近断层地震动下设置BRB的双向减隔震桥梁地震反应

在近断层地震动下桥梁结构将发生较大反应,减隔震设计是减轻地震损伤的重要手段。提出了在桥梁双柱墩横桥向设置防屈曲支撑(BRB),在纵桥向设置铅芯橡胶支座(LRB)的双向减隔震体系。利用Midas Civil软件建立3种不同减隔震方式的桥梁结构模型:LRB仅单向,LRB双向与LRB联合BRB,运用非线性时程分析方法计算了桥墩反应(墩顶侧移角、残余位移角和曲率延性)、LRB支座变形和BRB的耗能特性等。结果表明:在近断层地震动输入下联合设置LRB和BRB的双向减隔震桥梁减震效果明显,相比其它2种方式,能有效降低墩柱的塑性变形及起到保护桥墩的作用。在横桥向,桥墩最大侧移角、残余位移角和最大曲率延性系数都显著降低。

Seismic response of bidirectional isolation bridges using BRBs under near-fault ground motions

The bridge structures will be damaged greatly under the near-fault ground motions, so the seismic isolation design is an important way to reduce the earthquake damage of bridges. In this paper, a bidirectional seismic isolation system with BRBs in the transverse direction of the double-column bents and LRBs in longitudinal direction of the bridge is proposed. Three structural models are established by Midas-civil software, including LRBs isolation only in longitudinal direction of bridges, LRBs both longitudinal and transverse directions, and LRBs isolation in the longitudinal direction together with BRBs in the transversal direction of the bridge. The nonlinear time history analysis method is used to calculate the seismic responses of the column, including the displacement drift ratios, residual displacement ratios and curvature ductility. The deformations of LRBs and the energy dissipation characteristics of BRBs are also evaluated. The results show that the bidirectional seismic isolation of bridges with the combination of LRBs and BRBs has an obvious damping effect subjected to the near-fault ground motions. Compared to the two other isolated systems, it can effectively reduce the plastic deformation of the columns and prevent the columns from heavily damage. In the lateral direction of bridges, the maximum lateral displacement drift ratios, residual displacement ratios and the maximum curvature ductility coefficients of the columns are all significantly reduced.