环境湿度对混凝土徐变影响研究
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摘要
徐变作为混凝土一种重要的长期性能,对混凝土结构特别是大型混凝土结构有重要的影响。国内外已有众多对徐变的研究。在混凝土徐变的研究中,混凝土所处的环境因素一直是国内外学者关注的焦点。环境因素中的环境湿度被普遍认为是影响混凝土徐变的重要因素。自然环境中干湿循环、混凝土水分散失以及地下结构中高湿环境均会对混凝土长期徐变产生重要影响。目前国内研究中,混凝土内部湿度传导理论相对不足;混凝土徐变计算模型对环境湿度因素考虑较少,相对不完善,与实际相差较大。因此,混凝土湿度徐变的研究有重要的理论价值及工程意义。
基于以上的研究背景,本文依据混凝土湿度传导理论采用有限元方法模拟了混凝土处于不同外部湿度条件下其内部湿度场的分布,并且和已有的混凝土湿度传导经验公式作了对比。结果显示,采用有限元方法不仅可以计算环境恒定湿度条件及湿度变化条件下混凝土内部稳态湿度场和瞬态湿度场,计算模拟混凝土内部湿度场变化与实际吻合良好。根据混凝土内部湿度场的变化结合改进的微预应力固结理论,本文分析了湿度因素对混凝土徐变的影响,分析了恒定湿度条件下混凝土徐变规律以及湿度变化条件下混凝土徐变的规律。在现有分析结果的基础上和现有能考虑混凝土湿度徐变的模型作了对比。改进的微预应力固结理论能良好的反应混凝土在湿度作用下徐变的规律。而且有限元模拟湿度场与改进的微预应力固结理论相结合对于徐变因素考虑更加完整,计算更吻合工程实际。
Creep as one of the most important long-term properties of concrete has important influences on concrete structures especially large-scale concrete structure. Within the researches of concrete creep, environmental factors have always been the concern of many scholars. It is generally accepted that environment humidity as one of the environmental affects concrete creep considerably. The environmental humidity cycling, drying and high level humidity on concrete structures have significant effects on concrete creep. In present domestic researches, studies on humidity diffusion within concrete are relative inadequate; and few models can take comprehensive consideration on humidity factors. So study on effect of environmental humidity is quite helpful to both on theoretical research and engineering practice.
According to humidity diffusion theory of concrete, this paper studied the distribution of humidity field within concrete at both constant humidity condition and variable humidity condition using finite element method. The calculated results are compared with that using empirical method. It can be shown from the comparison that the finite element method it has satisfied accuracy on simulation of interior humidity field of concrete. Coupled with the changing of humidity field within concrete and improved microprestress solidification theory, creep of concrete at constant environment humidity and different humidity levels was studied. The results were compared with that calculated by B3 creep model. It can be concluded that the improved microprestress solidification theory can show the creep at different humidity condition well. Moreover, the coupling finite element method and the improved microprestress solidification theory can have a more comprehensive study on creep of concrete under environment humidity.
基于以上的研究背景,本文依据混凝土湿度传导理论采用有限元方法模拟了混凝土处于不同外部湿度条件下其内部湿度场的分布,并且和已有的混凝土湿度传导经验公式作了对比。结果显示,采用有限元方法不仅可以计算环境恒定湿度条件及湿度变化条件下混凝土内部稳态湿度场和瞬态湿度场,计算模拟混凝土内部湿度场变化与实际吻合良好。根据混凝土内部湿度场的变化结合改进的微预应力固结理论,本文分析了湿度因素对混凝土徐变的影响,分析了恒定湿度条件下混凝土徐变规律以及湿度变化条件下混凝土徐变的规律。在现有分析结果的基础上和现有能考虑混凝土湿度徐变的模型作了对比。改进的微预应力固结理论能良好的反应混凝土在湿度作用下徐变的规律。而且有限元模拟湿度场与改进的微预应力固结理论相结合对于徐变因素考虑更加完整,计算更吻合工程实际。
Creep as one of the most important long-term properties of concrete has important influences on concrete structures especially large-scale concrete structure. Within the researches of concrete creep, environmental factors have always been the concern of many scholars. It is generally accepted that environment humidity as one of the environmental affects concrete creep considerably. The environmental humidity cycling, drying and high level humidity on concrete structures have significant effects on concrete creep. In present domestic researches, studies on humidity diffusion within concrete are relative inadequate; and few models can take comprehensive consideration on humidity factors. So study on effect of environmental humidity is quite helpful to both on theoretical research and engineering practice.
According to humidity diffusion theory of concrete, this paper studied the distribution of humidity field within concrete at both constant humidity condition and variable humidity condition using finite element method. The calculated results are compared with that using empirical method. It can be shown from the comparison that the finite element method it has satisfied accuracy on simulation of interior humidity field of concrete. Coupled with the changing of humidity field within concrete and improved microprestress solidification theory, creep of concrete at constant environment humidity and different humidity levels was studied. The results were compared with that calculated by B3 creep model. It can be concluded that the improved microprestress solidification theory can show the creep at different humidity condition well. Moreover, the coupling finite element method and the improved microprestress solidification theory can have a more comprehensive study on creep of concrete under environment humidity.
引文
[1] ACI Committee 209, 2006, Modelling And Calculation Of Shrinkage And Creep In Hardened Concrete (ACI 209YR-XX), American Concrete Institute, Farmington Hills, Mich., 10 pp.
[2] ACI Committee 209. 1992. Prediction of creep, shrinkage, and temperature effects in concrete structures (209R-92) [M], American Concrete Institute
[3] Al-Alusi, H.R., Berterro, V.V., and Polivka, M., Einflusse der Feuchte auf Schwinden und Kriechen von Beton, Beton-und Stahlbetonbau, 73,No.l,1978,pp.18-23
[4] Ali, I. and C.E. Kesler. Mechanisms of creep in concrete, in American Concrete Institute -- Symposium on Creep of Concrete, 1964: American Concrete Institute, Detroit, MI, United States, 1964, pp. 35-63.
[5] Bazant Z P, Gianluca Cusatis, Luigi Cedolin. 2004. Temperature Effect on Concrete Creep Modeled by Microprestress-Solidification Theory [J]. Journal of Engineering Mechanics (7):691-699.
[6] Bazant Z P, Hauggaard A B, Baweja S. 1997b. Microprestress-solidification theory for concrete creep. II: Algorithm and verification [J], Eng. Mech., 123, 1195-1201
[7] Bazant Z P, Hauggaard, A B, Baweja S, Ulm F J. 1997a. Microprestress -solidification theory for concrete creep. I: Aging and drying effects [J], Eng. Mech., 123, 1188-1194
[8] Bazant Z P, Murphy W P. 1995. Creep and shrinkage prediction model for analysis and design of concrete structures-model B3 [J], Materials and Structures, 28: 357-365
[9] Bazant Z P, Prasannan S. 1989a. Solidification theory for concrete creep I: Formulation [J], Eng. Mech., 115, 1691-1703
[10] Bazant Z P. 1972a. Thermodynamics of interacting continua with surfaces and creep analysis of concrete structures [J], Nucl Eng Des, 20, 149-505
[11] Bazant Z P. 1972b. Thermodynamics of hindered adsorption with application to cement paste and concrete [J], Cement of concrete, (2): 1-16
[12] Bazant Z P. Prasannan, S. 1989b. Solidification theory for concrete creep II: Verification and application [J], Eng. Mech., 115, 1704-1725
[13] Bazant, Z. P. and Wittmann, F. H., Creep and Shrinkage in Concrete Structures, New York: John Wiley & Sons, 1982,305 pp.
[14] Bazant, Z.P. and Panula, L., Simplified prediction of concrete creep and shrinkage from strength and mix, Structural Engineering Report No.78-10/640S, Northwestern University, Evanston, Illinois, Oct. 1978, 24 pp.
[15] Bazant, Z.P. and S. Prasannan, Solidification Theory for Concrete Creep .1. Formulation. Journal of Engineering Mechanics-ASCE, 115(8): 1989, pp. 1691-1703.
[16] Bazant, Z.P., and Panula, L. 1978. Practical prediction of time-dependent deformation of concrete. Material and Structures (RILEM, Paris): PartIII Drying creep. Vol.11(1978),317-328
[17] Bazant, Z.P., et al., Microprestress-solidification theory for concrete creep .1. Aging and drying effects. Journal of Engineering Mechanics-ASCE, 123(11): 1997, p.
[18] Bazant, Z.P., Mathematical Modeling of Creep and Shrinkage of Concrete (RILEM Series). London: John Wiley& Sons, 1982
[19] Bazant, Z.P., Prediction of concrete creep and shrinkage: past, present and future. Nuclear Engineering and Design, 203(1): 2001, pp. 27-38.
[20] Bazant, Z.P., Xi,Y.,and Baweja, S. Improved prediction model for time-dependent deformations of concrete: part 7-Short form of BP-KX model, statistics and extrapolation of short-time data. Matericals and Structures, 26,567-574.
[21] Bemhardt,C.J.,Creep and shrinkage of concrete, Material and Structures, Paris,2,No.8,1969,pp.145-48.
[22] Fuller, A.H. and C.C. Moore, Time Tests of Concrete. ACI Journal, 12: 1916, 302 pp.
[23] Glucklich, J.and ISHAI, O., Creep mechanism in cement mortar, ACI Journal,59,1962,pp,923-48.
[24] Hansen, T.C., Creep and stress relaxation of concrete, Proc. No. 31, Swedish Cement Research Institute: Stockholm, 1960, 112pp.
[25] Hansen, T.C., Creep of Concrete, Bulletin No. 33, Swedish Cement and Concrete Research Institute: Stockholm, 1958, 48pp.
[26] Halt, W.K., Effect of Time Element in Loading Concrete. ASTM Proceedings: 1907,421 pp.
[27] Jensen, R.S. and F.E. Richart, Short-Time Creep Test of Concrete in Compression. ASTM Proceedings, 38: 1938, pp. 410-417.
[28] Kristek, V, Bazant, Z. P.; Zich, M.; and Kohoutkova, A., 2006, Box Girders Box Deflections, Concrete International, V. 23, No. 1, Jan., pp. 55-63.
[29] L'Hermite, R.G. and Mamillan, M., Further results of shrinkage and creep tests, Pro, Int. Conf. on the Structure of Concrete, Cement and Concrete Association: London, 1968,pp.423-33.
[30] Lyman, C.G., Growth and Movement in Portland Cement Concrete. London: Oxford University Press, 1934, 139.
[31] Neville A M, Dilger W H, Brooks J J. 1983. Creep of plain and structural concrete [M], London and New York: Construction Press
[32] Neville, A.M. and W.H. Dilger, Creep of concrete: plain, reinforced, and prestressed. Amsterdam, New York : North-Holland Pub. Co., American Elsevier, 1970, xix, 622.
[33] Neville, A.M., Properties of concrete. 4th and final ed: J. Wiley, 1996.
[34] Neville, A.M., Role of cement in creep of mortar. Journal of the American Concrete Institute, 30(9): 1959, pp. 963-984.
[35] Neville, A.M., Theories of Creep in Concrete. ACI Journal, 52: 1955, pp. 47-60.
[36] Neville, A.M., W.H. Dilger, and J.J. Brooks, Creep of plain and structural concrete: Construction Press, 1983.
[37] Pickett G. 1942. The effect of change in moisture content on the creep of concrete under a sustained load [J], ACI J. 38:333-355
[38] Power,T.C., (1965), Mechanism of shrinkage and reversible creep of hardened cement paste. Proc, Int. Conf. on the struct, of concrete. Cement and Concrete Association, London, U.K., 319-344.
[39] Powers, T.C. (1968). The thermodynamics of volume change and creep. Mat, and structure., Paris, France, 1(6), 487-507.
[40] Troxell, G.E., J.M. Raphael, and R.E. Davis. Long-term Creep and Shrinkage Tests of Plain and Reinforced Concrete.in Cement and Concrete.Los Angeles:ASTM Proceedings,1958,pp.1101-1120.
[41]Troxell,G.E.,RAPHAEL,J.M.and DAVIS,R.E.,Long-time creep and shrinkage tests of plain and reinforced concrete,Porc,ASTM,58,1958,pp.1101-20
[42]Wittmann F H.1980.Properties of hardened cement paste[C],Proc.Int.Congress on Chemistry of Cement(Paris),Vol.Ⅰ,Subtheme Ⅵ-2
[43]过镇海,时旭尔.钢筋混凝土的高温性能及其计算[M].北京:清华大学出版社.1996.
[44]蒋正武,王培铭,等温干燥条件下混凝土内部相对湿度的分布.武汉理工大学学报.2003.25(7):18-20
[45]王光远,论时变结构力学,土木工程学报,2000,33(6):105-107
[46]袁勇,混凝土结构早期裂缝控制,北京:科学出版社,2004
[47]中华人民共和国建设部,混凝土结构设计规范,北京:中国建筑工业出版社,2002.
[48]周履,陈永春.收缩徐变.[M].北京:中国铁道出版社.1994.
[2] ACI Committee 209. 1992. Prediction of creep, shrinkage, and temperature effects in concrete structures (209R-92) [M], American Concrete Institute
[3] Al-Alusi, H.R., Berterro, V.V., and Polivka, M., Einflusse der Feuchte auf Schwinden und Kriechen von Beton, Beton-und Stahlbetonbau, 73,No.l,1978,pp.18-23
[4] Ali, I. and C.E. Kesler. Mechanisms of creep in concrete, in American Concrete Institute -- Symposium on Creep of Concrete, 1964: American Concrete Institute, Detroit, MI, United States, 1964, pp. 35-63.
[5] Bazant Z P, Gianluca Cusatis, Luigi Cedolin. 2004. Temperature Effect on Concrete Creep Modeled by Microprestress-Solidification Theory [J]. Journal of Engineering Mechanics (7):691-699.
[6] Bazant Z P, Hauggaard A B, Baweja S. 1997b. Microprestress-solidification theory for concrete creep. II: Algorithm and verification [J], Eng. Mech., 123, 1195-1201
[7] Bazant Z P, Hauggaard, A B, Baweja S, Ulm F J. 1997a. Microprestress -solidification theory for concrete creep. I: Aging and drying effects [J], Eng. Mech., 123, 1188-1194
[8] Bazant Z P, Murphy W P. 1995. Creep and shrinkage prediction model for analysis and design of concrete structures-model B3 [J], Materials and Structures, 28: 357-365
[9] Bazant Z P, Prasannan S. 1989a. Solidification theory for concrete creep I: Formulation [J], Eng. Mech., 115, 1691-1703
[10] Bazant Z P. 1972a. Thermodynamics of interacting continua with surfaces and creep analysis of concrete structures [J], Nucl Eng Des, 20, 149-505
[11] Bazant Z P. 1972b. Thermodynamics of hindered adsorption with application to cement paste and concrete [J], Cement of concrete, (2): 1-16
[12] Bazant Z P. Prasannan, S. 1989b. Solidification theory for concrete creep II: Verification and application [J], Eng. Mech., 115, 1704-1725
[13] Bazant, Z. P. and Wittmann, F. H., Creep and Shrinkage in Concrete Structures, New York: John Wiley & Sons, 1982,305 pp.
[14] Bazant, Z.P. and Panula, L., Simplified prediction of concrete creep and shrinkage from strength and mix, Structural Engineering Report No.78-10/640S, Northwestern University, Evanston, Illinois, Oct. 1978, 24 pp.
[15] Bazant, Z.P. and S. Prasannan, Solidification Theory for Concrete Creep .1. Formulation. Journal of Engineering Mechanics-ASCE, 115(8): 1989, pp. 1691-1703.
[16] Bazant, Z.P., and Panula, L. 1978. Practical prediction of time-dependent deformation of concrete. Material and Structures (RILEM, Paris): PartIII Drying creep. Vol.11(1978),317-328
[17] Bazant, Z.P., et al., Microprestress-solidification theory for concrete creep .1. Aging and drying effects. Journal of Engineering Mechanics-ASCE, 123(11): 1997, p.
[18] Bazant, Z.P., Mathematical Modeling of Creep and Shrinkage of Concrete (RILEM Series). London: John Wiley& Sons, 1982
[19] Bazant, Z.P., Prediction of concrete creep and shrinkage: past, present and future. Nuclear Engineering and Design, 203(1): 2001, pp. 27-38.
[20] Bazant, Z.P., Xi,Y.,and Baweja, S. Improved prediction model for time-dependent deformations of concrete: part 7-Short form of BP-KX model, statistics and extrapolation of short-time data. Matericals and Structures, 26,567-574.
[21] Bemhardt,C.J.,Creep and shrinkage of concrete, Material and Structures, Paris,2,No.8,1969,pp.145-48.
[22] Fuller, A.H. and C.C. Moore, Time Tests of Concrete. ACI Journal, 12: 1916, 302 pp.
[23] Glucklich, J.and ISHAI, O., Creep mechanism in cement mortar, ACI Journal,59,1962,pp,923-48.
[24] Hansen, T.C., Creep and stress relaxation of concrete, Proc. No. 31, Swedish Cement Research Institute: Stockholm, 1960, 112pp.
[25] Hansen, T.C., Creep of Concrete, Bulletin No. 33, Swedish Cement and Concrete Research Institute: Stockholm, 1958, 48pp.
[26] Halt, W.K., Effect of Time Element in Loading Concrete. ASTM Proceedings: 1907,421 pp.
[27] Jensen, R.S. and F.E. Richart, Short-Time Creep Test of Concrete in Compression. ASTM Proceedings, 38: 1938, pp. 410-417.
[28] Kristek, V, Bazant, Z. P.; Zich, M.; and Kohoutkova, A., 2006, Box Girders Box Deflections, Concrete International, V. 23, No. 1, Jan., pp. 55-63.
[29] L'Hermite, R.G. and Mamillan, M., Further results of shrinkage and creep tests, Pro, Int. Conf. on the Structure of Concrete, Cement and Concrete Association: London, 1968,pp.423-33.
[30] Lyman, C.G., Growth and Movement in Portland Cement Concrete. London: Oxford University Press, 1934, 139.
[31] Neville A M, Dilger W H, Brooks J J. 1983. Creep of plain and structural concrete [M], London and New York: Construction Press
[32] Neville, A.M. and W.H. Dilger, Creep of concrete: plain, reinforced, and prestressed. Amsterdam, New York : North-Holland Pub. Co., American Elsevier, 1970, xix, 622.
[33] Neville, A.M., Properties of concrete. 4th and final ed: J. Wiley, 1996.
[34] Neville, A.M., Role of cement in creep of mortar. Journal of the American Concrete Institute, 30(9): 1959, pp. 963-984.
[35] Neville, A.M., Theories of Creep in Concrete. ACI Journal, 52: 1955, pp. 47-60.
[36] Neville, A.M., W.H. Dilger, and J.J. Brooks, Creep of plain and structural concrete: Construction Press, 1983.
[37] Pickett G. 1942. The effect of change in moisture content on the creep of concrete under a sustained load [J], ACI J. 38:333-355
[38] Power,T.C., (1965), Mechanism of shrinkage and reversible creep of hardened cement paste. Proc, Int. Conf. on the struct, of concrete. Cement and Concrete Association, London, U.K., 319-344.
[39] Powers, T.C. (1968). The thermodynamics of volume change and creep. Mat, and structure., Paris, France, 1(6), 487-507.
[40] Troxell, G.E., J.M. Raphael, and R.E. Davis. Long-term Creep and Shrinkage Tests of Plain and Reinforced Concrete.in Cement and Concrete.Los Angeles:ASTM Proceedings,1958,pp.1101-1120.
[41]Troxell,G.E.,RAPHAEL,J.M.and DAVIS,R.E.,Long-time creep and shrinkage tests of plain and reinforced concrete,Porc,ASTM,58,1958,pp.1101-20
[42]Wittmann F H.1980.Properties of hardened cement paste[C],Proc.Int.Congress on Chemistry of Cement(Paris),Vol.Ⅰ,Subtheme Ⅵ-2
[43]过镇海,时旭尔.钢筋混凝土的高温性能及其计算[M].北京:清华大学出版社.1996.
[44]蒋正武,王培铭,等温干燥条件下混凝土内部相对湿度的分布.武汉理工大学学报.2003.25(7):18-20
[45]王光远,论时变结构力学,土木工程学报,2000,33(6):105-107
[46]袁勇,混凝土结构早期裂缝控制,北京:科学出版社,2004
[47]中华人民共和国建设部,混凝土结构设计规范,北京:中国建筑工业出版社,2002.
[48]周履,陈永春.收缩徐变.[M].北京:中国铁道出版社.1994.