Research On Seismic Damage And Failure Modes Of Railway High Piers With Replaceable Components

Seismic design theory based on the non-collapse of bridge structures can reduce human casualties.However,as urbanization continues to develop,the economic losses caused by earthquakes are increasing.Based on the understanding of seismic damage,bridge designs that serve as lifeline engineering should be transformed into resilient functional structures.This will ensure that the system can be quickly repaired and restored to its normal function without affecting overall performance after an earthquake.This will improve the efficiency of earthquake resistance and rescue,and reduce the losses caused by earthquake disasters.This paper is based on actual engineering background,and studies the structural transformation of a new type of railway pier,which is a partially replaceable pier based on the concept of recoverable function.Nonlinear dynamic analysis calculations were performed using numerical simulation software to study its structural response under three seismic load cases: single transverse bridge direction,transverse + vertical bridge direction,and transverse + longitudinal+ vertical bridge direction.Based on the results of incremental dynamic analysis(IDA),IDA curves were drawn to explore the seismic damage characteristics of the main pier columns and replaceable steel trusses,and to seek differences in structural response under different seismic load cases.Through regression analysis,a probability function of damage surpassing based on capacity demand ratio was established to calculate the damage surpassing probability of vulnerable sections and components at different seismic performance levels,and to draw fragility curves.A probability-based seismic performance assessment of the structure was carried out using distribution functions.The research work mainly includes:(1)Analyzing the characteristics of the new pier structure,designing the original structure into a new pier with replaceable components,realizing the resilient design of the structure under strong earthquake,and establishing an Open Sees numerical analysis model.(2)Determining the damage indicators of the research object and clarifying the boundary values of damage indicators at various performance levels.(3)Selecting earthquake waves and gradually increasing the peak acceleration from 0.1g to 1.5g with a step size of 0.1g.Twelve sets of earthquake waves are inputted to the pier columns and replaceable steel trusses under three conditions for IDA analysis to draw IDA curves and analyze the damage process.(4)Based on the damage index,a capacity demand ratio model is used for curve fitting to establish fragility curves of pier columns and replaceable steel trusses and analyze their fragility.Through the above research work,the following conclusions are mainly drawn:(1)The pier columns of the replaceable component new pier basically remain undamaged or can be repaired in extremely rare seismic events.(2)The diagonal struts in the replaceable steel truss connectors yield in sequence from the first row to the seventh row as the peak acceleration increases step by step.In extremely rare seismic events,they basically remain undamaged or can be repaired.The vertical and chord members remain elastic under various seismic loads.(3)The peak acceleration at which the diagonal struts in the replaceable connector reach the limit values of various seismic performance levels is significantly higher than that of the pier columns,indicating that the yielding of the replaceable connectors in the structure plays a role in consuming seismic energy for the main bridge pier,achieving graded energy dissipation in seismic design.(4)Under the three load cases,the IDA curves of the structure show that the replaceable component new pier has good seismic performance and can be restored to normal use after an earthquake.