等效龄期方法在混凝土早期温度裂缝控制中的运用
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摘要
随着混凝土材料科学和结构科学的发展,兴建的混凝土工程日渐增多。同时,混凝土工程中因早期裂缝引起的结构失效和耐久性问题等也日益突出,混凝土的早期裂缝控制一直是困扰工程技术人员的难题之一。由温度梯度引起的温度变形以及结构的约束限制,使得早龄期混凝土结构很容易出现温度裂缝。
早期混凝土结构的温度裂缝预测,难点在于确定混凝土的水化热分布以及力学性能的发展与养护温度和时间的函数关系式。论文通过研究指出,基于Arrhenius方程的等效龄期方法,不仅能很好地预测养护温度和时间对混凝土性能的影响,与有限元软件(如ANSYS)一起使用,等效龄期方法还可以运用到混凝土结构的温度裂缝预测与控制中。论文以等效龄期方法在混凝土早期温度裂缝控制中的运用为主线,研究内容包括:
1)基于等效龄期的基本理论,建立混凝土抗压强度,抗拉强度与等效龄期的关系式,为不同养护温度——时间历程下混凝土力学性能的计算提供依据;
2)考虑到混凝土结构各点材料放热速率的差异性,提出基于等效龄期放热量与等效放热速率的混凝土热传导方程;
3)考虑到温度的影响,提出基于平均等效龄期概念的混凝土弹性模量计算方法,并将其运用到混凝土结构温度应力场的有限元计算中;
4)将温度应力场的计算结果与基于等效龄期的混凝土结构各点材料的抗拉强度值进行比较,为混凝土早期温度裂缝的预测与控制提供依据;
由试验结果、理论推导及有限元分析,论文得到如下结论:
1)基于Arrhenisus方程的等效龄期方法可以很好地预测混凝土基本力学性能(抗压强度、抗拉强度等)随养护温度和时间的发展;
2)引入等效龄期放热量与等效放热速率概念的混凝土热传导方程,使混凝土结构温度场的有限元计算在理论上更为合理;
3)与有限元软件一起使用,等效龄期方法还可以运用于混凝土结构的温度裂缝预测与控制中;
Quality control during construction is one of the challenges of today's engineering practice, with regard to both the loss of durability and the functionality of the structures being built. In concrete technology, cracking is a cause of major concern. As a result of temperature gradients and restraint conditions, thermal stress occurs and may induce cracks in concrete.Determining whether the cracks may develop is complicated by the fact that both the stress development and strength evolution are related to curing temperature and time. The equivalent age method based on the Arrhenius law can be applied successfully to predict the characteristics which are needed to control the risk of cracking in concrete through the use of numerical tools such as the finite element program ANSYS.The four main parts included in this thesis are as the following:1. The theoretical basis of the equivalent method is introduced and using the equivalent age method ,an aging model is established to describe the evolution of the mechanical properties of the material during the hydration process.2. The hydration heat model of concrete is established using the concept of equivalent age and the finite element program ANSYS is used to calculate the temperature field in concrete structures.3. The thermal stress field is calculated using the elasticity modulus which is calculated by the average equivalent age in concrete structures.4. The risk of thermal cracking is estimated by comparing induced thermal stress with concrete tensile strength and possible corrective actions to limit it are demonstrated.The study of this thesis has demonstrated the following conclusions: 1. The equivalent age method is perfectly suitable to predict the evolution of concrete mechanical properties even in constant temperature.
2. With the hydration heat model based on the equivalent age concept, the temperature field of early age concrete structure can be successfully calculated.3. The equivalent age method is extended successfully to the concrete cracking control in structures through the use of the finite element program ANSYS.
早期混凝土结构的温度裂缝预测,难点在于确定混凝土的水化热分布以及力学性能的发展与养护温度和时间的函数关系式。论文通过研究指出,基于Arrhenius方程的等效龄期方法,不仅能很好地预测养护温度和时间对混凝土性能的影响,与有限元软件(如ANSYS)一起使用,等效龄期方法还可以运用到混凝土结构的温度裂缝预测与控制中。论文以等效龄期方法在混凝土早期温度裂缝控制中的运用为主线,研究内容包括:
1)基于等效龄期的基本理论,建立混凝土抗压强度,抗拉强度与等效龄期的关系式,为不同养护温度——时间历程下混凝土力学性能的计算提供依据;
2)考虑到混凝土结构各点材料放热速率的差异性,提出基于等效龄期放热量与等效放热速率的混凝土热传导方程;
3)考虑到温度的影响,提出基于平均等效龄期概念的混凝土弹性模量计算方法,并将其运用到混凝土结构温度应力场的有限元计算中;
4)将温度应力场的计算结果与基于等效龄期的混凝土结构各点材料的抗拉强度值进行比较,为混凝土早期温度裂缝的预测与控制提供依据;
由试验结果、理论推导及有限元分析,论文得到如下结论:
1)基于Arrhenisus方程的等效龄期方法可以很好地预测混凝土基本力学性能(抗压强度、抗拉强度等)随养护温度和时间的发展;
2)引入等效龄期放热量与等效放热速率概念的混凝土热传导方程,使混凝土结构温度场的有限元计算在理论上更为合理;
3)与有限元软件一起使用,等效龄期方法还可以运用于混凝土结构的温度裂缝预测与控制中;
Quality control during construction is one of the challenges of today's engineering practice, with regard to both the loss of durability and the functionality of the structures being built. In concrete technology, cracking is a cause of major concern. As a result of temperature gradients and restraint conditions, thermal stress occurs and may induce cracks in concrete.Determining whether the cracks may develop is complicated by the fact that both the stress development and strength evolution are related to curing temperature and time. The equivalent age method based on the Arrhenius law can be applied successfully to predict the characteristics which are needed to control the risk of cracking in concrete through the use of numerical tools such as the finite element program ANSYS.The four main parts included in this thesis are as the following:1. The theoretical basis of the equivalent method is introduced and using the equivalent age method ,an aging model is established to describe the evolution of the mechanical properties of the material during the hydration process.2. The hydration heat model of concrete is established using the concept of equivalent age and the finite element program ANSYS is used to calculate the temperature field in concrete structures.3. The thermal stress field is calculated using the elasticity modulus which is calculated by the average equivalent age in concrete structures.4. The risk of thermal cracking is estimated by comparing induced thermal stress with concrete tensile strength and possible corrective actions to limit it are demonstrated.The study of this thesis has demonstrated the following conclusions: 1. The equivalent age method is perfectly suitable to predict the evolution of concrete mechanical properties even in constant temperature.
2. With the hydration heat model based on the equivalent age concept, the temperature field of early age concrete structure can be successfully calculated.3. The equivalent age method is extended successfully to the concrete cracking control in structures through the use of the finite element program ANSYS.
引文
【1.1】 裴勇,混凝土结构早期裂缝控制,北京,科学出版社,2004.
【1.2】 朱伯芳,大体积混凝土温度应力与温度控制,北京,中国电力出版社,1999.
【1.3】 王铁梦,工程结构裂缝控制[M],北京,中国建筑工业出版社,1997.
[1.4] 张与弛,建筑工程大体积混凝土裂缝控制研究[学位论文],西安交通大学,2004.
[1.5] 王难烂,张光颖,顾伯达.混凝土拱坝浇筑温度场的有限元仿真分析[J],武汉理工大学学报,2001
[1.6] 王嘉航,混凝土水化热特性对温度场和应力场的影响分析[学位论文],河海大学,2003
[1.7] Stig Bemander:, Avoidance of Thermal Concrete at Early Ages State of the Art Report on Fractical Measure to Avoiding Early Age Thermal Cracking in Concrete Structure, 1988
[1.8] Mats Emborg and Stig Bernander:, Assessmem of Risk of Thermal Cracking in Hardening Concrete, Journal of Structural Engineering, Oct. 1994, 2893-2912.
[1.9] M. Elgaaly, Thermal Gradients in Beams, Walls, and Slabs ACI Structural Jourmal, Jan-Feb, 1988, p, 76.
[1.10] Frank J. Vecchio, Nonlinear Analysis of Reinforced Concrete Frames Subjected to Thermal and Mechanical Loads, ACI Structural Journal Nov-Dec, 1987, 492-501
[1.11] Enrique Mirambell, Antonoi Aguado, Temperature and Stress Distributions in Concrete Box Girder Bridges, Journal of Structural Engineering, Sept. 1990, 2389-2409
[1.12] Wilson E. L, "The Determination of Temperature within Mass Concrete Structures (SMEReport No.68-17),Structures and Material Research",Department of Civil Engineering,University of California, Berkeley, Dec. 1986
[1.13] Tatro, Stephen B. and Ernest K., "Thermal Consideration for Roller Compacted Concrete" Journal of the American Concrete Institute,Vol.82, March-April, 1985
[1.14] Abifadel Nassin, Johnson Danical, "Evolution of Temperature for Roller Concrete Dams: Case Study Stagecoach Dam", Dam Engineering, 1992,3.
[1.15] 朱伯芳,朱伯芳院士论文集,中国电力出版社,1997,9.
[1.16] 潘家铮,水工建筑物的温度控制,水利电力出版社,1990,11
[1.17] 谢先绅,大体积混凝土结构三维温度场、应力场有限元仿真计算及裂缝成因机理分析,河海大学,2001
[1.18] 马杰,大体积混凝土温度和温度应力计算边界单元法[学位论文],清华大学,1993
[1.19] 陈德威,大体积混凝土结构的不稳定温度场和温度应力[学位论文],福州大学,1995
[1.20] 张旭升,混凝土底板与墩墙类结构温度裂缝的有限元研究[学位论文],河海大学,1993
[1.21] 崔亚强,大体积混凝土温度场裂缝控制理论研究与软件系统[学位论文],天津大学,1995
[1.22] Yan Zhou Niu,et al. Modeling of thermo mechanical damage of early concrete, Journal of Structural Engineering, 1995(4):717～726
[1.23] McIntosh JD. Effect of low temperature curing on the compressive strength of concrete. In: Proceedings of the RILEM Symposium on Winter concreting, vol B(Ⅱ). Copenhagen: Danish Institute for Building Research;1956. p. 3～17
[1.24] ASTM. Standard practice for estimating concrete strength by the maturity method, C 1074-93
[1.25] 博弈创作室,APDL参数化有限元分析技术及其应用实例,中国水利水电出版社,北京,2004.3
【1.2】 朱伯芳,大体积混凝土温度应力与温度控制,北京,中国电力出版社,1999.
【1.3】 王铁梦,工程结构裂缝控制[M],北京,中国建筑工业出版社,1997.
[1.4] 张与弛,建筑工程大体积混凝土裂缝控制研究[学位论文],西安交通大学,2004.
[1.5] 王难烂,张光颖,顾伯达.混凝土拱坝浇筑温度场的有限元仿真分析[J],武汉理工大学学报,2001
[1.6] 王嘉航,混凝土水化热特性对温度场和应力场的影响分析[学位论文],河海大学,2003
[1.7] Stig Bemander:, Avoidance of Thermal Concrete at Early Ages State of the Art Report on Fractical Measure to Avoiding Early Age Thermal Cracking in Concrete Structure, 1988
[1.8] Mats Emborg and Stig Bernander:, Assessmem of Risk of Thermal Cracking in Hardening Concrete, Journal of Structural Engineering, Oct. 1994, 2893-2912.
[1.9] M. Elgaaly, Thermal Gradients in Beams, Walls, and Slabs ACI Structural Jourmal, Jan-Feb, 1988, p, 76.
[1.10] Frank J. Vecchio, Nonlinear Analysis of Reinforced Concrete Frames Subjected to Thermal and Mechanical Loads, ACI Structural Journal Nov-Dec, 1987, 492-501
[1.11] Enrique Mirambell, Antonoi Aguado, Temperature and Stress Distributions in Concrete Box Girder Bridges, Journal of Structural Engineering, Sept. 1990, 2389-2409
[1.12] Wilson E. L, "The Determination of Temperature within Mass Concrete Structures (SMEReport No.68-17),Structures and Material Research",Department of Civil Engineering,University of California, Berkeley, Dec. 1986
[1.13] Tatro, Stephen B. and Ernest K., "Thermal Consideration for Roller Compacted Concrete" Journal of the American Concrete Institute,Vol.82, March-April, 1985
[1.14] Abifadel Nassin, Johnson Danical, "Evolution of Temperature for Roller Concrete Dams: Case Study Stagecoach Dam", Dam Engineering, 1992,3.
[1.15] 朱伯芳,朱伯芳院士论文集,中国电力出版社,1997,9.
[1.16] 潘家铮,水工建筑物的温度控制,水利电力出版社,1990,11
[1.17] 谢先绅,大体积混凝土结构三维温度场、应力场有限元仿真计算及裂缝成因机理分析,河海大学,2001
[1.18] 马杰,大体积混凝土温度和温度应力计算边界单元法[学位论文],清华大学,1993
[1.19] 陈德威,大体积混凝土结构的不稳定温度场和温度应力[学位论文],福州大学,1995
[1.20] 张旭升,混凝土底板与墩墙类结构温度裂缝的有限元研究[学位论文],河海大学,1993
[1.21] 崔亚强,大体积混凝土温度场裂缝控制理论研究与软件系统[学位论文],天津大学,1995
[1.22] Yan Zhou Niu,et al. Modeling of thermo mechanical damage of early concrete, Journal of Structural Engineering, 1995(4):717～726
[1.23] McIntosh JD. Effect of low temperature curing on the compressive strength of concrete. In: Proceedings of the RILEM Symposium on Winter concreting, vol B(Ⅱ). Copenhagen: Danish Institute for Building Research;1956. p. 3～17
[1.24] ASTM. Standard practice for estimating concrete strength by the maturity method, C 1074-93
[1.25] 博弈创作室,APDL参数化有限元分析技术及其应用实例,中国水利水电出版社,北京,2004.3