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Shaking Up Seismic Retrofitting
Shaking Up Seismic Retrofitting

It was in the dead of winter. The sun had long since set over the Pacific Northwest. Then, at around 9:00 p.m. on January 26th, the ground started shaking along a 621 mile stretch of the coast, from mid Vancouver Island to northern California where the undersea Cascadia thrust fault ruptured, causing one of the world’s largest earthquakes, a magnitude 9.0—so strong people couldn’t stand; the quake generated a massive tsunami that destroyed a village on Vancouver Island’s west coast, killing all of its inhabitance, and raced across the Pacific where it reaped untold devastation along the coast of Japan. That was 312 years ago, long before the Pacific Northwest was scored with vast metropolitan areas and home to millions of people.

While it’s impossible to say when or where the next “big one” will hit, how the cities it affects fair in its wake might depend, in part, on seismic retrofitting technology in development at Portland State University.

In the case of an earthquake, a building retrofitted with buckling restrained braces (BRBs) will have a greater chance of retaining structural integrity given the way the BRBs absorb a portion of the energy generated by the movement of the building. Unfortunately, many of these braces are built with incredibly heavy materials, making installation difficult and costly and their steel cores, cased in concrete, can corrode, rendering the braces ineffective. To address these design issues, Dr. Peter Dusicka, Associate Professor in the Department of Civil and Environmental Engineering, has designed an innovative, ultra-lightweight, corrosion-free buckling restrained brace.

“With regards to the current state of earthquake engineering,” Dr. Dusicka said, sitting down to talk with Innovation & Intellectual Property (IIP), “engineering and the building codes are geared toward saving lives, but that often means that after an earthquake the structure, be it a building or a bridge, isn’t usable. In our research, we’re trying to understand how to design structures for what we call ‘rapid return to occupancy,’ structures people can return to shortly after a seismic event.

“Buckling restrained braces have been in use for a decade and with behavior characteristics desirable in an earthquake, they’re fairly popular. The problem is that these braces are awkward and heavy so operating a building during retrofitting can be tricky.”

Dr. Dusicka’s solution to the problems he saw in current BRBs: gone were the steel cores and concrete. Gone also were the large mass and the potential for corrosion. To dissipate an earthquake’s energy and prevent structural damage to buildings and bridges, Dr. Dusicka developed a new BRB with a ductile aluminum core surrounded by a jacket of fiber reinforced polymers (FRPs).

With his plan for building a better BRB drawn and talks at conferences planned, Dr. Dusicka formally disclosed the design of the ultra-lightweight, corrosion-free buckling restrained brace to IIP in November 2011.

“Peter came to IIP after a presentation Joe Janda gave introducing IIP to Engineering faculty,” Rachelle Richmond of Innovation & Intellectual Property said. “I met with Peter to better understand the invention and explain the patent process. Given the early state the invention was in, we filed a provisional patent application to protect the invention and allow Peter time to further develop the technology and explore commercial partners.

“To date,” Rachelle Richmond went on, “Peter is working on a prototype, and has identified potential commercial partners to provide feedback on his designs. He is a hands-on inventor who prefers direct interaction with potential partners; I’m advising Peter as he proceeds with potential partners of issues pertaining to licensing relationships, funding and non-disclosure agreements; I’m also facilitating discussions with potential partners, and identifying networking and funding opportunities while managing patent protection of the invention.”

A few weeks before the completion of the BRB prototype, Dr. Dusicka sat down with IIP and discussed the benefits of his design: “The are two main advantages this design has over others available. One is weight. Installing a brace like this would not require heavy machinery. Even a full size, fully assembled brace could almost be handled by two construction workers. 

“The second advantage is the fact that it doesn’t corrode, so it can be used outside and in environments where corrosion is a concern. Typical braces have a steel core cased in concrete. Inspecting the brace is impossible. But with the lightweight brace we’ve developed, inspection isn’t an issue because neither aluminum nor FRPs are corroding materials. I think this brace would shine more than others on costal bridges where corrosive agents are ever-present and in places where installing current BRBs would cause a disruption to the building’s operation and would be detrimental in terms of cost, places like office buildings and hospitals.”

With a prototype BRB complete, Dr. Dusicka will be heading up testing of the new brace in PSU’s iStar Lab where the brace will be subject to cyclic deformation tests that simulate earthquake conditions. IIP is looking forward to learning the results of the tests, following Dr. Dusicka’s work as he continues advancing earthquake engineering technology and providing him with whatever help and advice he needs while the ultra-lightweight, corrosion-free buckling restrained brace moves from drawing board to testing lab and perhaps to buildings and bridges here in Portland and in earthquake prone cities around the world.