千米级斜拉桥横向减震体系振动台试验

Experiment on Transverse Isolation System for Kilometer-span Cable-stayed Bridges

工程中常采用的斜拉桥横向固定体系会增大桥墩、桥塔及其基础的抗震需求,从而增大斜拉桥在地震作用下的损伤破坏风险.为解决这一问题,以已研发的桥梁新型横向钢阻尼器为减震耗能装置,采用振动台试验方法,研究大跨度斜拉桥横向减震体系在近、远场地震作用下的减震效果.以苏通大桥为背景,设计1/35几何相似比的斜拉桥全桥试验模型,并分别进行横向减震体系和传统的横向固定体系的振动台试验.其中,将钢阻尼器与滑动型球钢支座并联布置于桥墩处、钢阻尼器布置于桥塔处形成横向减震体系.基于试验结果进行减震体系的减震行为分析.研究结果表明:在近、远场地震作用下,减震体系均能显著地减小主梁传递给桥墩和桥塔的地震力,其中墩梁、塔梁连接横向传力均减小50%以上,且将主梁位移限制在可接受范围内;减震体系也显著减小了塔身位移、曲率以及墩底曲率需求,其中,塔底截面曲率平均减小了34%,近塔辅助墩墩底曲率平均减小了67%;钢阻尼器拥有饱满的滞回曲线,但其滞回特性与地震输入有关;相对于支座的摩擦耗能,钢阻尼器的耗能能力更显著;在带有速度脉冲的近场地震作用下,钢阻尼器以及支座的位移响应具有明显的脉冲特点.

The transverse fixed system for cable-stayed bridges inevitably increases seismic demands at piers, towers, and their foundations. These in turn increase the risk of earthquake-induced damage to bridges. To address this problem, this study experimentally investigated the mitigation efficiency of a transverse isolation system using novel transverse steel dampers (TSDs) as energy dissipation devices for long-span cable-stayed bridges under near-and far-fault earthquakes. A series of shake table tests were conducted on a 1/35-scale model of the Su-tong Bridge. Tests on the transverse isolation system and a conventional transverse fixed system were conducted. For the transverse isolation system, the TSD together with two sliding spherical steel bearings were placed at deck-bent connections, and TSDs were placed at deck-tower connections. The seismic behaviors of the transverse isolation system were analyzed based on test data. Results indicate that under near-and far-fault ground motions, the isolation system significantly reduces laterally horizontal force at the deck-tower and deck-bent connections, and also reduces displacement and curvature demands along the tower shafts and bottom sections of bents. In addition, the displacement at deck-bent and deck-tower connections are limited to an acceptable practical level by TSDs. For both ground motions, the transverse seismic force at both the deck-tower and deck-bent connections are decreased by more than 50%, and curvature demands at tower-and bent-bottoms are decreased by 34% and 67%, respectively. TSD possesses a plump hysteretic loop, but its hysteretic behavior depends on the characteristics of ground motions. In general, the TSD has a greater capacity of energy dissipation than that of friction-type bearings. The pulse of velocity in a ground motion triggers the displacement pulse of both TSDs and bearings.