Effect of Flange Width of Vertical Link Beam on Cyclic Behavior of Chevron Braced Steel Frames

Among the passive dampers, using Vertical Link Beam (VLB) is one of the most effective and simplest methods, while not embedded in the floor they can be easily replaced after earthquakes. These dampers dissipate a major part of the input energy resulting in a minimized damage of the main structural components of system. This paper presents a numerical study on the impact of flange width of VLB on cyclic performance of chevron braced steel frames. Despite most previous research projects in which wide-flange I sections were considered for the VLB and the length of VLB was studied, here, the objective is to investigate the possibility of using narrower flange. Verification has been made on the basis of the experimental results from the IPE۱۶۰ model. By changing the flange width, the cyclic behavior has been investigated. The results show that while the vertical link beam has sufficient lateral support, in spite of the flange width reduction, stable hysteretic cycles still form accompanied with considerable energy dissipation. Based on the hysteretic curves, using modification of the narrower flange section, the shear force at last cycle increased about ۲۰.۷۴% and ۱۶.۱۷% in IPE۱۶۰ VLBs with a half and quarter flange width respectively, and the proportion of VLB in plastic energy dissipation increased from ۷۸.۹% to ۹۰.۴% in half flange VLB and from ۷۴.۲% to ۹۰.۹% in quarter flange VLB only by this simple modification, showing an increase in ductility of the system.

Keywords:

Vertical link beam , Chevron bracing , Eccentrically braced frame , Flange width , Passive Control