热膨胀系数时变性对混凝土温度应力仿真影响
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摘要
已有试验研究表明,混凝土的热膨胀系数具有明显的随龄期发展的特性.为了研究混凝土热膨胀系数时变特性,以及更好地模拟混凝土早龄期温度应力,分析热膨胀系数时变效应对混凝土温度应力仿真的影响,采用温度应力试验机进行试验,对混凝土热膨胀系数进行测定.引入等效龄期的概念,将混凝土早期变形分离为温度变形与自生体积变形,建立热膨胀系数与等效龄期之间的数学模型.通过室内试验试件的有限元数值模拟,验证热膨胀系数时变模型的合理性.将时变模型应用于大岗山特高拱坝施工期的温度应力仿真,通过对比研究,分析热膨胀系数时变效应对混凝土温度应力的影响.研究表明,混凝土热膨胀系数在早龄期变化较大,考虑其时变性对仿真防裂意义重大.尤其对于受通水等影响早期温降速率较快的混凝土,考虑热膨胀系数时变效应进行仿真计算应力水平较传统方法偏高,据此计算结果进行防裂设计更安全.
Previous studies have shown that the thermal expansion coefficient of concrete has obvious age-dependent characteristic. An experiment based on temperature-stress testing machine was designed to measure the thermal expansion coefficient, in order to study the time-varying characteristic of the thermal expansion coefficient of concrete and its effect on the thermal stress simulation, and to simulate the early-age temperature stress of concrete more accurately. The concept about the equivalent age was introduced. The temperature deformation and self-grown volume deformation were separated successfully. A mathematical model between the thermal expansion coefficient and the equivalent age was established. The rationality of this model was verified through the simulation of the laboratory test. Additionally, the effect of time-varying thermal expansion coefficient on temperature-stress simulation was discussed through the simulation of temperature-stress of Dagangshan super high arch dam. Results showed that the coefficient of thermal expansion of concrete changed greatly in early age. Considering the timevarying property of the coefficient of thermal expansion is significant for simulation and crack prevention. The simulated stress level calculated by considering the time-varying effect was higher than that of the traditional method, especially for the concrete with fast temperature drop rate at early age due to water flow. It is safer to carry out crack prevention design according to the new method.
Previous studies have shown that the thermal expansion coefficient of concrete has obvious age-dependent characteristic. An experiment based on temperature-stress testing machine was designed to measure the thermal expansion coefficient, in order to study the time-varying characteristic of the thermal expansion coefficient of concrete and its effect on the thermal stress simulation, and to simulate the early-age temperature stress of concrete more accurately. The concept about the equivalent age was introduced. The temperature deformation and self-grown volume deformation were separated successfully. A mathematical model between the thermal expansion coefficient and the equivalent age was established. The rationality of this model was verified through the simulation of the laboratory test. Additionally, the effect of time-varying thermal expansion coefficient on temperature-stress simulation was discussed through the simulation of temperature-stress of Dagangshan super high arch dam. Results showed that the coefficient of thermal expansion of concrete changed greatly in early age. Considering the timevarying property of the coefficient of thermal expansion is significant for simulation and crack prevention. The simulated stress level calculated by considering the time-varying effect was higher than that of the traditional method, especially for the concrete with fast temperature drop rate at early age due to water flow. It is safer to carry out crack prevention design according to the new method.
引文
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[21]SAUL A.Principles underlying the steam curing of concrete at atmospheric pressure[J].Magazine of Concrete Research,1951,2(6):127-140.
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[2]汝乃华,姜忠胜.大坝安全与事故:拱坝[M].北京:中国水利水电出版社,1995:5-6.
[3]ZHANG C,ZHOU W,MA G,et al.A meso-scale approach to modeling thermal cracking of concrete induced by water-cooling pipes[J].Computers and Concrete,2015,15(4):485-501.
[4]LIU X H,ZHANG C,CHANG X L,et al.Precise simulation analysis of the thermal field in mass concrete with a pipe water cooling system[J].Applied Thermal Engineering,2015,78:449-459.
[5]ZHOU W,FENG C Q,LIU X H,et al.A macro-meso chemo-physical analysis of early-age concrete based on a fixed hydration model[J].Magazine of Concrete Research,2016,68(19):981-994.
[6]ZHOU W,TANG L W,LIU X H,et al.Mesoscopic simulation of the dynamic tensile behaviour of concrete based on a rate-dependent cohesive model[J].International Journal of Impact Engineering,2016,95:165-175.
[7]ZHOU W,QI T Q,LIU X H,et al.A hygro-thermochemical analysis of concrete at an early age and beyond under dry-wet conditions based on a fixed model[J].International Journal of Heat and Mass Transfer,2017,115:488-499.
[8]江晨晖,杨杨,李鹏,等.水泥砂浆的早龄期热膨胀系数的时变特征[J].硅酸盐学报,2013,41(5):605.JIANG Chen-hui,YANG Yang,LI Peng,et al.Time dependence on thermal expansion behavior of cement mortar at early ages[J].Journal of the Chinese Ceramic Society,2013,41(5):605.
[9]张国梁,李松.用应变片测量水泥混凝土热膨胀系数的试验方法[J].城市道桥与防洪,2012(2):112-115.ZHANG Guo-liang,LI Song.Test method of strain gauge to measure thermal expansion coefficient of cement concrete[J].Urban Roads Bridges and Flood Control,2012(2):112-115.
[10]SELLEVOLD E J,BJONTEGAARD O.Coefficient of thermal expansion of cement paste and concrete:mechanisms of moisture interaction[J].Materials and Structures,2006,39(9):809-815.
[11]沈德建,申嘉鑫,黄杰,等.早龄期及硬化阶段水泥基材料热膨胀系数研究[J].水利学报,2012,43:153-160.SHEN De-jian,SHEN Jia-xin,HUANG Jie,et al.Research on current for determining coefficient of thermal expansion of cementbased materials at early ages and in hardening stage[J].Journal of Hydraulic Engineering,2012,43:153-160.
[12]马新伟,钮长仁.混凝土硬化早期热膨胀的量化方法研究[J].低温建筑技术,2005,43(2):8-9.MA Xin-wei,NIU Chang-ren.Quantification of thermal dilation of concrete at early age[J].Low Temperature Architecture Technology,2005,43(2):8-9.
[13]JENSEN O M,HANSEN P F.Influence of temperature on autogenous deformation and relative humidity change in hardening stage[J].Cement and Concrete Research,1999,29(4):567.
[14]KADA H,LACHEMI M,PETROV N,et al.Determination of the coefficient of thermal expansion of high performance concrete initial setting[J].Material and Structure,2002,35:35-41.
[15]王贤磊.混凝土温度线膨胀系数测定仪的研制与应用[D].北京:清华大学,2005.WANG Xian-lei.Development and application of an instrument for measuring the coefficient thermal expansion of concrete[D].Beijing:Tsinghua University,2005.
[16]ZHOU W,ZHAO C,LIU X H,et al.Mesoscopic simulation of thermo-mechanical behaviors in concrete under frost action[J].Construction and Building Materials,2017,157:117-131.
[17]崔溦,冀天竹,吴甲一.热膨胀系数对早期混凝土性态影响试验及数值模拟[J].同济大学学报:自然科学版,2016,44(3):355-362.CUI Wei,JI Tian-zhu,WU Jia-yi.Experimental study and numerical simulation for the effect of thermal expansion coefficient on the behavior of early concrete[J].Journal of Tongji University:Natural Science,2016,44(3):355-362.
[18]ZHAO Z F,MAO K K,JI S W,et al.Adiabatic temperature rise model of ultra-high-volume fly ash conventional dam concrete and FEM simulation of the temperature history curve[C]//Proceedings of the 10th International Conference on Mechanics and Physics of Creep,Shrinkage,and Durability of Concrete and Concrete Structures.Vienna:ASCE,2015:1410-1419.
[19]赵志方,李超,张振宇,等.超高掺量粉煤灰大坝混凝土早龄期抗裂性研究[J].水力发电学报,2016,35(7):112-119.ZHAO Zhi-fang,LI Chao,ZHANG Zhen-yu,et al.Cracking resistance behaviors of ultra-high-volume fly ash dam concrete at early age[J].Journal of Hydroelectric Engineering,2016,35(7):112-119.
[20]陈波,丁建彤,蔡跃波,等.基于温度-应力试验的混凝土早龄期应变分离及热膨胀系数计算[J].水利学报,2016,47(2):560-565.CHEN Bo,DING Jian-tong,CAI Yue-bo,et al.Strain separation and thermal coefficient calculation of early age concrete based on thermal stress test[J].Journal of Hydraulic Engineering,2016,47(2):560-565.
[21]SAUL A.Principles underlying the steam curing of concrete at atmospheric pressure[J].Magazine of Concrete Research,1951,2(6):127-140.
[22]ZHOU W,FENG C Q,LIU X H,et al.Contrastive numerical investigations on thermo-structural behaviors in mass concrete with various cements[J].Materials,2016,9(5):378.
[23]朱伯芳.大体积混凝土温度应力与温度控制[M].北京:中国水利水电出版社,2012.
[24]宋玲丽,黎满林,常晓林,等.大岗山拱坝横缝开度仿真分析[J].武汉大学学报:工学版,2013,43:446-450.SONG Lin-li,LI Man-lin,CHANG Xiao-lin,et al.Simulation analysis of transverse joints aperture for Dagangshan arch dam[J].Engineering Journal of Wuhan University,2013,43:446-450.