Shear Behavior in Fracture Process Zone of Concrete

混凝土结构中的大多数裂缝首先由最大主应力引发，并在随后的剪切和横向压缩或拉伸下扩展。为了研究开裂混凝土的抗剪性能，研制了一种双轴试验装置，该装置的垂直和水平荷载以及位移可由闭环伺服系统独立控制。对含有窄裂纹（位移控制中拉伸试验引入的断裂过程区）的试样进行了剪切试验，保持裂纹表面的法向位移或载荷恒定。讨论了正应力和剪应力与裂纹张开度和滑移量的关系，并通过裂纹面法线方向的边界条件进行了区分。根据双轴试验结果，推导出了裂缝中剪切保持因子β和剪切位移与法向荷载关系的表达式。

Most cracks in concrete structures are initiated first by the largest principle stress, and propagate under subsequent shear and transverse compression or tension. A biaxial testing device, with which the vertical and horizontal load as well as displacement can be independently controlled by closed-loop servo systems, has been developed in order to establish the shear behavior in cracked concrete. The shear tests on specimens containing narrow cracks (fracture process zone introduced by the tensile test in displacement control) have been carried out maintaining either normal displacement or load across the crack surface constant. The relation of normal and shear stresses to crack opening and sliding displacements was discussed and distinguished by the boundary conditions of the normal direction across the crack surface. Several expressions which give shear retention factor, β, and relations between shear displacement and normal load in cracks have been derived based on biaxial test results.