Subassemblage Cyclic Loading Tests of Buckling-Restrained Braced RC Frames with Unconstrained Gusset Connections

Abstract

An unconstrained gusset connection for buckling restrained braces in reinforced concrete frame structures is proposed and tested as an effort to mitigate the complicated and usually harmful interactions between the steel gusset plate and the adjoining reinforced concrete column. Local damage control incorporating the rearrangement of beam flexural strength is also proposed to enhance the reliability of the gusset connection by moving the potential plastic hinge of the beam away from the connection region. Two different connecting methods, one with posttensioned steel rods and the other embedded stud groups, were considered. The results of the cyclic loading tests on reinforced concrete (RC) beam-gusset connection subassemblies confirmed that both connecting methods are available as long as the local damage control is implemented, which is not only helpful in eliminating the unfavorable deformation loss at the connection, but more importantly, can prevent the buckling restrained braces (BRBs) from being dislocated as a result of the beam end failure in extreme earthquake events.