Seismic Performance Analysis Of Railway Bridge Piles Based On P-y Curve Method

According to the current seismic design method for the substructure of bridge,the pier becomes damaged structure under seismic effect,and the group piles foundation under the pile cap becomes protection of components,considering that the main of elastoplasticity deformation occurs only at pier and pile foundation only calculates deformation within the elastic range.Although according to this design method,we can avoid the problem not easy to be repaired due to the hidden positions of the pile foundation that is commonly under the ground,it can also cause the problems that making pile foundation design standard too high and more difficult to design,at the same time can also lead to great waste,but even so,the earthquake damage survey shows that under strong earthquakesthe,pile foundation will be also affected by different degree of damage.In view of this,this paper attempts to analyze the seismic performance of railway bridge pile foundation based on the p-y curve method,and the main tasks are:(1)The main research history and current situation of soil-pile-structure interaction are reviewed,and the main analytical methods are summarized;The basic theory of p-y curve method and the calculation methods of various p-y curves are summarized,and the validity of p-y curve method in simulating the interaction of pile-soil is verified by comparison of field test and power centrifuge test results.(2)The displacement ductility coefficient is an important indicator in design of bridge foundation,parameters analysis for the displacement ductility coefficient is performed by selecting single pile foundation and pier-group piles foundation and the main parameters axial compression ratio、height of the pier、longitudinal reinforcement ratio、pile diameter、the undrained shear strength of soil and p-y curve shape parameter are included,finally the influence of various parameters on displacement ductility coefficient of pile foundation are summarized.(3)A seismic performance evaluation to the pier-group piles foundation system is made.Because of the different components strength in system,there is a difference which part will get into the elastic-plastic state under the seismic effect,as a result it will lead、to different failure modes and for different failure modes,decision method is given.Pushover analysis and capacity spectrum method are important in seismic design of PBSD,the influence of different lateral load distribution model on the Pushover curve are studied,the results show that for pushover analysis of the bridge structure,concentrated force loaded on pier top is more appropriate than the other two.Different methods of construction of the capacity spectrum are summarized,at the same time,through being compared with the results of time history analysis method,find that when the system is the pile failure mode,FEMA440 method is more accurate than the two other methods and its error can be partly meet the requirements.With regard to railway bridges in China,which generally are simply supported girder bridges with gravity piers,a simplified seismic response analysis method is deduced,and through being compared with the calculation results of time history analysis,the method validity is verified.When regarded as a part of damaged components in system,the pile foundation according to the China railway engineering anti-earthquake design specification is recommended three-level seismic performance requirements,so in this text three kinds of evaluation methods and the corresponding index parameters range are set up from a different perspective,and a seismic performance evaluation to an engineering example are made under the design earthquake and the rare earthquake condition respectively.