Study On Seismic Performance Of Ultra High Performance Concrete Pier With High Ductility

China is located in the earthquake-prone zone of the world,and bridges are widely distributed in high-intensity areas.As an important component of bridge resistance to earthquakes,improving its seismic performance has a significant effect on bridge structure resistance to earthquakes.In order to improve the ductility and seismic performance of piers under earthquake,this paper uses the material characteristics of UHPC,high-strength reinforcement and prestressed reinforcement to replace ordinary concrete in plastic hinge area of piers with UHPC and ordinary reinforcement,and studies the influence of high-strength reinforcement replacement rate,prestressed reinforcement replacement rate and stirrup strength on seismic performance of UHPC composite piers.The nonlinear time history analysis of an actual pier is carried out,and the influence of parameters such as high-strength reinforcement and prestressed reinforcement on the seismic response of UHPC composite pier is obtained.The main research contents and conclusions of this paper are as follows:(1)RC and UHPC compression specimen models are established based on ABAQUS software,and the simulation results are compared with the test data through low cyclic loading numerical simulation,so as to verify the material constitutive relation and the rationality of the modeling method.(2)RC bridge pier model,UHPC plastic hinge bridge pier model,high-strength reinforced UHPC composite bridge pier model and prestressed UHPC composite bridge pier model are established respectively,and the effects of material characteristics,replacement rate of high-strength reinforcement,replacement rate of prestressed reinforcement and stirrup strength on seismic performance of bridge piers are studied.(3)When the plastic hinge is replaced by UHPC,the peak load,yield displacement,ductility coefficient and accumulated energy consumption of the pier increase by 7.7%,5.4%,80.5% and 100.2% respectively.Compared with UHPC composite piers,the seismic performance of high-strength reinforced UHPC composite piers and prestressed UHPC composite piers increases with the increase of steel bar replacement rate and stirrup strength.For example,when the replacement rate of steel bars is 2/3,the peak load,yield displacement and accumulated energy consumption of high-strength reinforced UHPC composite piers increase by 28.4%,27.1% and 36.4% respectively,while the characteristic load,yield displacement and accumulated energy consumption of prestressed UHPC composite piers increase by47.4%,16.4% and 39.4% respectively.(4)Taking the actual pier as the research object,RC pier model,composite pier model with plastic hinge UHPC,high-strength reinforced UHPC composite pier model and prestressed UHPC composite pier model are established.Through nonlinear time history analysis,the influence of different design parameters on the seismic performance of piers is studied.Compared with the common pier model,the maximum displacement responses of UHPC composite pier,high-strength reinforced UHPC composite pier and prestressed UHPC composite pier in earthquake are reduced by 7.4%,14.0% and 15.7%,respectively,and the seismic performance of composite pier with ultra-high performance concrete is obviously improved.