Wood has a long history as a sustainable material that has been used mainly for low-rise building construction. Over the past 20 years, mass timber technology has emerged, along with rapid construction approaches as a way to build taller with large engineered wood panel products. As this new building style is adopted by communities located within earthquake regions, a design method for tall wood buildings against earthquake hazards is needed.  

In this multi-institutional collaborative project, the research team focused on developing methods for designing and constructing tall earthquake-resilient wood buildings. The resilient building should not only protect people’s lives during large earthquakes, but also have minimal earthquake damage to be repaired quickly and economically following a major earthquake. A new “resilience-based seismic design” method for tall wood buildings was developed. Several innovative structural systems and details were conceived and tested, including a post-tensioned mass timber rocking wall system. However, to properly consider resilience, damage to the building’s nonstructural systems also needs to be limited. Nonstructural elements are not part of the load resisting functions but are essential for the building function after an earthquake. Examples include nonstructural walls, exterior façade (envelope), suspended ceilings, plumbing and sprinkler piping, mounted equipment for HVAC, and egress systems like stairs and elevators. This collaborative award focused on the design and detailing of the nonstructural systems, and their contributions to the quantification of the overall performance and assessment of recovery and resilience.

To verify and demonstrate the effectiveness of these systems, the research team (and their industry partners) designed and constructed a full-scale 10-story mass timber building on the world’s largest outdoor shake table (NHERI@UC San Diego facility). “Drift sensitive” nonstructural components – those that span floor-to-floor and thus are subjected to the building interstory movement – were incorporated into the test program. These included four different exterior façade assemblies, interior wall subassemblies, and a full 10-story stair tower. The assemblies incorporated details to accommodate the drift with joints that allowed for movement without damage. Details included some new and innovative details, some that are used in industry but have not been tested, and some control (standard details) for contrast. About ten major industry partners donated their products and in-kind support to contribute to the nonstructural scope.

The 112 ft tall building was then tested by imposing a variety of past earthquake records to the base shake table platform. The building successfully withstood 88 earthquake tests, about half of which were above the code design level intensity, without structural damage, permanent deformation, or any need for repair. For the most part, the components performed well and there was minimal visible damage, although typical cosmetic damage was not observed due to the unfinished details. Thus, the resilience objective was essentially met, and this could be attributed greatly to the fact that drifts in the timber structure remained relatively low, even at the highest intensity shaking. Limiting drifts was shown to be central for resilience of the components, and accelerations were not high in the rocking wall system.

On the other hand, the performance of various movement joints was far from perfect. Some were only partially activated, and a few did not appear to activate at all. However, it appears that the details provided flexibility compared to more rigid connections, and movement was accommodated through alternative low energy mechanisms. The industry has and continues to look for solutions for resilient detailing solutions, but the constructability of such details is also an important consideration, and several challenges were encountered in scaling up the details from an idealized laboratory setting to a full-scale structure.

As a whole, the collaborative projects provided training opportunities to nine Ph.D. students, seven M.S. students and 13 undergraduate students through the Research Experience for Undergraduates program. This project also supported several payloads and extensive international collaboration from foreign universities including Kyoto University (Japan), University of L’Aquila (Italy), Imperial College London (UK). During the testing phase of the project, several public testing events for media and industry groups were held, providing diverse stakeholders opportunities to learn about this effective technology and design approach that can enable mass timber buildings throughout the U.S. and world in moderate to high seismic regions.

Results from this project have been well-received by the building industry and disseminated through a variety of channels. The 10-story testing effort was recognized by Engineering News Record (ENR) as one of the top 25 News Makers of 2023. The principal investigators have spoken at numerous national and international conferences and workshops. Journal and conference publications highlighting the research outcomes have been published and are under development. This project also provided setup and comprehensive test data for other follow-up research and development projects, such as the effort to introduce the mass timber rocking wall system into the seismic design standards and codes.

Last Modified: 01/30/2025
Modified by: Keri L Ryan