Seismic collapse assessment of rocking buckling restrained braced frames subjected to crustal and subduction ground motion records

Buckling restrained braced frames (BRBFs) may have damage concentration in one or few stories during severe seismic excitations, because buckling restrained brace (BRB) yields in a certain story and the stiffness of that story is significantly reduced. Drift concentration is undesirable because it can lead to general instability resulting from the P-Δ effects or residual drift. For controlling damage concentration and achieving a uniform distribution of drift in all stories, a new system entitled rocking buckling restrained braced frame (RBRBF) is used. RBRBF system generates uniform story drifts over the height of structure and prevents the damage concentration in one or few stories. Unlike conventional braced frames, the braces on one side of the braced span along with the adjacent columns and ties are part of a vertical truss system that is hinged at the base and designed to remain elastic until the near collapse limit state is reached. This vertical truss system works as a strong support for preventing damage concentration in one or few stories of the braced frame. The braces on the other side of the braced span are BRBs and are designed to provide energy dissipation. The novelty of this paper is investigating the seismic collapse of this new structural system under the effect of subduction ground motion records, which have higher significant duration compared with crustal ground motion records. For this purpose, the considered structures are assumed to be located in Seattle, which is subjected to both subduction and crustal ground motions. The results indicate that RBRBFs can effectively reduce drift concentration using the displacement‐based design approach and under both crustal and subduction ground motion records have significantly better performance in terms of seismic collapse compared with BRBFs. In addition, all structures under subduction records have lower collapse capacity values compared with crustal records.