长期恒荷载作用下混凝土断裂过程的时变特性

Time-dependent characteristics of concrete fracture process under long-term constant loads

大体积混凝土结构的时变断裂行为关系到结构的安全。为研究在长期恒荷载作用下混凝土的时变断裂特性,采用三种尺寸的楔入式紧凑拉伸试件,进行了荷载水平为85%最大荷载的恒定荷载作用下的时变断裂试验。试验结果表明,时变裂缝口张开位移、时变裂缝尖端张开位移与时变裂缝口张开速率均呈现出减速、稳定发展和加速破坏三个阶段的发展特征。与单调加载静态断裂试验相比,在试件尺寸相同时,时变断裂试验的临界裂缝口张开位移更大。时变裂缝口张开位移与时变裂缝尖端张开位移具有较强的线性相关性。裂缝张开位移与裂缝扩展长度间的几何关系较好符合铰链模型。

Time-dependent fracture behaviors in mass concrete closely relate to the safety of concrete structures in service.To investigate these behaviors of concrete under sustained loads,this study conducts wedge-splitting tests under a long-term constant load at 85%of the maximum load,using compact tension specimens in three different sizes.The test results indicate three development stages occur in timedependent crack mouth and crack tip opening displacements and time variations in crack mouth opening rate:deceleration,stable development,and accelerated failure.Compared with the static fracture test on the same specimen size,a larger critical crack mouth opening displacement occurs in the present longterm constant load test.And a highly linear correlation can be observed between the displacements at the crack mouth and the tip.In addition,the geometry relation between the opening displacement and propagation length of cracks fits in well with the hinge model.