钢筋混凝土挡块抗震性能及改进试验

Experiment on Seismic Performance and Its Improvement of Reinforced Concrete Retainers

为提高桥梁横向挡块的抗震能力,针对挡块斜截面脆性剪断破坏的震害现象,提出了"限制破坏范围"和"提高塑性变形能力"2个抗震性能目标;采用拟静力试验研究了剪切钢筋与水平拉筋的相对数量关系,以及剪切钢筋布置方式、施工缝、加载位置等对挡块性能的影响;通过回归分析拟合了挡块的滑移强度,并提出了使挡块发生滑移破坏所需满足的配筋和构造细节。研究结果表明:挡块的破坏形态分为斜截面剪切、连接面剪切、连接面滑移3种;当发生连接面滑移破坏时,挡块及盖梁本身完好无损,两者仅在连接面上产生大位移相对滑动,挡块塑性变形能力最大,且便于震害修复;挡块的滑移强度与其剪切钢筋参数之间呈近似线性关系,利于工程设计计算。

In order to improve the seismic performance of transverse retainers in girder bridges, aimed at the seismic damage to the retainers subjected to diagonal brittle shear failure, two seismic performance targets were proposed, i. e. control of the retainer damage scope and enhancement of the retainer ductile deformation capacity. Quasi-static experiments were conducted to investigate the influences of relative amounts between shear reinforcement and horizontal tie reinforcement, configuration of shear reinforcement, construction joint and loading position on the behavior of retainer. Regression analysis was used to fit the sliding strength of the retainers, and the details of reinforcement and construction were proposed for the retainers designed so that a sliding shear failure would be expected. The results show that the retainers fail due to three mechanisms, i.e. diagonal shear failure, horizontal shear failure and sliding shear failure. When the sliding shear failure happens, the retainer and the cap beam themselves are protected from damage with only large-displacement relative sliding observed at the retainer/cap beam interface, with the best ductile deformation capacity of the retainer among the threemechanisms, which is convenient for post-earthquake repair. An approximate linear relationship exists between the retainer sliding strength and its shear reinforcement parameter, which is beneficial for the engineering design and computation.