脉冲地震下简支梁桥倒塌过程及响应分析

Collapse process and response analysis of simply supported beam bridge under pulse earthquake

为了模拟脉冲地震作用下简支梁桥的倒塌过程,基于LS-DYNA平台建立了简支梁桥的三维有限元模型,并人工合成了不同脉冲幅值和脉冲周期的地震动,研究了脉冲幅值和脉冲周期对简支梁桥倒塌过程和地震响应的影响,总结了地震作用下简支梁桥的灾变过程。研究表明:脉冲幅值对简支梁桥的倒塌模式影响显著,脉冲幅值较小时桥墩发生倒塌,脉冲幅值较大则会导致梁体落梁;脉冲幅值对桥梁位移响应影响较小,对内力响应和碰撞效应影响较大,增大脉冲幅值会加重梁间的碰撞效应,从而消耗大量地震能量;位移响应随脉冲周期的增大而增大,梁间碰撞力则与之相反;桥梁开始出现损伤的时间点与脉冲周期的大小有关,脉冲周期越小,开始出现损伤的时间越靠近地震加速度峰值时刻;脉冲地震作用下简支梁桥的倒塌表现为三个阶段:分别为正常运行阶段、损伤演变阶段和倒塌阶段。

In order to simulate the collapse process of simply supported beam bridge under impulse earthquake,a three-dimensional finite element model of simply supported beam bridge is established based on LS-DYNA platform.The ground motions with different pulse amplitudes and pulse periods are synthesized artificially.The effects of pulse amplitude and pulse period on the collapse process and seismic response of simply supported beam bridges are studied,and the catastrophic process of simply supported beam bridges under earthquake is summarized.Research shows:The pulse amplitude has a significant influence on the collapse mode of simply supported beam bridge.When the pulse amplitude is small,the pier collapses,and when the pulse amplitude is large,the beam will fall.The pulse amplitude has little influence on the displacement response of the bridge,and has a great influence on the internal force response and collision effect.Increasing the pulse amplitude will aggravate the collision effect between beams,thus consuming a lot of seismic energy.The displacement response increases with the increase of pulse period,while the collision force between beams is opposite.The time point when the bridge begins to damage is related to the size of the pulse period.The smaller the seismic pulse period is,the closer the time when the damage begins to appear is to the peak time of seismic acceleration.The collapse of simply supported beam bridge under pulse earthquake is shown in three stages,namely normal operation stage,damage evolution stage and collapse stage.