Research On Seismic Behavior Of Segmental Pier With Steel Sleeve Concrete Mortise And Tenon Joint

With the continuous promotion of the Belt and Road Initiative,further requirements have been put forward for the acceleration of bridge construction speed,but the cast-in-situ construction way of substructures lengthens the construction period of the bridges.However,the emergence of the concept of rocking segmental pier makes it possible to improve the construction speed of the substructure.Although segmental piers have excellent post-earthquake self-centering ability,the characteristics of shear slippage between segments and poor energy dissipation hinder their wide application in strong earthquake areas.Therefore,it is necessary to develop a kind of rocking self-centering segmental pier with strong resistance to shear slip and excellent performance in energy dissipation.In this paper,a kind of steel sleeve concrete mortise and tenon segmental pier is put forward,and the anti-shear ability and anti-seismic performance of the mortise and tenon joints are comprehensively studied.The main contents and conclusions are as follows:(1)The ABAQUS platform is used to simulate the direct shear test.First,the correctness of the modeling approach is verified.Then the effective measures to improve the shear capacity of the mortise and joint shear bonds of cylindrical concrete are discussed by setting different working conditions.The conclusions are as follows: The mortise and tenon shear key of plain concrete is brittle failure in shear failure.The shear failure mode of reinforced concrete is similar to that of plain concrete and the capacity lifting is very small compared to the former.The shear failure of mortise and tenon shear key of concrete covered by steel tube shows ductile and the capacity lifting is evident compared to that made of plain concrete.(2)A kind of segmental pier with mortise and tenon shear key(MTSP)is proposed and the seismic performance of MTSP is compared with that of monolithic cast-in-situ pier(MP)and flat joint pier(PSP)by simulating quasi-static test with ABAQUS.The conclusions are as follows: Compared with PSP,MTSP has certain improvement in bearing capacity and energy dissipation capacity,especially in the control of intersegment joint opening.Since the structural system of the rocking segmental pier is different from that of the monolithic cast-in-situ pier,the energy dissipation capacity of MTSP and PSP is quite lower than that of the MP of the same size,so additional energy dissipation devices are needed.In spite of the defect in energy dissipation,the residual displacement performance of the two segmental piers is better and they have a strong self-centering ability.(3)Based on MTSP,a kind of mortise and tenon pier with external mild steel damper at the bottom of the pier(MTSPD)is proposed,and the comparison between the mortise and tenon pier with energy dissipation bar inside(MTSPE)and MP is made.Finally,the parameters affecting the seismic behavior of MTSPD are studied.The conclusions are as follows: Under low cyclic loading,both MTSPE and MTSPD have obvious improvement in bearing capacity,energy dissipation capacity and stiffness compared with MTSP,and the lifting in energy dissipation capacity of MTSPE is about 20% higher than that of MTSPD,and they are close to each other in other aspects.Increasing the axial pressure ratio and prestress degree can improve the bearing capacity and energy dissipation capacity of bridge piers and reduce residual deformation and there are no apparent changes when change the prestressed tendon ratio.(4)10 earthquake waves are selected,and the amplitude of acceleration is modulated to the design earthquake and the rare earthquake,respectively.The dynamic time-history analysis of MP,MTSPE and MTSPD piers is carried out,and the pier top displacement response and residual displacement of the three piers are investigated by taking the mean value of pier response under the action of 10 seismic waves as the standard.The conclusions are as follows: Under design earthquake,the displacement of the top of the mortise and tenon pier is larger and the residual displacement is smaller.Under rare earthquake,the displacement and residual displacement are smaller.The displacement control at the top of MTSPD pier is better than that of MTSPE pier under both design earthquake and rare earthquake,and the residual displacement is slightly greater than that of MTSPE pier.