Journal of Civil Engineering and Management

ISSN 1392-3730

Vilnius Gediminas Technical University

Lithuanian Academy of Sciences

Journal of Civil Engineering and Management 2004, Vol X, No 4

Vilnius „Technika“ 2004

EDITORIAL BOARD Editor-in-Chief Prof Edmundas K. ZAVADSKAS, Lithuanian Academy of Sciences, Vilnius Gediminas Technical University, Saulëtekio al. 11, LT-10223 Vilnius-40, Lithuania Editors Building Materials and Structures

Structural Mechanics and Physics, Information Technologies

Construction Technology and Management

Prof Audronis K. KVEDARAS, Vilnius Gediminas Technical University, Saulëtekio al. 11, LT-10223 Vilnius-40, Lithuania

Prof Romualdas BAUÐYS, Vilnius Gediminas Technical University, Saulëtekio al. 11, LT-10223 Vilnius-40, Lithuania

Prof Artûras KAKLAUSKAS, Vilnius Gediminas Technical University, Saulëtekio al. 11, LT-10223 Vilnius-40, Lithuania

Managing editor Assoc Prof Darius BAÈINSKAS, Vilnius Gediminas Technical University, Saulëtekio al. 11, LT-10223 Vilnius-40, Lithuania International Editorial Board Dr Rogerio BAIRRAO, Portuguese National Laboratory for Civil Engineering, Av. Brasil, 101, 1700-066 Lisboa, Portugal Prof György L. BALÁZS, Budapest University of Technology and Economics, Mûegyetem rkp.3, H-1111 Budapest, Hungary Assoc Prof Erik BEJDER, Aalborg University, Fibigerstraede 16, 9220 Aalborg, Denmark Prof Adam BORKOWSKI, Institute of Fundamental Technological Research, Swiætokrzyska 21, 00-049 Warsaw, Poland Prof Michaù BOLTRYK, Biaùystok Technical University, Wiejska 45A, 15-351 Biaùystok, Poland Prof Patrick J. DOWLING, Felow Royal Society, University of Surrey, Guildford GU25XH, UK Prof Aleksandr A. GUSAKOV, Moscow State University of Civil Engineering, Dorogomilevskaja, 5/114, 121059 Moscow, Russia Prof Boris V. GUSEV, International and Russian Engineering Academies, Tverskaja 11, 103905 Moscow, Russia Assoc Prof Edward J. JASELSKIS, Iowa State University, Ames, IA 50011, USA Prof Oleg KAPLIÑSKI, Poznan University of Technology, Piotrovo 5, 60-965 Poznan, Poland Prof Herbert A. MANG, Austrian Academy of Sciences, Vienna University of Technology, Karlsplatz 13, A-1040 Vienna, Austria

Prof Rene MAQUOI, University of Liege, Building B52/3, Chemin des Chevreuils 1, B 4000 Liege, Belgium Prof Yoshihiko OHAMA, Nihon University, Koriyama, Fukushima-Ken, 963-8642, Japan Prof Friedel PELDSCHUS, Leipzig University of Applied Science, 132 Karl Liebknecht St, 04227 Leipzig, Germany Prof Karlis ROCENS, Latvian Academy of Sciences, Riga Technical University, Âzenes str. 16, Riga, LV-1048 Latvia Prof Les RUDDOCK, University of Salford, Salford, Greater Manchester M5 4WT, UK Prof Miroslaw J. SKIBNIEWSKI, Purdue University, West Lafayette, Indiana 47907-1294, USA Prof Martin SKITMORE, Queensland University of Technology, Brisbane QLD 4001, Australia Prof Zenon WASZCZYSZYN, Cracow University of Technology, Warszawska 24, 31-155 Krakow, Poland Prof Frank WERNER, Bauhaus University, Marienstrasse 5, 99423, Weimar, Germany Prof Nils-Erik WIBERG, Chalmers University of Technology, SE - 412 96 Göteborg, Sweden Prof Jiøí WITZANY, Czech Technical University, Prague, Thákurova 7, CZ 166 29 Praha 6, Czech Republic

Prof Antanas ALIKONIS, Vilnius Gediminas Technical University, Saulëtekio al. 11, LT-10223 Vilnius-40, Lithuania Prof Juozas ATKOÈIÛNAS, Vilnius Gediminas Technical University, Saulëtekio al. 11, LT-10223 Vilnius-40, Lithuania Prof Algirdas E. ÈIÞAS, Vilnius Gediminas Technical University, Saulëtekio al. 11, LT-10223 Vilnius-40, Lithuania Assoc Prof Juozas DELTUVA, Kaunas University of Technology, Studentø g. 48, LT-3028 Kaunas, Lithuania Prof Romualdas GINEVIÈIUS, Vilnius Gediminas Technical University, Saulëtekio al. 11, LT-10223 Vilnius-40, Lithuania Prof Arvydas JUODIS, Kaunas University of Technology, Studentø g. 48, LT-3028 Kaunas, Lithuania Prof Pranciðkus JUÐKEVIÈIUS, Vilnius Gediminas Technical University, Saulëtekio al. 11, LT-10223 Vilnius-40, Lithuania Prof Rimantas KAÈIANAUSKAS, Lithuanian Academy of Sciences, Vilnius Gediminas Technical University, Saulëtekio al. 11, LT-10223 Vilnius-40, Lithuania Prof Gintaris KAKLAUSKAS, Vilnius Gediminas Technical University, Saulëtekio al. 11, LT-10223 Vilnius-40, Lithuania

Prof Stanislovas KALANTA, Vilnius Gediminas Technical University, Saulëtekio al. 11, LT-10223 Vilnius-40, Lithuania Prof Ipolitas Z. KAMAITIS, Lithuanian Academy of Sciences, Vilnius Gediminas Technical University, Saulëtekio al. 11, LT-10223 Vilnius-40, Lithuania Prof Romualdas MAÈIULAITIS, Vilnius Gediminas Technical University, Saulëtekio al. 11, LT-10223 Vilnius-40, Lithuania Prof Gediminas J. MARÈIUKAITIS, Vilnius Gediminas Technical University, Saulëtekio al. 11, LT-10223 Vilnius-40, Lithuania Prof Josifas PARASONIS, Vilnius Gediminas Technical University, Saulëtekio al. 11, LT-10223 Vilnius-40, Lithuania Prof Vytautas STANKEVIÈIUS, Lithuanian Academy of Sciences, Lithuanian Institute of Architecture and Building Construction, Tunelio g. 60, LT-3035 Kaunas, Lithuania Prof Vytautas J. STAUSKIS, Vilnius Gediminas Technical University, Trakø g. 1/26, LT-01132 Vilnius, Lithuania

Local Editorial Board

249 ISSN 1392–3730

JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT http:/www.jcem.vgtu.lt

2004, Vol X, No 4, 249–253

INFLUENCE OF SOME TECHNOLOGICAL FACTORS UPON WALL CERAMICS FROST RESISTANCE Michaù Boùtryk, Vadim Nikitin, Beata Backiel-Brzozowska Biaùystok Technical University, Institute of Civil Engineering, Wiejska 45E Street, 15-351, Biaùystok, Poland. Tel.48 85 7469622. E-mail: [email protected] Received 3 Aug 2004; accepted 12 Nov 2004 Abstract. A polynomial model, which enables evaluation of the influence of amount and graining of sand in a ceramic mix and maximum temperature and duration of burning upon ceramics frost resistance, constructed on the basis of experimental results is presented in this work. During the experiment the mass loss of ceramic specimens was measured. Experimental results were prepared for further statistical analysis with regard to linear summing of mass losses. Statistical evaluation of the quality of the constructed model and physical interpretation of tested factors were made. In addition, the authors presented the results of the samples bulking investigation in comparison with the results of frostresistance test. Also the correlation of the results of both investigations was checked. Keywords: building ceramics, experimental-statistical models, burning process, ceramic mix composition, frost resistance, water bulking.

1. Introduction The durability of wall ceramic products exposed to an external environment can be determined on the basis of their frost resistance. Frost resistance is measured for a material totally saturated with water, subjected to destructive powers occurring during multiple freezing and thawing. It depends on many factors, among which the most important one is related to the porous capillary structure of material. This opinion is shared by many researchers who examine the durability of building materials [1–3, etc]. The better the material structure compensates unfavourable action of internal transfer of humidity in the form of gas, liquid and solid, the higher the material frost resistance is. The composition of the ceramic mix and parameters of the burning process significantly influence the porous structure of the material. Quantitative evaluation of these factors upon material frost resistance would allow forecasting this feature. This paper presents a polynomial model which allows quantitative evaluation of the influence of quartz sand in a ceramic mix (amount and graining) interacting with the maximum temperature and the duration of the burning process upon frost resistance of wall ceramics. Parameters of the model were evaluated by comparison with experimental data. 2. Characteristics of the tested object The test was carried out under laboratory conditions with cubic specimens (125 cm3) wet-molded from plas-

tic mix using press. The mix was of plastic clay from the ceramic factory “Lewkowo” and contained local river sand. It represented a fusible clay with a melting point of about 1200 °C and sintering range 50–60 °C. It is used for wall ceramics articles. It mostly contains the finest fraction – grains smaller than 10 µm make up to 88 % of its total mass and grains smaller than 2 µm from 50 to 60 %. The specific surface of dry clay is 128 m2/g. The main clay mineral is illite (hydromica), which includes minerals from chlorite and montmorillonite groups or laminar minerals (illite-montmorillonite). The chemical composition of clay in the form of percentage of oxides is as follows: SiO2 – 46–48 %; Al2O3 – 14–17 %; Fe2O3+FeO – 6,1–7,4 %; CaO – 9–10 %; MgO – 3,6– 4,1%; K2O+ Na2O – 3,8–4,6 %. Roasting weight loss is 12,5–13,1%. The amount of free quartz (SiO2) is about 10 %. The clay is susceptible to swelling during burning [4, 5] because the main clay mineral is hydromica, the finest grains make up the majority in grain size distribution, there is a high content of Fe2O3+FeO, K2O+Na2O and a low content of free SiO2 and a high roasting weight loss. During heating of hydromica clay, at the end of dehydration process, when incomplete burning of organic intrusions at 700 °C takes place, small stains in the liquid phase are formed between illite laminae. Formation of liquid phase in crystal lattice of hydromica is explained by presence of potassium, magnesium and ferric ions. Illite-like structures preserve their features during heating up to 1000 °C, and when temperature reaches

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1100 °C, ferric and magnesium spinels are formed and further precipitation of the liquid phase (or liquid-like phase) takes place [4, 6]. With the temperature increase up to 1200 °C spinels may disappear or pass to mullite. This description presents the character of main changes occurring in clay and hydromica during burning. The correcting admixture in the form of quartz sand (containing approximately 0,3 % of very small marl grains) has been introduced in order to regulate technical properties of clay. The majority (96 %) of sand grains is in the range of 0,06 to 1 mm. The shape of grains is spherical. Approximately 67 % of these grains is in the range of 0,25 to 1 mm. This sand is qualified as medium-grain sand. Unfortunately, there is no unity of options about the desired grain size distribution of sand in literature. According to Avgustinik [4] it is advisable to apply medium-grain sand (0,25–0,5 mm), but according to Rogovoj [5] – coarse-grain sand (0,5–2 mm). However, both authors agree that dusty sands cannot be used in building ceramics. 3. Estimation of damage moment in frost resistance examination Examination of ceramic material frost resistance was conducted on cubic specimens. Before freezing the specimens were saturated with water. Five sides of each cube were covered with rubber and thermal isolation. During cycles of freeze and thaw, heat transfer took place at the exposed surface of specimen. In this way a condition close to one-way frost action was created. Specimens saturated with water were frozen in an air-conditioned chamber to –18 °C. Freezing time was not shorter than 4 h. Specimens were thawed in temperature 20 °C. During thawing the exposed surface of each cube was under water. The duration of a freeze-thaw cycle was 24 h. The number of cycles of one side or volume freezing-thawing, which causes the first damage, has to be determined in standard wall ceramics frost resistance examinations. The moment of damage is determined after the appearance of destruction in a form of peel, chip, delamination (course), or cracks on a surface. The first two types of damage are the main criteria in frost resistance examination. All forms of destruction present an inaccurate estimation of the actual damage moment. In the investigation, processes of material destruction during cyclic freeze and thaw were estimated on the basis of weight loss, caused by peeling and chipping. It was observed that the process of mass loss from the exposed surface of a specimen Δm (kg/m2) has both a linear and a non-linear character. The widely known principle of linear summing of mass losses [6, 7] is valid up to Δ m ≈ 0,25 kg/m2. Further cyclic action of temperature led very quickly to the total destruction of specimens. The principle of linear summing of mass losses from the exposed surface of a material during cyclic freezing and thawing can be mathematically formulated as:

(1) Δm = c ⋅ N , where c = empirical coefficient of proportionality, which characterises the intensity of mass loss of examined specimens; N = number of freeze-thaw cycles. The correctness of the principle of linear summing of mass losses in a specified range is confirmed by data presenting the results of frost resistance examinations of ceramic material from different clays [8]. The maximum value of linear summing of mass losses from the exposed surface of specimens Δ mtr = 0,2 kg/m2 was accepted in the present study. The moment of sample damage corresponded with a number of freeze-thaw cycles causing a mass loss from the exposed surface of a specimen equal to or a little higher than the accepted threshold value Δ m ≥ Δ mtr. After comparing 11 pairs of specimens (a control one and one subjected to freezing-thawing cycles to Δ mtr) it was observed that the mean loss of compressive strength of examined ceramic materials was 7 %. 4. Model, experimental design and results The main features of ceramic materials are determined to a great extent by phase composition and porous structure, which is formed as a result of complex and often unidentified processes occurring in a ceramic mix during burning. Quartz sand plays a particular role in all these processes. It has been stated [9] that coarse quartz grains cannot react during heating and after burning quartz is partially not changed. Very fine quartz grains react in whole and they are a part of liquid phase. The author of work [10] also noticed that crystalline silica grains do not take part in forming liquid phase and they only undergo polymorphic transformation. According to [11], shrinkage of quartz related to volume changes during phase transition is so great that quartz grains remain separated from liquid phase. Probably it is the reason why the decrease of compressive strength and the increase of porosity of ceramic products are observed. Such unclear description of effects of the above phenomena allows formulating only some of premises, which should be considered while selecting mathematical models connecting in a quantitative way material features with amount and graining of sand in interaction with burning parameters. The number of input quantities (independent quantities) and scale (the level of variation of tested factors), which are the base of experimental design, should be established before selection of mathematical model. It has been assumed that the burning process is characterised by two factors: X1 – maximum burning temperature, X2 – duration of burning at maximum temperature. As known, the relation between ceramic properties and burning regimes is not linear. That is why parabolic dependency has been used. Factors X1 and X2 varied on three levels (lower, medium and upper): 900, 990, 1080 °C (X1); 1, 2, 3 hours (X2). At the same time the rate of increasing and decreasing the temperature was

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constant (3 °C/min). The total duration of burning was 10,8; 12,5 and 14,2 hours respectively. The third variable X3 was the content of sand in the ceramic mix: 5, 15, 25 % (by weight). Sand was composed of three fractions: fine-grained Z1 (grains up to 0,25 mm), mediumgrained Z2 (0,25–0,5 mm) and coarse-grained Z3 (0,5– 1,0 mm). The condition ΣZi=1 was satisfied at variation of grain-size (mass) factors Z1, Z2 and Z3. Dependency of frost resistance on technological factors X1, X2 and X3 was described by a second-order polynomial:

FR = b0 + b1x1 + b2 x2 + b3 x3 + b12 x1x2 + b13 x1x3 + b23 x2 x3 + b11x12 + b22 x22 + b33 x32 ,

Experimental design and experimental results of ceramic specimens frost resistance

β 23 Z 2 Z 3 + β123 Z1Z 2 Z 3 ,

(i, j = 1, 2,3; bij , i < j ).

1080

1

5

Frost resistance (cycle number) at different sand composition (fractions Z1, Z2, Z3 mixed of equal proportions) Z1 Z1 Z1 Z2 Z1 Z2 Z3 Z2 Z3 Z3 Z2 Z3 44 32 25 32 40 32 30

900

1

5

22

Technological factors X1 [°C]

(2)

where x1 = ( X i − 990) / 90 ; x2 = X 2 − 2 ; x3 = ( X 3 − 15) / 10 – are coded (non-dimensional) factors, which have equal levels in experimental design: –1 (lower), 0 (medium), 1 (upper). Xi is a natural value of input quantity. All coefficients of polynomial (2) are functions dependent on grain-size factors Zi and they are described by a reduced (incomplete) third-order polynomial:

b(0,i ,ij ,ii ) = β1Z1 + β 2 Z 2 + β3 Z 3 + β12 Z1Z 2 + β13 Z1Z 3 +

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X2 X3 [h] [%]

12

11

14

21

18

14

1080

3

5

50

42

30

40

40

40

42

900

3

5

24

15

13

14

14

19

18

1080

1

25

56

43

32

48

45

36

44

900

1

25

28

20

19

23

18

15

18

1080

3

25

56

44

29

47

42

32

44

900

3

25

35

23

16

22

17

16

18

900

2

15

22

17

14

23

19

15

18

1080

2

15

53

42

30

45

40

39

42

990

1

15

45

36

20

37

28

26

27

990

3

15

38

32

21

33

28

30

25

990

2

5

35

27

24

29

30

28

24

990

2

25

52

38

21

39

26

25

33

(3)

It was expected that the accepted model (2, 3) should reflect all complex interactions between grain-size factors Zi and technological factors Xi. In [12] that type of model was used to describe sorption humidity in ceramic brick and hardened cement mortar containing three types of salts. Literature gives also other examples of application of this model [13]. Composition-symmetrical experimental design containing 14 samples with different coded values of input quantity Xi [14] was used in order to obtain experimental data necessary to evaluate coefficients of polynomial (2). Each point of this design was repeated seven times at different proportions of three sand fractions Zi. These proportions were prepared according to simplex Scheffe’s design, which is commonly used at experimental design of composition-feature type [14] and to analyse material technology problems. The clearest picture of the chosen experimental design can be obtained after consideration of data in Table. According to this design, at maximum randomisation, N = 14×7 = 98 specimens were prepared. When analysing experimental data in rows and columns in Table 1 it can be noticed that values of frost resistance change approximately two or three times. It may be concluded that at least some effects of factors Xi and Zi are significant from the statistical point of view.

X2 and X3. Regression equations in the form of secondorder polynomial were determined for each column and than they were analysed and interpreted. Residuals of each equation were determined basing on Daniel’s method [15] in the form of empiric distribution function. The residuals were determined as a difference between empirical and theoretical value of frost resistance. As an example, the residuals distribution of one model formulated basing on data presented in one column, Z1=1 are shown in Fig 1. The residuals are approximately in accordance with normal distribution and standard devia-

5. Statistical analysis of experimental results Each column of experimental data in Table was analysed. Each column contains results of frost resistance tests of specimens with the same grain-size distribution of sand and prepared at different levels of factors X1,

251

Fig 1. Empirical cumulative distributions function of residuals (model of frost resistance for ceramic material consisting of only fine-grained sand – Z1)

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tion equals approximately 2,9, based on 4 degrees of freedom. Mean standard deviation for the family of models equals 2,67 (28 degrees of freedom). Then, at the selected significance level α = 0,05 and at experimental error s FR 2 = 7,15 according to Student’s t-test criterion (t0,05;28 = 2,05), statistically significant regression coefficients of equation (2) were determined. After approximation of coefficients of model (2) by polynomial (3), the final model for defining frost resistance of specimens was found:

FR = 42,5Z1 + 33,3Z 2 + 21,8Z 3 − 13,6 Z1Z 2 − 12 ,2 Z1ZZ 3 − 4 ,2 Z 2 Z 3 − 21,6Z1Z 2 Z 3 − (12,8Z1 + 11,6Z 2 + 7 ,3Z 3 − 2,4Z1Z 2 + 7 ,0Z1Z 3 + 12,3Z1Z 2 Z 3 ) x1 + (5,2Z1 + 4 ,0Z 2 + 1,4Z 3 + 1,6Z1Z 2 −

(4)

13,2Z1Z 3 − 10,8Z 2 Z 3 + 50,1Z1Z 2 Z 3 ) x3 + (−3,5Z1 − +4,3Z 2 + 7 ,0Z1Z 3 + 8,5Z 2 Z 3 + 21,2Z1Z 2 Z 3 ) x12. According to the model (4), frost resistance of ceramic material achieves the highest results are x1 = +1 and x3 = +1. After calculating values of frost resistance for every possible combination of coded value of technological factors x1 and x3, it was obtained that optimum conditions for technological factors are when maximum burning temperature is 1080 °C and 25 % of sand is added to a ceramic mix. After substitution of coded values for model (4) the following equation was obtained:

FRopt = 57 Z1 + 45Z 2 + 30,5Z 3 − 14,4Z1Z 2 − 11,4Z1Z 3 − 6,5Z 2 Z 3 + 62Z1Z 2 Z 3 .

(5)

6. Evaluation of the frost resistance on the base of the ceramic materials bulking in water There is an opinion in literature that frost resistance of the ceramic materials may be forecast on the base of the samples’ volume changes with the water saturation [16, 17]. For the sake of simplicity of the procedure and much shorter time needed to carry out the investigation of the samples bulking in water in comparison with the investigation of frost-resistance, the authors admitted to be advisable checking the correlation of the results of both investigations. Investigation of the ceramic material bulking was carried out in laboratory terms on 24 cubic samples moulded of the ceramic mass containing 15 % of the quartz-sand addition of the grain size composition Z1 = Z 2 = Z 3 = 0 ,33 . The samples were burned with the change of maximum temperature of the isothermal heat: 900 °C (7 samples), 990 °C (10 samples), 1080 °C (7 samples). The speed of heating and cooling was constant – 3 °C/min. After burning the samples were kept in water for 10 days and the changes in linear dimensions were measured. Then the frost resistance was investigated according to the method described in the article. During the investigation there was noticed that after 7–8 days of keeping in water the bulking of samples has stopped. In further analysis there was taken into account the maximal bulking of the samples. The numerical value of this indicator has decreased with increasing the temperature of samples burning. The measurement results of the samples’ linear dimensions changes and the frostresistance of 24 samples were shown in Fig 3, where one can see that the frost-resistance of samples increase when their bulking in water decrease approximately in

frost resistance (cycles number)

Equation (5) allows calculating the maximum value of frost resistance (optimum condition) for the specific grain-size distribution of sand. Geometrical picture of dependency (5) in the form of isolines of frost resistance on tricomponent diagram is presented in Fig 2.

According to this diagram, specimens with fine-grained sand (grains up to 0,25 mm) achieve the highest frost resistance (55 cycles). Specimens with gross-grained sand (0,5– 1,0 mm) are characterised by almost twice lower frost resistance (30 cycles).

40

30

20

10 0,05

Fig 2. Isolines of ceramic material frost resistance on tricomponent diagram of grain-size distribution of sand for optimum technological conditions

252

0,1

0,15

0,2

bulking in water (%)

Fig 3. Relation between the results of frost resistance test and bulking in water test

M. Boùtryk, et al  / JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT – 2004, Vol X, No 4, 249–253

linear dependence. The precision of the linear dependence between the values of those indicator/indexes characterises the negative correlation factor equal to 0,946. The presented dependency may be the base to work out the method of frost resistance evaluation of the ceramic samples on the basis of the materials bulking in water indicator. The estimation of stability of dependence between indicators requires carrying out special investigations.

253

5.

Rogovoj, M. I. Technology of artificial pore aggregates and ceramics (Òåõíîëîãèÿ èñêóññòâåííûõ ïîðèñòûõ çàïîëíèòåëåé è êåðàìèêè). Moscow: Strojizdat, 1974 (in Russian).

6.

Kartaðov, G. D. Methods of material examinations (Ìåòîäû ôîðñèðîâàííûõ èñïûòàíèé). Moscow: Znanie, 1979, p. 56–98 (in Russian).

7.

1. The experiment proved that not only parameters of the burning process and the sand content influence frost resistance of wall ceramics. Also, the grain-size distribution of sand has an impact on ceramics performance. 2. Formulated statistical-experimental models describe with sufficient accuracy results of a very complex mutual interaction between the considered factors; they allow solving different engineering problems, such as the prediction of the durability of a ceramic material. 3. The interdependence of frost resistance and bulking in water of ceramic material was confirmed.

Nikitin, V. & Lapko, A. Methods of service life predicting wall finishes in interior of monumental buildings (Metody oceny okresu przydatnoúxci uýytkowej elementów i wykoñczenia wnætrz w budowlach zabytkowych). In: Monumental Constructions, Proc. intern. symp. Biaùystok, Biaùystok Technical University, 1998, p. 198–204 (in Polish).

8.

Zelikin, S. I. & Zemlanski, V. N. & Civilev, R. P. Examination of material destruction kinetics using x-ray method (Èññëåäîâàíèå êèíåòèêè ðàçðóøåíèÿ ìàòåðèàëîâ ðåíòãåíî-ãðàôè÷åñêèì ìåòîäîì). Glass and ceramics (Ñòåêëî è êåðàìèêà), Vol 6, Moscow, 1979, p. 23–24 (in Russian).

9.

Worrall, W. Clays and ceramic raw materials. London, 1980.

The experiment was carried in Bialystok Technical University in the frame of Projects No W/IIB/1/03 & S/ IIB/1/02 supported by State Committee for Scientific Research.

11. Pavlov, V. F. Physical-chemical grounds of building ceramics burning (Ôèçèêî-õèìè÷åñêèå îñíîâû îáæèãà èçäåëèé ñòðîèòåëüíîé êåðàìèêè). Moscow: Strojizdat, 1977 (in Russian).

7. Conclusions

References 1.

2.

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3.

Zhang, B. Relationship between pore structure and mechanical properties of ordinary concrete under bending fatigue. Cement and concrete research, Vol 27, No 8, 1997.

4.

Avgustinik, A. I. Ceramics (Ceramika). Warszawa: Arkady, 1980 (in Polish).

10. Peregudov, V. V. & Pogovoj, M. I. Heating processes and installation of building articles and details technology (Òåïëîâûå ïðîöåññû è óñòàíîâêè â òåõíîëîãèè ñòðîèòåëüíûõ èçäåëèé è äåòàëåé). Moscow: Strojizdat, 1983 (in Russian).

12. Nikitin, V. & Guriev, V. & Ùapko, A. Modeling of sandwich concrete building structures production and service processes (Modelowanie procesów w produkcji i eksploatacji warstwowych konstrukcji budowlanych). Biaùystok Technical University, Biaùystok, 1999. 244 p. (in Polish). 13. Voznesenskij, V. A. & Vyrovoj, V. N. & Kerð, V. & Ljaðenko, T. V. Modern methods of composite materials optimization (Ïðèìåíåíèå ñòàòèñòèêè â ïðîìûøëåííîì ýêñïåðèìåíòå). Kiev: Budivel’nik, 1983 (in Russian). 14. Nalimov, V. V. Experimental design tables for factor and polynomial models (Ïëàíû ýêñïåðèìåíòà äëÿ ôàêòîðíûõ ïîëèíîìèíàëüíûõ ìîäåëåé). Moscow: Metalurgija, 1982 (in Russian). 15. Daniel, K. Statistics in industrial experiment (Ïðèìåíåíèå ñòàòèñòèêè â ïðîìûøëåííîì ýêñïåðèìåíòå). Moscow: Mir, 1979 (in Russian). 16. Kuzmin, I. D. & Seljuk, G. P. & Nikitina, O. I. & Nikitin, V. I. Estimation of frost resistance of building ceramics (Îöåíêà ìàðîçîñòîéêîñòè ñòåíîâîé êåðàìèêè). Building materials (Ñòðîèòåëüíûå ìàòåðèàëû), Vol 4, 1980, p. 22–23 (in Russian). 17. Blicharski, M. Introduction in materials engineering (Wprowadzenie do inýynierii materiaùowej). Warszawa: PWN, 1998 (in Polish).

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EXPERIMENTAL STUDY OF TRANSIENT THERMAL CREEP AND OTHER PHENOMENA OF CONCRETE AT HIGH TEMPERATURE Horacio Colina, Gilles Moreau, Daniel Cintra Laboratory of Material Analysis and Identification (LAMI), Institut Navier, ENPC-LCPC, 6 et 8 ave Blaise Pascal-Cité Descartes, Champs sur Marne – 77455 Marne-la-Vallée Cedex 2, France. E-mail: [email protected] Received 23 Sept 2004; accepted 10 Nov 2004 Abstract. This paper deals with experimental study of transient thermal creep and other parameters, as elastic and free thermal strain, of ordinary, high-strength and high-performance concrete at high temperature. An original test device can reproduce accident and service conditions with a homogeneous distribution of temperature inside the specimens. Constant values of heating rate and force (when the specimen is loaded) are applied. Successive constant temperature levels are reached and maintained during the necessary time to ensure internal stabilisation. To observe the importance of changes in concrete properties after a first heating cycle, some specimens are submitted to a second one. In order to show the performance of the experimental methods, some results are presented and discussed. Keywords: concrete at high temperature, experimental method, accident condition, service condition, transient thermal creep, elastic strain, free thermal strain.

1. Introduction High temperatures have a significant effect on concrete even for moderate heating rates. The internal structure of concrete changes and defects develop, owing to free and bound water loss, decarbonation and other physical and chemical phenomena. Macroscopically, damages are principally materialised by irreversible strains and variations of strength and elastic modulus [1–3]. The principal objective of this work is the experimental study of a particular form of thermal strain: the usually called transient thermal creep [2, 4, 5]. Above some values of temperature, strains are far different from those of the only effect of elastic strains, drying shrinkage and basic creep could be [6, 7]. Therefore, another strain component must to be considered for explaining clearly the concete behaviour at high temperatures. For temperatures near to 100 °C, transient thermal creep seems to adapt the thermal incompatibilities between the cement paste which shrinks and the gravel which expands [8]. For higher temperatures, changes caused by dehydration of the cement paste also take part in the phenomenon. The important magnitude of transient thermal creep helps avoiding excessive damage during heating. This effect is, however, restricted to the heating phase and does not appear during cooling, leading to irrecoverable strains [8, 9]. An accurate test device was mounted to follow the transient thermal creep evolution [10, 11]. It has also

permitted to study the free thermal strain and the evolution of the elastic strain with temperature. The determining factor of the test design has been used to obtain a quasi-uniform distribution of temperature inside the material in order to avoid gradient effects. Hereafter, tests for following the thermal strains on ordinary, high-strength and high-performance concrete are described. 2. Materials and test methods The RILEM recommendations TC 129-MHT concerning transient creep under service conditions [2] have been followed as a general framework for the design of the tests. One of the main recommendations concerns temperature gradients within the specimen thickness which are to be as limited as possible during the test. In order to calculate the real transient thermal creep, the instantaneous elastic strain has been measured during the tests. Other authors [1, 8, 12, 13] deduce only the initial elastic strain to determine the transient thermal creep strains, called in this case “load-induced thermal strains” (LITS). 2.1. Heating conditions Two heating conditions have been considered in the experimental programme: – Accident conditions, involving short-term exposure

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of drying concrete to high temperatures. According to Rilem recommendations [6] for the tested specimens (160 mm diameter), this condition can take place from a constant heating rate of 0,5 °C/min. – Service conditions, considering long-term exposure of drying or moisture saturated concrete to high temperatures. According to Rilem recommendations [6] for the tested specimens (160 mm diameter), this condition happens at a constant heating rate of about 0,1 °C/min. In practice, accident conditions correspond with temperatures that can reach 700 °C or more, while service conditions rarely go beyond 200 °C. In this paper, tests reproducing both conditions with drying concrete are described, although the principal results correspond to service conditions because it was the principal objective of the initial experimental programme [11]. Experiments reproducing accident conditions in high performance concrete are included in the experimental part of a PhD thesis, which results will be available in 2005 [14].

press 30 stainlessdisc

aluminium sheet 5

compress

-meter

heating

metallic element

4

640

3

300 2

thermal insulation

1 thermocoup

specime

170 press 30

160

Fig 1. Scheme of the transitional thermal creep test device (measures in mm)

2.2. Materials and specimens In order to obtain a uniform distribution of temperature within the specimens, hollow cylinders were cast to heat the specimens from the inside part, the external surface, the top and the bottom of the cylinder. A length/ diameter ratio of 4 has been chosen to permit an accurate measurement of strains in the central part of the specimen. The specimen dimensions were 160 mm for the external diameter, 30 mm for the internal one and 640 mm for the length. Fig 1 shows the specimen, scheme with details of the heating device, the metrology system and the test setting. Three different kinds of concrete were tested: an ordinary concrete, a high strength concrete and a high performance concrete, with 35 MPa, 60 MPa and 100 MPa as compressive strength respectively (for more information about concrete mix see [15]). A single batch of concrete for three 160×640 mm hollow specimens and four 160×320 mm cylinders for resistance controls was made at each opportunity. It was poured in the respective moulds and each layer used for filling up the moulds was vibrated with a vibrating needle. Immediately after casting, the moulds were hermetically closed and the specimens moist cured during 72 hours. After being removed from moulds, they were stored under water at 20 ± 2 °C, at least during 70 days, until the moment of the test. 2.3. Test device The choice of hollow cylinders has permitted to reduce the thickness of the heated zone: 65 mm in the radius direction instead of 160 mm for the full cylinder.

Heating was provided by heating collars, heating plates of the power press, and a metallic element of high thermal conductivity. This heating device ensured a uniform temperature within the specimen during the tests. The specimens were then heated from the external surface in the central part by three heating collars, through the two plates of the heating power press, specially adapted for the test, and from the inside part by the way of a heat-conductor metallic element. On the upper part, a particular stainless-steel disk has let thermocouple cables come out and has allowed the transmission of heat and pressure from the press plate. In order to keep the temperature of the lower and the upper part of the specimen near that of the central part, the external surface was covered with aluminium sheets and recovered with a 50 mm layer of thermal insulation. To measure length variations in the direction of the central axis of the specimen, a distance of 300 mm between two cross-sections situated at 170 mm of the top and the bottom respectively, was considered as basic length. Length variations during the test were then measured by a compressometer rig specially conceived for this experiment: two rings were clamped to the specimen at the level of each reference cross-section by three screws equally spaced around the circumference and connected to the rings by means of elastic strips. The displacements were measured employing three linear variable transducers (LVDT) located into invar supports mounted vertically at 120 °C intervals around the specimen. In case of exceeding the temperature limit of LVDTs, 70 °C, a water cooling system was provided in the upper part of the invar tubes.

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For measuring the internal temperatures, five thermocouples of K type, with 700 °C as maximum temperature tolerance, were placed inside the specimen (Fig 1): three at 10 mm from the external surface (numbers 1, 3 and 5) and two at 10 mm from the internal surface (2 and 4). Thermocouples 1 and 5 were situated at the level of the reference cross-section, number 3 at the middle and numbers 2 and 4 at 100 mm from their respective cross-section. The test machine was a heating press with 900 kN as closing power, 4000 W as heating power in each plate and 700 mm of separation between the plates when stopped. In Fig 2 we can see the test machine with the specimen and the equipment employed for the data acquisition during the experiment.

Fig 2. General view of the test device for transient thermal test of concrete

The test data were acquired by a National Instruments® data acquisition system connected to a PC computer, where the Labview® software permitted to observe in real time the evolution of temperature and strain during the experiment, and to store the numerical output for data processing. 2.4. Test development Before testing, the specimens were dried at 60 °C during 48 h, and the weight loss depended on the concrete type: 1,5 % for ordinary concrete, 1,0 % for highstrength concrete and 0,6 % for high-performance concrete, in average values. After that they were conveniently prepared: the lower surface of the specimen was rectified, and the aluminium sheets, the compressometer rig and the insulation layers were mounted. Finally, the thermocouples were put inside their correspondent cavities, the upper surface was covered with a thin layer of mortar, the stainless-steel disk was put on and the whole was set into the heating press. During a short time, a pre-compression of 1 MPa was applied in order to assure centring the specimen.

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After verification of the well positioning of the specimen, a uniaxial compressive load was applied at a rate of 1 MPa/s until the selected constant load was reached. In these experiments the 20 % reference “cold” (20 °C) strength value was chosen as the constant load. Immediately, the specimen was heated at a constant rate of 0,1 °C/min for service conditions or 0,5 °C/min for accident conditions, until the first level of constant temperature was reached. The stage was maintained till stabilisation of internal temperature, during a time which depends fundamentally on tests conditions (accident or service conditions) and constant temperature level (Figs 3–6). Then the constant heating rate was restarted in order to reach the next temperature stage. When the heating part was completed, the warm device was turned off to follow the “natural” cooling part of the cycle. At the test end, when ambient temperature was reached inside the material, the specimen was unloaded. The first temperature stage was always chosen at a temperature level higher than 105 °C in order to study the phenomenon after free water evaporation and the beginning of dehydration of C-S-H [2, 4, 8, 9]. To study whether the phenomenon can develop again after a cycle of heating-cooling at constant load, some specimens were submitted to a new cycle with two temperature stages: the first at a temperature level lower than the maximum temperature reached during the 1st cycle and the second one at a higher one (for further information, see [15]). In every test, the elastic strain was recorded at the beginning of the test when loading, during the temperature stages by means of an unloading-loading quasi-instantaneous process (not more than 2 min of duration), and at the end of the cycle when unloading the specimen already cold. The free thermal strain, also necessary for the determination of the transient thermal creep [2, 6], was obtained by submitting virgin specimens to a cycle of heating-cooling similar to the first cycle of heating-cooling with constant load but without loading the specimen [15]. 3. Results and discussion The results presented in this part include the evolution of temperature and total strain during two heatingcooling cycles at constant load, and during free thermal strain tests. From these data, the transient thermal creep may be calculated and compared for the different types of concrete [15]. In paper [15] the results obtained are treated in detail. Hereafter, a general review is given to show the pertinence of the test method. 3.1. General results The general evolutions of two mean temperatures and the total strain for both test conditions are given here.

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Ta represents the temperature evolution near the central axis and Tref in the central zone of the specimen. The |Ta – Tref| difference gives a measure of the uniformity of temperature inside the material. It has not exceeded 6 °C in any case [15]. The mean total strain etot is determined as the average of the three deformations obtained from the LVDT measures. The “peaks” in the strain curves correspond to the elastic strains. Concerning accident conditions, only one test at 0,5 °C/min was carried out because the initial research programme [11] was based on service conditions. Nevertheless, it has permitted to verify the performance of the test device for studying this kind of solicitation and it is actually employed in the experimental part of a Ph D thesis dealing with this subject [14]. Fig 3 shows the evolution curves for this test, which was performed with an ordinary concrete specimen. For service conditions, the specimens were heated at a constant rate of 0,1 °C/min up to successive temperature levels (of about 140, 190, 220 °C), which were maintained constant during the necessary time to ensure the stabilisation of internal temperatures. Figs 4, 5 and 6 show the general evolutions for ordinary concrete, high strength concrete and high performance concrete respectively.

2,00

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1200 1440 1680 1920 2160 2400 2640 time [min]

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Fig 5. Temperatures and total strain evolution for a high strength concrete under service conditions HPC .1 240

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Fig 3. Temperatures and total strain evolution for an ordinary concrete under accident conditions

200

Ta

After a period of at least a week at ambient conditions, some specimens were submitted to a new cycle of heating-cooling with two temperature stages: the first at a temperature level lower than the maximum already reached during the first cycle and the second at a higher one. In every case, the transient thermal strain has not developed during the first stage but it has appeared again at the second one. Fig 7 shows the correspondent curve for a high strength concrete specimen.

1,25 140

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Fig 6. Temperatures and total strain evolution for a high performance concrete under service conditions

1,50

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Fig 4. Temperatures and total strain evolution for an ordinary concrete under service conditions

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Fig 7. Temperatures and total strain evolution for a high strength concrete, under service conditions, during a new

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It is interesting to note the two equal values of elastic strain during the first temperature stage, which show that this strain depends only on load and temperature [2]. 3.2. Brief analysis and discussion The existence of a strain component, which reduces the material expansion when heating is clearly shown by the experimental method, used in this work. It can be seen in the temperature and total strain evolution curves of the first cycles of heating-cooling and those of the second cycles when the maximum temperature of the first one is exceeded. The residual strain at the end of the test shows that it is irrecoverable and that its value is important, varying with the kind of concrete. Complementary expansion test without load (free thermal strain) plus the elastic strains obtained during the principal test permit to estimate the values of transient thermal creep of concrete [15]. Thus, considering the additive approach valid to describe the strain behaviour [1, 2, 6, 7, 8], transient thermal creep Attc(Tj,I) can be estimated, for the temperature Tj corresponding to the j stage, by: Attc(Tj,I) = Atot(Tj,I) – Ael(Tj,I) – Ath(Tj,0),

The technique used for obtaining the elastic strains has also permitted to estimate the Young’s modulus and to follow its evolution during the process [10]. Its “hot” value can be estimated by the ratio between the constant stress and the “hot” elastic strain, which corresponds to the absolute value of the total strain difference measured during the quasi-instantaneous process of unloading and loading. Fig 8 shows the tendency obtained for the heating part of the 1st cycles of heating-cooling, for three concretes.

1st Cycle - Heating part 1,1

1,0

= E/E(20°C)

cycle of heating-cooling.

0,9

O.C. H.S.C.

0,8

H.P.C.:

0,7

ρ~ e

-0,03 θ

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-0,04 θ

H.S.C.

H.S.C.:

ρ ~ e

O.C.:

ρ~e

-0,05 θ

2

3

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O.C.

0,5 0

1

4

5

6

7

8

9

10

11

12

θ = (T[°C] - 20°C)/20°C

Fig 8. Young's modulus evolution with temperature for three concretes during the heating part of the 1st cycle

(1)

where: Atot(Tj,I) is the total thermal strain and Ath(Tj,0) the free thermal strain corresponding to the time when internal temperatures reached the Tj value, Ael(Tj,I) is the elastic strain measured during the j stage. The principal importance of transient thermal creep phenomenon is its beneficial effect when heating because it reduces the material expansion, but also its contribution to the strain values when cooling which can provoke tensile stress in concrete higher than its strength [8, 9]. When comparing the curves for ordinary concrete in accidental and service conditions, it is only possible to say that this concrete shows a higher thermal inertia to reach the internal stabilisation during accident conditions. Only one temperature stage was maintained the necessary time when testing at accidental conditions. The existence of a transient thermal strain can also be observed but it seems to be of lower intensity than under service conditions. More experiments will be made [14] to state further conclusions. Considering the second cycles of heating-cooling, it has been always found the same behaviour: any strain variation during the first temperature stages and a new development of the phenomenon for the second ones. Thus the transient thermal creep depends only on irrecoverable physical and chemical processes taking place in the material due to the temperature increase [15].

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Finally, it is interesting to observe (Figs 3–7) that with this test device the uniformity of temperature inside the central part of the specimen is assured: in any case |Ta – Tref| has exceeded 6 °C [15]. 4. Conclusions The experimental method presented here permits to observe temperature and strain evolutions of different kinds of concrete during cycles of heating–cooling. A special shape of the specimens and the heating system ensure a uniform temperature field inside the material, without temperature gradients, which is a principal condition for studying the transient thermal strains. The data acquisition system permits to follow in real time the evolution of temperatures, displacements and force and to make a detailed analysis of the results. The obtained results put in evidence the existence of a transient thermal strain, so-called transient thermal creep, which develops during the first heating process and also during a new one if the maximum temperature of the first cycle is exceeded. The experimental techniques used in this work allows to follow the total strain evolution under constant load and the elastic strain evolution with temperature, owing to the possibility of unloading and loading the specimen in a quasi-instantaneous way during the process. The free thermal strain is obtained with a similar test device without load.

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Thus, for the mean reference temperature of a stage, the transient thermal creep can be easily estimated from eq 1 with the total and free thermal strains values obtained from the strain-temperature curves, plus the “hot” elastic strain value determined during the stage. This technique also allows to estimate the Young’s modulus variation with temperature, for different concretes under the same test conditions, by the ratio between the constant stress and the values of the elastic strain at the beginning of the test, for each temperature stage and at the end of the experiment. The test by temperature stages is a relevant way for studying the thermal behaviour of concrete. In future works a more complete description of the phenomena, concerning accidental conditions, may be obtained by including more temperature stages and an accurate study of the length of each stage. References 1.

Khoury, G. A.; Grainger, B. N. and Sullivan, P. J. E. Transient thermal strain of concrete: Literature review, conditions within specimen and behaviour of individual constituents. Magazine of Concrete Research, 37 (132), 1985, p. 131–144.

2.

Schneider, U. Concrete at high temperatures – A general review. Fire Safety Journal, 13, 1988, p. 55–68.

3.

Guo, J. S. and Waldron, P. Development of the stiffness damage test (SDT) for characterisation of thermally loaded concrete. Materials and Structures, 33, 2000, p. 483–491.

4.

RILEM TC 129-MHT. Test methods for mechanical properties of concrete at high temperatures. Recommendations: Part 7: Transient creep for service and accident conditions. Materials and Structures, 31, 1998, p. 290–295.

5.

Küttner, C. H. and Ehlert, G. Experimental investigations of transitional creep of concrete at temperatures up to 130 °C and boundary moisture conditions. Wiss. Hochsch. Archit. Bauwes-B-Weimar, 38, 1992, p. 211–218.

6.

Khoury, G. A.; Grainger, B. N. and Sullivan, P. J. E. Strain of concrete during first heating to 600 °C under load.

Magazine of Concrete Research, 37 (133), 1985, p. 195– 215. 7.

Cheyrezy, M. Fire behaviour of high performance concrete. Continuing education course on fire security and concrete structures, Ecole Nationale des Ponts et Chaussées, Paris, 2000. 28 p. (in French).

8.

Khoury, G. A. Compressive strength of 1992, p. 291–309.

9.

Feraille-Fresnet, A. The water role in concrete behaviour at high temperature (Le rôle de l’eau dans le comportement à haute température des bétons). Ph D thesis, Ecole Nationale des Ponts et Chaussées, Paris, France, 2000 (in French).

10. Colina, H. and Moreau, G. Transient thermal creep of concrete: An interesting test method. In: Proceedings of the 8th international conference “Modern Building Materials, Structures and Techniques”, Vilnius, 19–22 May 2004. Selected papers, ed E. K. Zavadskas, P. Vainiûnas and F. M. Mazzolani. Vilnius: Technika, 2004, p. 379–383. 11. Colina, H. Study of transient thermal creep of concrete (Etude du fluage thermique transitoire du béton). Advancement report of CEA-ENPC research project, 2000. 27 p. (in French). 12. Thienel, K.-Ch. and Rostasy, F. S. Transient creep of concrete under biaxial stress and high temperature. Cement and Concrete Research, 26 (9), 1996, p. 1409–1422. 13. Pimienta, P. and Hager, I. Evolution of HPC characteristics submitted to high temperatures. Report of HPC 2000 National Project, France, 2000. 28 p. (in French). 14. Sabeur, H. Study of concrete behaviour under accidental conditions and high temperatures – A thermal-hydro-chemical-mechanical coupled approach (Etude du comportement du béton en conditions accidentelles sous hautes températures – Une approche Thermo-Hydro-ChimicoMécanique couplée). 1st-year advancement report of PhD thesis, Ecole Nationale des Ponts et Chaussées, Paris, France, 2004 (in French). 15. Colina, H. and Sercombe, J. Transient thermal Creep of concrete at temperatures up to 300 °C under service conditions. Accepted by Magazine of Concrete Research, 56, 2004.

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HARDENED MATERIAL PROPERTIES OF SELF-COMPACTING CONCRETE Klaus Holschemacher Leipzig University of Applied Sciences (HTWK Leipzig), Dept of Civil Engineering. Karl-Liebknecht-Strasse 132, D-04329 Leipzig, Germany. E-mail: [email protected] Received 24 Aug 2004; accepted 30 Nov 2004 Abstract. Self-compacting concrete (SCC) is an innovative construction material with a favourable rheological behaviour, which is caused by its modified concrete composition. Based on this fact SCC offers improved fresh concrete but also hardened material properties and therefore many advantages regarding the productivity and the design potential compared with normal vibrated concrete. Consequently, the amount of SCC, used for structural purposes has strongly increased worldwide in the last years. In this context it is necessary to know, if it is possible to apply the current design rules, eg Model Code 90 and Eurocode 2, that are based on years of experience on normal vibrated concrete, to structural members made of SCC as well. This paper represents the analysis of own and internationally published test results of the compressive strength, tensile strength, modulus of elasticity, bond behaviour and the time-dependent deformations of SCC in comparison with conventional concrete, in order to give a general statement regarding the agreements and differences between the hardened material properties of these concretes. Keywords: self-compacting concrete, hardened concrete properties, tensile strength, modulus of elasticity, creep and shrinkage, bond behaviour.

1. Introduction SCC, primarily invented in Japan in the late 1980’s [1, 2], has developed more intensively only in the last decade. In this time the application of SCC has increased and many investigations all over the world were carried out to find optimal and economical mix compositions, which guarantee the typical fresh concrete behaviour of SCC. Meanwhile, there are various concepts for the production of SCC-mixes, which vary mainly in the amount and kind of used additives and admixtures [3–5]. Due to the optimised combination of its mix components SCC is capable to compact itself only under its own weight without the internal or external vibration energy and deaerates itself almost completely while flowing in the formwork. Furthermore, SCC is able to fill all recesses and reinforcement spaces, even in high reinforced concrete members and flows free of segregation near to level balance. These specific material properties were achieved by the excellent coordination of deformability and segregation resistance. Based on these properties, SCC may contribute to a significant improvement of the quality of concrete structures and open up new fields for the application of concrete [6]. The designation “self-compacting” is based on the fresh concrete properties of this material and therefore the degree of compactability, the deformability and the viscosity in connection with different mix compositions

were investigated very frequently. However, it is also to verify, to what extent the modifications of the mix composition of SCC have an effect on the hardened concrete properties as well as the durability. This fact formed the basis of the creation of a database with currently known data of own and internationally published test results of hardened concrete properties of SCC. Thus the database represents the first step in the analysis and generalisation of the numerous investigations of individual researchers. 2. Scope of the investigation 2.1. Initial situation A good starting point to discuss the hardened material properties of self-compacting concrete is the mix composition of this material. Independent of the fact that SCC consists basically of the same components as normal vibrated concrete, there exist clear differences regarding the concrete composition in order to achieve the desired “self-compacting properties”. On the one hand, SCC has to reach a high segregation resistance and, on the other hand, a high deformability. Therefore the content of ultrafine materials at SCC is essentially higher. For this purpose various fillers, eg limestone powder, fly ash, blast furnace slag, quartzite powder and silica fume, are given to the mixture or the content of cement will be increased. Furthermore, a larger quantity of superplasticiser has to be added

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and stabiliser is used, if required. Fig 1 shows a typical mix composition of SCC compared with normal vibrated concrete in principle [7, 8]. On the basis of the stated differences between the mix composition of SCC and conventional concrete it is necessary to analyse the effects of these modifications on the hardened concrete properties. So, referring to this, the applicability of the currently existing design rules based on years of experience on normal vibrated concrete has to be examined carefully. Reasons for possible differences between the hardened properties of SCC and conventional concrete may be the modified mix composition as mentioned before, the better microstructure and homogeneity of SCC and the absence of vibration. The higher content of ultrafine materials and the accordingly lower content of coarse aggregates change the granular skeleton. This could influence the strength as well as the modulus of elasticity, since the modulus of elasticity of the several components defines that one of the concrete. Moreover, the addition of fillers leads to a different reaction with water and therefore in connection with the use of superplasticiser the water demand changes. Due to the increased content of ultrafines (cement, filler) in SCC the grain-size distribution and packing density will be improved and therefore the bulk of the cement paste is stable, coherent and flowable and the porosity of the interfacial transition zone (ITZ) between aggregate and cement paste is decreased. Consequently, the tensile strength of SCC could be increased compared with conventional concrete, because of the fact that the transfer of tensile loads is supplied by the adhesion of the cement matrix or the bond within the ITZ, by friction and by aggregate interlock between the crack flanks. Caused by the absence of vibration, gross defects by vibration cannot arise but on the other hand the selfdeaeration while flowing in the formwork has to be realised surely in order to avoid new sources of error.

2.2. Aim of the investigation The aim of the performed investigations was to compare the hardened material properties of SCC with those of normal vibrated concrete, ultimately to give a general estimation regarding the application of the current design codes or calculation methods respectively in case of the usage of SCC. Thereupon a database with results of own experimental investigations and a large number of internationally published data of design relevant to hardened material properties of several self-compacting concretes was created [9–11]. The data of properties such as compressive strength, tensile strength, modulus of elasticity, bond strength and the time-dependent deformations were documented and analysed particularly with regard to the given values and limits of the European design code “CEBFIB Model Code” [12]. This strategy seemed to be expedient because the [12] is the basis of the future uniform European rules, the Eurocode 2 [13]. A total overview of the test reports that were used for the creation of the data base is given in [9]. Reports regarding the hardening properties of SCC are quite frequently in literature, for example [6, 14, 15]. However, the import of the published test results into a database is frequently problematic owing to the following facts: – there are often insufficient statements concerning the exact mix compositions, curing conditions and dimensions of used specimens; – there exists a wide spectrum of different mix compositions; – the initial parameters of diverse investigations differ strongly from each other. Nevertheless, by the interpretation of the created database it is possible to recognise the basic relations and dependencies of the hardened properties of self-compacting concrete and to compare them with the wellknown rules, valid for normal concrete. For this purpose all utilised data of considered concrete properties are represented in diagrams. Based on the realities mentioned above, the following sections try to demonstrate the present level of knowledge regarding the most important design-relevant hardened concrete characteristics of SCC. 3. Parameter study of the hardened material properties of SCC 3.1. Compressive strength

Fig 1. Comparison of typical mix compositions of SCC and normal vibrated concrete

In general, in national and international codes concrete is classified on the basis of its compressive strength, because compressive strength is the most important mechanical property of concrete for the most applications. Since the compressive strength depends on the mechanical properties of the hardened cement paste and the adhesion within the ITZ, it is of interest whether the

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differences in the concrete composition and the positive changes in the microstructure, as mentioned before, have an effect on the short and long term load-bearing behaviour. Moreover, clarification is still necessary to determine whether the hardening process and the ultimate strengths of SCC and conventional concrete differ. Corresponding to the characteristic compressive strength fck of cylinders and cubes, concrete is classified in concrete grades. As is known, there exists a certain dependence on the specimen geometry with conventional concrete [9]:

f c, cyl (150 / 300) f c, cube (150)

= 0,8 ... 0,85.

f c, cube (150)

= 0,9 ... 1,00.

Mostly the compressive strength of SCC and normal vibrated concrete at the age of 28 days of similar composition does not differ drastically, but in a few cases higher values were observed for SCC. Compared with the majority of the published test results, the tendency becomes obvious that at the same water-cement ratios higher compressive strengths were reached for SCC. This fact gets along with the decreasing water-binder-ratio corresponding to the rising amount of fillers. However, an explicit research programme regarding this topic does not exist so far and therefore a generalised conclusion cannot be drawn. The strength development of SCC is subjected to similar dependencies like conventional concrete in general (Fig 2). Some of the published test results show that an increase of the cement content and a reduction of rel. com pressive strength ratio f cm (t) / f cm

filler content at the same time cause an increase in concrete strength. For young SCC (aged up to 7 days) the relative compressive strength spreads to a greater extent as given in the Model Code 90, whereas higher values as well as lower values are reached. Especially when limestone powder is used, higher compressive strengths are noticeable at the beginning of the hardening process. At higher concrete ages SCC often exceeds the valid range according to the given limits by Model Code 90. Using fly ash or silica fume this will be caused by the pozzolanic effect of these fillers. 3.2. Tensile strength

However, my own tests carried out in Leipzig have shown that this well-known relation between cylinders and cubes could not be confirmed with SCC in the expected magnitude. A clearly lower dependency was ascertained:

f c, cyl (150 / 300)

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All parameters, which influence the characteristics of the microstructure of the cement matrix and of the ITZ, are of decisive importance in regard to the tensile load bearing behaviour. Fig 3 shows the arranged data of the splitting tensile strength of several self-compacting concretes. By evaluating the created database it can be shown, that the most of the measured values are within the valid range of current regulations for normal vibrated concrete. However, in about 30 % of all data points clearly higher splitting tensile strengths were reached. Therefore, the tendency of higher tensile strengths of self-compacting concretes becomes obvious, especially if fly ash and silica fume is applied. Presumably the reason for this fact is given by the better microstructure again, especially due to the lower and more evenly distributed porosity within the interfacial transition zone with SCC, which is caused by the higher content of ultrafines. Further on, the denser cement matrix of SCC enables a better load transfer. The time development of the tensile strength of SCC and normal vibrated concrete is subject to a similar dependence. Only few publications about SCC refer to a more rapid increase of the tensile strength in comparison to compressive strength [14].

1.8 rapidly hardening cem ents acc. to C E B -F IB M o del C ode 90

slow ly hardening cem ents acc. to C E B -F IB M o del C ode 90

1.4

1.0

used fillers: fly ash, silica fum e lim eston e p ow d er, qua rtzite filler blast furnace slag w itho ut filler unknow n

0.6

0.2 13

7

21

28

fly ash + quartzite filler or silica fum e + lim esto ne pow de r or silica fum e + q uartzite fille r blast furnace slag + silica fu m e or blast furnace slag + fly ash

56

90 C oncrete age [days]

Fig 2. Development of compressive strength of SCC with time in comparison with the regulations of Model Code 90 [12]

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3.3. Modulus of elasticity As it is known, the modulus of elasticity of concrete depends on the proportion of the Young’s modules of the individual components and their percentage by volume. Thus, the modulus of elasticity of concrete increases with higher contents of aggregates of high rigidity, whereas it decreases with increasing hardened cement paste content and increasing porosity. For this reason lower values of modulus of elasticity can be expected, because of the higher content of ultrafines and additives as dominating factors and the accordingly lower content of coarse, stiff aggregates with SCC. The evaluation of the data really shows the fact that the modulus of elasticity of SCC is within the lower half of the scattering range according to the Model Code 90. More exactly, the average value valid for conventional concrete represents the upper limit for SCC, whereas all values were always referred to the mean compressive strength (Fig 4). 3.4. Time-dependent deformations

splitting tensile strength [M P a]

Shrinkage and creep are very complex processes regarding the restructuring several components of the concrete structure caused by changes in the humidity balance. Furthermore, these time-dependent investigations require time and high technological expenditure. Due to this fact only few data of the plastic shrinkage and the autogenous shrinkage of SCC as well as the time-dependent deformation behaviour under load are published in literature and very different conclusions about these material properties are stated. The drying shrinkage of SCC, however, is examined several times. A general agreement exists on the fact that SCC is influenced in the same way by the water-cement ratio and the curing method as normal vibrated concrete. The modified aggregate combination, especially the relation of coarse and fine aggregates as well as fineness (Blaine)

and content of ultrafines seems to influence the shrinkage deformations. Thus such deformations of SCC can increase due to a lower content of coarse aggregate and the minimum paste volume, which must be present for ensuring the optimal self-compaction of SCC without segregation. As a result, the conclusion could be drawn that the shrinkage deformations of SCC can achieve clearly higher values than the ones of comparable normal vibrated concretes. However, a denser microstructure of the cement paste can be achieved by addition of fillers with a fineness larger than that of cement, whereby the shrinkage can be affected positively. So, it is possible to modify the SCC mix in such a way that smaller shrinkage deformations appear, similar to those of normal vibrated concrete. Fig 5 shows the relationship between shrinkage and concrete age. The identified areas mark the limits for shrinkage deformations of C20 up to C80 with a relative humidity of 60 % and notional member size of 50 according to the Model Code 90, since all considered self-compacting concretes of the database meet these conditions. In the majority of the evaluated data the shrinkage of SCC is 10 to 50 % higher than the one of conventional concrete. Remarkable is the substantially steeper rise of the deformations, particularly for young concrete aged up to 28 days. With rising age the deformations approach to the limit values of the current standard. Partly similar and in some cases smaller deformations were observed, especially when limestone powder was used in the concrete mix. The early age shrinkage of SCC is substantially stronger pronounced in contrast to conventional concrete, which can be related to the increased flour grain portion. 3.5. Other aspects Due to the fact that the bond behaviour is strongly affected by the reinforcement properties on the one hand

10 used fillers: fly ash , silica fum e lim eston e p ow de r, qua rtzite filler blast furnace slag fly ash + q ua rtzite filler unknow n

9 8 7 6 5 4 3

range of sp litting tensile stre ngth a cc. to C E B -F IB M o d e l C od e 9 0

2 1 0

15

25

35

45

55

65 75 85 m ean com pressive strength [M P a]

Fig 3. Data base of the splitting strength of SCC with reference to the corresponding compressive strength in comparison with the regulations of Model Code 90 [12]

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50

40 rang e of m od ulus of elasticity acc. to C E B -F IB M odel C o de 90

30

20 used fillers: fly a sh, silica fum e lim e stone po w der, q uartzite filler blast furnace slag w ith out fille r

10

fly a sh + quartzite filler or silica fum e + lim estone pow der blast furnace slag + silica fum e unkn ow n

0 0

10

20

30

40

50

60 70 80 90 m ea n co m p ressive stren g th [M P a]

Fig 4. Data base of the modulus of elasticity of SCC with reference to the corresponding compressive strength in comparison with the regulations of Model Code 90 [12]

0

7 14 21 28 35

56 63

91

concrete age [days] 168 18 2

112

0 ra n g e o f sh rin ka g e fo r C 8 0 a cc. to C E B -F IB M o d e l C o d e 9 0

-200 ra n g e o f sh rin ka g e fo r C 2 0 a cc. to C E B -F IB M o d e l C o d e 9 0

-400

shrinkage [m m /m ]

-600 u se d fille rs: fly a sh , silica fu m e lim e sto n e p o w d e r, q u a rtzite fille r b la st fu rn a ce sla g silica fu m e + qu a rtzite fille r b la st fu rn a ce sla g + fly a sh w ith o u t fille r

-800

-1000

-1200

Fig 5. Data base of the shrinking deformations of SCC at different concrete ages in comparison with the regulations of Model Code 90 [12]

and the surrounding matrix on the other hand the bond behaviour of SCC is different from that one of conventional concrete. In our own tests an improvement of the bond stiffness in the serviceability limit state and a very ductile bond behaviour after reaching the maximum load was ascertained for SCC [16–20]. However, the maximum bond strength of SCC is lower than that of a normal vibrated concrete of comparable strength. A positive effect of the high segregation resistance of SCC is the better homogeneity. Hence, the concrete strength could be more evenly distributed referring to the overall member. Indeed, in some investigations it was found that the concrete strength measured at different locations of a construction member spreads less than in members of conventional concrete [21]. 4. Conclusions The described investigations show that an exact identity between the mechanical properties of SCC and normal

vibrated concrete does not exist. The results of the interpretation of the data base can be summarised as follows: – The concrete strength of SCC and conventional concrete is similar under comparable conditions, whereas the tendency is obvious that SCC shows higher strengths with same water-cement ratios. The definite relation, however, is still to be clarified. – The development of concrete strength with time is similar. Deviations are to be recognised depending on the type of filler. – The dependence of the compressive strength on the specimen geometry of SCC is only inarticulately pronounced compared with the well-known relation of conventional concrete. However, this fact is subject to review. – The splitting tensile strength achieves clearly higher values, partly up to 40 % higher than in the current standard. Thus, there is a need for action regarding the minimum amount of reinforcement. The modulus of elasticity of SCC is slightly lower

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but within the upper half of the standardised limits. – The shrinking deformations of SCC are up to 50 % higher, especially at concretes aged up to 28 days. Regarding the creep deformations there are only insufficient test results known, thus it is necessary to carry out further investigations. – The bond behaviour of reinforcement in SCC is partly better than in comparable vibrated concrete. Based on these facts, it can be concluded that extra design rules for SCC may not be necessary. However, it seems to be useful to add regulations regarding the minimum reinforcement and the time-dependent deformations to the current standards. In this regard further research projects are required to interpret the dependencies of the hardened material properties of SCC more precisely. Referring to this the influence of any parameter, eg type of cement and filler as well as their portion, water-binder/ -cement ratio, proportion of fine and coarse aggregates and fineness have to be investigated specifically. To benefit from the advantages of SCC not only the fresh concrete properties but also the design relevant hardened material properties have to be known accurately. Only in this way SCC can be used conveniently and a realistic calculation of structural members made of this innovative material is possible. References 1.

Okamura, H. Expectation to the New Concreting Material. Cement and Concrete Journal, No 475. Cement Association of Japan, 1986 (in Japanese).

2.

Okamura, H. and Ozawa, K. Mix Design for Self Compacting Concrete. Concrete Library International, No 25. Japan Society of Civil Engineers, June 1995, p. 107–120.

3.

Skarendahl, A. The Presnt – the Future. In: Proceedings of the 3rd International RILEM Symposium on Self-Compacting Concrete. Reykjavik, Iceland, 17-20 Aug 2003. Ed by O. Wallevik and I. Nielsson, RILEM Publication s.a.r.1, Bagneux, France, 2003, p. 6–14.

4.

Walraven, J. Structural Aspects of Self-Compacting Concrete. In: Proceedings of the 3rd International RILEM Symposium on Self-Compacting Concrete. Reykjavik, Iceland, 17–20 Aug 2003. Ed by O. Wallevik and I. Nielsson, RILEM Publication, Bagneux, France, 2003, p. 15–22.

5.

6.

Wallevik, O. Rheologa – a Scientific Approach to Develop Self-Compacting Concrete. In: Proceedings of the 3rd International RILEM Symposium on Self-Compacting Concrete. Reykjavik, Iceland, 17–20 Aug 2003. Ed by O. Wallevik and I. Nielsson, RILEM Publication, Bagneux, France, 2003, p. 23–31. Skarendahl, A. and Petersson, Ö (eds). Proceedings of the 1st International RILEM Symposium on Self-Compacting Concrete. Stockholm, Sweden, Sept 13-14, 1999. Cachan, France: RILEM Publications, 1999. 786 p.

7.

Holschemacher, K. and Weiße, D. Self-Compacting Concrete in Practice. Concrete Plant International, No 1, 2002, p. 74–81.

8.

Holschemacher, K. and Weiße, D. Structural Aspects of Self-Compacting Concrete. New Building Materials and Construction World, July 2002, p. 8–12.

9.

Holschemacher, K. and Klug, Y. A Data Base for the Evaluation of Hardened Properties of SCC. In: Leipzig Annual Civil Engineering Report No 7. University of Leipzig, Leipzig, 2002, p. 123–134.

10. Klug, Y. and Holschemacher, K. Material Properties of Hardened Self-Compacting Concrete. In: Proceedings of the International Conference on Performance of Construction Materials in the New Millennium – a New Era of Building, Cairo, Egypt, 18–20 Feb 2003. Ed by A. S. ElDieb, M. M. Reda Taha and S. L. Lissel, Elmaarefa Printing House, 2003. 11. Klug, Y. and Holschemacher, K. Comparison of the Hardened Properties of Self-Compacting and Normal Vibrated Concrete. In: Proceedings of the 3rd International RILEM Symposium on Self-Compacting Concrete. Reykjavik, Iceland, 17–20 Aug 2003. Ed by O. Wallevik and I. Nielsson, RILEM Publication, Bagneux, France, 2003. 12. CEB-FIB Model Code 1990. Design Code. Lausanne, Switzerland: Thomas Telford Services Ltd, 1991. 637 p. 13. Eurocode 2: Design of Concrete Structures. Draft July 2002. 14. RILEM Publications Pro 7: Proceedings of the 1st RILEM International Symposium, Stockholm, Sweden, 13–14 Sept, 1999. Ed by Å. Skarendahl and Ö. Petersson, RILEM Publications, France, 1999. 804 p. 15. RILEM Publications Pro 33: Self-Compacting Concrete. Proceedings of the 3rd International RILEM Symposium, Reykjavik, Iceland, 17–20 Aug, 2003, Ed by O. Wallevik and I. Nielsson, RILEM Publications, Bagneux, France, 2003. 1048 p. 16. Holschemacher, K.; Klug, Y.; Weiße, D.; König, G. and Dehn, F. Bond Behaviour of Reinforcement in Self-Compacting Concrete (SCC). In: Proceedings of the 2nd International Structural Engineering and Construction Conference (ISEC02), Roma, Italy, 23–26 Sept 2003. 17. König, G.; Holschemacher, K.; Dehn, F. and Weiße, D. Bond of Reinforcement in Self-Compacting Concrete under Monotonic and Cyclic Loading. In: Proceedings of the 3rd International RILEM Symposium on Self-Compacting Concrete. Reykjavik, Iceland, 17-20 Aug 2003. Ed by O. Wallevik and I. Nielsson, RILEM Publication, Bagneux, France, 2003, p. 15–22. 18. König, G.; Holschemacher, K.; Dehn, F. and Weiße, D. Self-Compacting Concrete - Time Development of Material Properties and Bond Behaviour. In: Proceedings of the 2nd International Symposium on Self-Compacting Concrete, Tokyo. Oct, 23–25, 2001, p. 507–516. 19. König, G.; Holschemacher, K.; Dehn, F. and Weiße, D. Determination of the Bond Creep Coefficient for Self-Compacting Concrete. In: Proceedings of the 3rd International Symposium on Bond in Concrete - From Research to Standards. Budapest, Hungary, Nov. 20–22, 2002. Ed by G. L. Balasz, P. J. M. Bartos, J. Cairns and A. Borosnyoi, 2002. 20. Holschemacher, K. and Weiße, D. Self-Compacting Concrete Made with Sand-Rich Particle Fractions. In: IABSE Symposium Towards a Better Built Environment – Innovation, Sustainability, Information Technology, Melbourne, Australia, 8–13 Sept, 2002. 21. Khayat, K. H.; Manai, K. and Trudel, A. In Situ Mechanical Properties of Wall Elements Cast Using Self-Consolidating Concrete. ACI Materials Journal, Vol 96, Issue 6, 1997, p. 491–500.

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JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT http:/www.jcem.vgtu.lt

2004, Vol X, No 4, 267–276

SCHEDULING CONSTRUCTION PROJECTS WITH RESOURCES ACCESSIBILITY LIMITED AND CHANGEABLE IN TIME Piotr Jaúkowski1, Anna Sobotka2 1Doctor

Eng, Faculty of Civil and Sanitary Engineering, Lublin University of Technology, ul. Nadbystrzycka 40, 20-618 Lublin, Poland. E-mail: [email protected] 2Assoc Prof, Faculty of Civil and Sanitary Engineering, Lublin University of Technology, ul. Nadbystrzycka 40,20-618 Lublin, Poland. E-mail: [email protected] Received 31 Aug 2004; accepted 28 Oct 2004

Abstract. This paper aims at solving the problem of minimising the construction project duration in deterministic conditions when the accessibility of renewable resources is limited and changeable in time (workforce, machines and equipment). Particular construction processes (with various levels of complexity) must be conducted in the established technological order and can be executed in different technological and organisational variants (different contractors, technologies, and ways of using resources). To solve this problem the authors are using evolutionary algorithm. For the assessment of solutions generated by evolutionary algorithm, the authors have worked out a heuristic algorithm (of resources allocation and project duration calculation). This methodology seems to produce similar outcomes when juxtaposed with other solutions obtained by research works carried out using comparable methodologies. The paper contains an example of practical application of evolutionary algorithm for construction project planning within resources and time constraints. Keywords: project scheduling, time and resources constraints, evolutionary algorithm, metaheuristic methods, suboptimal solution, minimising project duration.

1. Introduction The process of planning how to execute a construction project on every stage should take into account the existing conditions (eg feasible technologicalorganisational variants) and limitations (resources accessibility limits). As the result of planning, the optimal project schedule should be developed. The approaches in resources constrained project scheduling can be divided into: a) searching for optimal solutions using integer programming, branch and bound technique, dynamic and binary programming; b) searching for suboptimal solutions using heuristic algorithms, including: – specialised heuristics, – metaheuristic methods – taboo search method, simulated annealing, genetic algorithms. The artificial intelligence methods are also applied in the form of expert systems, neural networks and hybrid systems. 2. Literature review The issue of scheduling is often described as the task of integer programming. In such tasks the vector of

decision variables usually takes the form of binary vector [1–6]. Precise procedures of single-criterion optimisation of schedules are mainly based on the branch and bound method [2, 7]. Branch and bound algorithm allowing to determine a set of active schedules was worked out, among others, by Dorndorf et al. An active schedule is one in which no process can begin earlier without violating technological or resource limitations, or delay another process. The algorithm takes account of limitations and uses them to reduce the area of search. As a result, a set of possible dates for starting processes and thereby a set of feasible solutions (only feasible solutions) is restricted. Using precise algorithms to solve serious practical problems is impossible because of length of time needed for calculations and due to the limited memory capacity of the computer [4, 9, 10]. This has resulted in the formation of several approximation methods employing the heuristic approach. The methods can be divided into two groups: specialised heuristic and metaheuristic. Specialised heuristic methods are used to solve only one optimisation problem. In previous researches in the subject there are many examples for concrete problems and algorithms. For example, R. Marcinkowski [4] worked out a heuristic algorithm of project scheduling with various process technologies (multi-mode), time constraints

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and existing limits of renewable resources availability. To solve the problem the author used B. F. Talbot’s idea of algorithm [6]. M. Prystupa [5] worked out a heuristic algorithm for allocation of contractors and scheduling construction projects for situations where utility is maximised. He analyses the case where carrying out tasks will bring the investor profits which will depend on the time of their completion (usefulness is function of the completion date). This algorithm is based on iterative allocation of contractors for tasks. Among the most popular heuristics solving scheduling problems are priority heuristics. These methods include two phases. In the first one, a so-called priority list, a list of processes is prepared and arranged according to decreasing values of priorities calculated on the basis of an assumed rule. In the other, the start and finish times of these processes are calculated so as to keep all the constraints. In this phase, one of the two methods of tasks scheduling is used: parallel or serial, which differ in the way of solving resources conflicts. In the serial methods [11–14] only one process is considered at a time, the one with the highest priority, in order to define its start time. If a process cannot be started at a given moment because of the lack of resources, then its execution is put off till the earliest time possible when resources are available. The procedure ends with the last element in the list. In a parallel method [9, 10] more processes are considered simultaneously. In the successive steps of the algorithm, a set can be defined including processes with the highest priorities and which can start at the moment because all their predecessors were carried out. There are no best priority rule producing best results for different problems and structures of projects. For this reason, H. Khamooshi [15] has modified the existing approach to establish process priorities. The procedure worked out by him consists in dividing a project into parts and using different priority rule for each part. He presents this approach in the form of a dynamic programming model. R. Slowinski, B. Soniewski and J. Weglarz [10] suggested employing a cluster of many rules instead of one priority rule, and then choosing the best one. To solve single-criterion optimisation project scheduling problems, metaheuristic algorithms are used as well. They define only a certain pattern of optimisation procedure which must be adapted for particular applications. The most frequently used metaheuristic methods are as follows: simulated annealing, taboo search and evolutionary algorithms. Both simulated annealing and taboo search methods belong to the group of neighbourhood local search algorithms [16]. They search the area of feasible solutions passing from a current solution to a neighbouring one (the definition of „neighbourhood” and a way of neighbouring solutions generation, depend upon the nature of the problem). In taboo search method, the notion of neighbourhood refers to a given solution and to the algorithm step. In successive iterations the

best solutions found last are removed from neighbourhood. Such solutions are called taboo solutions, ie forbidden in next iterations. It makes easier to find global optimum and eliminate the area of local optimum. This approach also limits cycles in algorithm performance. In simulated annealing algorithms, if the neighbouring solution is better than a current one, it becomes a new current solution in the successive iteration. If it is worse, it can become a current solution in the successive iteration with certain probability dependent on the deterioration value of criterion function. The idea of imitating processes taking place in nature used in local search methods, is also used in evolutionary algorithms. Evolutionary algorithms work as computer systems for solving problems according to rules observed in the evolution of live organisms. The rules involve system structure, and ways of their functioning and adapting to existing conditions. A characteristic feature of this approach in solving optimisation problems is creating a population of individuals representing solutions in a form of chromosomes. As in nature, better adapted individuals – solutions better from the point of view of an objective function – stand a better chance of survival and development. Some examples of employing evolutionary algorithms for solving scheduling projects in industry (both in problems of job-shop type and network planning) were worked out by P. Husbands [17]. H. Li et al [18] use improved genetic algorithm to facilitate time-cost optimisation. M. Pawlak [11] uses evolutionary algorithm for resources levelling in scheduling of industrial production. He employed direct solutions in the form of chromosomes in which successive genes mark the beginning data of carrying out a process. It required working out a procedure repairing solutions (chromosomes) which would meet model limiting conditions (order dependencies between processes). Evolutionary algorithms are classified by many authors [3, 7, 17, 19] as methods based on artificial intelligence, ie algorithms acting like human behaviour. Apart from evolutionary algorithms, there are also artificial neural networks [20], expert systems [21] and hybrid systems [19], using evolutionary algorithms employed for solving scheduling problems. Because of the fact that practical application of accurate methods of project scheduling is limited (high level of complexity of the practical problems), and due to imperfection of heuristic methods, the authors search in the present study for the suboptimal schedules of construction projects basing on evolutionary algorithms. The method proposed by the authors does not provide the optimal solution, the results are close to the optimum and obtained in a short computation time. Because the evolutionary algorithms may be easily adapted to solving any type of problems, the proposed method is versatile and allows defining the case conditions and constraints freely.

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Data input Minimising project duration using evolutionary algorithm

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Initation

Individuals assessment – calculating Individuals assessment – calculating value of value of objective function using heuristic algorithm of objectiveheuristic function using algorithm of project project duration calculation duration calculation

Estimating solutions using the algorithm of project duration calculation

Remembering / protection of the best individual

Schedule of project Fig 1. Diagram of the method of construction project scheduling

Calculating value of individual fitness function

3. Description of a problem solution method A schematic diagram of the proposed method of solving construction project scheduling problems is shown in Fig 1. The project schedule is the result of calculations carried out by means of two algorithms described below. The evolutionary algorithm is used for searching the minimal project duration. The heuristic algorithm enables resource allocation for which the accessibility is limited and changeable in time and project duration calculation. Successive steps of evolutionary algorithm are shown in Fig 2. In Table 1 basic notions used in describing evolutionary algorithms are explained. Initiation consists in creating initial population – a specified number of individuals (chromosomes). In the article the authors used individuals’ representation (feasible solutions) in the form of genes’ string containing information about ways of carrying out processes and values of priorities (Fig 3).

Is termination condition met? no Selection

Explaining notions

Population

Set of individuals (solutions)

Individuals

Solutions encoded as chromosomes (strings of bits with information about ways of carrying out processes and processes priorities values)

Chromosomes

String of genes

Gene

Also called a feature, mark, detector; in the study genes encode ways of carrying out a given process or/and value of process priority depending on placing the gene in a chromosome

Fitness function It is the amount of adaptation of a given individual in population; it enables the selection of individuals best adapted in accordance with an evolutionary rule of surviving „the strongest” Generation

A successive iteration in the algorithm

Giving results

Cross-over Mutation

Fig 2. Evolutionary algorithm

Process number

Table 1. The notions used in evolutionary algorithm description Notion

yes

1

2

...

N

1

2

...

N

1

3

...

2

4

3

...

5

Codes of the way of carrying out processes

Values of processes priorities

Fig 3. Representation of feasible solutions (individuals) in the form of chromosomes

In the assumed way of individuals’ representation, the number of process is identified through the position of a gene in chromosome. Initial population is created randomly. The process consists of creating a number of chromosomes defined in advance. Particular genes assume values chosen randomly with equal probability from their variability interval. The procedure individual assessment is used to calculate the project duration for each individual of current population and thus it enables chromosomes assessment ASSES[i]. The algorithm of project duration calculation is shown in Fig 4. It consists in interactive allocation of renewable resources for processes and in setting dates

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P. Jaúkowski, A. Sobotka / JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT – 2004, Vol X, No 4, 267–276

1) TIME:=0 2) Setting a set of processes SET which can be alloted with resources at a moment TIME. yes

SET=∅?

no

3) Selecting NRPROC process with the highest priority from the set SET

yes 9)

4) Are the remaining resources for carrying out NRPROC process available?

Project duration calculation

no

5)

Change resourcesavailability availabilityengaged engagedinin Change in in resorces carrying out NRPROC process carrying out NRPROC process

6) Removing NRPROC process from the set SET

Removing NRPROC process from the set SET, adding it to set SET2

no

SET=∅? yes

7) Change in value of TIME variable

8) Processes i, for which 02,5), kuriuose yra maþas smulkiø daleliø kiekis. Tokiuose cemento skiediniuose efektyvu pakeisti 5 % cemento pelenais, nes gaunamos adekvaèios skiedinio savybës. Tiriant maþos ir vidutinës klasës stiprumo betonus buvo nustatyta, kad, padidinus cemento teðlos kieká pelenø priedu ir sumaþinus cemento kieká, galima gauti pakankamas betono savybes norimoms betono klasëms uþtikrinti, be to, pagerëja betono miðinio technologiðkumas ir iki 33 % sumaþëja portlandcemenèio sànaudos. Panaudojus pelenø priedà savaime susitankinanèio betono miðinio gamyboje, sumaþëja iðsisluoksniavimas ir vandens atsiskyrimas. Sukietëjusio betono tyrimø duomenys parodë, kad pelenø priedas padidina betono gniuþdomàjá stiprá (iki 15 %), sumaþina tûrines susitraukimo deformacijas (iki 31,6 %), padidina plastines deformacijas (iki 38 %), tamprumo modulá (iki 15 %) ir modifikuoja kitas betono savybes. Be to, pelenø panaudojimas padeda spræsti aktualià ekologinæ problemà – antriniø þaliavø panaudojimà betono miðiniø gamyboje. Raktaþodþiai: savaime susitankinantis betonas, pelenai, superplastiklis, hidratacija, gniuþdomasis stipris, susitraukimas, ilgaamþiðkumas.

P. Vainiûnas, V. Popovas ir A. Jarmolajev. Gelþbetoninës plokðtës praspaudimo suirimo netiesinis 3 d modeliavimas // Journal of Civil Engineering and Management. Vilnius: Technika, 2004, t. X, Nr. 4, p. 311–316. Ðiuolaikinës trimaèio kompiuterinio modeliavimo technologijos, taikant skaitinës analizës baigtiniø elementø metodus netiesinëje aproksimacijoje, leidþia tikroviðkai imituoti gelþbetoniniø konstrukcijø elgsenà sudëtingomis átempiø-deformacijø sàlygomis visuose apkrovimo etapuose, áskaitant tamprumo-plastiðkumo bûklës stadijà betone ir armatûroje, suirimo mechanizmo formavimàsi ir vystymàsi. Kritinës konstrukcijø elgsenos skaitmeninio modeliavimo metodai perþengia moksliniø tyrimø ribas ir yra vis daþniau taikomi projektavimo praktikoje sprendþiant sudëtingas inþinerines uþduotis, kai paaiðkëja, kad reglamentuojamo projektavimo normoms áprasto analizës metodo galimybës yra nepakankamos. Tokiu atveju labai svarbu patikrinti skaièiuojamuosius modelius pagal patikimus eksperimentinius skaitmeniniø analogiðkø modeliø tyrimus. Apþvelgiamas kompleksiniø, teoriniø eksperimentiniø ir skaitiniø plokðèios gelþbetonio perdangos plokðtës ir kolonos sujungimo mazgo skaièiavimo ir analizës metodø atvejis. Tyrimo objektas kelia ypatingà susidomëjimà, kadangi ðio tipo

SANTRAUKOS .....................................................................................................................................................................................

Ic

konstrukcijø praktiniams skaièiavimo metodus pagal skirtingø ðaliø projektavimo normas reikia tikslinti ir papildomai apdoroti. Pateikti ir sugretinti su natûriniø bandymø rezultatais gelþbetoninës perdangos plokðtës ir kolonos sandûros kompiuterinio modelio netiesinës skaitinës analizës rezultatai. Raktaþodþiai: projektavimo ir analizës metodai, eksperimentiniai tyrimai, 3D skaitinis modeliavimas, netiesinë analizë, praspaudimas, plokðtës ir kolonos sujungimas, pleiðëjimo vaizdas, átempiø deformacijø pasiskirstymas, suirimo mechanizmas.

S. Wandahl. Vizualios vertës iðaiðkinimas – metodas efektyviai veiklai // Journal of Civil Engineering and Management. Vilnius: Technika, 2004, t. X, Nr. 4, p. 317–326. Tirti statybos projektø konceptualizacijos procesai, t. y. proceso sutrumpinti apraðymai. Sprendþiama, kà reikëtø daryti, kad klientà pasiektø tinkama produkcija, t. y. bûtø nustatyti pagrásti klientø ir vartotojø poreikiai, á kuriuos atsiþvelgiant bûtø keliami reikalavimai pastatui. Tyrimas atliktas remiantis keitimosi informacija proceso analize. Iðaiðkëjo, kad ðiuo metu keitimosi informacija procesas tolimas nuo idealaus. Be to, buvo nagrinëta, kokie veiksniai lemia keitimosi informacija proceso efektyvumà, ir pasiûlytas ðio proceso valdymo metodas. Vizualios vertës iðaiðkinimo metodas (Visual Value Clarification) yra paprasta pagalbinë priemonë klientams ir projekto grupei keièiantis informacija. Ji padeda klientui suvokti savo poreikius ir juos tiksliau perduoti. Tai leidþia projekto grupei geriau suvokti kliento poreikius. Raktaþodþiai: keitimosi informacija procesas, reikalavimai, klientø poreikiai, efektyvumas, vertës, vizualizacija.

IIa

ÐÅÔÅÐÀÒÛ M. Áîëòðèê, Â. Íèêèòèí, Á. Áàöêåëü-Áæîçîâñêà. Âëèÿíèå îïðåäåëåííûõ òåõíîëîãè÷åñêèõ ïàðàìåòðîâ íà ìîðîçîñòîéêîñòü ñòåíîâîé êåðàìèêè // Journal of Civil Engineering and Management. Âèëüíþñ: Òåõíèêà, 2004, X ò., ¹ 4, c. 249–253. Ïðåäñòàâëåíà ìíîãîêîìïîíåíòíàÿ ìîäåëü, êîòîðàÿ ïîçâîëÿåò îïðåäåëèòü âëèÿíèå êîëè÷åñòâà è ñîñòàâà ïåñêà, ìàêñèìàëüíóþ òåìïåðàòóðó îáæèãà, à òàêæå âðåìÿ åå âëèÿíèÿ íà ìîðîçîñòîéêîñòü êåðàìè÷åñêèõ èçäåëèé. Ìîäåëü ïîñòðîåíà íà îñíîâå ýêñïåðèìåíòàëüíûõ èññëåäîâàíèé, ïðîâåäåííûõ ïî òåîðèè ïëàíèðîâàíèÿ ýêñïåðèìåíòà. Èçëîæåíû ðåçóëüòàòû ýêñïåðèìåíòà, â êîòîðîì èçìåðÿåìûìè âåëè÷èíàìè, â ÷àñòíîñòè, áûëè ïîòåðÿ ìàññû è íàáóõàíèå îáðàçöîâ âî âðåìÿ èõ íàñûùåíèÿ âîäîé. Ïîëó÷åííûå ðåçóëüòàòû îáðàáîòàíû ñòàòèñòè÷åñêè è âûâåäåíà ìàòåìàòè÷åñêàÿ ìîäåëü. Îñîáîå âíèìàíèå óäåëåíî êà÷åñòâó ñòàòèñòè÷åñêîãî è ôèçè÷åñêîãî àíàëèçà ïîëó÷åííîé ìîäåëè. Êëþ÷åâûå ñëîâà: ñòðîèòåëüíàÿ êåðàìèêà, ñòàòèñòèêî-ýêñïåðèìåíòàëüíîå ìîäåëèðîâàíèå, ïðîöåññ îáæèãà, ñîñòàâ êåðàìè÷åñêîé ñìåñè, ìîðîçîñòîéêîñòü, íàáóõàíèå â âîäå..

Ã. Êîëèíà, Æ. Ìîðî, Ä. Ñèíòðà. Ýêñïåðèìåíòàëüíîå èññëåäîâàíèå òåìïåðàòóðíîé ïîëçó÷åñòè è äðóãèõ ÿâëåíèé â áåòîíå ïðè âîçäåéñòâèè âûñîêèõ òåìïåðàòóð // Journal of Civil Engineering and Management. Âèëüíþñ: Òåõíèêà, 2004, X ò., ¹ 4, c. 255–260. Ïðåäñòàâëåíû ýêñïåðèìåíòàëüíûå èññëåäîâàíèÿ òåìïåðàòóðíîé ïîëçó÷åñòè, à òàêæå óïðóãîé è ñâîáîäíîé òåìïåðàòóðíîé äåôîðìàöèè îáû÷íûõ, âûñîêîïðî÷íûõ è âûñîêîêà÷åñòâåííûõ áåòîíîâ ïðè âîçäåéñòâèè âûñîêèõ òåìïåðàòóð. Ñ ïîìîùüþ íîâîãî îáîðóäîâàíèÿ ìîæíî ñîçäàòü êðèòè÷åcêîå è ýêñïëóàòàöèîííîå ñîñòîÿíèÿ ñ îäíîðîäíûì ðàñïðåäåëåíèåì òåìïåðàòóðû âíóòðè îáðàçöà. Èñïûòàíèå îáðàçöîâ ïðîèçâîäèëîñü ïðè ïîñòîÿííîì èçìåíåíèè ñêîðîñòè ðîñòà íàãðåâà è íàãðóçêè (ïðè âîçäåéñòâèè íàðóæíîé íàãðóçêè). Òåìïåðàòóðà ïîäíèìàëàñü èíòåðâàëàìè. Äëÿ äîñòèæåíèÿ âíóòðåííåé ñòàáèëèçàöèè òåìïåðàòóðà â êàæäîì èíòåðâàëå îïðåäåëåííîå âðåìÿ âûäåðæèâàëàñü ïîñòîÿííîé. Äëÿ îïðåäåëåíèÿ èçìåíåíèé ñâîéñòâ áåòîíà ïîñëå ïåðâîãî öèêëà íàãðåâà íåêîòîðûå îáðàçöû ïîäâåðãàëèñü íàãðåâó âî âòîðîì öèêëå. Ïðåäñòàâëåíû è îáñóæäåíû íåêîòîðûå ðåçóëüòàòû. Êëþ÷åâûå ñëîâà: áåòîí ïîä âîçäåéñòâèåì âûñîêèõ òåìïåðàòóð, ýêñïåðèìåíòàëüíûé ìåòîä, êðèòè÷åñêîå ñîñòîÿíèå, ýêñïëóàòàöèîííîå ñîñòîÿíèå, òåìïåðàòóðíàÿ ïîëçó÷åñòü, óïðóãàÿ äåôîðìàöèÿ, ñâîáîäíàÿ òåìïåðàòóðíàÿ äåôîðìàöèÿ.

K. Õîëøåìàõåð. Ñâîéñòâà çàòâåðäåâøåãî ñàìîóïëîòíÿþùåãîñÿ áåòîíà // Journal of Civil Engineering and Management. Âèëüíþñ: Òåõíèêà, 2004, X ò., ¹ 4, c. 261–266. Ñàìîóïëîòíÿþùèéñÿ áåòîí (ÑÓÁ) – íîâûé ñòðîèòåëüíûé ìàòåðèàë, êîòîðûé âñëåäñòâèå ìîäèôèêàöèè ñîñòàâà ñìåñè îáëàäàåò õîðîøèìè ðåîëîãè÷åñêèìè ñâîéñòâàìè. Âìåñòå ñ òåì èçìåíÿþòñÿ ñâîéñòâà íå òîëüêî òâåðäåþùåãî, íî è çàòâåðäåâøåãî áåòîíà. Áîëüøèì ïðåèìóùåñòâîì ÑÓÁ ïî ñðàâíåíèþ ñ îáû÷íûìè óïëîòíÿåìûìè áåòîíàìè ÿâëÿåòñÿ åãî òåõíîëîãè÷íîñòü.  ïîñëåäíèå ãîäû çíà÷èòåëüíî óâåëè÷èëîñü ïðèìåíåíèå ñàìîóïëîòíÿþùèõñÿ áåòîíîâ â ñòðîèòåëüíûõ êîíñòðóêöèÿõ. Îäíàêî âàæíî çíàòü, ìîæíî ëè ïðèìåíÿòü íîðìû ïðîåêòèðîâàíèÿ, ïðåäíàçíà÷åííûå äëÿ îáû÷íûõ áåòîíîâ (Model Code 90 è Eurocode 2), ïðè ïðîåêòèðîâàíèè êîíñòðóêöèé èç ÑÓÁ. Ñ ýòîé öåëüþ â ñòàòüå àíàëèçèðóþòñÿ ýêñïåðèìåíòàëüíûå èññëåäîâàíèÿ àâòîðà è äðóãèõ èññëåäîâàòåëåé. Èññëåäîâàëèñü ñâîéñòâà ñàìîóïëîòíÿþùèõñÿ áåòîíîâ: ïðî÷íîñòü ïðè ñæàòèè è ðàñòÿæåíèè, ìîäóëü óïðóãîñòè, ñöåïëåíèå áåòîíà è àðìàòóðû, äëèòåëüíûå äåôîðìàöèè. Ïðåäñòàâëåíû ðåçóëüòàòû ñðàâíèòåëüíîãî àíàëèçà. Êëþ÷åâûå ñëîâà: ñàìîóïëîòíÿþùèéñÿ áåòîí, ñâîéñòâà çàòâåðäåâøåãî áåòîíà, ïðî÷íîñòü ïðè ðàñòÿæåíèè, ìîäóëü óïðóãîñòè, ïîëçó÷åñòü è óñàäêà, ñöåïëåíèå áåòîíà è àðìàòóðû.

Ï. ßñêîâñêè, À. Ñîáîòêà. Ïëàíèðîâàíèå ñòðîèòåëüíûõ ïðîåêòîâ ïðè íàëè÷èè îãðàíè÷åííûõ ðåñóðñîâ è íåïîñòîÿííîì âðåìåíè // Journal of Civil Engineering and Management. Âèëüíþñ: Òåõíèêà, 2004, X ò., ¹ 4, c. 267–276. Öåëüþ ñòàòüè áûëî ðàçðåøèòü ïðîáëåìû, ñâÿçàííûå ñ óìåíüøåíèåì ïðîäîëæèòåëüíîñòè ñòðîèòåëüñòâà ïðè çàäàííûõ óñëîâèÿõ, îãðàíè÷åííûõ ðåñóðñàõ è íåïîñòîÿííîì âðåìåíè ýêñïëóàòàöèè òðóäîâîé ñèëû, ìàøèí, îáîðóäîâàíèÿ. Êîíêðåòíûå ñòðîèòåëüíûå ïðîöåññû äîëæíû âûïîëíÿòüñÿ â óñòàíîâëåííîì òåõíîëîãè÷åñêîì ïîðÿäêå è â ðàçíûõ òåõíîëîãè÷åñêèõ è îðãàíèçàöèîííûõ âàðèàíòàõ (ðàçíûå ïîäðÿä÷èêè, òåõíîëîãèè, ñïîñîáû èñïîëüçîâàíèÿ ðåñóðñîâ). Äëÿ ðåøåíèÿ ýòîé ïðîáëåìû àâòîðû èñïîëüçîâàëè àëãîðèòìû ðàçâèòèÿ. Äëÿ îöåíêè ðåøåíèé, êàñàþùèõñÿ ðàñïðåäåëåíèÿ ðåñóðñîâ è ðàñ÷åòà ïðîäîëæèòåëüíîñòè ñòðîèòåëüñòâà, ïîëó÷åííûõ ñ ïîìîùüþ àëãîðèòìà ðàçâèòèÿ, àâòîðû èñïîëüçîâàëè ýóðèñòè÷åñêèé àëãîðèòì. Áëàãîäàðÿ ýòîé ìåòîäîëîãèè ïîëó÷åí ðåçóëüòàò, àíàëîãè÷íûé ðåøåíèÿì, ïîëó÷åííûì ïî äðóãèì ìåòîäèêàì. Ïðåäñòàâëåí ïðèìåð ïðàêòè÷åñêîãî ïðèìåíåíèÿ àëãîðèòìà ðàçâèòèÿ äëÿ ïëàíèðîâàíèÿ ñòðîèòåëüíûõ ïðîåêòîâ ïðè îãðàíè÷åííûõ ðåñóðñàõ è âðåìåíè. Êëþ÷åâûå ñëîâà: ïëàíèðîâàíèå ïðîåêòîâ, îãðàíè÷åíèÿ âðåìåíè è ðåñóðñîâ, àëãîðèòì ðàçâèòèÿ, ìåòà-ýóðèñòè÷åñêèå ìåòîäû, ñóá-îïòèìàëüíûå ðåøåíèÿ, óìåíüøàåìàÿ ïðîäîëæèòåëüíîñòü ïðîåêòà.

ÐÅÔÅÐÀÒÛ ....................................................................................................................................................................... IIb À. Þîçàïàéòèñ, À. Íîðêóñ. Aíàëèç ïåðåìåùåíèé íåñèììåòðè÷íî çàãðóæåííîé âèñÿ÷åé íåðàñòÿæèìîé íèòè // Journal of Civil Engineering and Management. Âèëüíþñ: Òåõíèêà, 2004, X ò., ¹ 4, c. 277–284. Èññëåäóåòñÿ ïîâåäåíèå íåñèììåòðè÷íî çàãðóæåííîé ãèáêîé âèñÿ÷åé íåðàñòÿæèìîé íèòè ïàðàáîëè÷åñêîãî î÷åðòàíèÿ. Àíàëèçèðóþòñÿ âåðòèêàëüíûå è ãîðèçîíòàëüíûå êèíåìàòè÷åñêèå ïåðåìåùåíèÿ ãèáêîé âèñÿ÷åé íèòè ïîä äåéñòâèåì äîïîëíèòåëüíîé ðàâíîìåðíî ðàñïðåäåëåííîé íà ïîëîâèíå ïðîëåòà íàãðóçêè. Ïðèâîäÿòñÿ àíàëèòè÷åñêèå âûðàæåíèÿ ïî îïðåäåëåíèþ êèíåìàòè÷åñêèõ ïåðåìåùåíèé äàííîé íèòè. Ðàññìàòðèâàåòñÿ äåôîðìàòèâíîñòü ãèáêîé âèñÿ÷åé íåðàñòÿæèìîé íèòè îòíîñèòåëüíî èçìåíåíèÿ åå êðèâèçíû. Àíàëèçèðóþòñÿ ìåðû ïî ñòàáèëèçàöèè íà÷àëüíîé ïàðàáîëè÷åñêîé ôîðìû ãèáêîé âèñÿ÷åé íèòè. Ïðèâîäÿòñÿ ðåçóëüòàòû ÷èñëåííîãî ýêñïåðèìåíòà. Êëþ÷åâûå ñëîâà: âèñÿ÷èå êîíñòðóêöèè, íåñèììåòðè÷íîå çàãðóæåíèå, íåëèíåéíûé àíàëèç, íåóïðóãèå (êèíåìàòè÷åñêèå) ïåðåìåùåíèÿ.

Ð. Ìà÷þëàéòèñ, À. Êè÷àéòå, Ä. Íàãðîöêåíå, Ã. Êóäàáåíå. Îïðåäåëåíèå ìîðîçîñòîéêîñòè îáëèöîâî÷íûõ êåðàìè÷åñêèõ ïëèòîê // Journal of Civil Engineering and Management. Âèëüíþñ: Òåõíèêà, 2004, X ò., ¹ 4, c. 285–293. Ïðîáëåìà ìîðîçîñòîéêîñòè àêòóàëüíà äëÿ âñåõ îáëèöîâî÷íûõ ìàòåðèàëîâ, îñîáåííî äëÿ êåðàìè÷åñêèõ ãëàçóðîâàííûõ ïëèòîê. Àíàëèçèðóÿ ðàçðóøåíèÿ êåðàìè÷åñêèõ ïëèòîê, ñëåäóåò îáðàòèòü âíèìàíèå íà íà÷àëüíûå ïðèçíàêè ðàçðóøåíèÿ.  ðàáîòå ïðåäñòàâëåíà íîâàÿ îöåíêà ýêñïëóàòàöèîííîé ìîðîçîñòîéêîñòè ïî îñòàòî÷íîé ïëîùàäè è îñòàòî÷íîé ìàññå ïîñëå ìîäåëèðîâàííûõ ýêñïëóàòàöèîííûõ öèêëîâ. Èñïîëüçóÿ íîâóþ îöåíêó, ìîæíî ïðîãíîçèðîâàòü ìîðîçîñòîéêîñòü ïëèòîê äàæå â ñàìûõ àãðåññèâíûõ óñëîâèÿõ ýêñïëóàòàöèè. Êàê è äëÿ äðóãèõ êåðàìè÷åñêèõ èçäåëèé, â àñïåêòå ìîðîçîñòîéêîñòè âàæíûì ïîêàçàòåëåì ÿâëÿåòñÿ ïîêàçàòåëü ðåçåðâíîñòè ïîðîâîãî ïðîñòðàíñòâà. Äëÿ îïåðàòèâíîãî îïðåäåëåíèÿ ìîðîçîñòîéêîñòè ñëåäóåò èñïîëüçîâàòü íåñêîëüêî ïîêàçàòåëåé, ìíîãîìåðíî êîððåëèðóþùèõ ñ ïîêàçàòåëåì ýêñïëóàòàöèîííîé ìîðîçîñòîéêîñòè. Êëþ÷åâûå ñëîâà: ýêñïëóàòàöèîííàÿ ìîðîçîñòîéêîñòü, êåðàìè÷åñêèå ãëàçóðîâàííûå ïëèòêè, ðåçåðâíîñòü ïîðîâîãî ïðîñòðàíñòâà, îñòàòî÷íàÿ ìàññà ïëèòêè, îñòàòî÷íàÿ ïîâåðõíîñòü ïëèòêè.

Ð. Íîðâàéøåíå, À. Áóðëèíãèñ, Â. Ñòàíêÿâè÷þñ. Èññëåäîâàíèå äîëãîâå÷íîñòè êðàøåíûõ øòóêàòóðíûõ ôàñàäîâ çäàíèé ñ èñïîëüçîâàíèåì èñêóññòâåííûõ äîæäåé // Journal of Civil Engineering and Management. Âèëüíþñ: Òåõíèêà, 2004, X ò., ¹ 4, c. 295–302. Íàðóæíàÿ ïîâåðõíîñòü ñòåí çäàíèé íàõîäèòñÿ ïîä ïîñòîÿííûì âîçäåéñòâèåì íàòóðàëüíûõ êëèìàòè÷åñêèõ ôàêòîðîâ è óñëîâèé àíòðîïîëîãè÷åñêîé äåÿòåëüíîñòè. Äî íàñòîÿùåãî âðåìåíè ìíîãèå èññëåäîâàíèÿ áûëè ïîñâÿùåíû äîëãîâå÷íîñòè ôàñàäíûõ êðàñîê, îäíàêî íå ó÷èòûâàëîñü âëèÿíèå àòìîñôåðíîãî çàãðÿçíåíèÿ, êîòîðîå, áåçóñëîâíî, îêàçûâàåò âîçäåéñòâèå íà ýñòåòè÷åñêèå è ôèçè÷åñêèå ñâîéñòâà êðàñî÷íûõ ïîêðûòèé. Ïîýòîìó ïîñëå èçó÷åíèÿ ñîñòàâà êèñëîòíûõ äîæäåé è èõ ïðîäîëæèòåëüíîñòè áûë ñîñòàâëåí öèêë âîçäåéñòâèÿ óâëàæíåíèÿ–ñóøêè. Âî âðåìÿ öèêëà óâëàæíåíèÿ îáðàçöû ïîëèâàëèñü äèñòèëëèðîâàííîé âîäîé è èñêóññòâåííûì êèñëîòíûì âîäÿíûì ðàñòâîðîì. Ïîñëå ïðîâåäåíèÿ èñïûòàíèé íà öèêëè÷åñêîå âîçäåéñòâèå óâëàæíåíèÿ è ñóøêè íà îáðàçöû ñ èñïîëüçîâàííûì äèñòèëëèðîâàííîé âîäû è ðàñòâîðîâ îêèñë¸ííîé âîäû ñòàëî î÷åâèäíî, ÷òî áîëåå êèñëûå âîäÿíûå ðàñòâîðû ñèëüíåå ðàçðóøàþò îêðàøåííûå ïîêðûòèÿ è ïîýòîìó ïðîïîðöèîíàëüíî óâåëè÷èâàåòñÿ âîäîïîãëîùåíèå öåìåíòíîèçâåñòêîâîé øòóêàòóðêè. Ïîêðûòèÿ êðàñîê, óìåíüøàþùèå âîäîïîãëîùåíèå øòóêàòóðêè ÷åðåç îêðàøåííóþ ïîâåðõíîñòü, çàäåðæèâàþò ïðîöåññ êàðáîíèçàöèè â îêðàøåííîé øòóêàòóðêå. Êðèâûå ïîãëîùåíèÿ âîäû îáðàçöàìè ïîñëå ïðîõîæäåíèÿ 40, 70, 100 öèêëîâ ñâèäåòåëüñòâóþò î òîì, ÷òî â ðåçóëüòàòå óòðàòû çàùèòíûõ êà÷åñòâ ïîêðûòèé â öåìåíòíî-èçâåñòêîâîé øòóêàòóðêå ïðîèñõîäÿò ïðîöåññû, óìåíüøàþùèå ìàêñèìàëüíîå âîäîïîãëîùåíèå îáðàçöà, õîòÿ ñêîðîñòü âîäîïîãëîùåíèÿ è óâåëè÷èâàåòñÿ. Ñ öåëüþ óñòàíîâëåíèÿ äîëãîâå÷íîñòè ñòðîèòåëüíûõ ìàòåðèàëîâ, èñïîëüçóåìûõ äëÿ îáëèöîâêè çäàíèé â ìåñòíîñòÿõ ñ ÷àñòûìè êèñëîòíûìè äîæäÿìè, â êëèìàòè÷åñêèå èñïûòàíèÿ íà äîëãîâå÷íîñòü öåëåñîîáðàçíî âêëþ÷àòü ôàêòîð âëèÿíèÿ êèñëîòíûõ îñàäêîâ. Êëþ÷åâûå ñëîâà: êëèìàòîñòîéêîñòü, äîëãîâå÷íîñòü, êèñëîòíûå îñàäêè, öèêë âîçäåéñòâèÿ óâëàæíåíèÿ–ñóøêè, âîäîïîãëîùåíèå, êàðáîíèçàöèÿ.

Æ. Ðóäæ¸íèñ, Ý. Èâàíàóñêàñ. Èññëåäîâàíèÿ ïî ýôôåêòèâíîìó ècïîëüçîâàíèþ çîëû â áåòîíàõ // Journal of Civil Engineering and Management. Âèëüíþñ: Òåõíèêà, 2004, X ò., ¹ 4, c. 303–309. Èññëåäîâàíî âëèÿíèå çîëû èç òåðìîôèêàöèîííûõ ýëåêòðîñòàíöèé íà ïðîöåññû ãèäðàòàöèè öåìåíòà, ñâîéñòâà öåìåíòíîãî òåñòà è êàìíÿ, ðàñòâîðà, îáû÷íîãî è ñàìîóïëîòíÿþùåãîñÿ áåòîíà, âî âðåìÿ êîòîðûõ ÷àñòü öåìåíòà áûëà çàìåíåíà ÷àñòüþ çîëû (îò 5 % äî 33 %). Áûëî óñòàíîâëåíî, ÷òî ñâîéñòâà öåìåíòíîãî êàìíÿ è òåñòà, èçãîòîâëåííîãî èç ñìåñè çîëû è öåìåíòà, óëó÷øàþòñÿ ïðè èñïîëüçîâàíèè ñóïåðïëàñòèôèêàòîðà „Visco Crete-3“ íà îñíîâå ïîëèêàðáîêñèëüíîé êèñëîòû. Òàêæå áûëî óñòàíîâëåíî, ÷òî äîáàâêà çîëû îêàçûâàåò íåîäèíàêîâîå âëèÿíèå íà ïðîöåññû ãèäðàòàöèè öåìåíòà: êîëè÷åñòâî ñâîáîäíîãî Ñà(ÎÍ)2 â öåìåíòíîì êàìíå óìåíüøàåòñÿ, à êîëè÷åñòâî ñòàáèëüíûõ ãèäðîñèëèêàòîâ óâåëè÷èâàåòñÿ. Ýòî ïîçâîëÿåò óòâåðæäàòü, ÷òî óâåëè÷èâàåòñÿ êîððîçèîíîñòîéêîñòü è äîëãîâå÷íîñòü öåìåíòíîãî êàìíÿ. Ïðè èññëåäîâàíèè öåìåíòíûõ ðàñòâîðîâ áûëî óñòàíîâëåíî, ÷òî çîëó ëó÷øå èñïîëüçîâàòü ñ êðóïíûì ïåñêîì (Ìêð>2,5), ñ íåáîëüøèì êîëè÷åñòâîì ìåëêèõ ÷àñòèö.  òàêèõ öåìåíòíûõ ðàñòâîðàõ

IIc

..................................................................................................................................................................................... ÐÅÔÅÐÀÒÛ ýôôåêòèâíà çàìåíà 5 % öåìåíòà çîëîé, òàê êàê â ðåçóëüòàòå ïîëó÷àþòñÿ àäåêâàòíûå ñâîéñòâà ðàñòâîðà. Ïðè èññëåäîâàíèè áåòîíà íèçêèõ è ñðåäíèõ êëàññîâ ïðî÷íîñòè áûëî óñòàíîâëåíî, ÷òî áëàãîäàðÿ óâåëè÷åíèþ êîëè÷åñòâà öåìåíòíîãî òåñòà â ðåçóëüòàòå äîáàâëåíèÿ çîëû è óìåíüøåíèþ ðàñõîäà öåìåíòà ìîæíî ïîëó÷èòü äîñòàòî÷íóþ ïðî÷íîñòü áåòîíà äëÿ ïðîåêòèðóåìîãî êëàññà, óëó÷øèòü òåõíîëîãè÷íîñòü áåòîííîé ñìåñè è óìåíüøèòü ðàñõîä öåìåíòà äî 33 %. Áëàãîäàðÿ èñïîëüçîâàíèþ çîëû äëÿ ïðîèçâîäñòâà ñàìîóïëîòíÿþùåãîñÿ áåòîíà óìåíüøàåòñÿ ðàññëàèâàíèå è âîäîîòòàëêèâàíèå. Èññëåäîâàíèÿ çàòâåðäåâøåãî áåòîíà ïîêàçàëè, ÷òî äîáàâêà çîëû ïîâûøàåò ïðî÷íîñòü áåòîíà (äî 15 %), óìåíüøàåò óñàäêó (äî 31,6 %), óâåëè÷èâàåò ïëàñòè÷íûå äåôîðìàöèè (äî 38 %), ìîäóëü óïðóãîñòè (äî 15 %) è ìîäèôèöèðóåò äðóãèå ñâîéñòâà áåòîíà. Ïðè èñïîëüçîâàíèè çîëû ðåøàåòñÿ àêòóàëüíàÿ ýêîëîãè÷åñêàÿ ïðîáëåìà – óòèëèçàöèÿ âòîðè÷íûõ ìàòåðèàëîâ â ïðîèçâîäñòâå áåòîííûõ ñìåñåé. Êëþ÷åâûå ñëîâà: ñàìîóïëîòíÿþùèéñÿ áåòîí, çîëà, ñóïåðïëàñòèôèêàòîð, ãèäðàòàöèÿ, ïðî÷íîñòü, óñàäêà, äîëãîâå÷íîñòü.

Ï. Âàéíþíàñ, Â. Ïîïîâ, À. ßðìîëàåâ. Òðåõìåðíîå íåëèíåéíîå ìîäåëèðîâàíèå ðàçðóøåíèÿ æåëåçîáåòîííîé ïëèòû ïðè ïðîäàâëèâàíèè // Journal of Civil Engineering and Management. Âèëüíþñ: Òåõíèêà, 2004, X ò., ¹ 4, c. 311–316. Ñîâðåìåííûå òåõíîëîãèè òðåõìåðíîãî êîìïüþòåðíîãî ìîäåëèðîâàíèÿ ñ èñïîëüçîâàíèåì êîíå÷íî-ýëåìåíòíûõ ìåòîäîâ ÷èñëåííîãî àíàëèçà â íåëèíåéíîé ïîñòàíîâêå ïîçâîëÿþò äîñòîâåðíî èìèòèðîâàòü ðåàëüíîå ïîâåäåíèå æåëåçîáåòîííûõ êîíñòðóêöèé â óñëîâèÿõ ñëîæíîãî íàïðÿæåííî-äåôîðìèðîâàííîãî ñîñòîÿíèÿ íà âñåõ ýòàïàõ èõ ðàáîòû ïîä íàãðóçêîé, âêëþ÷àÿ ñòàäèþ óïðóãî-ïëàñòè÷åñêîãî ñîñòîÿíèÿ â áåòîíå è àðìàòóðå, ôîðìèðîâàíèÿ è ðàçâèòèÿ ìåõàíèçìà ðàçðóøåíèÿ. Ìåòîäû ÷èñëåííîãî ìîäåëèðîâàíèÿ êðèòè÷åñêîãî ïîâåäåíèÿ êîíñòðóêöèé âûõîäÿò çà ðàìêè ÷èñòî íàó÷íûõ èññëåäîâàíèé, íàõîäÿ âñ¸ áîëåå øèðîêîå ïðèìåíåíèå â ðåàëüíîé ïðàêòèêå ïðîåêòèðîâàíèÿ ïðè ðåøåíèè íåòðèâèàëüíûõ èíæåíåðíûõ çàäà÷, êîãäà âîçìîæíîñòè àíàëèòè÷åñêîãî ïîäõîäà, ïðèíÿòîãî â äåéñòâóþùèõ íîðìàõ ïðîåêòèðîâàíèÿ, îêàçûâàþòñÿ íåäîñòàòî÷íûìè. Ïðè ýòîì îñîáîå âíèìàíèå ñëåäóåò óäåëÿòü âåðèôèêàöèè ðàñ÷¸òíûõ ìîäåëåé ïî ðåçóëüòàòàì äîñòîâåðíûõ ýêñïåðèìåíòàëüíûõ èññëåäîâàíèé àíàëîãîâ ÷èñëåííûõ ìîäåëåé.  ñòàòüå ðàññìîòðåí ñëó÷àé êîìïëåêñíîãî ýêñïåðèìåíòàëüíî-òåîðåòè÷åñêîãî è ÷èñëåííîãî ìåòîäîâ ðàñ÷¸òà è àíàëèçà óçëà ñîåäèíåíèÿ ïëîñêîé æåëåçîáåòîííîé ïëèòû ïåðåêðûòèÿ ñ êîëîííîé. Îáúåêò èññëåäîâàíèÿ ïðåäñòàâëÿåò îñîáûé èíòåðåñ, ïîñêîëüêó ïðàêòè÷åñêèå ìåòîäû ðàñ÷¸òà äàííîãî òèïà êîíñòðóêöèé ïî íîðìàì ïðîåêòèðîâàíèÿ ðàçíûõ ñòðàí íóæäàþòñÿ â óòî÷íåíèè è äîðàáîòêå. Ïðåäñòàâëåíû è ñîïîñòàâëåíû ñ ðåçóëüòàòàìè íàòóðíûõ èñïûòàíèé äàííûå íåëèíåéíîãî ÷èñëåííîãî àíàëèçà òð¸õìåðíîé êîìïüþòåðíîé ìîäåëè ñòûêà æåëåçîáåòîííîé ïëèòû ïåðåêðûòèÿ ñ êîëîííîé. Êëþ÷åâûå ñëîâà: ìåòîäû ðàñ÷åòà è àíàëèçà, ýêñïåðèìåíòàëüíûå èññëåäîâàíèÿ, òðåõìåðíîå ÷èñëåííîå ìîäåëèðîâàíèå, íåëèíåéíûé àíàëèç, ñòûê ïëèòû ñ êîëîííîé, êàðòèíà òðåùèíîîáðàçîâàíèÿ, ðàñïðåäåëåíèå íàïðÿæåíèé è äåôîðìàöèé, ìåõàíèçì ðàçðóøåíèÿ.

Ñ. Âàíäàë. Visual Value Clarification – ìåòîä ýôôåêòèâíîé äåÿòåëüíîñòè ing and Management. Âèëüíþñ: Òåõíèêà, 2004, X ò., ¹ 4, c. 317–326.

// Journal of Civil Engineer-

Ñòàâèëàñü öåëü èññëåäîâàòü ïðîöåññû êîíöåïòóàëèçàöèè ïðîåêòîâ, ò. å. ïðåäñòàâèòü èõ êðàòêîå îïèñàíèå. Ïðîàíàëèçèðîâàíî, êàê îáåñïå÷èòü ñíàáæåíèå êëèåíòà íåîáõîäèìîé ïðîäóêöèåé, îïðåäåëèòü ïîäëèííûå è îáîñíîâàííûå ïîòðåáíîñòè ïîòðåáèòåëåé è òðàíñôîðìèðîâàòü èõ â òðåáîâàíèÿ, ïðåäúÿâëÿåìûå ê ñîîðóæåíèÿì. Èññëåäîâàíèå îñíîâàíî íà àíàëèçå ëèòåðàòóðû íà òåìó îáìåíà èíôîðìàöèåé. Óñòàíîâëåíî, ÷òî â íàñòîÿùåå âðåìÿ ïðîöåññ îáìåíà èíôîðìàöèåé äàëåêî íå èäåàëåí. Òàêæå ðàññìàòðèâàëîñü, êàêèå ôàêòîðû îêàçûâàþò âëèÿíèå íà ýôôåêòèâíîñòü ïðîöåññà îáìåíà èíôîðìàöèåé. Ïðåäëîæåí ìåòîä óïðàâëåíèÿ ýòèì ïðîöåññîì. Ìåòîä ðàñøèôðîâêè âèçóàëüíîãî çíà÷åíèÿ (Visual Value Clarification) ÿâëÿåòñÿ ïðîñòûì ñïîñîáîì îêàçàíèÿ ïîìîùè êëèåíòàì è êîìàíäå ïðîåêòèðîâùèêîâ â ïðîöåññå îáìåíà èíôîðìàöèåé. Îí ïîìîãàåò êëèåíòàì îñîçíàòü ñîáñòâåííûå ïîäëèííûå íóæäû, ñîçäàòü ëó÷øóþ ôîðìó ïåðåäà÷è èíôîðìàöèè è òåì ñàìûì ïîìî÷ü êîìàíäå îïòèìèçèðîâàòü ïðîåêò. Êëþ÷åâûå ñëîâà: ïðîöåññ îáìåíà èíôîðìàöèåé, òðåáîâàíèÿ, ïîòðåáíîñòè êëèåíòîâ, ýôôåêòèâíîñòü, çíà÷åíèÿ, âèçóàëèçàöèÿ.

REVIEWERS The Editor–in-Chief and the Editors wish to express sincere gratitude to the following people for reviewing papers submitted to the Journal of Civil Engineering and Management during 2003 and 2004: Piotr Aliawdin University of Zielona Góra, Poland Antanas Alikonis Vilnius Gediminas Technical University, Lithuania Leonid A. Aliphanov Sibproektstal konstrukcija, Russia Jonas Amðiejus Vilnius Gediminas Technical University, Lithuania Arnolds Apse Riga Technical University, Latvia Juozas Atkoèiûnas Vilnius Gediminas Technical University, Lithuania Darius Baèinskas Vilnius Gediminas Technical University, Lithuania Rogerio Bairrao Portuguese National Laboratory for Civil Engineering, Portugal Toader A. Balan MIDASoft Inc, USA. Gyorgy L. Balazs Budapest University of Technology and Economics, Hungary Robertas Balevièius Vilnius Gediminas Technical University, Lithuania Audrius Banaitis Vilnius Gediminas Technical University, Lithuania Rimantas Barauskas Kaunas University of Technology, Lithuania Romualdas Bauðys Vilnius Gediminas Technical University, Lithuania Zoja Bednarek The Main School of Fire Service, Poland Erik Bejder Aalborg University, Denmark Rimantas Belevièius Vilnius Gediminas Technical University, Lithuania Wolfgang J. Berger University of Natural Resources and Applied Life Sciences, Austria Michal Boltryk Bialystok Technical University, Poland Adam Borkowski Institute of Fundamental Technological Research, Poland Janis Brauns Latvia University of Agriculture, Latvia Marios Chryssanthopoulos University of Surrey, UK Horacio Colina Laboratory of Material Analysis and Identification, France Andrzej Czyýewski Gdansk University of Technology, Poland Algirdas E. Èiþas Vilnius Gediminas Technical University, Lithuania Donatas Èygas Vilnius Gediminas Technical University, Lithuania

Petras Èyras Vilnius Gediminas Technical University, Lithuania Juozas Deltuva Kaunas University of Technology, Lithuania Janis Dolacis Latvian State Institute of Wood Chemistry, Latvia Patrick J. Dowling University of Surrey, UK Eugedijus Dulinskas Vilnius Gediminas Technical University, Lithuania Sergiy Yu. Fialko Kiev National University of Buildings and Architecture, Ukraine Albinas Gailius Vilnius Gediminas Technical University, Lithuania Evaldas Garðka Vilnius University, Lithuania Romualdas Ginevièius Vilnius Gediminas Technical University, Lithuania Olexander Y. Grigorenko National Academy of Sciences, Ukraine Aleksandr A. Gusakov Moscow State University of Civil Engineering, Russia Christian Hellmich Vienna University of Technology, Austria Edward J. Jaselskis Iowa State University, USA Vidmantas Jokûbaitis Vilnius Gediminas Technical University, Lithuania Arvydas Juodis Kaunas University of Technology, Lithuania Arvydas Jurkða Vilnius Gediminas Technical University, Lithuania Pranciðkus Juðkevièius Vilnius Gediminas Technical University, Lithuania Arnas Kaèeniauskas Vilnius Gediminas Technical University, Lithuania Rimantas Kaèianauskas Vilnius Gediminas Technical University, Lithuania Artûras Kaklauskas Vilnius Gediminas Technical University, Lithuania Gintaris Kaklauskas Vilnius Gediminas Technical University, Lithuania Stanislovas Kalanta Vilnius Gediminas Technical University, Lithuania Ipolitas Zenonas Kamaitis Vilnius Gediminas Technical University, Lithuania Antanas Kaminskas Institute of Thermal Insulation, Lithuania Kazys Algirdas Kaminskas Vilnius Gediminas Technical University, Lithuania Oleg Kapliñski Poznan University of Technology, Poland Jûratë Karbauskaitë Institute of Architecture and Construction, Lithuania Asta Kièaitë Vilnius Gediminas Technical University, Lithuania

Antanas Klibavièius Vilnius Gediminas Technical University, Lithuania Halina Koczyk Poznan University of Technology, Poland Ireneusz Kreja Gdansk University of Technology, Poland Antanas Krutinis Vilnius Gediminas Technical University, Lithuania Jurij J. Kuvshynov Moscow State University of Civil Engineering, Russia Audronis K. Kvedaras Vilnius Gediminas Technical University, Lithuania Antanas Laukaitis Institute of Thermal Insulation, Lithuania Alfredas Laurinavièius Vilnius Gediminas Technical University, Lithuania Maùgorzata Lelusz Bialystok Technical University, Poland Mindaugas Leonavièius Vilnius Gediminas Technical University, Lithuania Hau Yan Leung Chu Hai College, Hong Kong Romualdas Maèiulaitis Vilnius Gediminas Technical University, Lithuania Herbert A. Mang Vienna University of Technology, Austria Rene Maquoi University of Liege, Belgium Gediminas Marèiukaitis Vilnius Gediminas Technical University, Lithuania Vytautas Martinaitis Vilnius Gediminas Technical University, Lithuania Sigitas Mitkus Vilnius Gediminas Technical University, Lithuania Dþigita Nagrockienë Vilnius Gediminas Technical University, Lithuania Algirdas Jonas Notkus Vilnius Gediminas Technical University, Lithuania Yoshihiko Ohama Nihon University, Japan Ainars Paeglitis Riga Technical University, Latvia Josifas Parasonis Vilnius Gediminas Technical University, Lithuania Sabina Paulauskaitë Vilnius Gediminas Technical University, Lithuania Friedel Peldschus Leipzig University of Applied Sciences, Germany Petras Pukelis Vilnius Gediminas Technical University, Lithuania Virgaudas Puodþiukas Lithuanian Road Administration, Lithuania Saulius Raslanas Vilnius Gediminas Technical University, Lithuania Erich Raue Bauhaus University Weimar, Germany Karlis Rocens Riga Technical University, Latvia Eugeniusz Roguski The Main School of Fire Service, Poland Sascha van Rooijen CAP SD, Netherlands

Les Ruddock University of Salford, UK Þymantas Rudþionis Kaunas University of Technology, Lithuania Aleksandras Vytautas Rutkauskas Vilnius Gediminas Technical University, Lithuania Leonas Saulis Vilnius Gediminas Technical University, Lithuania Vladimir A. Semionov Eurosoft, Russia Dmitrijs Serdjuks Riga Technical University, Latvia Valery Simbirkin Belarusian Research Institute for Construction, Belarus Henrikas Sivilevièius Vilnius Gediminas Technical University, Lithuania Miroslaw J. Skibniewski Purdue University, USA Martin Skitmore Queensland University of Technology, Australia Alfonsas Skrinska Vilnius Gediminas Technical University, Lithuania Gintautas Skripkiûnas Kaunas University of Technology, Lithuania Brian Sloan Napier University, UK Vytautas Stankevièius Institute of Architecture and Construction, Lithuania Vytautas J. Stauskis Vilnius Gediminas Technical University, Lithuania Vincentas Stragys Vilnius Gediminas Technical University, Lithuania Antanas Ðapalas Vilnius Gediminas Technical University, Lithuania Ritoldas Ðukys Vilnius Gediminas Technical University, Lithuania Romualdas Tamoðaitis Vilnius Gediminas Technical University, Lithuania Tadeusz Trzaskalik Karol Adamiecki University of Economics, Poland Leonas Ustinovièius Vilnius Gediminas Technical University, Lithuania Romualdas Vadlûga Vilnius Gediminas Technical University, Lithuania Egidijus Rytas Vaidogas Vilnius Gediminas Technical University, Lithuania Henryk Walukiewicz Gdansk University of Technology, Poland Zenon Waszczyszyn Cracow University of Technology, Poland Frank Werner Bauhaus University Weimar, Germany Jiri Witzany Czech Technical University, Czech Republic Darius Zabulionis Vilnius Gediminas Technical University, Lithuania Edmundas Kazimieras Zavadskas Vilnius Gediminas Technical University, Lithuania Ipolitas Þidonis University of Ðiauliai, Lithuania Ramunë Þurauskienë Vilnius Gediminas Technical University, Lithuania

ISSN 1392–3730. JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT – 2004, Vol X, No 1

R. BALEVIÈIUS, A. DÞIUGYS, R. KAÈIANAUSKAS Discrete element method and its application to the analysis of penetration into granular media ........... 3 J.-F. DEMONCEAU, J.-P. JASPART Recent investigations into composite sway frames ........................................................................................ 15 M. KOSIOR-KAZBERUK, W. JEZIERSKI Surface scaling resistance of concrete modified with bituminous addition ................................................. 25 M. LELUSZ, D. MALASZKIEWICZ Identification of phenomena occurring in porous structure of cement concrete subjected to cyclic freezing and thawing .......................................................................................................................... 31 J. MALAIÐKIENË, R. MAÈIULAITIS New possibilities of quality regulation for ceramic products ......................................................................... 37 J. MOTAK, J. MACHACEK Experimental behaviour of composite girders with steel undulating web and thin-walled shear connectors Hilti Stripcon ......................................................................................................................... 45 S. RIMKUVIENË, N. LEPKOVA Analysis of experience and efficiency of distance learning Master’s degree programme in construction economics and property management ................................................................................... 51 B. SIEWCZYÑSKI Computer visualisation in urban planning of highway surroundings ............................................................ 61 V. SIMBIRKIN, R. BALEVIÈIUS Long-term strength and deformational analysis of reinforced concrete columns ....................................... 67 E. K. ZAVADSKAS, A. KAKLAUSKAS, A. GULBINAS Multiple criteria decision support web-based system for building refurbishment ........................................ 77

ISSN 1392–3730. JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT – 2004, Vol X, No 2

J. HILDEBRAND, F. WERNER Change of structural condition of welded joints between high-strength fine-grained and structural steels ................................................................................................................................................... 87 R. KARKAUSKAS Optimization of elastic-plastic geometrically non-linear lightweight structures under stiffness and stability constraints ...................................................................................................................................... 97 R. KLIUKAS, A. KUDZYS Probabilistic durability prediction of existing building elements ................................................................... 107 I. KREJA, T. MIKULSKI, C. SZYMCZAK Application of superelements in static analysis of thin-walled structures ................................................. 113 I. POVILAITIENË, A. LAURINAVIÈIUS Reduction of external rail wearing on road curves ...................................................................................... 123 L. SCHUEREMANS, D. VAN GEMERT Assessing the safety of existing structures: reliability based assessment framework, examples and application ................................................................................................................................. 131 Y. SIEFFERT, G. MICHEL, D. MARTIN, D. KELLER AND J.-F. JULLIEN Analysis of diaphragm behaviour in composite multi girder railway bridges ............................................ 143 E. K. ZAVADSKAS, L. USTINOVICHIUS, A. STASIULIONIS Multicriteria valuation of commercial construction projects for investment purposes ............................... 151 KRONIKA ............................................................................................................................................................................ 167

ISSN 1392–3730. JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT – 2004, Vol X, No 3 A. ALEJEV, M. GRIÐKEVIÈIUS, R. ÐUKYS, I. FRITH, A. NORTA Review of fire hazard analysis of Ignalina nuclear power plant ................................................................ 169 J. BRAUNS, K. ROCENS The effect of material strength on the behaviour of concrete-filled steel elements ............................... 177 B. FAGGIANO, G. DE MATTEIS, R. LANDOLFO, F. M. MAZZOLANI Behaviour of aluminium alloy structures under fire ..................................................................................... 183 A. GARSTECKI, A. KNITTER-PIÀTKOWSKA, Z. POZORSKI AND K. ZIOPAJA Damage detection using parameter dependent dynamic experiments and wavelet transformation ....... 191 M. A. GIZEJOWSKI, C. J. BRANICKI, A. M. BARSZCZ, P. KROL Advanced analysis of steel frames with effects of joint deformability and partial strength accounted for ..................................................................................................................................................... 199 H. Y. LEUNG Flexural capacity of concrete beams reinforced with steel and Fibre-reinforced polymer (FRP) bars . 209 A. NORKUS, R. KARKAUSKAS Truss optimization under complex constraints and random loading .......................................................... 217 G. SKRIPKIÛNAS, M. DAUKÐYS Dilatancy of cement slurries with chemical admixtures ............................................................................... 227 V. J. STAUSKIS Changes in subjective acoustical indicators in halls with long and short reverberation times ............. 235 A. ÐAPALAS Composite and interaction effects in steel-concrete structures for higher fire resistance ...................... 241 CHRONICLE ........................................................................................................................................................................ 247

ISSN 1392–3730. JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT – 2004, Vol X, No 4 M. BOÙTRYK, V. NIKITIN, B. BACKIEL-BRZOZOWSKA Influence of some technological factors upon wall ceramics frost resistance ......................................... 249 H. COLINA, G. MOREAU, D. CINTRA Experimental study of transient thermal creep and other phenomena of concrete at high temperature ................................................................................................................................................ 255 K. HOLSCHEMACHER Hardened material properties of self-compacting concrete .......................................................................... 261 P. JAÚKOWSKI, A. SOBOTKA Scheduling construction projects with resources accessibility limited and changeable in time ............. 267 A. JUOZAPAITIS, A. NORKUS Displacement analysis of asymmetrically loaded cable ............................................................................... 277 R. MAÈIULAITIS, A. KIÈAITË, D. NAGROCKIENË, G. KUDABIENË Evaluation of service frost resistance of ceramic facing tiles .................................................................... 285 R. NORVAIÐIENË, A. BURLINGIS, V. STANKEVIÈIUS Durability of the painted rendered facades, when introducing artificial acidic rain solution .................. 295 Þ. RUDÞIONIS, E. IVANAUSKAS Investigations into effective fly ash used in concrete ................................................................................. 303 P. VAINIUNAS, V. POPOVAS, A. JARMOLAJEV Non-linear 3d modelling of RC slab punching shear failure ...................................................................... 311 S. WANDAHL Visual value clarification – a method for an effective brief ....................................................................... 317

Reviewers ........................................................................................................................................................ 333

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o Payment has been made by Bank Transfer to: Vilniaus Bankas AB, Gedimino pr. 12, LT-01103 Vilnius, Lithuania. Account No. LT767044060000317763; Swift Code: CBVI LT 2X All subscriptions are payable in advance. Subscribers are requested to send payment with their order whenever possible. Issues will be sent on receipt of payment. “Technika” contact details: VGTU Publishing House “Technika”, Sauletekio al. 11, LT-10223 Vilnius, Lithuania. Telephone: + 370 5 274 50 38 n Fax: + 370 5 2700112 E-mail: [email protected] n Internet: http://www.jcem.vgtu.lt

Journal of Civil Engineering and Management To order your FREE sample copy, complete and return this order card By post: n VGTU Publishing House “Technika”, Sauletekio al. 11, LT-10223 Vilnius, Lithuania. or n Fax: + 370 5 2700112 To request a sample copy please visit the “Technika” website at http://www.jcem.vgtu.lt

Journal of Civil Engineering and Management 2004 Institutional Subscription Rate ISSN 1392-3730 n Volume 10 (2004) n Frequency: 4 times a year (1 volume of 4 issues)

o Europe and rest of World: 140 EUR JCEM provides a forum for discussion and debate relating to all areas of civil engineering and management. “Technika” contact details: VGTU Publishing House “Technika”, Sauletekio al. 11, LT-10223 Vilnius, Lithuania. Telephone: + 370 5 274 50 38 n Fax: + 370 5 2700112 E-mail: [email protected] n Internet: http://www.jcem.vgtu.lt