铁路连续刚构桥近断层地震响应分析研究

摘要

研究目的:近断层地震动的加速度峰值(PGA)、速度脉冲等特征与远场地震有较大差异,对桥梁结构的破坏力更大.因此,为获得铁路连续刚构桥在近断层地震作用下的响应特点与破坏形式,以指导川藏铁路等近断层铁路桥梁的设计,本文以川藏铁路采用的典型连续刚构桥为对象,利用FRAME(3D)软件建立全桥有限元分析模型,开展铁路连续刚构桥近断层地震响应分析与破坏形式研究.研究结论:(1)有能量脉冲的、长周期成分丰富的近断层地震动对桥梁结构的破坏较远场地震更严重;(2)桥墩损伤程度与PGV/PGA的关系明显,其比值越大,破坏越严重,可将PGV/ PGA作为判断地震动是否对结构产生严重破坏的重要指标;近断层地震动中,PGV/PGA＞0.2 s出现的比例高,桥墩损伤严重;(3)连续刚构桥在地震作用下的损伤主要集中在墩底、墩顶或系梁部位;(4)近断层桥梁结构抗震中,既要考虑断层地震脉冲式大功率输入的因素,又要考虑高强低周疲劳效应的累积损伤;(5)本研究成果可为近断层铁路连续刚构桥的设计建造与抗震设防提供技术支撑.%Research purposes:The acceleration peak value (PGA) and velocity pulse of near fault ground motion have great difference with the far field earthquake,which is more destructive to the bridge structure.Therefore,in order to obtain the railway continuous rigid frame bridge response characteristics and failure modes in the near fault earthquake and the guideline of design the near fault bridge in the railway from Sichuan to Tibet,this paper takes the typical continuous rigid frame bridge in the railway from Sichuan to Tibet for example,establishes the finite element analysis model of the bridge by using FRAME (3D) software,then studies the near fault earthquake response of railway continuous rigid frame bridge.Research conclusions:(1) The damage of near fault ground motion with energy pulse,rich long-period components to the bridge structure is more serious than the far field earthquake.(2) The relationship between damage degree of bridge pier and PGV/PGA is obvious,the larger the ratio of PGV/PGA is,the more serious the damage is,thus,the PGV/PGA can be used as an important indicator to determine whether the ground motion has a serious damage to the structure;In the near fault ground motion,the ratio of PGV/PGA ＞ 0.2 s is high,and the bridge pier is badly damaged.(3) The damage of the continuous rigid frame bridge under earthquake is mainly concentrated in the pier bottom,the pier top or the beam position.(4)The seismic design of the near fault bridge structure should not only consider the factor of high power input of fault earthquake pulse type,but also consider the cumulative damage of high strength and low cycle fatigue.(5)This study can provide guidelines to seismic design for the railway continuous rigid frame bridge located on near-fault zone.