受约束混凝土早龄期温湿度应力计算
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摘要
为了探讨受混凝土受约束构件在干缩和温度变化影响下的早龄期应力变化规律及开裂风险,以受约束混凝土棱柱体构件为例,建立了混凝土受约束构件在湿度场和温度变化作用下早龄期收缩应力解析计算方法。采用松弛徐变系数法对混凝土徐变的影响作了修正,应用该模型对不同环境湿度、不同单日温度变化和不同约束三种情况的混凝土构件应力应变进行了计算分析。结果表明:约束度越大,应力越大,开裂风险越大;当环境湿度与混凝土内部湿度接近时,环境湿度对混凝土的应力应变影响最明显;单日温度骤降对4 d龄期内的混凝土应力应变影响较为明显。因此,内外约束和环境湿度是影响构件早龄期应力变化的主要影响因素。
This study aimed to explore the change law of early-age stress and crack risk of concrete-constrained components under dry shrinkage and temperature. With a restrained concrete prism component as an example,a calculation method for the early-age shrinkage stress of the restrained concrete components under the action of moisture field and temperature was developed. Relaxation and creepage coefficient were applied to revise the effect of concrete creepage. The model was adopted for the calculation and analysis of the stress and strain of concrete components under different environmental humidity,temperature changes within a single day,and constraints. Results show that a high degree of restraint led to large stress and risk of cracking. When the moisture of the environment was close to the internal humidity of concrete,the greatest effects on the stress and strain of concrete were observed. A sudden decrease in temperature within a single day apparently affected the stress and strain of concrete lying within the age of 4 days. Therefore,the inside and outside constraint conditions and environmental humidity were the main factors affecting stress changes in early age.
This study aimed to explore the change law of early-age stress and crack risk of concrete-constrained components under dry shrinkage and temperature. With a restrained concrete prism component as an example,a calculation method for the early-age shrinkage stress of the restrained concrete components under the action of moisture field and temperature was developed. Relaxation and creepage coefficient were applied to revise the effect of concrete creepage. The model was adopted for the calculation and analysis of the stress and strain of concrete components under different environmental humidity,temperature changes within a single day,and constraints. Results show that a high degree of restraint led to large stress and risk of cracking. When the moisture of the environment was close to the internal humidity of concrete,the greatest effects on the stress and strain of concrete were observed. A sudden decrease in temperature within a single day apparently affected the stress and strain of concrete lying within the age of 4 days. Therefore,the inside and outside constraint conditions and environmental humidity were the main factors affecting stress changes in early age.
引文
[1]朱伯芳.大体积混凝土温度应力与温度控制[M].北京:中国电力出版社,1999.ZHU Bofang.Thermal stresses and temperature control of mass concrete[M].Beijing:China Electric Power Press,1999.
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[3]KIM J K,LEE C S.Moisture diffusion of concrete considering self-desiccation at early ages[J].Cement and concrete research,1999,28(8):1921-1927.
[4]ZHANG Jun,HOU Dongwei,HAN Yudong.Micromechanical modeling on autogenous and drying shrinkages of concrete[J].Construction and building materials,2012,29(3):230-240.
[5]侯东伟.混凝土自身与干燥收缩一体化及相关问题研究[D].北京:清华大学,2010.HOU Dongwei.Integrative studies on autogenous and drying shrinkage of concrete and related issues[D].Beijing:Tsinghua University,2010.
[6]康明.施工期钢筋混凝土构件的约束收缩变形性能研究[D].重庆:重庆大学,2010.KANG Ming.Research on restrained deformation properties of reinforced concrete members due to early shrinkage during construction[D].Chongqing:Chongqing University,2010.
[7]ZHANG J,QI K,HUANG Y.Calculation of moisture distribution in early-stage concrete[J].ASCE journal of engineering mechanics,2009,135(8):871-880.
[8]YUAN Y,WAN Z L.Prediction of cracking within earlyage concrete due to themal,drying shrinkage and creep behavior[J].Cement and concrete research,2002,32(7):1053-1059.
[9]ANTON K S,KEVIN J F.Heat of hydration models for cementitious materials[J].ACI materials journal,2005,102(1):24-33.
[10]张智博,张君.混凝土收缩与环境湿度的关系研究[J].建筑材料学报,2006,9(6):720-723.ZHANG Zhibo,ZHANG Jun.Experimental study on relationship between shrinkage strain and environmental humidity of concrete[J].Journal of building materials,2006,9(6):720-723.
[11]BENTZ D P,GARBOCZI E J,QUENARD D A.Modeling drying shrinkage in reconstructed porous materials:application to porous vycor glass[J].Modeling and simulation in materials science and engineering,1998,6(3):211-236.
[12]JENSEN O M.Autogenous deformation and RH-changeself-desiccation and self-desiccation shrinkage[M].Denmark:The Technical University of Denmark,1993.
[13]BAZANT Z P,PANULA L.Practical prediction of time dependent deformation of concrete[J].Materials and structures,Parts I and II,1978,11(65):307-328.
[14]BAZANT Z P,PANULA L.Practical prediction of time dependent deformation of conerete[J].Materials and structures,PartsⅡandⅣ,1978,11(66):415-434.
[15]BAZANT Z P,PANULA L.Practical prediction of time dependent deformation of conerete[J].Materials and structures,PartsⅤandⅥ,1978,13(69):169-173.
[16]陈萌.混凝土结构收缩的机理分析与控制[D].武汉:武汉理工大学,2006.CHEN Meng.The mechanical analysis and control on shrinkage cracking for concrete structure[D].Wuhan:Wuhan University of Technology,2006.
[17]SPRINGENSCHMID R.Prevention of thermal cracking in concrete at early ages[M].London:E&FN Spon,1998:60-62.
[2]BAZANT Z P,NAJJAR L J.Nonlinear water diffusion in nonsaturated concrete[J].Materials and structures,1972,5(1):3-20.
[3]KIM J K,LEE C S.Moisture diffusion of concrete considering self-desiccation at early ages[J].Cement and concrete research,1999,28(8):1921-1927.
[4]ZHANG Jun,HOU Dongwei,HAN Yudong.Micromechanical modeling on autogenous and drying shrinkages of concrete[J].Construction and building materials,2012,29(3):230-240.
[5]侯东伟.混凝土自身与干燥收缩一体化及相关问题研究[D].北京:清华大学,2010.HOU Dongwei.Integrative studies on autogenous and drying shrinkage of concrete and related issues[D].Beijing:Tsinghua University,2010.
[6]康明.施工期钢筋混凝土构件的约束收缩变形性能研究[D].重庆:重庆大学,2010.KANG Ming.Research on restrained deformation properties of reinforced concrete members due to early shrinkage during construction[D].Chongqing:Chongqing University,2010.
[7]ZHANG J,QI K,HUANG Y.Calculation of moisture distribution in early-stage concrete[J].ASCE journal of engineering mechanics,2009,135(8):871-880.
[8]YUAN Y,WAN Z L.Prediction of cracking within earlyage concrete due to themal,drying shrinkage and creep behavior[J].Cement and concrete research,2002,32(7):1053-1059.
[9]ANTON K S,KEVIN J F.Heat of hydration models for cementitious materials[J].ACI materials journal,2005,102(1):24-33.
[10]张智博,张君.混凝土收缩与环境湿度的关系研究[J].建筑材料学报,2006,9(6):720-723.ZHANG Zhibo,ZHANG Jun.Experimental study on relationship between shrinkage strain and environmental humidity of concrete[J].Journal of building materials,2006,9(6):720-723.
[11]BENTZ D P,GARBOCZI E J,QUENARD D A.Modeling drying shrinkage in reconstructed porous materials:application to porous vycor glass[J].Modeling and simulation in materials science and engineering,1998,6(3):211-236.
[12]JENSEN O M.Autogenous deformation and RH-changeself-desiccation and self-desiccation shrinkage[M].Denmark:The Technical University of Denmark,1993.
[13]BAZANT Z P,PANULA L.Practical prediction of time dependent deformation of concrete[J].Materials and structures,Parts I and II,1978,11(65):307-328.
[14]BAZANT Z P,PANULA L.Practical prediction of time dependent deformation of conerete[J].Materials and structures,PartsⅡandⅣ,1978,11(66):415-434.
[15]BAZANT Z P,PANULA L.Practical prediction of time dependent deformation of conerete[J].Materials and structures,PartsⅤandⅥ,1978,13(69):169-173.
[16]陈萌.混凝土结构收缩的机理分析与控制[D].武汉:武汉理工大学,2006.CHEN Meng.The mechanical analysis and control on shrinkage cracking for concrete structure[D].Wuhan:Wuhan University of Technology,2006.
[17]SPRINGENSCHMID R.Prevention of thermal cracking in concrete at early ages[M].London:E&FN Spon,1998:60-62.