近场地震作用下简支梁桥倒塌分析

Collapse analysis of simply supported beam bridge under near-field earthquake

为了模拟近场地震作用下简支梁桥的倒塌过程,基于ANSYS/LS-DYNA平台建立了简支梁桥的三维有限元模型,研究了方向性脉冲和滑冲脉冲地震作用下简支梁桥的倒塌机理,并分析了两类脉冲地震作用下简支梁桥的动力响应变化趋势。研究表明:方向性脉冲和滑冲脉冲地震作用下简支梁桥的倒塌过程主要表现为墩底混凝土大面积失效而引起的桥墩承载能力不足,进而导致整个桥梁出现倒塌;当墩底开始出现损伤时,桥墩进入塑性,墩底弯矩变化较小;脉冲型地震作用下简支梁桥的破坏倒塌过程分为地震作用下正常运行阶段、损伤演变阶段和倒塌阶段;滑冲脉冲地震作用下简支梁桥的墩顶位移、墩底剪力和弯矩分别为方向性脉冲地震作用时的1.28、1.35和1.06倍,而方向性脉冲地震作用下桥梁从出现损伤到进入倒塌阶段的时间比滑冲脉冲短。

In order to simulate the collapse process of simply supported beam bridge under near-field earthquake,a three-dimensional finite element model of simply supported beam bridge is established based on ANSYS/LS-DYNA platform.The collapse mechanism of simply supported beam bridge under directional impulse and sliding pulse earthquake is studied,and the dynamic response trend of simply supported beam bridge under two kinds of impulse earthquake is analyzed.The research shows that:the collapse process of simply supported beam bridge under directional pulse and sliding impulse earthquake is mainly manifested in the lack of bearing capacity of piers caused by large-area failure of concrete at the bottom of piers,which leads to the collapse of the whole bridge.When the pier bottom begins to be damaged,the pier enters plasticity,and the bending moment at the pier bottom changes slightly.The collapse process of simply supported beam bridges under impulse earthquake can be divided into normal operation stage,damage evolution stage and collapse stage under earthquake action.The pier top displacement,pier bottom shear force and bending moment of the simply supported beam bridge under the sliding pulse earthquake are 1.28,1.35 and 1.06 times of those under the directional pulse earthquake,respectively.However,the time process from damage to collapse of the bridge under the directional impulse earthquake is shorter than that under the sliding impulse earthquake.