Seismic Behavior Study Of Concrete-filled Square Steel Tubular Frame-thin Steel Plate Shear Walls With Vertical Stiffeners

The concrete-filled square steel tubular frame(CFST)-thin steel plate shear walls(SPSWs)combines CFST-frames which have advantages such as high bearing capacity and good ductility pretty well with thin SPSWs noted for its high lateral-resistance stiffness and stable hysteretic behavior.It has high bearing capacity and well seismic behavior.The vertical stiffeners can enhance SPSWs buckling load and initial stiffness,reduce the out-of-plane deformation.The mechanical behavior of the steel plate shear wall is improved.By using experimental research and finite element analysis and with combination of theoretical research,this dissertation study on the seismic behavior and lateral force resistant capacity of the CFST frame-thin SPSWs with vertical stiffeners.The main works are listed as follows:(1)The low-cyclic loading tests on two one-bay two-story CFST-thin SPSWs with a reduced scale of 1/3 are conducted.The seismic behavior of SPSWs with cross stiffeners was studied and compared with that of unstiffened SPSWs.The experimental results show that CFST frame-thin SPSWs have higher load carrying capacity and lateral stiffness,favorable ductility and energy dissipation capacity.The vertical stiffeners not only decrease the height-to-thickness ratio of SPSWs,enhance the out of plane stiffness,reduce the out-of-plane deformation,but also reduce the “pinch” of the hysteresis curve,and enhance energy dissipation capacity.(2)Through the comparison between finite element software ABAQUS 6.10 and experimental results,the accuracy of finite element modeling is verified.The hysteretic behavior,deformation,stress development and failure mechanism of the SPSWs were investigated.(3)The influences of column axial compression ratio,number of stiffeners the ratio height-to-thickness of the SPSW and column flexibility factor on the hysteretic behavior of full size finite element models of CFST frame-thin SPSWs with vertical stiffeners are studied.The results show that the bearing capacity and ductility decrease with the increase ratio of axial compression,and the increase of ratio of axial compression has little effect on energy dissipation and the degradation of stiffness.The number of stiffeners have considerable influence on hysteretic behavior,but it has little effect on the bearing capacity and stiffness degradation.The ratio of height-to-thickness of the SPSW and column flexibility factor have great influence on the bearing capacity,energy dissipation and stiffness degradation.(4)the theoretical calculating formulas for lateral stiffness of thin SPSWs with vertical stiffeners and lateral-resistant capacity of thin SPSWs with vertical stiffeners considering post-buckling strength of infill panel were presented,calculating formula agree well with those of finite element analysis results.The influence of vertical load on the lateral performance of thin SPSWs with different vertical stiffening forms was researched.The results show that vertical load can weaken lateral behavior of thin SPSWs with vertical stiffeners.The more the vertical load,the more obvious the out-of-plane deformation.The vertical load in thin SPSWs with vertical stiffeners has great influence on lateral stiffness,but has little effect on lateral-resisting capacity.Increasing the number of stiffeners can significantly reduce this influence of lateral stiffness on vertical load of thin SPSWs with vertical stiffeners.The vertical load in SPSWs with vertical stiffeners would increase the axial force of frame column,when the horizontal load action,it will produce P-? effect,and reduce the edge of the frame column bending capacity.