One mass timber building in Southern California has survived more major earthquakes than any similar structure in the world, and it did it all while the neighborhoods around it remained tremor-free.
A collaboration between Think Wood and lumber industry organizations including the Softwood Lumber Board, WoodWorks, and the Binational Softwood Lumber Council; university research teams; and other stakeholders saw the construction of a 10-story mass timber tower on the shake table at the University of California San Diego (UCSD). In May of this year, that tower—the tallest building ever to be tested on a shake table at full scale—underwent rigorous testing to further investigate the capacity of tall mass timber buildings to withstand major seismic events with minimal damage, allowing for the possibility of quick repair, rather than the need for replacement, of structures post-quake.
The robust university-backed testing process, conducted under the umbrella of the Natural Hazards Engineering Research Infrastructure (NHERI) TallWood Project, is using earthquake simulations generated by the world’s largest shake table to assess mass timber’s resilience in the face of one-in-a-millennia quakes. Phase one testing focused on proving the seismic resilience of mass timber structural systems, including that of a new mass timber rocking-wall assembly designed by LEVER Architecture and Timberlab that provides an alternative design option for mass timber buildings in seismic areas.
From May 1 to May 22, a total of 100 tests were conducted by a research team led by investigators from the Colorado School of Mines, including 88 earthquake simulations with different ground motion intensities. Of these simulations, 46 replicated small earthquakes common in seismically active regions, 26 replicated seismic events at magnitudes nearing the structure’s designed-for tolerance, and 16 earthquakes exceeded designed tolerances. Among those tests were simulations of four historic 7.0+ magnitude earthquakes—the type that occur, on average, once in 2,500 years.
This project was an 'all-hands-on-deck' approach and speaks to the highly collaborative network of AEC partners who are pushing the boundaries of mass timber construction. It has been a rewarding experience to watch this project come together, with each partner equally invested in the seismic potential of wood construction.
Preliminary results from this phase one testing released in late summer proved promising: The test building was inspected for damage between all major earthquake simulations during the testing period, and no visible structural damage was found. In fact, the building remained plumb after all tests without the need for any repair. Non-structural systems installed in the test building (façade panels, partition walls, and stairs) also remained intact after most simulations; minor drywall and connector damage was observed for tests that exceeded the design’s tolerance levels, but all the damage was repairable and posed no safety concern.
Though tall mass timber structures are already being built in compliance with code in earthquake-prone areas, the results of this testing “prove mass timber’s viability as a safe and effective, as well as sustainable, alternative to steel-and-concrete buildings in seismically active areas, paving the way for broader adoption in taller mass timber structures nationwide,” says SLB President and CEO Cees de Jager. The results of the testing process—which WoodWorks President and CEO Jennifer Cover calls “a sharpening of the pencil” for building with mass timber in seismic zones—could pave the way for changes in building codes for residential and commercial structures that could lead to more widespread adoption of mass timber as a sustainable, strong, and versatile building material.
The full findings from the construction and testing of the building, as well as new resources from WoodWorks that architects and engineers can share with clients, lenders, and insurers to help educate them on the resilience of mass timer structures, are slated to be released later this year.