预制桥墩节段节点抗剪性能研究—–拟静力试验

预制节段拼装桥墩在节段接缝处混凝土断开, 仅通过纵向钢筋和剪力键连接相邻节段, 节点抗剪承载能力是设计工程师所关心的关键设计变量. 通过拟静力单调加载直接剪切试验研究了3组节段节点的抗剪性能, 试验参数包括剪力键的数量和长度、平接缝、接触面约束应力等. 分析了试验得到的剪切力—滑移曲线、受力阶段和破坏机理, 根据试验结果的回归分析得到了预制节点抗剪承载力经验公式, 并与AASHTO和已有文献中的回归公式进行了比较. 结果表明, 带剪力键试件的剪切破坏形式为多个阳齿的剪断和单个阴齿的斜裂缝, 平接缝试件的剪切破坏形式为滑移和截面的拉伸裂缝, AASHTO公式计算结果与试验结果趋势一致. 多剪力键干接缝试件发展了较好的延性剪力—滑移响应, 可作为推荐的预制拼装桥墩接缝构造形式.

Shear resistant performance investigation of segment joints in precast columns: Quasi-static test

The segment concrete of precast segmental bridge column is discontinuous at the joint. Longitudinal reinforcement and shear keys are used to connect the two adjacent segments. The shear resistant capacity of joint is a key design quantity concerned by design engineers. The shear performance of three groups of segment joints was studied through quasi-static monotonic direct shear loading test. The parameters of test included number and length of shear keys, flat joint, and confinement stress of joint. The shear force-slip displacement curve, loading stage and damage mechanism were analyzed. The empirical formula of shear resistant capacity of precast joint was derived through test regression analysis. The proposed equation was then compared with that suggested by AASHTO and other literature. The results show that the damage pattern of the keyed dry joints was shear-off of multiple convex shear keys and diagonal crack of single concave shear key. The damage form of the flat dry joint was slippage and tensile crack on interface. The calculation results by AASHTO formula had same tendency with the test results. Multi-keyed specimens developed satisfying ductile shear force-slip displacement response. So it is recommended to be the preferred configuration of precast segmental column joints.