【作者】 段安；

【导师】 钱稼茹；

【作者基本信息】 清华大学 ， 土木工程， 2009， 博士

【摘要】 抗冻融是混凝土结构耐久性的重要方面。寒冷地区的水工、海工、桥梁混凝土建筑物常因冻融循环造成表面剥落、内部疏松开裂,影响结构的正常使用。进行了冻融环境下素混凝土受压应力-应变全曲线试验研究。首先按照GBJ82-85规定的快速冻融试验方法,对三批共85个尺寸为100mm×100mm×300mm的混凝土棱柱体试件进行了冻融循环,试件的变化参数为混凝土立方体抗压强度和冻融循环次数。然后对试件进行了单轴抗压破坏试验。回归试验结果,提出了适用于立方体抗压强度为30MPa-50MPa的受冻融循环作用混凝土应力-应变全曲线方程及确定其参数的公式。可以应用于冻融循环环境下的混凝土结构、构件的非线性分析。为实现混凝土冻融过程的数值模拟,以热力学和孔隙弹性力学为基础,在已有数值模型的基础上,发展建立了一套混凝土冻融过程的控制方程。然后应用Comsol Multiphysics软件对4个模型进行了三维有限元模拟,预测出饱和砂浆试件在受冻过程中的变形、孔隙压力及温度分布。计算值与实验值吻合较好,说明了本文数值模拟方法的合理性。进行了冻融环境下箍筋约束混凝土应力-应变全曲线试验研究。按照快速冻融试验方法,对两批共54个尺寸为150mm×150mm×450mm、配箍特征值分别为0.317和0.145的混凝土棱柱体试件进行了冻融循环;对其中46个试件进行了轴心抗压破坏试验,得到试验应力-应变全曲线。回归试验结果,提出了本文试验的受冻融循环作用箍筋约束混凝土的应力-应变全曲线方程及确定其参数的公式。可以应用于寒冷地区受冻融作用的钢筋混凝土结构、构件的非线性分析。基于本文研究得到的冻融环境下混凝土应力-应变全曲线方程,用Response-2000软件,对3个冻融环境下的钢筋混凝土构件进行了截面计算,并分析了其抗冻性能。更多还原

【Abstract】 Freeze-thaw resistance is an important aspect of durability of concrete structures. Hydraulic structures, offshore concrete structures and bridges in cold regions often suffer from surface scaling or internal cracking under freeze-thaw cycles.To study the complete compressive stress-strain curve of concrete subjected to freeze-thaw cycles, three groups of 85 concrete prism specimens with dimensions of 100mm×100mm×300mm were exposed to rapid freeze-thaw cycles in water according to the national standard GBJ 82-85. The parameters of the specimens were cubic strength of concrete and freeze-thaw cycle numbers. Then all specimens were tested under uni-axial compressive loading. Based on the test results the complete compressive stress-strain curve equations for frozen-thawed concrete with necessary parameters were suggested. The equations, which are suitable for concrete with cubic strength of 30MPa-50MPa, could be used for nonlinear analysis of concrete structural elements experienced to freezing-thawing cycles in cold regions.In order to simulate the physical processes involved in freezing and thawing of concrete, a mathematical model was developed based on thermodynamics and poroelastic theory. By using Comsol Multiphysics finite element program, the pore pressure, strain and temperature induced into saturated concrete specimens during freezing were predicted. The rationality of the numerical simulation was illustrated by comparing of the analytical results with available experimental data .The stress-strain relationship for stirrup-confined concrete after freez-thaw cycles was investigated. Two series of 54 concrete prism specimens with dimensions of 150mm×150mm×450mm and with stirrup characteristic value of 0.317 or 0.145 were exposed to rapid freeze-thaw cycles in water according to GBJ 82-85. The axial compressive loading tests of 46 specimens were carried out to obtain the complete stress-strain curves of confined concrete. Based on the test results, complete stress-strain curve equations for confined concrete subjected to freeze-thaw cycles were established. The equations could be used for nonlinear analysis of reinforced concrete structural elements experienced to freezing-thawing cycles in cold regions.Based on the stress-strain relationship of the frozen-thawed concrete, the sectional load-deformation response of three reinforced concrete elements subjected to freeze-thaw cycles were predicted by using Response-2000 program. The freeze-thaw resistance of these elements was analyzed .更多还原