UNR Researchers Test Bridge During Earthquake Simulation
Researches at UNR are using shake tables to create safer bridges and improve standards.
Researchers at the University of Nevada are using shake tables to simulate an earthquake. The experiment comes after two years of research and construction of a 100-ton, 70-foot-long concrete bridge. The structure is unique because it represents a prefabricated bridge.
"Once all the pieces are in place, bring them to the site and rather than spend a year-and-a-half to build a bridge, do it in six months," Saiid Saiidi, Professor of Civil & Environmental Engineering said.
Most of the parts were built in the laboratory, but in regular construction, it is built off-site. The faster pace of construction has less of an effect on traffic and saves money.
"They know that time is money and if they can accelerate the construction of a bridge, and it be safe and survive, and in this case, more than survive," Ian Buckle, Director of the Earthquake Engineering Laboratory said. "It's functional. You can get emergency vehicles over this bridge."
"We are building bridges in a faster way but at the same time, we want to keep those bridges safe under a ground motion," Jose Benjumea said.
Wednesday's first test represented a magnitude 6.5-6.8 earthquake. Once the shaking was finished, students checked the bridge for cracks and other damage.
"We are designing them so that certain parts of the structure will be damaged but the structure should not collapse," Saiidi said.
Once that was completed, researchers increased the amount of shaking to simulate magnitude 7.5 earthquake. Researchers say these tests could lead to structural improvements that could save lives.
"There was some damage, some concrete falling but we didn't have any collapse of the bridge," Benjumea said. "So it would preserve life."
Buckle says the University of Nevada's research is followed by departments of transportation around the world, and it has led to stronger building codes.
"We, of course, have worked with NDOT a lot on bridges on (Interstate) 80, which is a lifeline, in and out," Buckle said. "If any of these bridges came down, Virginia over 80 could close 80 and we couldn't get out. Emergency services couldn't get in."
The shake-table experiment comes after two years of research and construction. The $900,000 project was funded by Caltrans to see if prefabricated bridges are safe enough to withstand large earthquakes.
"The idea for conventional steel and concrete is that those bridges should not collapse but getting damaged is expected," Saiidi said.
The 7.1 magnitude earthquake in Mexico City shows that many older buildings were built before stricter codes were put in place. The research and data from the University of Nevada experiments are used all over the world and could be beneficial for future construction in Mexico.
"Certainly, they can use this technology in their bridges for sure because they are using a lot of prefabricated bridges and they are in a high seismic zone," Saiidi said. "Our work has been implemented in the field and has impacted the profession."
Nevada is third-most-seismically-active state in the country, and officials say this research is vital to future infrastructure projects.
"What we do is vital to the recovery of the area, as well as minimizing injury and loss of life," Buckle said.
Buckle says part of that is also retrofitting older buildings to withstand large earthquakes. Lincoln Hall was recently retrofitted on the UNR campus.