Study On Buckling-restrained Brace Reinforcement Technology For Frame Structure With Additional Grid Roof

In recent years,the demand for building retrofit and strengthening has gradually increased.Because stiffness and hysteretic energy dissipation capacity of the buckling-restrained brace,it has been widely used in building retrofit and strengthening projects.But buckling-restrained brace is often used in steel frames or concrete frames.In this situation,there are few researches on the steel-concrete hybrid frame structures.A frame structure with an additional grid roof on an upper part in Xi’an is the research object.Through the analysis and comparison of the general support and buckling-restrained brace strengthened schemes of the structure,the seismic performance of the buckling-restrained brace strengthened steel-concrete hybrid structure is studied.The main contents of this dissertation are as follows:(1)In this dissertation,the steel-concrete hybrid structure is analyzed by finite element simulation tool named SAP2000.Considering the cooperative work effect,the effect of adding a grid roof to the upper part of the concrete frame is studied.It is found that although the stiffness in the plane of the gird roof can enhance the lateral stiffness of the top layer of the structure.Overall mass of the structure increases after the addition of the grid,and the structure period decreases.Although the interlayer displacement angle at the top of the structure has been reduced,the maximum interlayer displacement angle still exceeds the limit,and some components do not meet the bearing capacity requirements,so it is planned to use buckling-restrained brace to reinforce structure.(2)The herringbone arrangement mothed of buckling-restrained braces is adopted because of the large distance between the columns.The lateral stiffness of the single-span buckling-restrained brace is calculated,and the displacement based seismic design method is used to obtain the required stiffness of the structure under the target displacement,so as to obtain the area and quantity of the buckling-restrained brace required for strengthening.The buckling-restrained brace is arranged under the premise of not affecting the space of the structure to improve the even distribution of stiffness of the hysteretic structure.(3)The buckling-restrained brace is simulated in SAP2000 using plastic link elements,and the Bouc-Wen model is used as the hysteretic model to stablish the finite element model of the structure after the buckling-restrained brace is arranged.Establish an ordinary steel brace strengthened structure model with the same strengthening plan for comparison.The difference in seismic performance of the two strengthened structures is compared through the modal response spectrum analysis,the linear time history analysis and nonlinear time history analysis.The analysis results show that under the action of frequent earthquakes,the floor displacement angle of the ordinary brace strengthened structure exceeds the limit under the action of frequent earthquakes,and the top displacement,floor displacement angle and axial force of brace are not much different with the buckling-restrained brace strengthened structure.And under the action of severe earthquakes,the top displacement,floor displacement angle,and base shear of the buckling-restrained brace strengthened structure under severe earthquakes are less than that of the ordinary brace strengthened structure.The ordinary support is in the failure stage,and buckling-restrained brace exerts a hysteretic energy dissipation effect through the elastic-plastic deformation and is still in a normal working state.The analysis results show that the strengthening performance of the buckling-restrained brace is much better than that of the ordinary brace under severe earthquakes.