Experimental and Numerical Simulation of a Three-Story Mass Timber Building with a Pivoting Wall and Buckling-Restrained Boundary Elements

Abstract

Steel energy dissipators can be combined with mass timber in integrated seismic lateral force–resisting systems to achieve designs with enhanced seismic performance and sustainability benefits. Examples of such integration include the use of mass timber post-tensioned rocking walls equipped with steel energy dissipation devices. This study proposes a solution using buckling-restrained boundary elements (BRBs) with mass timber walls detailed to pivot about a pinned base. This design allows the walls to rotate with minimal flexural restraint, distributing drift demands more uniformly with building height and reducing crushing damage at the wall base. Experimental quasi-static cyclic tests and numerical simulations were used to characterize the first- and higher-mode behavior of a full-scale three-story building featuring a mass timber gravity system and the proposed mass timber-BRB system. Under first-mode loading, the specimen reached 4% roof drift ratio with stable hysteretic behavior and a nearly uniform story drift profile. While residual drifts were nonnegligible due to the lack of self-centering, analytical estimates indicate realignment is likely feasible at the design earthquake level. Under second-mode loading, the specimen exhibited near-linear behavior with high stiffness. Experimental results were corroborated with numerical simulations for the isolated gravity frame, first-mode-like, and second-mode-like loading protocols. It is expected that results from this study will facilitate greater use of mass timber seismic lateral force–resisting systems.