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Strong, elastic ‘smart materials’ aid design of earthquake-resistant bridges

Posted August 29, 2013
Strong, elastic 'smart materials' aid design of earthquake-resistant bridges

Strong, elastic ‘smart materials’ aid design of earthquake-resistant bridges
Traditional bridge columns are constructed from concrete and reinforced steel, which are seldom effective against earthquakes. But new research suggests that replacing concrete and steel with smart materials is a good alternative. From left: cement-polyvinyl fiber mixture; fiberglass column; carbon fiber column; nickel titanium shape memory alloy, or nitinol. Credit: Dr. M. Saiid Saiidi, [email protected] of Nevada, Reno

Bridges are a main component of the transportation infrastructure as we know it today. There are no less than 575,000 highway bridges nationwide, and more than $5 billion are allocated yearly from the federal budget for bridge repairs.

Over the past couple of decades, increasing seismic activity around the world has been identified as an impending threat to the strength and well-being of our bridges. Earthquakes have caused bridge collapses in the U.S., Japan, Taiwan, China, Chile, Turkey, and elsewhere. Therefore, we need to find ways to minimize seismic effects on bridges, both by improving existing bridges and refining specifications and construction materials for future bridges.

A large majority of bridges are made of steel and concrete. While this combination is convenient and economical, steel-concrete bridges don’t hold up as well in strong earthquakes (7.0 magnitude or higher). Conventional reinforced columns rely on the steel and concrete to dissipate energy during strong earthquakes, potentially creating permanent deformation and damage in the column and making the column unusable.

Under earthquake loading, engineers allow for damage in column hinges to dissipate energy and prevent total bridge collapse. While that practice is widely accepted, the effects of hinge damage can interfere with disaster recovery operations and have a major economic impact on the community.

With funding from the National Science Foundation (NSF) and using NSF’s George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES), civil engineer M. Saiid Saiidi of the University of Nevada, Reno (UNR), and his colleagues have discovered a solution. They’ve identified several smart materials as alternatives to steel and concrete in bridges.

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