Timber's comeback: CLT and seismic retrofits
With 1,700 unreinforced masonry buildings in Portland that will likely soon be either demolished or upgraded, a new seismic retrofit tool being studied in Corvallis might help save both money and historical buildings.
Safer historic buildings and more timber industry jobs are the goals of a partnership between an Oregon State University structural engineer researcher and a newly formed nonprofit, Cascadia Seismic Strategies.
Oregon has numerous intage masonry structures like the Harding Building, the focus of this project, that would be particularly damaging in case of an earthquake: this type of material is expected to shake down and hurt people near and inside these buildings, if not reinforced before a major incident.
Andre Barbosa of the OSU College of Engineering is collaborating with Cascadia Seismic Strategies on a $150,000 project to study the use of cross-laminated timber (CLT) panels for seismic retrofits on unreinforced masonry buildings, an engineering project scheduled to begin this August.
"This comes from what we've been learning by visiting different earthquake sites, like Napa (California) and Nepal," Barbosa said. "We keep learning and try to bring back that knowledge and share it with communities, including by creating a model for affordable seismic retrofits for historic buildings. This is a grassroots, community-driven solution for a big problem, a huge Cascadia quake."
Portland-based KPFF Consulting Engineers will handle most of the structural engineering, led by Reid Zimmerman, with Barbosa lending his expertise in cross-laminated timber and seismic retrofits.
"We'll build prototypes that will provide details that will let engineers and construction folks see how things go together," said Barbosa, also volunteer with Cascadia Seismic Strategies.
Barbosa is one of the original members of the group, named after the subduction zone that lies off the coast of Oregon.
The OSU College of Engineering program is among the nation's largest and most productive. Since 1999, it has tripled its research expenditures to $42.4 million by emphasizing highly collaborative research and innovation that solve global problems, leading in precision health, clean energy, resilient infrastructure and advanced manufacturing.
OSU is also a leader in developing new wood products such as CLT and in growing forest-products jobs amid reduced harvest levels.
Oregon Main Street, the primary funding organization, is a Main Street America coordinating program administered by the State Historic Preservation Office. It works with Oregon communities to develop comprehensive, incremental revitalization strategies based on a community's unique assets, character and heritage.
The grant covers approximately 66 percent of the project's total costs, and was coordinated by the Downtown Corvallis Association (DCA) and Oregon Main Street. It is funding mockups of CLT retrofit systems of the 107-year-old Harding Building along Third and Madison Streets in Corvallis — and a cornerstone of the original Third Street business district.
"The DCA is concerned about the potential devastation that a Cascadia Subduction Zone mega-quake would wreak," said Cascadia Seismic Strategies spokeswoman Roz Keeney. "Members of the DCA's design committee recruited structural engineers, historic architects and other building professionals to join in a conversation about earthquake preparedness and historic building preservation. This group went on to form Cascadia Seismic Strategies, which is now focused on this cutting-edge project to develop a low-cost reinforcement method using local wood products and off-the-shelf steel connectors."
The grant for the 34-month project underwrites multiple design and construction strategies for dealing with weaknesses in unreinforced masonry buildings, as well as production of a video demonstrating how to implement upgrades that can serve as a guide for other communities such as Portland wanting to use similar strategies in preservation and retrofitting efforts.
"This project identifies seismic retrofits for historic buildings that improve their safety performance without compromising their historic integrity," said Sue Licht, project manager and historic preservation architect. "It also demonstrates that historic rehabilitation can create local, site-specific jobs that cannot be outsourced."
With the results of the research, cities across the state could be safer in case of a quake — and reinstate jobs in the timber industry, leading the nation and the globe in building sustainably with CLT.