| After earthquake events,the steel bridges are often seriously damaged,so it is urgent to improve the seismic capacity of the steel bridge.The steel truss is an important lateral force resisting component of the steel arch bridge,and the brace directly affected the performance of the steel truss.The seismic performance of steel structures can be enhanced by setting up energy dissipation braces.However,there were few theoretical studies and related experiments on the strengthening of steel bridges with energy dissipation braces,and the strengthening effect had not been accurately verified.The previous research had not analyzed the influence of different energy dissipation braces on other members in steel bridges and not profoundly explored the interactive relationship between the energy dissipation of braces and the steel truss.Therefore,a truss of steel bridge was selected as the research object.Different types of energy dissipation braces were applied to the truss for experimental study,and the influence of different braces on the seismic capacity of the steel truss was compared.The hysteretic behavior and failure mode of the truss were discussed by numerical simulation,and the design suggestions of the truss were given.The main contents are as follows:(1)In chapter 2,the experimental study of trusses was carried out to evaluate the hysteretic behavior,and failure mode of the trusses.The influence of different braces on the energy dissipation capacity and ductility of trusses was analyzed.The test results showed that The seismic capacity of the steel truss with traditional braces was poor.The steel truss with BRBs can be loaded with larger displacement amplitude,which can resist greater earthquake action.(2)In chapter 3,ABAQUS was used to establish the numerical model of the brace truss with square steel tubes.Based on the experimental study in chapter 2,the failure modes and hysteretic performance of trusses were further discussed,and the principle of the equivalent plastic strain of the lower chord and the middle web was researched.Based on the refined finite element model,a simplified model was proposed.Based on the refined model,a simplified numerical model is proposed to further study the fatigue fracture problem.(3)In chapter 4,the ABAQUS finite element model of the truss with BRBs was established and a simplified simulation model for buckling restrained brace was proposed.The plastic damage of the members with large deformation in specimens was evaluated based on the study of two kinds of steel trusses with buckling restrained brace.(4)In chapter 5,the design suggestions of the BRB truss were given.The thickness of the gusset plate has little effect on the bearing capacity of the specimen.Increasing the thickness of the gusset plate can effectively delay the damage of the gusset plate and ensure that the gusset plate still had good performance under repeated reciprocating action.The lateral stiffness of the brace and truss should be better matched to make the brace play its advantages. |
