Research And Improvement On Seismic Performance Of Integral Assembled Self-Centering Pier

Compared with the traditional cast-in-place reinforced concrete bridge piers,the integral assembled self-centering bridge piers have the advantages of fast construction speed,little influence by environmental factors,small residual displacement after earthquake and easy repair,which are increasingly valued by designers.Two typical integral assembled self-centering piers(numbered PT2 and HBD2)were selected,and the seismic performance of different types of piers was analyzed by pseudo-static and nonlinear time-history analysis and comparison with cast-in-place piers.Based on this,a new type of integral self-centering bridge pier with cushion layer is proposed,and the superiority of the structure is verified by nonlinear time-history analysis.The main research contents of this paper and the main conclusions are as follows:(1)According to the stress state of the energy-dissipating bar under the horizontal seismic force,the stress process of the pier is divided into three stages,and the pier top displacement,pier bottom moment and shear capacity limit of the pier under critical state and limit state are analyzed,which compensates for the defect that the energy-dissip'ating bar is neglected at present and the force state of the integral assembled self-centering bridge pier is determined by the height of the compression zone.The research shows that the shear capacity of the integral assembled self-centering piers depends on the friction of the joints at the bottom of the pier.Under normal circumstances,shear failure will not occur in the joints at the bottom of the pier.(2)Based on the previous scholars' researches,the Abaqus solid models of PT2 and HBD2 piers were established,and the validity of the models was verified by pseudo-static analysis.After that,the cast-in-place model with the same configuration and parameters was established,and the difference in seismic performance between the integral assembled self-centering bridge piers and the cast-in-place pier was compared and analyzed.The axial compression ratio,prestressing degree,prestressed bars ratio,energy-dissipating bars ratio,unbonded length of energy-dissipating bars,position of energy-dissipating bars and shear-to-span ratio are also analyzed for the seismic performance of the integral assembled self-centering bridge pier.Studies have shown that increasing the axial compression ratio and prestressing degree,reducing the shear span ratio,and increasing the reinforcement ratio of energy-dissipating bars can improve the seismic performance of such piers,while the prestressed bar ratio and the length and position of the energy-dissipating bars have little effect on its seismic performance.(3)Establish nonlinear dynamic time-history analysis models of PT2,HBD2 and cast-in-place pier,select LOMA seismic wave,compare and analyze the difference between the dynamic response of PT2,HBD2 and cast-in-place pier.The research shows that the base bending moment and shearing force of the integral assembled self-centering piers are much smaller than those of the cast-in-place pier,but the base axial force is much larger than that of the cast-in-place pier.The axial force of the HBD2 integral assembled self-centering pier is smaller than that of the PT2,so it can use reasonable configuration of energy-dissipating bars to reduce the base axial force of the self-centering bridge pier.(4)In order to make up the defect that integral assembled self-centering bridge pier has excessive base internal force under the earthquake,this paper proposes a new seismic structure of steel-rubber cushion in integral assembled self-centering bridge pier.By comparing the seismic response of the original piers with that of the new piers under the nonlinear dynamic time history,it is concluded that the new structural form in integral assembled self-centering bridge pier can effectively reduce the internal force response of the integral assembled self-centering bridge pier,and the base internal force decreases as the thickness of the cushion layer increases.