Gusset plate connections to circular hollow section braces under inelastic cyclic loading

Braces are commonly used to provide lateral stiffness and strength to steel framed buildings subjected to wind or earthquake loading. Of the structural sections that can be employed as brace members, hollow structural sections represent a very good solution due to their excellent structural properties in compression. Nevertheless, their use has been hitherto compromised for seismic applications mainly due to a lack of simplified connection details that avoid brittle failures. At present, slotted hollow structural section connections are popular in seismic zones but the hollow section is typically reinforced with steel cover plates to increase the net area at the critical location to avoid premature fracture under tension loading cycles. This reinforcing practice can likely be avoided, for circular hollow sections, if both the tube and the plate are slotted in such a manner that the weld terminates at the tube gross cross section. The potential of this innovative detail is demonstrated by means of three large-scale specimen tests under pseudodynamic loading.