-16, 2005. Postelnicu T., at al., 2001. Guidelines For Seismic Rehabilitation, Technical University of Civil Engineering of Bucharest, Reinforced Concrete Department, 2001 Postelnicu T., at al., 2005. Report on the Framework of the Manual for Seismic Evaluation of Existing Buildings in Romania September, NCSRR report Sharpe Richard, 2005. Earthquake engineering a science or an art, 2005 Personal communication. Solari, G., Lungu, D., Bartoli, G., Righi, M., Văcăreanu, R., Villa, A, August 2002, “Brancusi Endless Column, Romania: Dynamic response and reliability under wind loading”, The Second International Symposium on Advances in Wind and Structures (AWAS'02), Pusan Convention Center, Pusan, Korea WP Documents
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Beg, D., (2005). Report on Workpackage 4: Intervention Strategies (Slovenia contribution), FP6-2002-INCO-MPC-101, PROHITECH project. Chemrouk M., Attari N. E., Derradj Z., Bouzid F., (2005). Report on Workpackage 4: Intervention Strategies (Algerian contribution), FP6-2002-INCO-MPC-101, PROHITECH project. Doc. N..15.04.01.02. Demonceau, J.F., Jaspart J.P. (2005). Report on Workpackage 4: Intervention Strategies (Belgian contribution), FP6-2002INCO-MPC-101, PROHITECH project. Doc. N..02.04.01.01. El Hammoumi A., Iben Brahim A, Toto A., El Mouraouah A., Kasmi M., Birouk A., (2005). Report on Workpackage 4: Intervention Strategies (contribution of the Moroccan team), FP6-2002-INCO-MPC-101, PROHITECH project. Doc. N.13.04.01.02. Güneysi E. M., Sanrı I., Altay G., (2005). Report on Workpackage 4: Intervention Strategies (contribution of the Turkey team), FP6-2002-INCO-MPC-101, PROHITECH project. Doc. N..10.04.01.02. De Matteis G., Esposto M., Landolfo R., Mazzolani F. M., 2005. Report on Workpackage 4: Intervention Strategies (Italian contribution), FP6-2002-INCO-MPC-101, PROHITECH project. Doc. N..01.04.01.02. Lungu, D., Arion, C. 2005. Report on Workpackage 4: Intervention Strategies (Romanian contribution), FP6-2002-INCOMPC-101, PROHITECH project. Doc. N..08.04.01.01. Zahabi El M., Mourad S., 2005. Report on Workpackage 4: Intervention Strategies (Egyptian contribution to WP4), FP62002-INCO-MPC-101, PROHITECH project. Doc. N..12.04.01.01. Vayas I., Papantonopoulos K., Marinelli K., 2005. Report on Workpackage 4: Intervention Strategies, FP6-2002-INCOMPC-101, PROHITECH project. Doc. N..04.04.01.01.
WP4 MEMBERSHIP UNINA B MK GR NA-ARC ROPUT ROTUB SL TR EG MOR AL UNICH
(PTN. No. 1) (PTN. No. 2) (PTN. No. 3) (PTN. No. 4) (PTN. No. 5) (PTN. No. 7) (PTN. No. 8) (PTN. No. 9) (PTN. No. 10) (PTN. No. 12) (PTN. No. 13) (PTN. No. 15) (PTN. No. 16)
Federico Massimo MAZZOLANI Jean-Francois DEMONCEAU Elena DUMOVA – JOVANOSKA, Zoran MILUTINOVIC Ioannis VAYAS Raffaele LANDOLFO Victor GIONCU Dan LUNGU Darko BEG Gulay ALTAY (ASKAR) Mohamed EL ZAHABI Aomar IBEN BRAHIM Mohamed CHEMROUK Gianfranco DE MATTEIS
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LIST OF CONTRIBUTORS
Gulay ALTAY Boğaziçi Unıversıty, Department of Civil Engineering, Istanbul, Turkey Cristian ARION Technical University of Civil Engineering Bucharest, Structural Safety for Natural Hazard Research Centre, Bucharest Romania Nasser eddine ATTARI School of Architecture and Urbanism (EPAU), Algiers, Algeria Darko BEG University of Ljubljana, Faculty of Civil Engineering and Geodesy, Institute of Structures and Earthquake Engineering, Ljubljana, Slovenia Abdelouhad BIROUK Centre National pour la Recherche Scientifique et Technique, Morocco Farid BOUZID School of Architecture and Urbanism (EPAU), Algiers, Algeria Mohamed CHEMROUK Université of Science and Technology Houari Boumediene, (USTHB), Algiers- ALEGRIA Gianfranco DE MATTEIS University of Chieti/Pescara G. d’Annunzio, PRICOS, Pescara, Italy Jean-Francois DEMONCEAU University of Liege, Department of Structures and Materials, Liege, Belgium Zoubir DERRADJ School of Architecture and Urbanism (EPAU), Algiers, Algeria Abdallah EL HAMMOUMI Mohamed Vth University, Agdal, Morocco M. ESPOSTO University of Naples Federico II, Department of Constructions and Mathematical Methods in Architecture, Naples, Italy Esra Mete GÜNEYSI, Boğaziçi Unıversıty, Department of Civil Engineering, Istanbul, Turkey Sherif MOURAD Cairo University, Engineering Center for Archaeology and Environment (ECAE) Faculty of Engineering, Cairo, Egypt Azelarab EL MOURAOUAH Centre National pour la Recherche Scientifique et Technique, Morocco Aomar IBEN BRAHIM Centre National pour la Recherche Scientifique et Technique, Morocco Jean-Pierre JASPART University of Liege, Department of Structures and Materials, Liege, Belgium Mohamed KASMI Centre National pour la Recherche Scientifique et Technique, Morocco
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Raffaele LANDOLFO University of Naples Federico II, Department of Constructions and Mathematical Methods in Architecture, Naples, Italy Dan LUNGU Technical University of Civil Engineering Bucharest, Structural Safety for Natural Hazard Research Centre, Bucharest Romania Katerina MARINELLI National Technical University of Athens, School of Civil Engineering, Athens, Grecee Federico M. MAZZOLANI University of Naples Federico II, Department of Structural Analysis and Design, Naples, Italy Kostas PAPANTONOPOULOS National Technical University of Athens, School of Civil Engineering, Athens, Grecee Işıl SANRI Boğaziçi Unıversıty, Department of Civil Engineering, Istanbul, Turkey El Arbi TOTO Ibn Tofail University, Morocco Ioannis VAYAS National Technical University of Athens, School of Civil Engineering, Athens, Grecee El Mohamed ZAHABI Cairo University, Engineering Center for Archaeology and Environment (ECAE) Faculty of Engineering, Cairo, Egypt
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Content 4.1 GENERAL & TERMINOLOGY ....................................................................................................................................1 4.2 INTERVENTION SOLUTIONS AND CRITERIA FOR SEISMIC UPGRADING & REHABILITATION OF CONSTRUCTIONS ...............................................................................................................................................................4 4.2.1 The Repair and Strengthening Design Process......................................................................................................5 4.2.1.1 Criteria of Repair and Strengthening..................................................................................................................6 4.2.1.2 Structural investigations .....................................................................................................................................6 4.2.1.3 Damage evaluation and selection of a repair and strengthening solution..........................................................7 4.3 OPTIONS FOR INTERVENTION STRATEGY ..........................................................................................................8 4.3.1 TECHNICAL STRATEGIES ................................................................................................................................................8 4.3.1.1 Reducing seismic requirements ...........................................................................................................................9 4.3.1.2 Improving the mechanical characteristics of the construction............................................................................9 4.3.1.3 Choice of intervention systems ..........................................................................................................................10 4.3.2 REPAIR & STRENGTHENING OF EXISTING BUILDINGS ...................................................................................................10 4.3.2.1 Strengthening unreinforced masonry buildings ................................................................................................11 4.3.2.2 Strengthening reinforced concrete buildings ....................................................................................................12 4.3.2.3 Repair and strengthening of historical buildings ..............................................................................................14 4.3.2.4 Materials and construction techniques .............................................................................................................16 4.3.2.5 Foundations.......................................................................................................................................................20 4.3.3 PASSIVE CONTROL OF STRUCTURES—ENERGY ISOLATING AND DISSIPATING DEVICES ..................................................21 4.3.3.1 Introductory remarks.........................................................................................................................................21 4.3.2.2 Isolation from seismic motion ...........................................................................................................................22 4.3.3.3 Analysis concepts of damage controlled structures ..........................................................................................24 4.3.3.4 Seismic isolation using flexible bearings ..........................................................................................................25 4.3.3.5 Rocking structures.............................................................................................................................................25 4.3.3.6 Energy dissipators for seismically-isolated structures.....................................................................................26 4.3.3.7 Energy dissipators for non-isolated structures .................................................................................................26 4.3.4 CONCLUSIVE REMARKS ...............................................................................................................................................31 4.4 COUNTRY SEISMIC LEGISLATION & ACTIONS FOR SEISMIC INTERVENTION ON CONSTRUCTIONS .............................................................................................................................................................31 4.4.1 SEISMIC RISK MANAGEMENT LEGISLATION AND ACTIONS .............................................................................................31 4.4.1.1 Algeria...............................................................................................................................................................31 4.4.1.2 Belgium .............................................................................................................................................................33 4.4.1.3 Egypt .................................................................................................................................................................33 4.4.1.4 Italy ...................................................................................................................................................................34 4.4.1.4 Maroc ................................................................................................................................................................38 4.4.1.5 Romania ............................................................................................................................................................39 4.4.1.6 Slovenia.............................................................................................................................................................42 4.4.1.7 Turkey................................................................................................................................................................42 4.4.2 BUILDING CODES AND CODES INTER-BENCHMARK PERIODS ........................................................................................54 4.5. SUCCESSFUL REVERSIBLE INTERVENTION FOR CULTURAL HERITAGE CONSTRUCTIONS ..........67 4.5.1 STRENGTHENING OF A CHURCH USING STEEL MEMBERS..............................................................................................67 4.5.1.1 Description of measures....................................................................................................................................67 4.5.2 THE CASES OF TOSCANA AND CAMPANIA REGIONS (ITALY)...........................................................................................72 4.5.2.1 The case of Toscana Region..............................................................................................................................72 4.5.2.2 The case of Campania Region...........................................................................................................................72 4.5.3 REINFORCEMENT TECHNIQUES BY THE ADDITION OF A NEW STRUCTURE ......................................................................73 4.5.4 BRANCUSI ENDLESS COLUMN IN ROMANIA...................................................................................................................74 4.5.5 REHABILITATION AND CONSERVATION OF HISTORIC CAIRO: MANAGERIAL STRATEGIES .................................................79 REFERENCES .....................................................................................................................................................................81
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