A faculty-student engineering research project at California State University, Fresno, aims to make highway overpasses better able to withstand earthquakes.
Mike Wesson, a graduate student from Fresno, Chris Abela, a senior from Santa Maria, and Dr. Thomas Attard, an assistant professor in the Department of Civil and Geometrics Engineering, first replicated support columns from a Selma freeway bridge.
They are building three scaled-down bridges based on that design to test on an earthquake simulator in the university’s Structural Laboratory.
Attard said the columns will be sheathed “in a Saran Wrap-like covering” of carbon, then subjected on the simulator to force equivalent to the 1994 Northridge earthquake.
“Our calculations show that by increasing confinement and ductility in the reinforced concrete columns using the carbon wraps, the columns will remain held together during an earthquake” helping protect the bridge from significant damage, said Attard.
The research is necessary, Attard added, because about 25 percent of California’s bridges are either structurally deficient or functionally obsolete. “California’s in-service bridges are the fifth worst in the U.S., and with significant seismic activity being projected in the near future, the potential effects may be disastrous,” he said.
Some highway bridges were built before 1965, when little consideration was given to seismic resistance, Attard said, and have not been strengthened or otherwise protected from quake damage.
The three-phase Fresno State research study began in February. The first test is of an “as-is” bridge model whose columns aren’t protected. Next is a “pristine-carbon” test in which the columns are wrapped before shaking.
Finally, an unprotected bridge is shaken until it has minimal damage, then, the columns are carbon wrapped for more violent shaking to gauge increased retrofit strength.
The third test is vital, Attard said, because “it is unrealistic to believe that in-service bridges have no pre-existing damages” caused by small earthquake tremors over time or by wear and tear from vehicles driving on the bridges.
Materials for the project were donated by Commercial Metals Company (NYSE: CMC), based in Irving, Texas, and BASF (NYSE: BF), an international chemical company headquartered in Germany.
Attard said if test results are positive, additional funding support will be sought from Caltrans for further study.
For more information, contact Attard at email@example.com.
For more information contained in this release, please go to the following Web site(s):
Earthquake Simulator at Fresno State