Cyclic performance and fracture of wide flanged concentrically steel braced frames

Concentrically braced steel frames (CBFs) are often used in buildings to resist lateral loads induced by wind and seismic excitations. Large-size wide-flange (WF) steel brace members could be selected and used in these frames. In the current study, a finite element model (FEM) with a strain-based fracture rule is presented to investigate the performance of a large-size WF brace member in single-storey CBF with different sizes of beams and columns when subjected to reversed axial displacements. The effects of restraining the far ends of the beam bottom-flange, increasing the thickness of tab-plates, increasing the number of bolts used to connect the tab-plates to the web of the beam, and the location of the work-point along the brace with respect the beam-column assembly, on the hysteresis response of the frame are investigated. Results suggest that it may be advantageous to reduce the number of bolts and to increase the bolt size to allow for an increase in the thickness of the tab-plates to resist the extreme rotational demand in high seismic regions, thereby preventing fracture of the weld between the tab-plates and the column flange.