Experimental and numerical studies on buckling restrained braces with posttensioned carbon fiber composite cables

Abstract

SummaryThere has been an increasing interest in using residual deformation as a seismic performance indicator for earthquake resistant building design. Self‐centering braced structural systems are viable candidates for minimizing residual deformations following a major earthquake. Hence, this study proposes an alternative type of buckling restrained brace (BRB) with externally attached posttensioned (PT‐BRB) carbon fiber composite cables (CFCCs). The steel core of the brace is used as an energy dissipator, whereas the CFCCs provide the self‐centering force for minimizing residual story drifts. Three proof‐of‐concept specimens are designed, fabricated, and cyclically tested at different posttensioning force levels. The CFCC behavior to obtain cyclic response, including the anchorage system, is examined closely. A parametric study is also conducted to show the effect of the different configurations of PT‐BRBs on the inelastic response. Furthermore, optimal brace parameters are discussed to realize design recommendations. The results indicated that the implementation of partially self‐centering BRBs in building frames can lead to the target residual displacements. A stable behavior is obtained for the proposed PT‐BRBs when subjected to the loading protocol specified in the American Institute of Steel Construction (AISC) 2016 Seismic Provisions.