Analytical Study of the Seismic Performance of Steel-Braced Frames with Masonry Infill

Special concentrically braced frames (CBFs) are widely used as efficient lateral-load resisting systems in seismic regions. In this study, experimentally validated finite-element (FE) models are used to investigate the effects of masonry infill and gusset-plate configuration on the seismic performance of CBFs. It is shown that the presence of masonry infill can increase the initial stiffness and ultimate strength of CBFs by up to 35 and 52%, respectively. However, the frame-infill interaction imposes high plastic strain demands at the horizontal re-entrant corner of gusset plate connections, which may lead to premature failure of fillet welds under strong earthquakes. Whereas using tapered gusset plates can significantly increase the fracture potential at fillet welds, gusset plates with elliptical clearance of eight times the plate thickness can lead to up to 54% lower equivalent plastic strain demands at both gusset plate connections and brace elements. Although the effects of masonry infill are usually ignored in the seismic design process, the results highlight the importance of considering those effects in the seismic design of CBF elements and gusset plate connections.