可牺牲抗震挡块的两水准设计方法

Dual-level Design Method of Sacrificial Aseismic Retainers

为了改变中国桥梁抗震设计中挡块无规范可循的现状,针对挡块斜截面脆断的典型震害,采用拟静力试验对挡块的合理构造及抗震性能进行了研究,结合试验结果与现行桥梁抗震规范,基于"保险丝"思想提出了可牺牲抗震挡块及其两水准性能目标,并明确了其配筋计算方法和构造设计要求,最后通过实桥运用对比分析了其抗震效果。结果表明:使挡块在盖梁顶面发生滑移剪切破坏可大幅提高挡块的塑性变形能力,并防止盖梁的地震破坏;采用两水准设计的可牺牲抗震挡块在中震、小震下可有效限制主梁的位移和橡胶支座的变形,充分发挥其限位作用并使其处于弹性或强度发展阶段;在大震下由于发生强度退化甚至剪断破坏,降低了下部墩柱的地震响应需求,从而发挥"结构保险丝"的作用。

To change the situation that there is no standard code for the aseismic retainer design of bridges in China,aimed at the typical seismic damage of the retainer subjected to diagonally brittle failure,quasi-static experiments were conducted to analyze reasonable configuration and seismic behavior of the retainer.Combining the experiment results with the current seismic bridge design code,and based on the philosophy of structural fuse,a kind of sacrificial aseismic retainer as well as its dual-level performance targets was proposed,and the calculation method for reinforcement and the structure design requirements were also elaborated.Finally based on a realistic bridge,the anti-seismic effect was comparatively investigated.The results show that the sliding shear failure of retainer on the top surface of cap beam will significantly improve the ductile deformation capacity,and also can prevent seismic damage of the cap beam.Applying the dual-level design method,the sacrificial aseismic retainer is very efficient in controlling the displacement response of girder and the deformation response of rubber bearing when the bridge is subjected to small or moderate earthquakes,and it plays the controlling role and remains inarange of elastic or strength-hardening phase. When the bridge is attacked by intensive earthquakes,the substructural seismic response demand can be decreased due to intensive deterioration and shearing destruction,which implies that the sacrificial aseismic retainer acts as structural fuse.