McAndrews overpass may, or may not, handle a quake

The west McAndrews overpass work is finally finished. With all the talk of bridges collapsing, I wondered if they improved earthquake capabilities of the overpass while they were at it. If it goes, the train track below it is gone too. Can we have any confidence that it might survive an earthquake?

— Kathy H., Medford

Will the overpass withstand an earthquake? Medford Public Works Director Cory Crebbin isn't making any promises.

"It depends on how big the earthquake is, and that applies to all bridges," he said.

"Earthquake ground motions come from different directions, and there are different kinds of earthquakes. An earthquake is not just an earthquake."

Kathy, the recent construction on the bridge was not seismic retrofitting, just some simple deck patching, but don't begin mapping out alternative routes, yet. Crebbin assured us that engineers calculate lateral loads, or seismic movement, and factor the information into their designs.

Also, every couple of years, the state conducts bridge inspections and assigns bridges a score. Bridges with a low score are recommended to Oregon's bridge program for funding.

The West McAndrews overpass is currently not on that list so it must be OK, Crebbin said.

Send questions to "Since You Asked," Mail Tribune Newsroom, P.O. Box 1108, Medford, OR 97501; by fax to 541-776-4376; or by email to youasked@mailtribune.com. We're sorry, but the volume of questions received prevents us from answering all of them.


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