近场脉冲型地震动影响下公路常规梁桥的位移响应分析

Displacement Response Analysis of Regular Highway Girder Bridges Under Near-fault Pulse-type Ground Motions

为研究近场速度脉冲型地震动影响下公路常规梁桥的延性需求和震后残余位移,将公路常规梁桥简化为非线性单自由度体系,并采用简单脉冲模型模拟近场速度脉冲型地面运动,通过NSPECTRA软件,系统分析了速度脉冲幅值、脉冲周期以及自振周期、刚度和强度退化、捏拢等对体系延性需求和震后残余位移的影响规律;并采用正交试验设计的极差和方差分析方法,对近场速度脉冲型地震动的特征参数和自振周期间的耦合效应进行了分析。研究结果表明:自振周期和速度脉冲幅值是影响结构延性需求和震后残余位移的主要因素;震后残余位移总体上随速度脉冲幅值的增大而增大;脉冲周期主要影响与最大延性需求对应的自振周期,对震后残余位移的影响较小,且没有规律性;刚度退化和捏拢均会显著增大短周期体系的延性需求,而对长周期体系的影响则可以忽略不计;体系刚度、强度退化或捏拢越严重,其震后残余位移也越大;除自振周期与速度脉冲幅值之间存在一定的耦合效应外,其他参数之间的耦合效应很小。

In order to investigate the ductility demands and post-earthquake residual displacement of regular highway girder bridges under near-fault ground motions with velocity pulse, the bridges were simplified as nonlinear single degree of freedom （SDOF） systems, and a simple pulse model was used to simulate the near-fault ground motions with velocity pulses. Influences of amplitude and duration of velocity pulse, the natural period, as well as stiffness and strength degradation and pinching of the SDOF system on the ductility demand and residualdisplacement were systematically analyzed by dint of NSPECTRA software. The key parameters of near-fault ground motions with velocity pulse and the coupling effect of the natural period of the SDOF system were analyzed by range analyses and variance analyses of the orthogonal test design. The results show that the natural period and amplitude of velocity pulse are two main factors affecting the ductility demands and post-earthquake residual displacement of the SDOF systems, and the post-earthquake residual displacement of the SDOF systems generally increases with the increasing amplitude of velocity pulse. The duration of velocity pulse mainly affects the natural period at the peak point of the ductility demand spectrum, with less influence on the post-earthquake residual displacement. Both stiffness degradation and pinching will remarkably increase the ductility demand and post-earthquake residual displacement of the SDOF system in a short natural period, and have little influence on the SDOF system in a long natural period. The post-earthquake residual displacement increases with the development of stiffness degradation, strength degradation or pinching of the SDOF system. Besides, there is the coupling effect between the natural period of the SDOF system and the amplitude of velocity pulse, but the coupling effects of others are very small.