墩身高阶振型对高墩地震反应影响

采用增量动力分析的方法,全面讨论了墩身高阶振型对桥梁结构地震反应的影响.首先分析了现有规范中的桥梁抗震设计方法应用于高墩的局限性;随后采用了增量动力分析方法,在考虑墩身高阶振型效应的情况下,对高墩桥梁结构在地震作用下的性能进行了研究.结果表明:由于墩身高阶振型贡献,高墩在强震作用下可能沿墩身产生多个塑性区域;墩顶位移与墩底曲率不再同步变化,高墩墩顶极限位移不能采用规范中的方法进行计算;高墩墩身的地震剪力及弯矩需求也会由于墩身高阶振型的显著影响而变得十分复杂.最后提出了针对高墩抗震设计的一些改进措施.

Seismic Performance of Tall Piers Influenced by Higher mode Effects of Piers

Many bridges in the mountainous areas of southwest China are built with tall piers that are characterized by great structural flexibility and significant distributed mass. Seismic performance of these bridges are influenced by higher-mode effects of the tall piers. In this paper, incremental dynamic analysis was used to investigate the effects of higher modes on seismic reposes of tall piers. Firstly the limitation of current design method focusing on conventional bridges was presented. Then the seismic performance of tall piers was investigated by incremental dynamic analysis method. The results show that with the contributions of higher modes of massive piers, multiple plastic zones are formed along the pier height under strong earthquake. The ultimate displacement at the pier top cannot be estimated by methods in current design codes, and the displacement varies out-of-phase with the curvature at the pier bottom. Further, the distribution patterns of shear force and bending moment along pier height are more complex than the linear and triangular distributions of conventional piers. Finally, some improvements for seismic design of tall piers are proposed.