Improvement of Steel Shear Wall Behavior Based on Link Beam Approach

In seismic-prone countries like Japan, structures are designed against earthquakes and reinforced concrete shear walls, steel shear walls or steel bracing are usually used as seismic resistant elements. However, their hysteretic characteristics in plastic region, ductility and capacity of energy absorption are not always good. The use of steel plate shear wall systems (SPSW) is more advantageous than many lateral load resistant systems considering performance and economy. The steel plates are so strong and ductile, and their weight is so light that they are suitable as a material of shear wall. Despite the many advantages of steel shear walls, this system is not widely used. Some of the underlying reasons include a lack of understanding of the behavior of the system and the significant size of the columns around the wall compared to the concrete shear wall. Over the last two decades, the semi-supported steel shear wall at the edges (SSSW) has been introduced as an alternative to the traditional shape of the steel plate shear wall system. In this system, the infill steel plate is not attached to the main frame columns and instead is attached to the secondary columns. Removing the connection of the steel plate to the main columns will reduce the demand for the peripheral columns, thereby reducing their size of cross section. However, due to buckling of the steel plate, the phenomenon of pinching still exists in hysteresis curves. This reduces the area under the hysteresis curves and consequently, reduces the energy dissipation in the system.
The aim of this study is to improve the behavior of the above defined system by utilizing shear behavior of the plate and secondary columns around it and utilizing the maximum system capacity. In this research, plate and secondary columns are considered as shear link beam in eccentrically bracing frame (EBF) systems, with plate and secondary columns playing the role of web and flanges of shear link beam, respectively. In this system, a shear panel consisting of infill steel plate, perpendicular stiffeners and secondary columns is positioned in the midspan of the steel frame with simple connections. Unlike the conventional steel plate shear wall system and the semi-supported steel shear wall system at the edges, the buckling of the steel plate is prevented and the energy dissipation is due to the shear failure mechanism.
In this study, the effect of infill steel plate thickness, distance of perpendicular stiffeners and ratio of shear panel width to height on system behavior is investigated. For this purpose, different samples are modeled in the nonlinear finite element software and their cyclic behaviors have been studied. The results showed that the increase of steel plate thickness and ratio of shear panel width to its height has been lead to an increase in the ultimate capacity of system and area under the hysteresis curves. Adding stiffeners can increase the shear strength of the system up to 35%. In addition, increasing the distance of the stiffeners by up to 2 times the value specified for short-link beams has no effect on the system hysteresis behavior. The results also showed that the use of this system in steel frames compared to conventional steel plate shear walls increases the energy dissipation and area under hysteresis curves and reduces the pinching phenomenon in hysteresis curves. Other benefits of the system include a significant reduction in column demand, adaptability to architecture, stable cyclic curves, and no impact of the proposed system on the behavior of beam-to-column connections and thus no need for rigid connections, usability in High-rise buildings as well as usability in the seismic rehabilitation and retrofit of existing buildings.