Study On RSAPS Based Refined Simulation Models For Seismic Damage Analysis Of RC Bridge Components

With the rapid development of the transportation infrastructures in China,stupendous achievement has been acquired in highway bridges and railway bridges.At the same time,China located at the junction of the world’s two major earthquake zones and earthquake disaster is a serious concern.Seismic disaster reduction for bridges is always concerned by the researchers in earthquake engineering.Refined numerical models for main bridge members were established and the nonlinear behavior of bridge could be simulated efficiently and accurately,which can provide an important basis for seismic design and performance evaluation of bridges.Therefore,it is of great value to conduct research on refined modeling theory and simulation method for RC bridges.In this paper,focusing on RC bridges,an intensive research was conducted on refined modeling theory and simulation method for main members of RC bridges,seismic isolated bearing and whole bridges.The main achievements are as follows:(1)Based on Timoshenko beam theory,a flexure-shear fiber element based on explicit algorithm was developed and implemented in the refined simulation analysis platform RSAPS,with a combination of 2D constitutive law for concrete material based on Modified Compression Field Theory(MCFT)and the theory of fiber element.The hysteretic behavior of RC columns having flexure failure/flexure-shear failure/shear failure with rectangular and circular cross-sections was simulated using the RSAPS platform.The simulation results were compared with the experimental results and the simulation results using the flexure fiber element ignoring the shear deformation.It was found that both the flexure fiber element ignoring the shear deformation and the developed flexure-shear fiber element can well simulate the hysteretic behavior of RC columns having flexure failure with small shear deformation.Howerer,for RC columns having flexure-shear failure/shear failure with big shear deformation,the analytical results using the flexure fiber element ignoring the shear deformation tended to overestimate the initial stiffness,energy dissipation and the shear strength for shear-dominated columns,while the developed flexure-shear fiber element was able to capture the behavior of strength and stiffness degradation and capture the confinement effect of stirrups on concrete.The response predicted with the developed flexure-shear fiber element showed a very good correlation with the experimental results,and the computational efficiency was high.(2)Experimental study on seismic behavior of eight short RC columns subjected to uni-lateral and bi-lateral cyclic load with a constant axial load was conducted.The test variables included the loading path,the longitudinal and the transverse reinforcement ratio,and the axial load ratio.Based on the research results,very strong coupling was observed between the strong axis and weak axis direction of the specimens,and the maximum strength of the columns in each direction of the biaxial test was lower than that from the corresponding uniaxial test,with an increased hysteretic energy dissipation.The loading path,the axial load ratio,the longitudinal and the transverse reinforcement ratio did not affect the stiffness degradation significantly,but affected the strength degradation and energy dissipation,especially the total dissipated energy until conventional collapse.(3)The 3D Modified Compression Field Theory was modified to account for the cyclic loading condition.A 3D flexure-shear fiber element based on explicit algorithm with a combination of modified 3D MCFT and the theory of fiber element was proposed and implemented in the RSAPS platform to develop the multi-demensional nonlinear analysis module.Interaction between the axial,biaxial shear and biaxial bending can be considered.The tests of RC columns subjected to uni-lateral and bi-lateral cyclic loads were simulated using the RSAPS platform.The results showed that the nonlinear hysteretic behavior of 2D and 3D RC columns could be simulated efficiently by the developed multi-demensional nonlinear analysis module on the RSAPS platform.The simulated results showed a very good correlation with the experimental results.The seismic responses of a RC bridge were simulated using the RSAPS platform.The results showed that the analytical results of shear-dominated pier using the fiber element ignoring shear deformation tended to underestimate the pier displacement and overestimate the shear strength and energy dissipation.The developed 3D flexure-shear fiber element should be used for modeling the responses of shear-dominated members.(4)Based on the RSAPS platform,a damage analysis method for RC columns was proposed,and the fiber element module for damage analysis was established with a uniaxial damage concrete constitutive model introduced into RSAPS/MAT.In order to simulate the bond-slip effects,a section element combined with a steel stress-slip model was developed and implemented in the RSAPS platform.A pseudo-static test of a RC column and a shaking table test of a RC pier were simulated using the RSAPS platform.The results indicated that the simulation results showed a very good correlation with the experimental results when the bond-slip effects were considered.The damage analysis for RC members could be run effectively using the RSAPS platform,and the damage distribution,the damage evolution process,and the weak zone of RC members coudl be shown clearly.Therefore,the RSAPS platform is very efficient for engineering applications.(5)An isolation element model for static and dynamic analysis was developed based on the RSAPS platform.The model combined the Bocu-Wen model that considered bi-lateral coupling effects with the two-spring model that considered vertical stiffness variation.The critical load at a given lateral displacement was determined using the overlapping area method.The loading/unloading condition was chosen depending on the isotropy behavior of the isolation bearing.A bi-lateral displacement-controlled test,a shaking table test of lead–rubber bearings under bi-lateral seismic excitations and a shaking table test of a scaled isolated bridge were simulated using the proposed model on RSAPS.The results showed that the proposed model was able to consider the bi-lateral coupling effect of lead-rubber bearing,and effectively simulate the static and dynamic behavior of seismic isolation bearings.Decreasing of the critical load with increasing of the lateral displacement could also be simulated by the proposed model on RSAPS.The seismic responses of a bridge in the isolated and non-isolated cases were simulated using the RSAPS platform.The results showed that LRB bearings could reduce the pier base shear,pier damage and the deck acceleration to some extent,and seismic isolation with LRB bearings was effective.