Engineering. “This unique project is one of the first demonstrations of mass timber reuse and of mass timber’s seismic resilience.” Barbosa, in collaboration with Arijit Sinha, professor of wood science and engineering and JELD-WEN chair in wood-based composites science at the College of Forestry, originally started investigating the systems using a three-story mass timber structure. The test structure was built inside the Oregon State University A.A. “Red” Emmerson Advanced Wood Products Laboratory lab at the TallWood Design Institute. This allowed the team to investigate initial design methods, assumptions and obtain results before refining them for the larger sixstory building seismic testing at UC San Diego. “This work is vitally important to validate the use of mass timber and other technologies as vehicles to make buildings safer and more resistant to earthquake activity while simultaneously storing carbon,” Sinha said. “This creates a synergistic combination for enhanced structural and environmental performance.” The test structure will undergo a three-phase test process (see figure 1), employing different seismic lateral force-resisting systems in each test. These systems employ a variety of vertical elements in the construction of buildings to help transfer lateral loads like heavy winds or earthquake ground motion shaking. They also allow a building to rock, sway and dissipate the energy, and selfcenter after shaking, therefore minimizing damage. In November 2023, the Converging Design team completed Phase 1. They found the mass timber structure experienced virtually no damage after nearly fifty ground motion shakes from the shake-table, demonstrating the resilience of the building system. Phase 2, completed in January 2024, showcased the resilient nature of the post-tensioned mass timber walls with buckling- restrained braces. The remaining phase of testing is expected to be complete by spring 2024. To follow along, find live updates on the TallWood Design Institute website at beav.es/qjt. Figure 1. The project tests different resilient lateral force resisting systems (LFRS) over three phases to advance seismic resiliency. Phase 1 involves testing post-tensioned rocking wall systems (both cross-laminated timber [CLT] and mass plywood panels [MPP]) similar in nature to the LFRS used in the College of Forestry’s Peavy Forest Science Center. This system uses steel U-shaped flexural plates for energy dissipation and tensioned rods for self-centering action. Phase 2 features post-tensioned MPP shear walls reinforced with buckling-restrained braces (BRBs), which are placed at the bottom of the walls instead of along their entire length, such as with U-shaped flexural plates. Phase 3 will explore a hybrid wood-steel system, replacing the mass timber shear walls with a resilient steel moment/braced frame hybrid system, but keeping mass timber floors. Shear Key Post-Tensioned Rods Post-tensioned Mass Timber Walls with UFPs PHASE ONE U-Shaped Flexural Plates (UFPs) PHASE TWO Post-tensioned Mass Timber Walls with BRBs Buckling-Restrained Braces (BRBs) Rocking Wall Toe Resilient Combined Moment-Resisting Frame/Concentrically Braced Frame with Yield-Link Moment and Brace Connection PHASE THREE 11 FOCUS - SPRING 2024
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