Simulation Of The Whole Collapse Process Of Simply Supported Girder Bridge Under Near Field Pulse Earthquake And Analysis Of Bearing Parameters

In the development process of the western development strategy and urbanization construction of the public railway network system,the bridge structure,as an important node of the traffic line,has achieved great development and great progress.The fault sources in the western region are densely distributed and earthquakes occur frequently.The seismic resistance of near-fault or cross-fault bridges has become an unavoidable problem.This paper firstly summarizes the research status of near-fault ground motion response spectrum,near-fault ground motion characteristics,bridge collapse criteria and collapse process by referring to relevant domestic and foreign literatures.Taking a three span simply supported beam bridge as the engineering background,based on ANSYS / LS-DYNA nonlinear finite element software,the three-dimensional finite element nonlinear analysis model of the bridge is established to simulate the whole process of dynamic disaster of the simply supported girder bridge under the action of near fault earthquake.To exploring the collapse mechanism and response variation of simply supported girder bridges under near-fault earthquakes.The main research work of this paper is as follows:(1)The significance of seismic research of bridges in near-fault area,ground motion response spectrum near fault,ground motion characteristics,bridge damage and collapse criteria,and research status of collapse process are reviewed;(2)Based on ANSYS / LS-DYNA nonlinear finite element software,a nonlinear finite element three-dimensional model of a three span simply supported girder bridge is established.The effects of different near fault pulse mechanisms,pulse amplitudes and pulse periodic ground motions on the collapse process and seismic response of the simply supported girder bridge are considered;(3)The simulation calculation of the dynamic response of the simply supported girder bridge and the whole collapse process under different earthquake conditions is completed,and the failure modes of the simply supported girder under earthquake action are summarized into three types,namely: the pier is damaged,but it is not enough to cause large-scale damage to the pier,and the overall structure maintains basic functions;large-scale element failure of bridge piers and gradual loss of bearing capacity causing bridge collapse;the pier has a certain degree of damage and large rotation,and finally the beam falls due to the excessive relative displacement of pier beam.In addition,according to the collapse mode and structural response,the catastrophic process of simply supported girder bridge is divided into three stages,namely the normal operation stage,the damage evolution stage and the collapse stage;(4)Based on the simulation analysis of the catastrophe process of the simply supported girder bridge under the near fault earthquake,the seismic performance and parameters of the bearing have an important impact on the nonlinear dynamic response of the simply supported girder bridge.The fifth chapter explores the change trend of bridge response and the evolution of collapse when the bearing adopts different shear stiffness by adjusting the material parameters of the bearing.The results show that the small shear stiffness of the bearing will cause large seismic response,especially the collision effect between beams and between beams and abutments;If the shear stiffness is too large,the duration of damage evolution stage of simply supported beam bridge will decrease.