s. a.a. hosseinzadeh

During the recent past decade, semi-supported steel shearwalls (SSSW) have been introduced as an alternative tothe traditional type of steel plate shear walls (SPSW).In this system, the shear wall does not connect directlyto the main columns of the building frame, instead, itis connected to a pair of secondary columns that do notcarry gravity loads. However, a SSSW system, comparedto the corresponding SPSW system in which theinll plate is connected to the main frame columns, has alower span width (or lower inll plate width) and, thus,lower strength, stiness,energy dissipation capability.To oset these eects, one eective,practical approachis the use of ber-reinforced-polymers (GFRPs)for strengthening the steel inll plate. GFRP laminatescan be easily attached to one or both sides of the inllplates by the use of adhesive. In this paper, the behaviorof semi-supported steel shear walls reinforced byglass-ber-reinforced-polymers (GFRPs) is studied usingthe nite-element method,compared with thecorresponding systems without the reinforcement. Anumber of semi-supported steel shear walls with differentplate aspect ratios, plate thicknesses, secondarycolumn proles,with,without opening of varioussizes is considered for this research. Both pushoverand cyclic analyses are performed. The adequacy ofthe nite-element modeling approach for representingthe pushover,cyclic responses of SPSWs is veriedthrough comparisons with experimental results. Resultsshow that the use of GFRP laminates, especially for thesystem with thinner inll plate thickness, can signi-cantly increase the system strength, initial stiness, andenergy dissipation, while it partially decreases the systemductility. In turn, the improvement of the systemstrength,energy dissipation capability is mainly dueto the improvement of the SSSW inll plate behavior. Infact, the use of GFRP laminates does not aect much thehysteresis,pushover behavior of the SSSW frames.

Many previous experimental and analytical studies have shown that the column demands, especially column axial force demands, in a traditional multi-story steel shear wall (SPSW) system are extremely large for typical systems. Such configuration, in turn, results in large column dimensions and prohibits the use of narrow walls, thereby reducing the system's economy. Further, most of the column axial forces, especially in multi-story cases, come from plate tension forces on interfaces with the columns at different stories of the system. Thus, releasing the infill wall from the columns can help the column axial force demands to be reduced significantly. In the present paper, the behavior of steel shear walls connected to frame beams only is investigated using the finite-element method and compared with that of the corresponding system with fully connected infill walls (typical SPSW), in terms of strength, initial stiffness, ductility and max of out-of-plane deformation. In this study, the effects of different system aspect ratios, various infill plate thicknesses and application of end plate stiffeners on the free edges of the infill plates are also considered. SPSWs are analyzed using the nonlinear pushover analyses. The adequacy of the finite element modeling approach to representing the pushover responses of SPSWs is verified through comparison with experimental results. Results show that releasing of the infill wall connection to the columns limits the widespread yielding of the infill plate. This, in turn, affects the strength, initial stiffness and ductility of the system. Notably, the behavior of SPSW frames is not affected much by such configuration. Increasing the infill plate thickness in proportion to the decrease of its strength, not only offsets the effect of this configuration on the system strength, but also improves the system behavior in terms of initial stiffness and ductility (compared to the corresponding system with infill plate connected to boundary columns and beams). Application of end-plate stiffeners on the free edge of the infill plates in semi-connected systems can effectively reduce the out-of-plane deformation of the infill wall, but it has no significant effect on the system strength.