Hysteretic Energy Dissipation in Laterally Restrained Steel Tube and Solid Bar Braces

This paper describes an experimental investigation into the seismic behavior and efficiency of steel frames with special bracing infills. Cold formed steel studs (CFSS), typically used in nonstructural partition walls, were studied to determine if they could be used to laterally restrain braces against buckling and thus enhance their seismic performance. Four specimens were ductile designed and then tested under cyclic loading. Specimens have either single diagonal tube or solid bar X braces with and without CFSS and U brackets providing out-of-plane and in-plane buckling restraint respectively. Behavioral characteristics of the specimens are quantified with an emphasis on hysteretic energy dissipation. Experimental results show that, at the same ductility levels, the cumulative energy dissipation of braces can be significantly increased when CFSS members are used. However, when tubular cross sections are used for braces, local buckling led to a reduced fracture life compared to the case without CFSS members. CFSS members appear to be relatively more effective when solid bar braces having large slenderness (tension-only braces) are used, since the difference between dissipated energies obtained with and without studs is substantial.