| The damage of bridge piers leads to serious damage or even collapse of bridge structures,which is the main feature of bridge seismic damage.It is of great significance to improve and develop the seismic reinforcement methods of existing piers.In order to restore the performance of earthquake-damaged piers,the rapid repair of piers after earthquake is realized and the loss after earthquake is reduced.In this thesis,ultra-high-performance concrete and HTRB600 E high-strength steel bars are used to expand the cross-section of prefabricated square bridge piers with severe bending damage,in order to restore and improve the performance of seismic damaged bridge piers.The specific research content are as follows:(1)Combined with UHPC,a new material with high toughness and high durability,and high-strength steel bars with high strength and stable mechanical properties,the practicability and feasibility of strengthening earthquake-damaged prefabricated piers based on UHPC and high-strength steel bars were discussed.(2)The seismic reinforcement design method of prefabricated pier based on UHPC and high strength steel bar is proposed.For the prefabricated square piers with bending failure,the seismic design method of using UHPC and HTRB600 E high-strength steel bars to reinforce the prefabricated square piers with severe bending failure is proposed.Combined with the seismic reinforcement requirements of flexural failure piers,two seismic reinforcement piers based on UHPC and high-strength steel bars were fabricated.(3)The influence of UHPC reinforcement layer on the seismic performance of assembled piers with different structures is studied.The quasi-static test of prefabricated square piers based on UHPC and high-strength steel bars was carried out.The hysteretic curves,skeleton curves,energy dissipation curves,stiffness degradation,residual displacements and pier curvature of the prefabricated piers before and after reinforcement were compared and analyzed.The quasi-static test results show that the section enlargement method based on UHPC and high-strength steel bars significantly improves the flexural capacity,energy dissipation capacity and initial stiffness of the strengthened specimens,effectively restores and improves the seismic performance of the assembled piers,and the seismic strengthening effect is obvious.Under the action of reciprocating load,the deformation of the reinforced section of the pier body is small,no obvious plastic failure occurs,and the unreinforced pier body part shows obvious bending and shear failure characteristics.The top pier body of the reinforced section first develops into a plastic hinge zone.(4)Numerical simulation based on finite element software ABAQUS.Combined with the quasi-static test results of seismic reinforcement,a refined finite element model of assembled piers was established,and the correctness of the finite element model was verified by the test results.Based on this model,the influence of key parameters on the seismic performance of assembled piers was studied by changing the thickness and height of UHPC reinforcement layer and the strength of steel bars.Finally,according to the test results and finite element parametric analysis,the optimization and improvement suggestions of prefabricated square piers based on UHPC and high-strength steel reinforcement are proposed,and the existing unsolved problems and possible future research directions are prospected. |
