July 11, 2007

Sacramento State begins seismic bridge experiment

The Engineering Department recently conducted bridge stress tests that have nation-wide applications. Top row left: Brett Anthony, Janice Gainey, Prof. Eric Matsumoto, Dave Van Zanen and Jim Ster. Front row: Andy Wilson, Tom Buno, Joe Graziano and Josh Larson.
The Engineering Department recently conducted bridge stress tests that have nation-wide applications. Top row left: Brett Anthony, Janice Gainey, Prof. Eric Matsumoto, Dave Van Zanen and Jim Ster. Front row: Andy Wilson, Tom Buno, Joe Graziano and Josh Larson.
Behind-the-scenes video look at the design and construction of the bridge specimens (real player)

The bridge in Sacramento State’s Structural Engineering department came “tumbling down,” but, then, that was the whole point of the experiment.

More than 20 faculty, staff and students are taking part in a nationally funded test program to develop innovative pre-cast concrete bridge connections that are expected to speed up bridge construction while safely withstanding all levels of earthquakes.

The first connection test was conducted earlier this month with more scheduled throughout the summer, says civil engineering professor Eric Matsumoto, who is overseeing the project.

Presently, most bridge columns are built using concrete that is poured into frames on site. The new method would have some beams, called “bent caps,” pre-cast elsewhere and then delivered to the construction site for assembly. This approach provides a more controlled and safer environment, better quality, and less impact to traffic since the bent cap can be installed more quickly.

But will the new method produce structures that can stand up to potential earthquakes in high-seismic activity areas? That’s the question Matsumoto and his team have set out to answer with tests that are being closely monitored by academic and industry experts.

Armed with a $550,000 grant provided by pooled funds from the departments of transportation of all 50 states, and in conjunction with UC San Diego, the researchers built large-scale portions of a bent cap and column.

A powerful overhead vice puts 25 tons of pressure on the specimen, simulating the scaled weight of the bridge. Then a horizontal arm pushes and pulls the structure back and forth, simulating an earthquake. All the while, dozens of gauges on the specimen’s interior and exterior monitor the event.

The first specimen tested this month was deliberately designed to fail prematurely. The breakdown of the joint, with chunks of concrete falling from the supporting column, gave engineers a better idea on how to strengthen the assembly. “The best way to prevent a failure is to know how it will fail and then to design against that,” Matsumoto says. The remaining four tests will look at connections built for severe earthquake standards.

In addition to producing new standards for bridge building, the project also creates partnerships between Sacramento State and private industry, and provides students a chance to work on a venture with implications that go beyond the classroom.

Jeremy Wright, the lead graduate assistant, helped design and build the specimens. “You get to see real life bridges built and do the groundbreaking testing that’s going to be the future of bridge construction,” Wright says.

Thomas Buno was a freshman last year when he began working on the project, and is now a team leader, coordinating the fabrication of the components with Clark Pacific in West Sacramento. “I didn’t know I could come in as a freshman and be involved in a funded research project,” Buno says.

“To team up with us on this is really a great experience for the students,” Matsumoto says, adding that several recent research students landed jobs in the bridge industry.

For more project information and dates of future tests, contact Eric Matsumoto at (916) 278-5177 or at ematsumoto@csus.edu. For media assistance, call Sacramento State’s Public Affairs office at (916) 278-6156.