Technical-Economical Comparison Between Vertical Link Beam and Knee Brace Systems in Mid-Rise Steel Buildings

In knee brace and shear panel systems, unlike eccentric braced frames, energy absorption is achieved through plastic deformation when sub-members yield by shear forces or bending moments caused by bracing members during severe earthquakes. Several studies have been conducted on the behavior of these two systems which resulted in design methods to obtain the best structural performance. The present study attempted to design frames using these methods, and then to compare them in terms of technical and economic factors. In this regard, to obtain a pattern of the frames behavior, a 3-span 5-storey frame was modeled for three different types of brace system (coaxial, knee and shear panel) using ANSYS software. After performing pushover nonlinear static analysis, behavior coefficients were determined and the force-lateral displacement curves of the systems were compared. In the next step, 3-span 5- 8- and 12-storey frames were analyzed and designed using ETABS software and were compared in terms of the parameters such as relative lateral displacement, normal period of system, structural weight, and shear force into foundation. The results indicate that using the above-mentioned systems, structure will exhibit more ductility which leads to reduced design base shear. The forces applied to main structural members (beams, columns, and braces) are reduced by the use of knee brace and shear panel systems. This will affect the design and sometimes increases or decreases weight of these members.