Study On Pounding Effect On Seismic Response Of Simply Supported Bridge Considering Soil-Abutment Interaction Under Earthquakes

Several investigations of earthquake disaster find that:pounding between the abutment and the superstructure is a kind of typical seismic response for small span girder-bridges.During the pounding,the displacement of the superstructure is limited by the abutment,when the seismic force is transmitted to the abutment-soil system,and the nternal forces in this system will be generated.If the impact force is too large,the abutment-soil system may undergo plastic deformation or even failure.The sudden change of the boundary condition will lead to the change of the seismic response of the bridge.Therefore,for the seismic design of the bridge,it is very essential to analyze the dynamic interaction between the superstructure and the abutment-soil system.Based on this background,this dissertation takes T-beam bridge as the analysis object,and carry out some study on pounding effect of simply supported bridge considering soil-abutment interaction under earthquakes,the main research contents and results are as follows:(1)According to the research on the dynamic interaction between abutment and soil,we build a nonlinear dynamic analysis model for a three-span simply supported T beam bridge by using Open Sees.And then,by comparing the responses from two cases that with and without considering the pounding between the abutment and the superstructure,we find that: the abutment-soil system can effectively restrain the longitudinal movement of the superstructure,but the collision between the superstructure and the abutment will cause the system to withstand a huge impact.As a result,the seismic response of the soil behind the abutment and the pile foundation of abutment will increase obviously.(2)Through parametric analysis,some factor’ effects on seismic response of simply supported bridge are studied,and the factors include collision stiffness,the friction of the rubber bearing,the abutment-girder expansion joint width and the pounding location.The results show that: the above parameters can affect the displacement of the superstructure,the seismic force borne by the abutment system,etc.(3)Considering that the abutment backwall may be damaged during the seismic impact,we take the former abutment as the reference structure and then study the failure mode and mechanical properties of the abutment backwall.The research results show that: as the load increasing,the connection between the abutment backwall and the abutment cap will be broken,and the longitudinal bars in the structure will yield.In addition,when the loading position on the structure decreases and the thickness of abutment backwall increases,the yield load and the ultimate bearing capacity of abutment backwall will increase.(4)On the basis of considering that the damage of the abutment backwall may affect the pounding effects of the bridge,we improve the Open Sees model.And then we analyze the seismic response of the whole bridge.The research results show that:the impact force between the abutment and the superstructure is greatly reduced when considering abutment backwall damaged.However,the displacement of the superstructure will increase.In addition,some factor’ effects on seismic response of simply supported bridge are studied.The results show that: decreasing the abutment-girder expansion joint width、lower the impact position and increasing the yield force of abutment backwall can enhance the limiting effect of abutment-soil system on the superstructure in different degrees.But the abutment-soil system will withstand a large impact force from the main girde,which causes the seismic responses of the soil and the abutment pile foundation increasing significantly.