罕遇地震作用下高速铁路减隔震简支梁桥合理计算模型的探讨

Investigation on Rational Analytical Model for High-speed Railway Simply-supported Girder Bridge with Steel Dampers under Strong Earthquake Motion

以往在分析减隔震桥梁的地震响应时,由于考虑到桥墩和基础应保持弹性工作状态,在基于强度的设计中偏于安全考虑桥墩一般采用毛截面刚度建立弹性梁单元模型。实际上,在罕遇地震作用下,桥墩墩底截面虽然未达到屈服状态,仍然会出现保护层混凝土开裂,并导致桥墩刚度降低。此时,应考虑对桥墩刚度进行适当修正以估计桥梁的各项地震响应参数,这也有利于实现减隔震桥梁基于位移的抗震设计。结合西部高速铁路中典型的简支梁桥结构形式,分别采用弹塑性纤维梁柱单元、弹性梁柱单元、考虑刚度修正的弹性梁柱单元模拟桥墩建立3种计算模型,探讨适用于罕遇地震作用下的高速铁路减隔震桥梁的合理计算模型。结果表明,当罕遇地震作用下桥墩位移延性超过0.5时,考虑刚度修正的弹性梁柱单元模拟桥墩的计算模型能够较好地估计桥梁各项地震响应参数。

Elasticity beam-column element with gross section stiffness is generally used to simulate seismic response of isolated bridge piers in force-based seismic design method, because pier and foundation are considered to keep elastic state for the sake of safety. Actually, cracking of cover concrete in the bottom section of the pier appears before yield state under rare occurrence earthquake, and may lead to stiffness reduction. Therefore it is appropriate to estimate earthquake response parameters using elasticity beam-column element with stiffness correction of pier, which is helpful for the displacement-based seismic design. For simply- supported girder of high-speed railway in West China, three numerical analysis models are constructed to give rise to the rational model ofhigh-speed railway simply-supported girder bridges with steel dampers under strong earthquake motion. The numerical model is a numerical analysis model respectively with elastic-plastic fiber beam-column element, elasticity beam-column element, as well as elasticity beam-column element in consideration of stiffness correction of pier. The results show that the numerical analysis model with elasticity beam- column element considering stiffness correction of pier is suitable for calculating earthquake response parameters of bridge in case the displacement ductility of pier is more than O. 5.