Earthquake

The University of Nevada has carried out an earthquake simulation bridge test. Visit their site for some excellent broadcast quality video of the event.

RENO, Nev. – At 11:04 a.m. today a rumbling was heard at the northeast end of the University of Nevada, Reno as an “earthquake” shook a four-span 110-foot concrete bridge with motions comparable to an 8.0 earthquake. The bridge was in the University’s world famous earthquake simulation laboratory.

The bridge, constructed over many months atop three enormous shake tables, is a test bed for cutting-edge construction technologies of the future. Many of the new materials–including nickel-titanium bars, elastomeric materials, and polyvinyl fiber concrete–are being tested in a bridge system for the first time.

The bridge columns swayed and cracked, with small chunks of concrete falling off the structure. The 400 sensors relayed gigabytes of data through 400 channels as the 10-second quake stressed the quarter-scale model bridge with its 60 cubic yards of concrete and 16,000 pounds of steel.

“These were all new designs, and we’ve learned they performed better than conventional construction,” Professor M. Saaid Saiidi, principle researcher said. “Of the three new designs we tested, two of them had very little damage, we are quite pleased with the results so far.”

This test is the largest of its kind in the United States. The test was part of a series of three tests of materials and design to make bridges safer. The first test in Feb. 2007 used a standard design bridge of the same size and the third bridge test will continue the look at new innovative designs and materials.

“There is no other facility in the country as big and with the equipment we have to conduct these types of tests,” Saiidi said.

Three 50-ton capacity shake tables acted in unison to shake the 200 tons of concrete and steel that swayed, buckled and cracked as twice the acceleration intensity of the 1994 Northridge, Calif. earthquake tore at the structure. The bridge model was shaken with bidirectional forces to realistically simulate an earthquake.

The UNR research team is taking advantage of unique features of materials such as nickel/titanium alloys, polyvinyl fibers mixed with cement, and rubber materials to potentially revolutionize seismic design of future bridges to help protect lives, prevent damage and avoid bridge closure even when there’s a strong earthquake.

“To save lives bridges are made so they do not collapse, even though they are no longer usable,” Saiidi, said. “The question is, what is the impact of having to close numerous damaged bridges in a city like New York, Los Angeles or San Francisco at a time when these bridges are needed the most for fire trucks, ambulances, and other emergency vehicles?”

The experiment is part of a larger multi-university project funded by the National Science Foundation (NSF) under the George E. Brown Jr. Network for Earthquake Engineering Simulation (NEES) research program. Other UNR faculty involved in the $2.4 million project are Dr. I. Buckle and Dr. G. Pekcan. Researchers from U.C. Berkeley, U.C. San Diego, Florida International University, Georgia Tech, Stanford University, Kansas University and University of Illinois, Chicago, Tokyo Institute of Technology, and the University of Ljubljana have been involved in other aspects of the project.