Research On Nonlinear Seismic Response And The Most Critical Input Direction Of Curved Bridges

The bridge structure inevitably enters the plastic stage under the action of strong earthquakes,and often exhibits strong nonlinear characteristics.Therefore,it is necessary to analyze the nonlinear time-history response;compared with the linear bridge,the seismic response of the curved bridge structure is affected by The influence of the seismic input direction is more significant,and the most critical input directions corresponding to different positions or different responses in the same position are different;in addition,influenced by different components such as elastoplastic state and seismic intensity,the analysis of the seismic response considering the most unfavorable input direction becomes more complicated.In the past,the most critical input direction of the curved beam bridge was discussed based on the elastic stage of the component,while the research on the most critical input direction of the plastic state of the component was far from enough.Therefore,this paper takes curved beam bridge as the research object,the nonlinearity of the support and the nonlinearity of the pier was considered,the nonlinear seismic response of the component and the most critical input direction was studies.The main work and conclusions of this paper are as follows:1.Use SAP2000 to build a 3-span curved beam bridge model and perform nonlinear time-history analysis on the structure,compare the nonlinear seismic response of the curved beam bridge under different input directions,and study the response of each member when the support is in a linear and nonlinear state The most critical input direction,and discuss the impact of seismic input direction and seismic intensity on the seismic reduction rate.The results show that the most critical input directions of each response are different when the bearing state is linear,weakly nonlinear and strong nonlinear;both the seismic input direction and seismic intensity have an effect on the seismic reduction rate.The multi-angle input of seismic waves should be considered and the minimum value should be taken into account while the shock absorption rate of seismically isolated curved beam bridge is studied.2.Based on the nonlinear seismic response of the curved beam bridge pier,discuss the most critical input direction change of each response after the bridge pier enters the nonlinear and the impact of the seismic input direction on the seismic reduction rate.The results show that the most ciritical input direction of the seismic·response of the curved girder bridge changes after the bridge pier enters non-linearity;there is a significant difference in the seismic absorption rate under different seismic input directions,and the impact of the seismic input direction on the seismic reduction rate should be considered.3.Through the equivalent linearization method of the support,explore the seismic analysis of the isolated curve beam bridge and the simplified method to determine the most critical input direction.The results show that when the peak value of the response in the tangential direction(tangential or radial)is used as the criterion for the most unfavorable input direction,the difference between the most unfavorable input direction of each response obtained by the equivalent linearization method is less than the nonlinear time history result.It can be used to determine the most critical input direction of the seismic isolation beam bridge,and it is more simple than the nonlinear time history analysis method;when the peak value of the response in the direction is used as the criterion,the error is bigger.