新型滑移挡块的设计、试验及防震效果研究

针对目前国内桥梁挡块抗震效果低下的现状,结合"限位"和"传力"两个性能指标提出了一种新型的防震挡块。对常规挡块和新型挡块的抗震性能进行了拟静力对比试验研究,根据实测力-变形曲线建立了两种挡块的简化滞回分析模型,并用于实桥防震效果的对比分析。结果表明:新型挡块在破坏时相对盖梁/台帽发生了大位移的滑移剪切现象,盖梁与台帽基本完好无损,有利于震后修复或替换;与常规挡块发生斜截面脆性剪断破坏相比,新型挡块的极限变形能力和变形延性系数大幅提高;在防震效果上,新型挡块对主梁侧移及橡胶支座的剪切变形限制能力更好,在中小地震下,新型挡块对墩柱地震响应的影响更小;在大震下,新型挡块依靠良好的变形延性能力可在主梁产生更大侧移的情况下保护支座,防止落梁。

DESIGN AND EXPERIMENTAL INVESTIGATION OF A NEW TYPE SLIDING RETAINER AND ITS EFFICACY IN SEISMIC FORTIFICATION

The regular retainer is ineffectual in seismic fortification for girder bridges in China. A new type aseismic retainer is proposed to achieve the improvement with respect to two performance indices: displacement control and force transfer. Quasi-static experiments are designed to comparatively investigate the seismic performance of the new retainer and the regular retainer. Simplified hysteretic analytical models are established for the two types of retainers respectively based on the recorded force-deformation relationship curves, and are used in comparative research of seismic fortification for a real bridge. The results show that the new retainer fails due to large-displacement sliding shearing on the top surface of the cap beam while the cap beam remains intact, which is favorable for post-earthquake repair or replacement. Compared with the regular retainer subjected to diagonally brittle shear failure, the ultimate deformation capacity and deformation ductility of the new retainer are significantly large. Furthermore, the new retainer is more efficient than the regular retainer in controlling the displacement of girders and the shear deformation of elastomeric bearings. Under small to moderate earthquakes, the new retainer has less effect on the seismic response of pier; but under large earthquakes, the new retainer, due to its large deformation ductility, is able to protect the elastomeric bearings and to prevent the unseating of girders when a larger transverse displacement response occurs.