| Steel plate shear wall(SPSW)connected with beams only is a lateral load–resisting system in which infill steel wall panels are no longer connected with boundary frame columns but only connected with the frame beams,so as to avoid the adverse effect of the tension field action(TFA)from infill wall panels on the frame columns.At the same time,such connection of infill wall panels provides convenience for the construction compared with the conventional four-side connected SPSWs.However,the lack of connection between the panel and columns will lead to the insufficient development of TFA,which significantly weakens the lateral stiffness,strength and energy dissipation capacity of the structure.Arrangement of stiffeners on the infill wall panels is expected to improve the development of TFA of the beam-only-connected panels and effectively improve the seismic performance of the structure.However,the research on the stiffened SPSW connected with beams only is relatively insufficient at present.In this paper,the buckling,lateral and seismic performance of SPSW connected with beams only with various stiffened types were studied through theoretical analysis and numerical simulation using ABAQUS software,and some design suggestions were put forward.The main research works are listed as follows:(1)420 wall panel models with different in-plane stiffened types(unstiffened,vertically stiffened,horizontally stiffened and diagonally stiffened)were established for elastic buckling analysis.The results showed that vertical or diagonal stiffeners could significantly increase the elastic shear buckling stress of wall panels connected with beams only with the small aspect ratio,and horizontal or diagonal stiffeners could economically and effectively increase the elastic shear buckling stress of wall panels connected with beams only with large aspect ratio.The buckling modes of the wall panels with different stiffeners were mainly affected by the shape of the subplate and the width of the wall plate.The formula for calculating the elastic buckling shear stress of stiffened wall panels connected with beams only under different elastic boundary conditions was derived by using P-Ritz method,and its validity was verified by the results of finite element analyses.(2)34 finite element analysis(FEA)models of single-story single-bay SPSW connected with beams only with different forms of in-plane stiffeners were established,and the nonlinear pushover analyses were conducted.The lateral resistance mechanism and performance of the SPSWs connected with beams only with different in-plane stiffened types were studied,and the effects on the wall panel’s lateral performance of key design factors,such as panel width,number of stiffeners,section forms of stiffeners and boundary-stiffener connection types were studied.The results showed that in the cases with the aspect ratio in the range of 0.5-2.0 studied in this paper,all these types of stiffeners could significantly improve the lateral stiffness of the panels,with an increase of more than 40%;but for the capacity of the panels,horizontal and diagonal stiffeners could also significantly increase the peak lateral capacity with an increase of more than 30%,while the improvement of the lateral capacity of the vertical stiffeners was limited when the wall panel was thin,because that although the vertical stiffener could effectively improve the shear buckling stress of the wall panel,it could not effectively increase the TFA development.The formulas for calculating the ultimate bearing capacity of the beam-only-connected wall panels without in-plane stiffeners,with horizontal stiffeners or with diagonal stiffeners were derived based on the principle of virtual work.(3)268 FEA models of single-story single-bay SPSWs with beam-only-connected wall panels without in-plane stiffeners or with diagonal stiffeners were established for nonlinear pushover analyses.The effects of design parameters,such as lateral stiffener’s thickness,thickness of wall panels,stiffness ratio of stiffeners to panel and the aspect ratio of wall panels,on the ultimate lateral capacity of beam-only-connected wall panels with diagonal stiffeners were studied,and the "enhancement coefficient of wall panel self-bearing capacity" was put forward and fitted.The formula for calculating the ultimate lateral capacity of beam-only-connected wall panels with diagonal stiffeners was given.(4)12 FEA models of two-story single-bay SPSWs with beam-only-connected wall panels with different types of in-plane stiffeners were established for nonlinear pushover analyses,and the effects of panel aspect ratio,stiffened types and frame joint types on the shear force occurred in the boundary beam segment with no wall panels connected to were studied.The results showed that the for the shear force occurred in the boundary beam segment with no wall panels connected to,the shear force in the diagonal-stiffened SPSW model was the largest while the smallest value was occurred in the model without in-plane stiffeners.With the increase of the aspect ratio of the panels,the shear force occurred in this segment increased at first and then decreased,and the influence of the stiffened types was gradually weakened.The shear design formula for the boundary beams was put forward by using the freebody analysis and capacity design method,which was in good agreement with the finite element results.(5)18 FEA models of two-story single-bay SPSWs with beam-only-connected wall panels with different types of in-plane stiffeners were established,and hysteretic analyses were conducted.The effects of the aspect ratio of panels,stiffened types,thickness of middle beam webs and the types of frame joints on the hysteretic performance of the structure were explored.The results showed that horizontal or diagonal stiffeners would obviously improve the lateral stiffness,peak bearing capacity and energy dissipation capacity of SPSWs connected with beams only,and the effect of horizontal stiffeners was more obvious;with the aspect ratio of wall panels increased,the lateral stiffness and peak bearing capacity of shear wall structure were significantly improved,but the phenomenon of hysteretic pinching was more obvious;when the boundary beam web met the shear demand,compared with the semi-rigid joint,the rigid joint of beam and column could improve the lateral stiffness,peak bearing capacity and energy dissipation capacity of the shear wall structure.The improvement of the diagonal stiffeners on the energy dissipation capacity was more obvious when the aspect ratio was large,while the improvement of horizontal stiffeners on the energy dissipation capacity was not affected by the aspect ratio of wall panels.(6)Some suggestions for the design of the SPSW connected with beams only with different in-plane stiffeners were provided: the out-of-plane stability of the compression-bending members should be checked for the T-section formed by the side stiffeners and the adjacent wall panels;and for the horizontal stiffeners,the compression-shear combined forces should be considered to ensure its out-of-plane stability;considering the plate-frame interaction,diagonal stiffeners were not recommended to be too strong,and the requirement of "threshold stiffness" was put forward. |
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