强震作用下高墩桥梁抗震性能特点分析

Analysis of Seismic Performance Characteristics of Bridge with High Piers under Strong Earthquake Motion

摘要:

西部山区高墩桥梁通常是线路中的控制工程,本文结合西部山区典型高墩桥梁,基于纤维模型的有限元方法建立了高墩桥梁的非线性数值分析模型。通过采用增量动力分析法,即IDA方法对高墩桥梁结构进行了非线性动力时程分析,探讨了在横桥向强震作用下该结构墩身截面曲率的分布特点、墩身中部塑性区域的形成和发育、以及不同频谱特性的地震动激励下的破坏模式和损伤过程,在此基础上以截面曲率作为性能指标对高墩桥梁结构进入塑性后的抗震性能特点展开讨论,揭示高墩桥梁结构在高阶模态影响下抗震性能的复杂性。

Abstract:

With the implementation of Western Development Program in recent years,many highways and railways have been planned and erected in West China.For bridges in mountainous areas with high piers,a nonlinear numerical analysis model is constructed on the basis of the fiber.Finite element analysis is simulated by code OpenSees developed by Pacific Earthquake Engineering Research （PEER）.The Mander model is used to imitate the constitutive model of concrete,and the Giuffré-Menegotto-Pinto model is used to imitate the constitutive model of reinforcement.Incremental dynamic analysis （IDA） is used to research the distribution features of pier section curvature under strong earthquake motions.As a result of the effects of higher modal contribution,the seismic response and performance of bridges with high piers are complicated.The formation and development of the plastic range in the pier upper position,as well as the damage process and failure mechanism of high piers,are studied under various earthquake motions.Results indicate that high pier base section curvature and its top displacement are not simultaneous; therefore,the latter is not inappropriate for representing the performance index.Therefore,seismic performance characteristics of bridges with high piers in the plastic stage are discussed in which pier section curvature is used as the performance index.In addition,the seismic performances of such bridges are more complex due to higher mode contribution,and are strongly influenced by the spectral characteristics of ground motion.In this study,six earthquake waves are selected from a database of PEER Ⅱ class sites.Because of space constraints,this study involves the seismic performances of only bridges with high piers under transversal earthquake action.Careful analysis reveals that the base section curvature of one pier is greater than that in other piers when all piers are plastic,and the location of the pier depends on the degree of higher mode contribution.Damage to higher piers could be more substantial than that to low piers,and the envelopes of section curvature above the pier base plastic region do not exhibit a linear trend.The occurrence of plastic hinges at middle and upper parts of piers is attributed to the contribution of higher modal shape,and the extent and size of this plastic region are affected by Therefore,bridges with high piers are not safe in earthquakes when designed according to existing specifications.