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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.
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Phase 1: Pivoting Mass Ply Panel (MPP) Wall and Buckling-Restrained Boundary (BRB) Elements:Subtitle
A lateral force resisting system (LFRS) comprised of one eight-foot-wide Mass Ply Panel (MPP) with Buckling-Restrained Braces (BRBs) was attached to the building frame and tested following a cyclic quasi-static loading protocol up to 4% roof drift ratio. This system was designed to pivot about a pinned base, allowing the wall to rotate with minimal flexural restraint, thereby distributing drift demands more uniformly across the building height and reducing crushing damage at the wall base. Under first-mode loading, the system exhibited stable hysteretic behavior with a nearly uniform story drift profile, while second-mode loading revealed near-linear behavior with high stiffness. Experimental results provide valuable insights into the behavior of mass timber seismic lateral force-resisting systems and can be reused to develop and validate design guidelines for their broader implementation in seismic regions.
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- Award ID(s):
- 2120683
- PAR ID:
- 10571022
- Publisher / Repository:
- Designsafe-CI
- Date Published:
- Subject(s) / Keyword(s):
- quasi-static cyclic loading MPP VLT mass timber BRB UFP self-centering rocking wall lateral system seismic performance
- Format(s):
- Medium: X
- Location:
- Oregon State University
- Institution:
- AA “Red” Emmerson Advanced Wood Product Lab
- Sponsoring Org:
- National Science Foundation
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Mass timber products are gaining popularity in North America as an alternative to traditional construction materials as part of both the gravity and lateral force-resisting system. 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 wall spine systems consisting of mass ply panels (MPP) and steel buckling-restrained braces (BRBs) as energy dissipators. The proposed BRB-MPP spine assembly makes up the lateral force-resisting system of a three-story mass-timber building segment that will be tested under cyclic quasi-static loading at Oregon State University. The proposed design methodology follows displacement-based design principles to determine the minimum required stiffness to limit inelastic story drift ratios at the design earthquake level. The MPP spine and BRB-to-MPP connections were capacity designed to resist forces transferred by the BRBs at roof drift ratios beyond the risk-targeted Maximum Considered Earthquake (MCER). This design solution provides an interesting alternative for the design of modern mass timber buildings. The results obtained in the experimental campaign will be used to validate the design methodology and the behavior of the innovative structural system.more » « less
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