Study On Seismic Performance Of Long Span Rigid Frame-Continuous Bridge Subjected To Near-Fault Pluse Like Ground Motions

The seismic response of continuous rigid frame bridge with Long-Span and High-Pier built increasingly in the near field of a rupturing fault in recent years,with the development of highway and railway construction,can be significantly different from those observed in the far field due to the different characteristics in the ground motions.One of the most important characteristics of near-fault events concerning the field of structural and civil engineering is the impulsive character of the velocity and displacement ground motions occurring over long periods and thereby having a severe influence on the structures.The existing seismic design codes for buildings neither improve the seismic design force requirements of the structures nor forbid the building of important structures in hazardous areas including the near-fault source.This is further improvement in the design of Continuous Rigid Frame Bridge with Long-Span and High-Pier in hazardous areas is required.This thesis presents results of a study aimed at evaluating the near-fault effects on the dynamic response and seismic damage of Continuous Rigid Frame Bridges with Long-Span and High-Pier.The main research content is as follows:1? The seismic research status of bridges with Long-Span and High-Pier in the near field of a rupturing fault and what needs to be improved as well as the most important characteristics of near-fault events were summed and reviewed.Following that,the research subject on the seismic response of Continuous Rigid Frame Bridges with Long-Span and High-Pier in the near field of a rupturing fault was proposed.2? An artificial simulation method of non-stationary near-fault pulse-type ground motions was proposed.Four power spectra of near-fault pulse-type ground motions,near-fault non-pulse-type ground motions,the high frequency components of near-fault pulse-type ground motions and far-fault ground motions were firstly analysed and compared based on the seismic records during the 1999 Chi-Chi,Taiwan,Earthquake.After considering the superposition between the high frequency components of near-fault pulse-type ground motions and random impulsive models,an artificial simulation method of non-stationary near-fault pulse-type ground motions was then proposed,which could apparently reduce the variance of response spectra of earthquake ground motions.3? The work for validating the near-fault pulse-type ground motions energy-based identification method was carried out using selected near-fault and far-fault ground motions.Following that,the difference of pulse effects on different directions was analysed in depth.The influence of the velocity and direction effects of pulse-type ground motions on the seismic response of the bridge with Long-Span and High-Pier was then investigated very carefully using a typical engineering examplein the southwest mountainous area based on ANSYS numerical simulation.4? The nonlinear seismic response of continuous rigid frame bridge with Long-Span and High-Pier in the mountains subjected to near-fault ground motions with multiple pulses was investigated in depth,and the applicability of near fault pulse identification method to multi pulse ground motion was validated.Then,the nonlinear seismic response of continuous rigid frame bridge with Long-Span and High-Pier in the mountains subjected to non-pulse like ground motion,near-fault ground motions with multiple pulses and single pulses was investigated in depth based on its nonlinear dynamic models built in the Open Sees framework.5? The effects of the spatial variation of seismic ground motions on continuous rigid frame bridge with Long-Span and High-Pier was investigated carefully.The nonlinear seismic response of bridge structures under multi-point excitations was carried out considering the effects of the spatial variation of seismic ground motions used the artificial waves under different site conditions with various apparent wave velocities calculated by wavelet method.Furthermore,the effects of the spatial variation of seismic ground motions on continuous rigid frame bridge with Long-Span and High-Pier was investigated.6?The IDA curves,including piers relative displacements and supports relative displacements,of continuous rigid frame bridge with Long-Span and High-Pier subjected to uniform excitations and multi-support excitations were firstly obtained by using incremental dynamic analysis(IDA)based on twenty seismic records during the 1999 Chi-Chi,Taiwan,Earthquake.Considering the IDA curves and seismic fragility analysis method,fragility curves of this kind of structures subjected to uniform excitations and multi-support excitations with the impulsive character were then analysed to evaluate seismic behaviors of this kind of structures.