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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. 

Mass timber buildings are gaining popularity in North America as a sustainable and aesthetic alternative to traditional construction systems. However, several knowledge gaps still exist in terms of their expected seismic performance and plausible hybridizations with other materials, e.g. steel energy dissipators. This research explores the potential use of mass plywood wall panels (MPP) in spine systems using steel buckling-restrained braces (BRBs) as energy dissipators. The proposed BRB-MPP spine assembly makes up the lateral load-resisting system of a three-story mass-timber building segment that will be tested under cyclic quasi-static loading at Oregon State University. The specimen geometry and material properties result in BRBs that are shorter and of smaller core area than in most common steel structural applications. Small BRBs are prone to exhibit a hardened compressive response and fracture due to ultra-low-cycle fatigue when subjected to repeated cycles of large strain amplitude. These issues, along with the limited availability of test data, make small BRBs difficult to model. To support the experimental testing program, a material model with combined kinematic and isotropic hardening is calibrated against the available experimental data for three BRB specimens to estimate the behavior of BRBs of short length (≤3,500 mm [138 in]) and small core area (≤2,600 mm2 [4 in2]), similar to the ones designed for the test specimen. The calibrated model is used to predict the behavior of the BRB-MPP spine experiment.