Analysis And Design Of Fabricated Partially Connected Buckling-restrained Steel Plate Shear Walls

Buckling-restrained steel plate shear walls(SPSWs)as a novel lateral load resisting system exhibits high performance on ductility,initial stiffness,shear resistance and energy absorption capacity.However,due to the initial gap between the reinforced concrete(RC)cover plate and the inner steel plate,the high-order buckling deformation generally develops in the steel plate under shear.Hence,the vertical boundary element(VBE)shall have sufficient stiffness so that the tension field will fully develop in the steel plate.As a result of this,large member size is generally required for the VBEs to satisfy the stiffness requirement and this implies more cost for the SPSW system.Set against this background,a novel partially connected SPSW system is proposed with an aim to reduce the tension force acting on the boundary elements.The main novelty of this system is that only the quarter height and width of the steel plate at the four corners are bolted to the boundary elements by the gusset plates and equal angle plates,whereas the corresponding mid portions of the plate are not connected to the boundary elements.The main research works is following as:(1)In this paper,four one-third scaled test specimens were prepared and tested under quasi-static cyclic loads to investigate their hysteretic behaviours.The tests also evaluated the effect of the plate slenderness ratio and the influence of reinforced concrete cover plate on the seismic behaviour on the partially connected buckling-restrained SPSW.The test results showed that the partially connected buckling-restrained SPSWs have high initial stiffness and shear resistance,adequate ductility,good energy adsorption,and full hysteretic loops.The RC cover plates provide out-of-plane stiffness to prevent the inner steel plate from buckling,which greatly improves the structural performance of the partially connected SPSW.The shear resistance,initial stiffness,and hysteresis behavior of partially connected SPSW with or without RC cover plates are generally improved as the steel plate thickness is increased.Therefore,the proposed shear wall system could provide an effective solution to dissipate energy due to reversal wind or earthquake loads.(2)The SPSW test specimens in the present paper come with specific dimensions and parameters which do not cover the full range of cases that might be encountered in practice.It is,therefore,necessary to develop a numerical model to investigate the behaviour of partially connected SPSW with different geometry,avoiding a large expense of conducting additional tests.Parametric analyses were then carried out to study the effects of plate slenderness ratio,plate aspect ratio(width/height),stiffness of the boundary frame members,RC cover plate thickness,bolt spacing,and initial plate imperfection on the lateral load resisting behaviour of the proposed steel plate shear wall system.The nonlinear finite element analyses on the partially connected SPSWs shows that the shear resistance and hysteretic behaviour are greatly improved as the aspect ratio of steel plate and the stiffness of VBEs are increased.The lateral load resistance of the SPSWs increases with the decrease of the slenderness ratio of the infill steel plate.In terms of the plate initial out-of-plane deflection,if the magnitude is less than 3mm the effect is very small and can be neglected.Thus,it is recommended that the initial geometric imperfection of the infill plate should be kept within 3mm(h/1000).Moreover,the effect of aspect ratio,slenderness ratio,and stiffness of VBEs on the partially connected buckling-restrained SPSWs is identical with the partially connected SPSWs.In addition,the shear resistance,initial stiffness,and energy absorption capacity are substantially increased as the RC cover plate thickness is thickened.Up to a certain limiting value,its influence is small and can be neglected.The structural performance of the shear wall system is also increased as the bolt spacing is shortened.However,after the minimum value is reached,the influence generally becomes negligible.When the magnitude of the gap between the RC cover plate and the inner steel plate is less than 5mm,its effect is small and can be neglected.It is,therefore,recommended that the initial gap between he RC cover plate and the inner steel plate should be kept within 5mm(h/600).Finally,the shear resistance share between the frame and the inner steel plate is studied using nonlinear finite element method,which shows that the inner steel plate resist a great amount of shear force before the inner steel plate yields.(3)Based on the high-order buckling deformation analyses,an analytical method is proposed to predict the shear resistance,the RC plate thickness requirement,and the minimum required stiffness of VBEs.The available data obtained from the tests and finite element modeling was compared with those predicted by the analytical method and a reasonable agreement was observed.(4)In addition,an equivalent brace model is developed to evaluate the nonlinear behavior of the partially connected buckling-restrained SPSW subjected to cyclic loading.The high-order buckling modes of the equivalent brace under compression are taken into account meanwhile a hysteresis model is proposed to describe the stress-strain relationship of the equivalent brace.The comparison with the test and FE results shows that the equivalent brace model with the proposed hysteresis properties can reasonably predict the shear resistance,hysteretic behaviors of the novel partially connected buckling-restrained SPSWs.