Posted 12/29/2005 04:59:00 PM by Douglas

Watch out for falling bridges.

Forty-five years of corrosive road salt draining onto one side of an overpass and a history of trucks hitting its underside likely caused a 53-foot-long, 60-ton concrete beam to come crashing onto Interstate 70 in Washington County Tuesday evening.

"We believe it was a combination of age, wear and tear in the structure, a history of being hit by trucks and, very recently, another hit" that took its toll, said Gary Hoffman, a career civil engineer and No. 2 in the PennDOT hierarchy. "The bridge slopes toward the beam and the effect of road salt is one thing we'll be looking at in a forensic analysis."

Maybe it's the engineer in me that wants to play jail-house lawyer here, but how could a structure be deemed structurally deficient and still remain in service?

On a scale of 1 to 10, with 10 being excellent condition, the Lake View Drive overpass received a score of 4, a rating that means the bridge was "structurally deficient," Mr. Hoffman said. Still, the overpass was judged structurally capable of carrying 40-ton trucks, the maximum legal load in Pennsylvania. The overpass is lightly traveled, mostly by locals.

Seems like PennDOT needs to revamp their 1 to 10 scale if a '4' is going to collapse under its own weight.

The concrete beams in the overpass were designed to last 40 to 50 years and are nearing the end of their expected life, according to the Pre-stressed Concrete Association of Pennsylvania.

Design life? 40-50 years. Age? 45 years. So how could something that inspectors deemed 'structurally deficient' collapse under its own weight? That's a real head-scratcher, isn't it.

"That does not mean the bridge is no longer useful. It simply means you need to pay more attention to it," said Hank Bonstedt, executive director of the Allentown, Pa.-based association.

Apparently you should pay more attention to it as it falls on your car.