FVD与FPB在大跨长联减隔震体系梁桥中的联合作用机理研究

为验证液体黏滞阻尼器(FVD)与摩擦摆支座(FPB)组合在大跨长联减隔震体系梁桥中的应用效果,以一联(50+8×100+50) m预应力混凝土连续梁桥为工程背景,建立全桥有限元模型,通过输入场地地震安评报告提供的50年超越概率为2%的三条人工模拟地震波,开展单独及组合使用液体黏滞阻尼器和摩擦摆支座的大跨长联梁桥减隔震研究,从能量耗散的角度揭示液体黏滞阻尼器与摩擦摆支座组合在大跨长联减隔震体系梁桥中的联合作用机理。结果表明,大跨长联梁桥仅使用黏滞阻尼器,其长周期特性激发黏滞阻尼器充分发挥耗能,但无法避免对固定墩的地震损伤;仅使用摩擦摆支座隔震在纵(横)向强震下会引起支座位移超限;摩擦摆支座与黏滞阻尼器组合的减震机理为摩擦摆支座提供墩梁间的弱连接,激发墩梁间的相对速度,促进黏滞阻尼器(速度型)充分发挥阻尼耗能作用。另外,组合减震方案中摩擦摆支座为辅助耗能装置,黏滞阻尼器为主要耗能装置,且主控梁体位移;相比仅使用摩擦摆支座隔震,由于黏滞阻尼器激发的阻尼力增强了墩梁间约束,这种组合减隔震可能使结构输入能量增加,从而导致地震反应加剧。

Combined Action Mechanism of FVD and FPB in Large-span and Long-unit Bridges with a Seismic Isolation System

To verify the effect of the application of a fluid viscous damper (FVD) and friction pendulum bearing (FPB) in large-span and long-unit bridges with a seismic isolation system, we established a finite element model of a prestressed-concrete continuous-beam bridge. By inputting three artificial seismic waves with a 50-year exceedance probability of 2%, we conducted an isolation study of the bridge with an individual or combined use of an FVD and FPB. With respect to energy dissipation, we determined the combined action mechanism of an FVD and FPB in large-span and long-unit bridges. The results indicate that if only an FVD is used, the FVD will dissipate energy effectively because of its long-period characteristics, but seismic damage to a fixed pier cannot be avoided. Using only an FPB will cause bearing displacement beyond the design specifications under longitudinal (horizontal) strong earthquakes. The isolation mechanism operating under the combined action of FVD and FPB is that the FPB provides a weak connection between the pier and beam, generates relative velocity between them, and thus facilitates the effective dissipation of energy by the FVD. In addition, the FPB serves as an auxiliary energy dissipation device, with the FVD being the main energy dissipation device controlling the beam displacement. Compared with the use of only the FPB, the combined system may increase the energy input to the structure, thus resulting in an intensified seismic response.