近断层地震动下可更换构件铁路高墩易损性分析

Fragility analysis of railway high pier with replaceable components under near fault ground motions

针对一种具有可更换构件的新型铁路高墩结构,以各排可更换杆件为研究对象,对其进行地震易损性对比分析。借助OpenSees平台建立全桥有限元动力分析模型,以可更换构件的材料应变作为损伤指标,地震动峰值加速度为地震动强度指标,输入294条地震波,进行增量动力分析(IDA),得到各排可更换构件的IDA曲线簇。结合定义的极限状态,建立易损性曲线,获得各排可更换构件处于各极限状态的超越概率,并从概率角度对可更换构件高墩结构的抗震性能进行评价。研究结果表明:次要可更换构件的斜腹杆随着地震强度的增大逐排屈服,实现了分级耗能;各排斜腹杆在9度罕遇地震动作用下超越可修复性损伤状态的概率不足11%,处于基本完好状态概率较大。9度巨震作用下墩顶及墩中区域的1至5排斜腹杆超越可修复性损伤的概率均大于70%,大概率处于严重损伤状态。次要可更换构件中的竖杆及弦杆在9度巨震作用下,承担的地震内力较小,故始终保持弹性状态。主要结构墩柱在9度巨震作用下大概率处于可修复性损伤状态,发生严重损伤状态的概率不足1%。可更换杆件集中结构塑性损伤,达到预期的损伤控制效果,满足可恢复性高墩结构基于强震作用下主要结构无损伤或低损伤,次要构件可更换或可修复的设计理念。

For a new high pier structure with replaceable components,the seismic vulnerability of each row of replaceable components was compared and analyzed.The finite element dynamic analysis model of the whole bridge was established with the help of OPENSEES platform.Taking the material strain of replaceable components as the damage measure,the peak ground acceleration as the ground motion intensity measure,294 seismic waves were input for incremental dynamic analysis(IDA).The IDA curve clusters of each row of replaceable components were obtained.Combined with the defined limit state,the vulnerability curve was established.The exceeding probability of each row of replaceable components in each limit state was obtained.The seismic performance of replaceable member high pier structure was evaluated from the perspective of probability.The results show that the inclined web components of secondary replaceable components yield row by row with the increase of seismic strength,and the graded energy consumption is realized.Under the action of 9 degree rare ground motion,the probability of exceeding the repairable damage state of each row of diagonal web components is less than 11%,and the probability of being in basic intact state is high.Under the action of magnitude 9 earthquake,the probability of beyond repairable damage of one to five rows of diagonal web components at the pier top and in the pier middle area is greater than 70%,and the probability is in a state of serious damage.The vertical bar and chord bar in the secondary replaceable member bear less seismic internal force under the action of 9 degree earthquake,so they always maintain an elastic state.The pier column of the main structure is probably in the repairable damage state under the action of magnitude 9 earthquake,and the probability of serious damage state is less than 1%.Replaceable components concentrate the plastic damage of the structure,achieve the expected damage control effect,and meet the design concept of recoverable high pier structure.Based on the design concept that the main structure has no damage or low damage under strong earthquake,and the secondary components can be replaced or repaired.