1 Earthquake Resiliency of Confined Masonry ...

12 downloads 0 Views 468KB Size Report
Jun 5, 2010 - and housing stock, collapse of buildings in earthquakes, earthquake ..... Accra Region has two (2) metropolitan areas, six (6) municipal areas and two (2) district ..... Publication, SP-147, American Concrete Institute, Detroit, pp.
Earthquake Resiliency of Confined Masonry Construction in Accra-Tema, Ghana Abstract: Purpose: We conducted exploratory research in Accra-Tema metropolis to examine residents’ perception of safety and resiliency of their houses of confined masonry construction in a strong earthquake of between magnitude M6.0 and M7.5 by analogy to Haiti and Turkey. We also assessed the enforcement of the National Building Regulation, LI 1630, (1996). Method: We undertook a questionnaire survey and documentary review. The literature review was done searching relevant books, journals and from websites using keywords like: earthquake resiliency and housing stock, collapse of buildings in earthquakes, earthquake emergency preparedness. The National Disaster Management Organization Act 517 (1996) and the National Emergency Preparedness Plan of 1997 were analyzed to determine how those have collectively prepared the communities. Finding: The research found that 56% of the owners of the building stock in Accra-Tema metropolis did not feel their houses were resilient. About 90% of the single storey and medium rise buildings constructed in 1910 – 2010, have sandcrete block infill. There are numerous problems with insufficient mortar cohesion and other weathering phenomena associated with mortar holding block infill to concrete beams and columns. Social Implications: Residents in Ghana appear to harbor irrational fear of earthquakes because they think their houses are not resilient, which needs to be addressed. Originality: This is the first paper on the risk posed by confined masonry construction in earthquake in Ghana, which should be of interests to all. Keywords: Accra-Tema, confined masonry, resiliency, earthquake, risk reduction Introduction: The National Building Regulation, L.I. 1630, 1996 In Ghana today, masonry construction has replaced traditional building types. The building stock, however, consists of traditional single storey mud-timber laced houses, confined masonry and reinforced masonry constructions as well as wooden and metal shacks and kiosks.

A typical ‘Atakwame’ house in Ghana

1

Traditional Timber-laced housing: Labaragaga Mosque, Ghana

Traditional Timber-laced housing in Ghana

Courtesy: Trasaco Valley Home: Confined masonry construction, Ghana*

The first two types are more popular. From the 1920s until after the Second World War, the building construction style in rural and peri-urban Ghana was dominated by „Atakwame‟ construction (Andam, 2004). Atakwame is the nomenclature for traditional timber-laced masonry. The name Atakwame came about also because the masons who worked on the timberlaced masonry initially came from a town in northern Togo, called Atakpame. In the urban centers, the preferred building construction type is the confined masonry construction. Confined masonry is construction which is reinforced with additional steel, timber or concrete elements. That is to say, the block works are confined with reinforced concrete and metal tie-beams and tie-columns. In confined masonry, the walls are the main load bearing elements, which are 2

expected to resist both gravity and lateral loads, through relatively large beams, columns and their inter-connections. The masonry in-fills are not load-bearing walls (Brzev, 2007).

A typical confined masonry structure, confined at the corners and lintel

A typical housing structure without tie-columns and tie-beans

Confined masonry construction has gained popularity in many nations due to its performance in past earthquakes in countries and regions of extremely high seismic risk, such as Turkey, Iran and Haiti. In Ghana, confined masonry construction gained wide currency after the June 2 nd, 1939 earthquake with a magnitude of M6.5 and which killed many of the local population along the coast. The reconstruction of houses and other life lines, copied the building style of the British settlers whose houses escaped the onslaught of the earthquake with little or no property damage. The confined masonry construction has since been the style and the base technology for all types of housing including single storey buildings, multi-dwellings, multi-storey buildings, low-rise commercial properties and high-rises (Brzev, 2007; Aguilar and Alcocer, 2001). The behavior of confined masonry buildings in earthquake is varied depending on the intensity of ground acceleration. In this situation the tie-columns and tie-beams act as trusses with the masonry walls providing support as diagonal struts subject to compressive strength, concrete reinforcement of the confining members and the strength of the lateral earthquake forces. In Ghana, a Building Guide developed by the National Disaster Management Organization in 2011, recommends that „the compressive strength of masonry units in a wall of a house of one or two storey, shall be not less than [2.75N/mm2 ] for blocks and [5.5N/mm2] for bricks. The compressive strength of bricks and blocks for non-load bearing partitions shall be not less than [1.4N/mm2] provided the bricks and blocks are satisfactory in other respects‟. The quality 3

assessment of the blocks and bricks was left to the subjective judgment of the mason, the owner or the artisanal producers of such bricks and blocks (NADMO, 2010; Moroni et al., 2004). In confined masonry construction, there can be two forms of failure, namely, shear failure which may develop as a result of in-plane seismic load acting along the plane of the walls of the structure. The other kind of failure is flexural which may develop either in-plane or out of plane and which may run perpendicular to the walls of the structure. The failure would show on the wall of the plane as tear or crack. The more earthquake proof the foundational under-structure, tie-beans and tie-columns, the greater the resistance to the gravitational forces and thus ensuring the vertical integrity of the building (Meli, 1994). The race to meet demands on Housing Building technology is subject to local conditions such as cost and integrity of building materials, the abilities, skills and knowledge of the workers, tools, soil properties and weather. In Ghana the building industry is largely unregulated. This is because, there does not appear to be the political will to alter the status quo when it comes to building and site inspection, evaluation of building permits, the acquisition of permits before the commencement of construction works and the absence of quality controls of building inputs. This situation makes it plausible to assume that builders; in their bid to save money and cut cost; would not willfully comply with the requirements of the Building Code (Allotey, et al., 2010; Akoto, 2010). Between 2010 and 2011, there were two confined masonry, multi-storey buildings that suffered catastrophic structural failure midway during construction and collapsed in pancake function without the instigation of seismic activity. The first structure was in Kumasi and the second collapsed building was on the Spintex Road, Accra on 5th June, 2010 (Daily Graphic, 2010). The poverty levels in developing countries are manifested in the physical conditions of their human settlements.

Building collapse at Spintex Road, Accra, Ghana, 5th June, 2010

The World Bank and national researchers observe that poorly planned development can turn a natural phenomenon into a human and economic disaster. Examples of these are allowing dense populations in floodplains, the use of poor or inadequate building codes in earthquake zones, the non-enforcement of building regulations, and the degradation of natural resources (World Bank, 2002; Allotey et al, 2010).

4

Poorly planned neighborhood in Cape Coast, Ghana

All of the reasons articulated in the World Bank report and by other researchers were present in the two instances where there were structural failures in the buildings under construction. Additionally, the domestic dwellings and other buildings that are being constructed, use different building units such as mud and stone, sandcrete blocks, clay tiles and concrete blocks, which may or may not be reinforced with concrete/metal pillars at the corners with concrete/metal tiebeams and tie-columns. The main reason for opting for sandcrete blocks in Ghana is that it is cheaper in price compared to pre-cast concrete blocks, slabs and concrete in-fill. This situation calls for stringent application and interpretation of the Building Regulation on the ground in order to ensure resiliency in the housing stock of the nation against earthquakes (Andam, 2004). Ghana‟s housing stock deficit in 2010-2011 was estimated by the government of Ghana to be about one million. Due to rapid urban migration and population growth, there is tremendous pressure on developers and the government to provide more affordable housing. Due, again, to the urgency of the demand, there is haste on the part of stakeholders in the housing development sector to skip pre-development engineering assessment of the geotechnical properties of the potential land to be used. The geotechnical problems include liquefaction, landslides, lateral spreading, flooding, and ground subsidence coupled with inadequate and poor foundation understructures (Ministry of Finance and Economic Development, 2010). Ghana’s Exposure to Earthquake Ghana's exposure to earthquake is modest considering the peak ground acceleration of 10% in 50 year time in terms of seismic activity on the probabilistic seismic hazard map of Africa and the Middle East (International Studio, 2003; Amponsah, 2004; Ofori-Quaah, 1997). Historically, Accra and the nearby coastal areas of which Tema is one, have experienced four seriously damaging earthquakes on Richter magnitude of about 6 during the last 400 years. The significant ones were in 1858, 1863, 1883, 1907, 1911, 1918, 1923, 1925, 1930, and 1933-35. The major ones were 1635, 1862, 1906 and 1939. The most destructive earthquake that struck the then Gold Coast, (Ghana) and caused a lot of damage, loss of life and property, was on the 2 nd June 1939. In 1939, seventeen people were killed and one hundred and thirty three injured. Its magnitude was 6.5 on the Richter scale. In more recent times, earthquakes and strong tremors some with magnitude of 4.9 on the Richter scale have been experienced in 1964, 1969, 1979, 1985, 1995, and 1997 (Amponsah, 2004; Ayetey, 1983). Despite the apparent assurance from the probabilistic seismic map, it is generally believed among the residents that the country is long overdue for a big earthquake. Should this eventually 5

happen, the result would be devastating to the nation. Based on Accra-Tema metropolis‟ present population of approximately 4.5 million, even the most conservative estimate (where population affected is [675,000] = 15%, with event fatality rate of = 0.6%), shows the potential for significant mortality of (4,050 deaths) in the occurrence of a strong earthquake in Ghana. Such an event would probably scale back the current level of development in Accra-Tema metropolis and in Ghana proper for, perhaps, 50 years. According to Akoto, (2011) the probability of a large stock of buildings collapsing in an earthquake with such magnitude is extremely high with a death toll of over 5,000. Prior to 1996, there was no national standard for housing even though the Public Works Department of the Ministry of Housing and Construction adopted ad hoc codes for building government financed housing projects and other developments. We do not have information or data on the construction history of the buildings in the twin cities and cannot do a retrospective analysis of how they were constructed. We can only assess the risk being faced by Ghana with respect to earthquakes by analogy. Therefore, we turn to Turkey, Iran and Haiti. In 1999, earthquake of magnitude M7.6 occurred in the Turkish town of Kocaeli and destroyed many buildings including scores of primary and secondary schools (Yuzugullu, et al., 2004). And in 2003, in the ancient town of Bam, Iran, earthquake of magnitude M6.6 on the Richter scale and similar to the June 2 nd, 1939 earthquake in Ghana, spread over 10 seconds, killed more than 40,000 inhabitants or about half of the population. Most of the dead in Bam occurred in buildings that were recently constructed and were under 40 years of age. In the case of the Haiti‟s earthquake of M7.0 there were over 250,000 deaths, with about 230,000 residences destroyed and 30,000 commercial buildings also destroyed. In all three cases, it has been noted that the failure of the rather newer and modern confined masonry buildings, was more massive than the historic ones, particularly in Bam. These outcomes raised serious questions about confined masonry construction practices in that region and in other regions as well (Yuzugullu, et al., 2004; Gulkan and Langenbach, 2004). The reasons as to why so many people died in the Haitian earthquake are many but the main reason is that too many of the modern buildings collapsed on top of people and crushed them to death, due in part to poor construction practices. That is to say, to gain earthquake resiliency in the building stock of a particular area, certain basic modalities have to be in place, but which were not in place in Haiti. In Ghana, these modalities are enumerated in the National Building Regulations, L. I. 1630. National Building Regulations The National Building Regulations, L.I 1630 of 1996, Part V, Subpart 1, section 43 (1) page 28, instructs architects, builders and contractors that, “buildings and other structures shall be designed and constructed to safely resist earthquakes effects or seismic forces in accordance with the relevant provisions of the British Standard Code of Practice or the equivalent Ghana Standards”. The quotation above lies at the center of the challenges in the building industry in Ghana. The geotechnical properties of the land in Ghana differs from that of Britain and even within the same city from one part of Accra city to another part, the geotechnical properties are most likely to be different from each other. Thus to prepare a Building Code to the specifications used in Britain appears to have not considered the unique qualities of each location. For example, according to research conducted by Meli, (1994) in Mexico City after the 1985 Mexico earthquake, the Mexico City Building Code imposed stringent wall density requirements on masonry buildings. This is because wall density is believed to be one of the key parameters influencing the seismic performance of confined masonry buildings. Thus a five-storey building in that city is now required to provide wall density of 6%, whereas in the more earthquake prone 6

area of Guererro State, the wall density is about 10% in relation to total floor area of the building. This result emerged out of local initiative to address local problems associated with attaining a greater building resiliency within that locale in the event of seismic disturbance. The National Building Regulation is supposed to contain the standards for Ghana based upon the geotechnical benchmark that builders in Ghana are supposed to meet. Linkage of L. I. 1630 (1996) to the National Disaster Management Organization Act (1996) The other problem is that the L.I. 1630 of 1996 is not legislatively linked to the National Disaster Management Organization Act 517 of the same year. No reference of either Act or law is made in either of them even though both Acts were passed in the same year. Due to this oversight, the dissemination of the “National Building Guide for Lightly Loaded Structures in Disaster Prone Areas in Ghana‟, produced by NADMO in November of 2011 with financial assistance from UNDP has met exasperated resistance from other stakeholders on the justification that NADMO is not mandated to prepare and disseminate such a Guide. In order to create a climate for mainstreaming Disaster Risk Reduction and the concept of a National Platform for disaster management in Ghana particularly in the building industry, real attention needs to be paid by the law makers and law drafters to establish the legislative linkages of the laws that affect the known disasters in the nation. Method: Field research We did a baseline, explorative study which consisted of questionnaire survey and documentary review. The literature review was done searching relevant books and journals and from websites using keywords like: earthquake resiliency and housing stock, collapse of buildings in earthquakes, earthquake and emergency preparedness. The National Building Regulation and the National Disaster Management Organization Act 517 of 1996 together with the National Emergency Preparedness Plan of 1997 and other related national documents were analyzed to determine how those have collectively prepared the communities with basic earthquake survival skills. Discussion of the national preparedness plan and the legal framework were based on the authors‟ understanding of disaster and emergency preparedness particularly for earthquake and international best practice. Study population and Sample size estimation for the Field Research The data-set used in this study formed a part of a larger study on risk communication in earthquakes in Accra-Tema metropolis. Location The study was conducted in the West African nation of Ghana in 2011.

7

The map of Ghana showing the administrative regions

There are ten (10) administrative regions in Ghana which are divided into a total of 138 metropolitan, municipal and district assemblies. The study was carried out in the Greater Accra Region with Accra as its capital (this is also the largest city and capital of Ghana). The Greater Accra Region has two (2) metropolitan areas, six (6) municipal areas and two (2) district assemblies. However the two (2) metropolitan areas and three (3) of the municipalities were considered in the sample selection due to their close proximity, high population densities and also because communities found in these areas represent both the indigenes and also the large number of migrants and settlers from the entire country. Sample selection was random but the sampling frame may be considered convenient as the location of houses and neighbourhoods are fixed. The classification of the communities is reported in Table 1. Sampling was of a simple random nature. Stratification was carried out by gender and by residence type according to the various classifications provided by the Accra Metropolitan Authority (AMA) and Tema Metropolitan Authority (TMA), i.e. First class, Second class, Third class and Fourth class residential. Tema uses numbers to label respective suburbs such as Community One, Community Two. The sampling units were selected equally from sampling locations according to the various classifications provided by the Accra Metropolitan Authority (AMA) and Tema Metropolitan Authority (TMA) regarding the location and residential types, i.e. First class, Second class residential. To estimate sample size in such a situation the formula is 𝑛 =

𝑍1−𝛼 /2

2

𝑑2

𝑝(1−𝑝)

where 𝑧1−𝛼/2 =

1.96, is a critical point on the standard normal distribution using 𝛼 = 0.05 as the significance level and 1 − 𝛼 as the confidence level, assuming a normally distributed population. 𝒑 is the

expected proportion of the main attribute of interest in our sample and d is the acceptable margin of error of estimating within the true population proportion. Using the highest combination of p and 1-p and d=0.05 gives the following: 1.96 2 (0.5𝑋0.5) 𝑛= = 384.14 𝑤ℎ𝑖𝑐ℎ 𝑖𝑠 𝑟𝑜𝑢𝑛𝑑𝑒𝑑 𝑜𝑓𝑓 𝑡𝑜 𝟒𝟎𝟎 (0.5)2

8

Therefore, the sample size was 400.

Sampling procedure: Sex Distribution, proportionate sampling and data analysis The 2010 Ghana census puts the proportion of males at 48.72% and females at 51.28%. Using this as a guide, out of the sample size of 400, we selected 195 males and 205 females. These were selected equally by proportion and randomly from each of the four (4) classes of locations according to the AMA/TMA classification system. In each residential area, we did the selection of samples from the center of that area and sampled every 5 th house until we obtained the required allocation for that area. Sampling from Tema was purely random based on similarities with the distribution within Accra. The total from each residential class was 100. The number of females from each class was 51.28% but rounded up to 52%. The overall total of respondents sampled was 404 due to rounding off, Table 1. Data analyses were carried out to find the demographic characteristics of the respondents. These were done using the Statistical Package for Social Sciences (SPSS), and also STATA where there were low cell counts. Logistic analysis was carried out to investigate if the following predictor variables: level of concern if residents were to hear an alarm for earthquake in progress, the effect on sleep and the help received from disaster/security officials can be used to predict reaction in an earthquake. Table 1: Classification of sampled in AMA and TMA Table 1: Classification of sampled in AMA and TMA 1st Class Accra

2nd Class Accra

3rd Class Accra

4th Class Accra

Tema Area

Abelemkpe Airport Residential Area Asylum Down

Abelemkpe

Nii Boi Town

Aborfu

Abossey Okai

Ashaiman

Accra New Town

North Kaneshie

Alajo

Asere

Bethelehem

Achimota

North Labone

Avenor Area

Bukom

Kpone

Burma Camp

Agbogbloshie

Nungua

Bubuashie

Dansoman

Akokorfoto

Odawna

Chemuna

Dzorwulu

Akweteman

Odorkor

Dansoman Amanhoma

Chorkor Nungua Town Teshie Town

East Cantonments

Alajo

Okaishie

Darkuman

Ussher Town

Tema Community 2

East Legon

Apenkwa

Old Dansoman

Gbegbeyise

Zongo

Tema Community 3

East Ridge

Asylum Down

Osu

Korle Gonno

Tema Community 4

Kotobabi

Tema Community 5

Mamobi

Tema Community 6

Old

Sakumono Tema Community 1

Independence Avenue

Avenor

Kanda Estates

Chorkor

Osu Estates Sahara

Kuku Hill

Dansoman

Sakaman

Mampose

Tema Community 7

North Dzorwulu

Darkuman

Sempe New Town

New Fadama

Tema Community 8

North Labone

East Legon East Legon (Okponglo)

South Amanhoma

New Mamprobi

South Kaneshie

Nima

Kokomlemle

South Labadi

North Labone

Ridge

Kotobabi

South Odorkor

Nungua-Zongo

Ringway Estates

Kwashieman

Tesano

Odorkor

Roman Ridge

Labadi-Aborm

Teshie New Town

Osu Ako-Adjei

Tema Community 9 Tema Community 11 Tema Community 18 Tema Community 19 Tema Community 20 Tema Newtown

South Shiashie

Lartebiokorshie

W/Okponglo

Osu Alata/Ashante

Nungua East Police Area

Headquarters

Ako-Adjei

Lashibi Old

9

T/Junction

Link Road

Shiabu

Tesano

Mantseman

South Shiashie

Teshie-Nungua Estates

Mataheko

Sukura

Zoti Area

New Abossey Okai

Zabramaline

NB: Some locations fall under multiple classes due to their large size and differences between them. First Class properties attract the highest rates, Second Class attracts higher rates, Third Class attracts high rates and Fourth Class attracts low rates. Tema township property rates are determined by flat community rates since the township is subdivided into communities and not by suburbs.

1.

Outcome of Field investigation: Basic demographics, knowledge and resiliency of earthquakes

There were 398/400 valid returns from respondents. The mean age was 29.38. The median age was 26 with the minimum being 17 and the maximum age being 85, (Std. deviation=10.58). Of the (n=398) figure, 50.8% were female. The majority of the respondents were single registering (66.16%), but those married were (30.05%). The rest were cohabiting (1.26%), divorced (0.76%), widowed (0.76%) or separated (1.01%). The majority of the respondents reported that they were Christians (93.18%), and those reporting themselves as Muslims were (5.81%). The rest were traditional African religion or atheists. Most reported that they were employed (57.92%). Another (37.16%) described themselves as students with the unemployed being (4.10%). The rest were retired. When respondents were asked if they knew what emergencies such as earthquakes or tremors are (84.17%) answered correctly that they did. However, only (41.91%) of those who reported correctly that they knew what an earthquake is, were able to describe what causes earthquake with statements such as “when one earth crust shifts over the other”, or “when a tectonic plate moves”, and “when the ocean moves our earth a little”. Of the number that knew the cause of earthquake correctly, (84.17%) reported that they had experienced earthquake before. Of the (53.18%) that had experienced earthquake before, in (92.42%) of the cases, their experiences were in Ghana. Of those who knew the cause of earthquake and tremors, [129/313(41.2%)] had secondary education, and another [146/313 (46.6%)] reported having tertiary education with a (p-value= 0.016). Approximately (64%) of this figure were employed and another (31.3%) were students, (p-value= 0.005). In the same table, we notice that employment [192/300 (64%)], secondary education [146/313 (47%)], and tertiary [(58%) 57/99] education and income [51/98 (52%)] showed significant correlates between knowledge and causation of earthquakes. Tertiary education was the most striking variable that clearly showed a distinction between knowledge and cause. Of those with tertiary education, (58%) correctly knew the cause of earthquakes, compared to (39%) of those with secondary education, that correctly knew the cause of earthquakes. About (59%) of the respondents said they did not think their current homes offered adequate resiliency against an earthquake event, although no earthquake magnitude or severity indicator was given. 2.

Roof structure of Single Family Houses

The single-storey single-family dwellings predominantly accommodate the middle to upper classes. These are the educated and bureaucratic classes, as well as the essential workers in health and allied industries, the teachers, the university professors and government functionaries. These houses are normally but not always roofed with untreated wooden planks or rafters on which concrete or clay roof tiles are placed. The average five bedroom single family house carries a load of between 5,000 kilograms or 5 tons and 8,000 kilograms or 8 tons of its roof structure depending upon the room sizes. The weight of the roof is equivalent to parking three or four cars with 1.8 liter engine on top of such a house. The standard house in Ghana is erected on 10

a below ground foundation which is between 24 and 18 inches deep. During heavy rainfall, the foundations of many houses are threatened, because the foundations were not sunk deep enough. Some foundations are as shallow as 9 inches into the ground, particularly in poor neighborhoods. Consequently, when it rains heavily, and there is a lot of water run-off, the foundations of such houses are often exposed. 3.

Non-Resilient Buildings

The study found that many of the buildings erected between 1954 and 2004 were raised without the appropriate building permit. From searches conducted at the offices of the Town and Country Planning Departments of the two metropolitan assemblies, about 50% of the houses were built without architectural drawings, supervision and approval. The evaluation of the building stock in Accra City against the resiliency requirements of L.I. 1630 of 1996, estimated that about 50%t of the buildings built in this time range, 1954 and 2004, would not be able to meet the parameters set out in the Regulation and are therefore substandard. Outcome of the literature review 1.

Damage assessment in other cities and nations

In jurisdictions such as Turkey, extensive studies on damage assessment have been done (Balamir, 2003). They have concluded that, „on the basis of two independent approaches (intensity-based and spectral displacement-based approaches), some 35,000 to 40,000 buildings (about 5 per cent of the total building stock) can be expected to be damaged beyond repair (complete damage). Most casualties can be expected in this damage group, especially in a subset of this group where collapse will occur in the “pancake” form. When a building collapses in pancake mode, the floors pile up on top of each other rendering very difficult conditions for search and rescue. In the case of Turkey, the estimate for the pancake mode of collapse is 5,000 to 6,000 buildings. We have noticed this phenomenon recently in several multi-storey structures that have collapsed in Kumasi and Accra during construction, where rescue was hampered for days. Furthermore, about 70,000 buildings will receive extensive damage and another 200,000 will be moderately damaged‟. This estimate was conducted on buildings found to be mediumrise (4-7 storey), reinforced concrete frame buildings and built before 1975. On buildings in Turkey constructed before 1980, vulnerability was found to be high. While the death toll was similar to the 1975 buildings, the degree of damage to buildings was greater. Intensity-based analysis yielded 600,000 household damages figure while spectral-displacement approach gave out 430,000 households destroyed with their occupants requiring shelter in a proposed earthquake scenario (Balamir, 2003). Perhaps, the quality of housing in Turkey is, on the whole, similar or of superior quality, to the buildings in Ghana. Though variables such as building codes, zoning, soil types and other constructional practices need to be analyzed before comparing buildings in the two jurisdictions, it is fair to say that the application of the same tests or approaches to Ghana would yield either similar figures or even higher damage-death ratios. Renovations of some older homes in Accra have revealed little or no iron reinforced concrete works. Possibly the new buildings are better built, but one cannot be completely sure.

11

Discussion and Conclusion Ghana Building Regulations could be redesigned to address the problems in the building industry and should be divorced from that of Britain. Britain‟s topography is very different from that of Ghana. Ghana‟s exposure to earthquakes is different to that of Britain. Thus, to build houses in Ghana in the same way that a house in the UK would be built is unreasonable. The British administrative oversight agencies bring a higher level of professionalism to their work. They control the building industry in terms of pre-inspection of buildings sites, building permits and other procedures. This is in stark contrast to the lackluster attention paid to the Ghanaian building industry by its administrative agencies, the ministry of finance, the central bank and the various investment houses. There is no national clearing house where one could go to; to obtain figures on building start-ups within a given financial period. Although there is ample empirical evidence to support the view that a large portion of the residential buildings in Accra-Tema metropolis are neither built well nor are our neighborhoods planned well, developers continue to build non-resilient houses in vulnerable parts of the nation and in unplanned neighborhoods. The average commercial or residential multi-storey building in Accra-Tema area takes more often than five years to complete. The concrete beams, pillars and lintels are cast in-situ, left to stand in the vagaries of the weather for long durations and are thus exposed to various levels of deterioration. Weather deterioration of the mortar can be a result of its original composition. This includes the type of aggregate used, the binder/aggregate ratio, which determines the physiomechanical properties of the material and the mineralogical composition that influences the durability of the mortar in the environment. Environmental factors, including salt contamination play an important role in the deterioration process. Accra is situated along the coast. Its air is laden with saline properties that cause oxidation of metal and other iron surfaces at a more rapid rate than on similar structures in the hinterlands. The overwhelming majority of the bricks and blocks used in the building and construction industry are made by young, often illiterate men, who do not even know, let alone understand, the logic of measurement and cement to sand ratios. The situation is even more compounding and confounding, when a similar group of young men, who still do not know how to read, write or design, are given primary constructional responsibilities to design and build houses without the understanding of, or appreciation for, gravitational effects of structures and super-structures to and on each other, or soil type and density. Until October 25, 2005 the Ghana Standards Boards (GSB) did not have the capabilities to test locally made blocks and bricks to assess their “compressive strength” for the thousands of houses and hundreds of high rises that have been constructed in the last few years. Even though the „GSB‟ now has the capacity to test blocks and bricks for “compressive strength”, it is impossible for one bureaucratic entity to test all the millions of blocks and bricks used in the construction industry on a monthly basis throughout the nation. Acknowledgements: We are grateful to Mr. Mawuli Akoto, Lecturer at the Department of Geology, University of Ghana for providing additional insight into this paper. *We are also grateful to Trassaco Valley and Ghana Houses for the use of the images in this paper. Reference: 1. 2.

Aguilar, G., and Alcocer, S. M. 2001. “Effect of Horizontal Reinforcement on the Behavior of Confined Masonry Walls under Lateral Loads”. Center for the Prevention of Disasters, Mexico City, Mexico, pp 181 Allotey, N. K., Arku, G., Amponsah, P. E. 2010. Earthquake-disaster preparedness: the case of Accra. International Journal of Disaster Resilience in the Built Environment. Vol. 1 No. 2: 140-156.

12

3. 4.

5.

6. 7.

8. 9. 10. 11. 12. 13. 14. 15. 16. 17.

18.

19. 20.

Amponsah, P, E. 2002. Seismic Activity in relation to fault systems in Southern Ghana. Journal of African Earth Science 35:227-234. Andam, K. 2004. “Bricks, Blocks and the Future Administrative Capital of Ghana”. Kwame Nkrumah University of Science and Technology, Kumasi. Ghana Academy of Arts and Sciences Inaugural Lecture, British Council Hall, pg 57 Ayetey, J. K. & Frimpong, E. M. 1983. “Site investigations and foundation problems and review of applicable solutions in the seismic situation of Accra, Building and Road Research Institute Special Report”. Building and Road Research Institute, Kumasi, Ghana Balamir M. 2003. “Local Administration and Risk Management”/pg:1(http://info.worldbank.org/etools/docs/library/114715/instanbul 03/02 balamir 3-n(1 Gulkan, P., and Langenbach, R. 2004. “The Earthquake Resistance of Traditional Timber and Masonry Dwellings in Turkey”. 13th World Conference on Earthquake Engineering, Vancouver, B. C., Canada. Available also from www.conservationtech.com. International Studio. 2003. “Disaster Resilient Accra, Ghana”. http://www.arch.columbia.edu/studio/spring 2003/UP/Accra/html/hazard.html last visited 15/11/2005, pg 1-5 Mawuli Akoto. 2010. Personal Communications on fatalities after a major earthquake, Ghana Television Broadcasting Corporation: Earthquakes in Ghana, what is the national preparedness, Oct, 2010. Accra, Ghana Meli, R. 1994. “Structural Design of Masonry Buildings: the Mexican practice”. Masonry in the American, ACI Publication, SP-147, American Concrete Institute, Detroit, pp. 239-262 Ministry of Finance, Government of Ghana Annual Budget Statement, 2010, Ministries, Accra. Moroni, M. O., Astroza, M., Acevedo, C. 2004. “Performance and Seismic Vulnerability of Masonry Housing Types Used in Chile”. Journal of Performance of Constructed Facilities, ASCE, Vol. 18, No. 3, pp. 173-179 Ofori-Quaah, A. 1997. The Accra Earthquake sequence of January–March 1997.1-20. NADMO Archives, Headquarters, Kanda, Accra, Ghana Porter, K. A., Kiremidjian, A. S., and LeGrue, J. S., 2001. “Assembly-based vulnerability of buildings and its use in performance evaluation”, Earthquake Spectra 17, 291–312. Svetlana Brzev, 2007. “Earthquake-Resistant Confined Masonry Construction”. Department of Civil Engineering. British Columbia Institute of Technology, Burnaby, BC, Canada. The Daily Graphic Newspaper. 2010. Storey Building Collapses, 1B, June 5th, 2010 The Getty Conservation Institute, (2003) “Preservation of Lime Mortars and Plasters”, pg 1, The GCI Project Bibliographies series, (http://www.getty.edu/conservation/publications/pdf_publications/Impbib_alpha.pdf) last visited 23/11/2005 World Bank/UNDP Global Report, “Reducing Disaster Risk”, chapter Two, International Patterns of Risk, pg 29-56. In Ofori, G. (2002), citing Badiane, A. (2001) “Construction Industry Development for Disaster Prevention and Response”, Dept., of Building, National University of Singapore, 4 Architecture Drive, Singapore 117566 World Bank/UNDP. 2002. “Reducing Disaster Risk‟, A challenge for Development, NUDP, Bureau for Crisis Prevention and Recovery, pg 13 (1.3.1) (www.undp.org/bepr) last visited 23/11/2005. Yuzugullu, O., Barbarosoglu, G., and Erdik, M. 2004. “Seismic Risk Mitigation Practices in School Buildings in Instanbul Turkey”. Kandilli Observatory and Earthquake Research Institute, Bogazici University, Turkey.

13