Studies On Design Method Of Unstiffened Or Buckling-Restrained Steel Plate Shear Wall Structures

The design of lateral-force resisting member in high-rise buildings has always been focused by the structural designers widely. The behavior and design method of two kinds of lateral-force resisting element, namely Unstiffened Steel Plate Shear Wall(USPSW) and Buckling-Restrained Steel Plate Shear Wall (BR-SPSW), was studied in this paper.An obvious effective region with regard to slenderness ratio of the panel was uncertain for the traditional analytical models developed previously for USPSW, namely the Strip Model(SM) and Modified Strip Model(MSM). The results obtained show that the SM and MSM can not be used to well replace the USPSW with arbitrarily varying slenderness ratio.As most pratical steel panels behave and work in an intermidiate stress state between pure shear and pure tension fields, a new analytical model, namely the Unified Strip Model(USM) considering a combination of the pure shear and pure tension fields, is proposed in this paper. It is then confirmed by numerical analysis that the USM gives a better prediction for overall behavior of USPSW than other models, SM and MSM.Careful comparing tests have been conducted among three specimens of two-story, single-bay strucures, namely, steel frame+USPSW , steel frame+BR-SPSW and steel frame+C-SPSW (Composite Steel Plate Shear Wall). The results obtained demonstrate that the BR-SPSW performs the best and its unfavorable effects on the adjacent columns are substantially lower than the other two types. The superiority of the BR-SPSW structure is well presented in this experiment.According to the work mechanism of infill steel panel in BR-SPSW , an analytical model, namely the Bidirectional Strip Model(BSM) for the BR-SPSW, is developed. The form of BSM is identical to the USM for USPSW except that the propotion of pure shear stress. It is verified that the BSM gives satisfactory caculation accuracy in elastic force analysis of frames, pushover analysis, and elasto-plastic time history analysis. The development of a tension field in USPSW was closely dependent on the bending stiffness of surrounding columns, and the critical requirement value towards cloumn inertia moment defined as Traditional Threshold Stiffness(TTS) in this paper has been developed previously. However, it is found that the cloumn section determined by TTS can be considerably reduced in case that the slendness ratio of infill panes is non-compact or compact. In order to obtain a reasonable requirement value for arbitrarily slenderness panel from slender to compact, the research refines the TTS and proposes the Modified Threshold Stiffness(MTS). In addition, it is no longer necessary, unlike the USPSW, to examine the inertia moment of surrounding cloumns in BR-SPSW structrues based on the numerical results.For a dual lateral-force resisting system, the shear-bearing ratio of frames in SPSW structures no longer follow the criteria of hybrid structures of reinforced concrete core wall-steel frames due to the good ductility of SPSW. Hence, it is proposed and verified an interactive working model convenient to ascertain the shear force shared by the frames in SPSW structures, and this will provide a powerful tool to study the shear-bearing ratio of frames under severe earthquake.The results obtained indicate that the USPSW being subjected to a preliminary pressure due to the axial compression of boundary columns will adversely affect its lateral-resisting behavior. So the wall plate should be welded or finally fastened with the surrounding frame at a later time than the time of building the major structure. If the aforesaid principle is irrealizable, it is recommended that the ultimate shear capacity of USPSW be reduced accordingly, meanwhile a simple computing formula for reduction is given.