Research On Damage Index For Seismic Fragility Analysis Of High Bridge Pier

Bridge plays a key role in the transportation system,it may cause huge social and economic losses once it is destroyed.Plenty of high pier bridges have been built in the west of China where are high intensity seismic areas,however,the current seismic codes do not provide universal standards for the seismic design of high pier bridges.There is no unified understanding of the damage index that can evaluate the damage of high pier perfectly at present,on account of high pier is greatly affected by its own high order mode,its damage evolution process is more sensitive to seismic wave spectrum characteristics too.In this paper,the seismic vulnerability of high pier is analyzed by using the near-fault seismic records.The main work and conclusions of this dissertation as follows:(1)The development of seismic design theory is introduced,the present situation of seismic fragility analysis of bridges is summarized,the seismic fragility analysis of high pier bridge is carried out.(2)Pushover analysis is carried out to obtain the force-displacement curve of the high pier model.The displacement damage index is defined and quantified based on the displacement values of each performance point of pier.Moment-curvature analysis is carried out for the high pier,and the curvature damage index was quantified according to the analysis results.A composite index is proposed based on the deformation and energy failure criteria.(3)The seismic fragility curves of high pier are established using different damage indexes based on advanced ground motion parameter.In the case of slight and moderate damage,the damage evaluation of high pier is close to each other according to fragility curves.With the increase of damage degree,displacement index is no longer applicable,and its assessment of pier damage is more serious.(4)Standard deviation analysis and regression analysis are used to analyze the applicability of damage indexes.The composite damage index considered the dual effects of deformation and energy,which has small dispersion and good stability,it is may provide useful reference for damage assessment of high pier.