Experimental Research On Seismic Behavior Of Self-centering Precast Segmental CFST Bridge Piers With Replaceable Composite Panels

Self-centering precast segmental concrete-filled steel tube(CFST)bridge piers have broad application prospects in the field of bridge engineering due to its convenient construction and small residual displacement after earthquakes.However,the stress concentration at the toe of bridge pier under the earthquake is likely to cause the outer steel tube buckling and local concrete crushing,which brings certain difficulties to realize quick recovery of the bridge functions after earthquakes.Based on this,an innovative self-centering precast segmental CFST bridge pier with replaceable composite panels(RCPs)is proposed.The bottom segment of the bridge pier is divided into the wine-cup shape core area of concrete-filled steel tube and the peripheral area of RCPs,and it can also equip with replaceable tension-only energy dissipation(RTED)components.The RCPs are used to concentrate the elastoplastic deformation under the earthquake,protect the main structure of the bridge pier,and the RCPs could be quickly replaced to achieve the goal of recovering functions after the earthquake.Based on the experiment research,finite element simulation and theoretical analysis,the following studies have been carried out on the seismic performance of the self-centering precast segmental CFST bridge pier with replaceable composite panels:(1)The cycle tests of four 1:3 scale bridge piers have been completed.The effects of the posttensioning(PT)force level and the RTED components on the seismic performance of bridge piers are studied,and the specimen with RTED components was selected for rapid repair.The research results show that the assembly and replacement of the bridge pier is easy to operate,and the seismic performance of the replaced bridge pier is basically the same as the original one,which means the bridge pier could achieve the goal of the structural function recovery after the earthquake.The damage of the specimen under the cyclic loading is concentrated on the replaceable composite panels and the RTED components,and the wine-cup shape core area of CFST is basically intact.Increasing the PT force level could effectively improve the initial stiffness,lateral strength,and energy dissipation capacity,but the ductility performance will be slightly reduced.The installation of RTED bars could significantly improve the lateral strength and energy dissipation capacity of the bridge pier,the ductility performance has been improved,and there is basically no effect on the residual displacement.(2)The 3D solid and 2D fiber element analysis models of the bridge piers are established respectively,and the applicability of the two modeling methods is compared with the test results.The finite element analysis of the bridge piers is carried out,and the influence law of RCP sizes,material type and amount of RTED components,axial load ratio,PT force level,shear span ratio,compressive strength of core concrete and the nominal yield strength of outer steel tube on the seismic performance of bridge piers are given.The results show that dividing the bottom segment into the core and peripheral areas effectively protects the main structure of the bridge pier,making it basically in an elastic state at 4.5% drift.The RCPs produce elastoplastic deformation and effectively dissipate seismic energy.In order to ensure the self-centering capacity of the bridge pier,the contribution of RTED bars to lateral strength should be no more than 65%.The axial load ratio,PT force level,shear span ratio and compressive strength of core concrete have a significant impact on the seismic performance of the bridge pier.However,the yield strength of the outer steel tube has a limited impact on the seismic performance of the bridge pier.(3)The calculation formula of the skeleton curve characteristic points is determined by the analysis and fitting.A new restoring force model is deduced and compared with the test results.The displacement-based seismic design method of the precast segmental CFST bridge piers with replaceable composite panels is given,and a full-scale bridge pier is designed.The design method is verified through the elastoplastic time history analysis of the full-scale bridge pier under 10 natural seismic waves.