Research On Seismic Behavior And Design Method Of Self-centering Piers Considering SSI Effects

The traditional seismic design of bridge piers is based on the concept of ductile design.During the earthquake,energy is dissipated through plastic deformation.After the earthquake,the structure will experience significant residual deformation and structural damage,which will affect the normal use of the bridge and make it difficult to repair after the earthquake.In order to improve the seismic performance of traditional piers,a new type of self-centering FRP(Fiber Reinforced Polymer)-concrete-steel composite hollow pier is proposed in this paper,which can reduce the residual deformation and structural damage of the piers after the earthquake,and the application of corrosion-resistant materials can improve the durability of the piers in the severe natural environment.Based on this new type of bridge pier structure,this thesis intends to study the seismic performance and design method of self-centering bridge piers considering Soil-Structure Interaction(SSI)by means of experiment,theoretical analysis and numerical simulation.The main work and conclusions are as follows:(1)Nonlinear spectral analysis of self-centering structures considering SSI effects.The numerical model of single-degree-of-freedom self-centering structure considering SSI effects was established using Matlab,and the influence of structural parameters and soil property parameters on the inelastic displacement ratio was studied.The functional relationship among the inelastic displacement ratio,the strength reduction coefficient and the structural period was established through regression analysis method.(2)Cyclic loading tests of the self-centering pier.A total of five tests were carried out on the proposed new self-resetting bridge pier,and the effects of initial prestress size,the diameter and configuraton of the energy dissipation bar on the seismic performance of the bridge pier were studied.The test results show that the self-centering bridge pier proposed in this paper has the advantages of self-centering after earthquake and the main structure is basically non-destructive.(3)Finite element simulation of seismic performance of self-centering pier.Based on the finite element analysis software Open Sees,the finite element analysis model of self-centering pier is built,and the accuracy of the finite element analysis model is verified based on the cyclic loading test results.Thereafter,the finite element model of self-centering pier considering SSI effect is established,and the results are compared with the numerical model based on Matlab.The results show that the calculation results of the finite element model built on Open Sees and the numerical model built on Matlab are in good agreement,which validates the rationality of the two models.(4)Research on the design method of self-centering bridge pier considering SSI effects.A seismic design method for the self-centering bridge pier considering SSI effects is investigated.Taking a self-centering bridge pier on the class E soil site for example,the seismic design is made,and 30 earthquake ground motions are selected for nonlinear time-history analyses.Good agreement is observed between the calculated responses and the design demands,demonstrating the accuracy of the design method.(5)Seismic performance evaluation of self-centering piers considering SSI effects.Based on the self-centering pier designed above,the finite element model of the self-centering piers with and without considering the SSI effects are established to conduct incremental dynamic analysis,and the relationship between the elastic-plastic response and ground motion intensity of the structure is established.According to the fragility curves,when the maximum drift is taken as the seismic performance index,and Sa is less than1.5g,the exceeding probability of the self-centering pier considering SSI effect is less than that of the selfcentering pier without considering SSI effect.When residual drift is taken as the performance index,and Sa is less than 3g,the exceeding probability of self-centering pier considering SSI effect is less than that of the self-centering pier without considering SSI effect.