University of Nevada lab tests new quake prevention

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Scientists at a Nevada earthquake lab in the US on Wednesday tested new bridge designs with connectors they say are innovative and could to better withstand violent temblors and speed up reconstruction efforts after major quake damage.

University of Nevada, Reno engineers performed the experiments on a giant "shake table" to simulate violent motions of an earthquake to rattle a 100-ton (91-metric ton), 70 foot (21-meter) bridge model to determine how well it would hold up.

Graduate students at the University of Nevada, inspect a bridge model for damages after tests were done to intended a massive earthquake. /AP Photo

The tests, conducted a day after a big quake struck Mexico, shook large concrete columns and beams back and forth for about 30 seconds at a time, displacing some nearly a foot before returning largely to their original position.

Graduate students measured and marked indications of tiny fractures but no major structural damage was observed in the initial review of the experiments.

"The bridge has done better than we expected," said Saiid Saiidi, a professor of civil and environmental engineering who served as the project leader. He’s done related research for more than 30 years.

University of Nevada graduate students inspected a new bridge concept for damages after installing a shake table intended to simulate violent earthquake activity. /AP Photo

Although many bridges were designed able to withstand earthquakes, but were often found unsafe for travel after big quakes. He said the designs that were tested used special types of connectors to link prefabricated bridge parts, including ultra-high performance concrete.

"Earthquakes by themselves don’t kill people — it’s the structures," Saiidi said.

The elements have been tested on their own but never before combined in a bridge model subjected to realistic earthquake motions, like the 1994 Northridge, California quake. Wednesday’s test inside the University of Nevada’s Earthquake Engineering Laboratory simulated the activity of a quake as large as magnitude 7.5.

Graduate students at the University of Nevada, inspect a bridge model for damages after tests on a giant shake table. /AP Photo

Some design work by the engineers has been incorporated into a highway off-ramp under construction in Seattle. It’s the first bridge in the world that uses flexible columns and reinforcement bars made out of a metal alloy with titanium that bends and then springs back into shape when quakes hit.

Among other things, the innovative connectors allow for prefabricated concrete and other materials to be attached to an existing bridge foundation so as to speed repair and reconstruction

Part of the research centers on a so-called "pipe pin" connection developed by the California Department of Transportation’s bridge designers for use in connecting certain beam interfaces in bridge construction.

A worker walks under a portion of a new offramp for Highway 99 where a tunnel for the roadway is still being constructed in Seattle, US, September 19, 2017. /AP Photo

A portion of a new offramp, center right, for Highway 99, stands completed and adjacent to the entrance for northbound traffic into the Highway 99 tunnel still being constructed in Seattle, US, September 19, 2017. /AP Photo

The pin consists of a steel pipe that is anchored in the column and extended into a steel can be embedded in the beam. A gap between the steel pipe and the can enable the extended segment to freely rotate inside the steel can and prevents bending of the protruded segment inside the can.

The University of Nevada’s Earthquake Engineering Lab is the largest of its kind in the United States.

The latest project is funded by the California Department of Transportation, which currently is developing plans for 10 pilot projects based on the developing bridge connector technology.

"This study today is going to allow them to make observations of those designs," Saiidi said.

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Source(s): AP