A new, leading-edge bridge design was tested in the Earthquake Engineering Laboratory on campus on Wednesday, Sept. 20. A large-scale, two-span bridge was knocked around using a new design, which was made with the goal of not only cutting down construction time, but making a more earthquake-resistant structure.
The project is headed by Professor Saiid Saiidi, a member of the university’s Department of Civil Engineering and director of the Center for Advanced Technology in Bridges and Infrastructure.
The new bridge design features pre-cast concrete columns and beams, which will allow construction crews to assemble the structure faster. Quicker construction means crews will spend less time working on or near roadways, making the project safer for both construction crews and drivers.
Faster construction also contributes to shorter periods of traffic congestion, detours and lane closures on highways and roads.
New connection designs, that were designed by Saiidi, were integrated into the design. Other similar connections have been tested individually, but not all together. A major aspect of the project is investigating how they work together when combined.
“The good seismic performance of a component does not guarantee that the entire bridge will resist the earthquake,” Saiidi said.
Modern bridges are designed to not collapse during earthquakes, but can still be unsafe afterward and can require major repairs. The new design incorporates flexible beams, as well as reinforcement bars, that bend and move with the quake, but return to their original position afterwards.
According to Saiidi, “the experiment, with the largest motions at 200 percent of the design earthquake, was a success, showing the components performed well.”
The shaking produced visible cracks, but Saiidi said the 100-ton, 70-foot-long bridge held up well to the tests. In between the shakes, a team of graduate students went about collecting data and documenting the cracks that had developed.
Saiidi says the team will have their hands full for a few months analyzing the data collected from the test. There were approximately 400 collected channels of data collected to be used in the extensive post-test analysis.
The project is funded by a grant from the California Department of Transportation. The university’s Earthquake Engineering Lab and Large Scale Structures Lab are the largest and most versatile large-scale structures and earthquake/seismic engineering facilities in the country, according to the National Institute of Standards and Technology.
The simulated earthquake mimicked the shaking from the 1994 earthquake in Northridge, California. The 6.7 magnitude temblor was responsible for an official death toll of 57 people 23 years ago.
The lab in which the test was run includes three biaxial shake tables and a six-degree-of-freedom table that are often used to test buildings, non-structural systems, as well as other bridges.
The test comes just days after a 7.1 magnitude earthquake devastated Mexico City, the country’s second major earthquake endured in a 12-day span.
University President Marc Johnson and Manos Maragakis, Dean of the College of Engineering, were both in attendance for the public test.
Kevin Bass can be reached at firstname.lastname@example.org and on Twitter @NevadaSagebrush.