Effect of Flange Width-Thickness Ratio on Eccentrically Braced Frames Link Cyclic Rotation Capacity

An analytical study was conducted to investigate the influence of the flange width-thickness ratio on the rotation capacity of links in eccentrically braced frames. Finite element models, verified using experimental data, were used to investigate the performance of 112 links. Models simulated strength degradation associated with flange and web local buckling that may occur during cyclic loading. The models provided data for short, intermediate, and long links with a range of flange width-thickness ratios. Results indicate that a relaxation of the flange width-thickness ratio requirement in current AISC seismic design provisions is justified. It was also found, however, that the provisions specify nonconservative design rotations for some intermediate links. This is shown to be related to web stiffener spacing and not the flange width-thickness ratio.