Dynamic Numerical Simulation And Experimental Study Of The Integral Bridge Abutment Subjected To Earthquake Loads

The earthquake is one of the most dangerous natural disasters, which causes a greatthreat to the human life, property and safety. Fast transportation is very important inorder to ensure, that the post-disaster relief work can be carried out smoothly. As a newform of abutments, the integral bridge abutments have a very good seismic resistance.However, in China the research about the integral bridge abutments is very limited, thusit is necessary to further study the seismic performance of this kind of structures. In thispaper, a dynamic constitutive model was developed, which can consider pressurehardening, non-linearity and hysteresis properties of soil. Also the numerical model forthe FLAC compute program was developed. Using the FLAC, the dynamic response oftwo different bridge abutments subjected to earthquake loads was studied. Theparametric analysis of the integral bridge abutment dynamic performance was carriedout. In addition, the integral abutment dynamic tests, using geotechnical centrifuge withshaking table, were done. The research results are presented below:(1) A linear elastic soil column response under dynamic loads using atwo-dimensional finite element program FLAC was carried out. The results werecompared with the data, which were got using the finite element program Marc. Theconclusion about the effectiveness of the FLAC for analyzing this kind of problems wasdrawn.(2) A dynamic constitutive model, that can consider hardening pressure, non-linearbehavior and hysteresis of soil, was developed using the FLAC. The model was used tostudy three different kinds of loading conditions. Using two models: the nonlinearconstitutive model and the Mohr-Coulomb model, the dynamic response of integralbridge abutment subjected to earthquake loads was calculated. The calculation resultsshowed, that the data from two different types of models, is very similar. However, theMohr-Coulomb model proved to be more efficient for the research of dynamicresponse of an integral bridge abutment.(3) The dynamic responses of cantilever abutments and integral abutmentssubjected to earthquake loads were calculated using the FLAC program. The resultsshow, that the existing MO method, which is used in the National standards for thecalculation of dynamic earth pressure behind the abutment, cannot give a true description of the earth pressure behind the abutments and the resulting load position.(4) The parametric study of an integral bridge abutment dynamic response showed,that the increase of the earthquake peak acceleration makes the dynamic response ofabutment, like the bending moment, shear force and earth pressure, increase as well; theearthquake wave form has little effect on the dynamic response of the integral bridgeabutment; the increase of the bridge span leads to increase of the earth pressure behindabutments, bending moment and shear force; the increase of abutment height causes theslip of the bottom of the abutment and makes bending moment in the middle of thebridge larger; the increase of the stiffness of the abutment leads to the increase ofbending moment and shear force in the abutment, the foam isolation layer weakens theabutment soil resistance to the lateral deformations leading to the increase of thebending moment in the abutment; the reinforced soil behind the abutment can reducethe earth pressure, bending moment and shear force in the abutment during theearthquake.(5) The results of centrifuge shaking table test shows that: accelerationamplification effect exists when the model wave propagates upward, at the same heightabutment acceleration amplification effect is more obvious than the soil; at the time ofthe biggest dynamic response, the up earth pressure is larger than the MO method whilethe down earth pressure is little different with the MO method.