面向均匀损伤的不等高墩连续刚构桥抗震优化分析

Uniform Damage Oriented Seismic Optimal Analysis of Continuous Rigid Frame Bridges with Unequal High Piers

高墩桥梁的桥墩端部在地震作用下易产生严重损伤和显著的塑性铰破坏,且各桥墩损伤程度并不相同,易出现单一桥墩严重破坏而导致桥梁整体功能失效的情况,并未充分发挥桥梁整体抗震能力.为了实现桥梁抗震性能优化设计,提出桥梁均匀损伤设计的理念.在此基础上选用基于弹塑性耗能差的损伤指标进行损伤量化分析,并提出单肢墩、双肢墩考虑桥墩构成的时变塑性铰长度的概念和计算方法,进而确立均匀损伤的桥梁优化设计的流程.以一不等高墩连续刚构桥为例,实现面向均匀损伤的抗震优化设计和分析.针对原方案、普通提升方案和均匀损伤优化方案,利用塑性铰处损伤指数、墩顶位移、墩底耗能、时变塑性铰长度等指标以及地震易损性分析等方法进行精细对比分析,由结果可知,在各性能指标方面,均匀损伤优化后方案较原方案和普通提升方案均有所提升,表明面向均匀损伤的桥梁优化设计可以显著提高桥梁整体抗震性能.

The pier ends of high-pier bridges are prone to serious damage and the significant plastic hinge can occur when the bridge is subjected to rare earthquake.Furthermore,the damage degrees of each pier are different.If one single pier is seriously damaged,the integral failure of the bridge can occur,so the overall seismic capacity of bridge is not adequately fulfilled.In order to optimize the seismic performance of bridges,the concept on uniform damage design of bridges is proposed.Since the damage index based on elastic-plastic energy dissipation difference can accurately characterize the seismic damage evolution process,it can be used as a quantitative damage assessment index.In view of the limitations of the existing plastic hinge length in damage assessment,the concept and calculation method of the time-varying plastic hinge length of single pier and double pier are proposed.Finally,the uniform damage oriented optimal design process of bridge considering seismic fragility is proposed.Taking a continuous rigid frame bridge with unequal high piers as an example,the seismic optimization design and analysis for uniform damage are carried out.For the original design scheme,the normal improvement scheme and the uniform damage optimization scheme,the damage index at the plastic hinge,the displacement at the top of the piers,the energy dissipation at the bottom of the piers,the length of the time-varying plastic hinge and the seismic fragility analysis are used to carry out an intensive comparison and analysis.The results show that the uniform damage optimization scheme can enhance the performance of each index.The uniform damage oriented bridge optimization design can significantly improve the damage state and the integral seismic performance of the bridge.