One of the world’s most powerful earthquake simulators has been used to test the mettle of an innovative new pre-cast concrete bridge.
The bridge, designed and built by engineers from the University of Washington, Seattle and the University of Nevada, Reno, managed to endure the most extreme seismic shocks that can be replicated by means of modern earthquake simulators.
The rocking, pre-tensioned bridge, which measures over 20 metres in length and weighs a total of 52 tonnes, was made from pre-cast concrete components as part of efforts to develop a bridge which can be built on site in a shorter time period and with less disruption to the surrounding environment, yet which will still possess enhanced resilience and strength.
“By building the components off-site we can save time with construction on-site, minimising interruptions in traffic and lowering construction costs,” said David Sanders, Foundation Professor from the University of Nevada, Reno.
The concrete columns and beams for the bridge were pre-cast and tensioned at the University of Washington in Seattle, while other parts were built at the University of Nevada in Reno.
Following the preparation work, all the requisite components were then transported to the University of Nevada’s Earthquake Engineering Lab, where the bridge was built in a period of just a month on top of three 14-by-14 foot, 50-ton capacity hydraulically driven shake tables.
The bridge was then subjected to the most extreme seismic disruptions the laboratory is capable of simulating, including massive ground movements similar to those produced by the 6.9 magnitude earthquake which struck the Japanese city of Kobe in 1995.
According to the designers of the bridge, the structure performed remarkably well under such extreme conditions, surpassing current design requirement by a factor of 2.2.
While the bridge was eventually broken by the immense stresses to which it was subjected, John Stanton, civil and environmental engineering professor from the University of Washington, pointed out that the structure nonetheless managed to remain erect, a fact which alone attests to its extraordinary resilience.
“The important thing is it’s still standing, with the columns coming to rest right where they start, meaning it could save lives and property,” said Stanton.