Close-up of a Md. bridge

Inspection is largely a matter of educated looking, listening

August 04, 2007|By Nicole Fuller | Nicole Fuller,Sun reporter

Bang a pick hammer along the concrete- and steel-encased underbelly of any bridge and listen for the "ping!"

It's a happy sound that echoes through the rumbling of the cars and trucks above. The ping is good.

It means the concrete and steel are holding strong, not cracking or rusting under the beating of potentially corrosive salt from snowy roads that can damage the girders, cross-braces and bolts -- all made of steel -- that keep bridges structurally sound.

Pounding a hammer against the substructure of a piece of the Interstate 70 bridge that rises 17 feet over Route 97 in Howard County yesterday while teaching the news media a thing or two about the intricacies of bridge inspection was Joseph Miller, deputy director of bridge inspection and remedial engineering at the State Highway Administration.

Bridge Inspection 101, according to Miller, who has inspected the structures since 1979, amounts to alert eyes and ears.

"That's good to my ear. It's a nice ping-y sound," Miller said, as he rapped the concrete on the eastbound lanes.

Since the bridge collapse this week in Minneapolis, the inspection process and condition of bridges across the country have come under greater scrutiny.

In 1990, the federal government gave the failed Minneapolis bridge a rating of structurally deficient for significant corrosion in its bearings. The bridge is one of 77,000 in that category in the nation -- 1,160 in Minnesota alone. The designation means that some portions of the bridge need to be scheduled for repair or replacement.

Maryland's SHA, operating with an annual budget of about $25 million, inspects each of the 2,584 bridges under its jurisdiction at least once every two years. No engineering degree is required of inspectors, just a two-week course from the Federal Highway Administration in bridge inspection.

In Maryland, state highway inspectors conduct "hands-on" inspections of each of its bridges, which entail close inventory of a bridge's substructure, superstructure and deck. Officials said these inspections are not federally required.

The state ranks well below the national average in the number of "structurally deficient" bridges -- 8.1 percent versus 12.4 percent.

With the exception of larger structures such as the 4-mile Chesapeake Bay Bridge, inspecting a bridge generally takes about two days and not a lot of fancy technology -- eight hours of field inspecting, including time spent in a bucket truck taking digital pictures. Then a written report must be filed.

Constructed in 1973, the section of the I-70 bridge in Howard County is generally in good shape, according to state highway officials. It is reinforced by seven steel pillars that cut down the risk of structural failure.

On a scale from zero to nine, it earned a five for its superstructure and a six for both its deck and substructure in its last inspection. Its structural sufficiency rating was 83.9 out of a possible 100 -- meaning it is generally safe.

"I don't have any zeros. I don't have any nines," Miller said, adding that he has not inspected any bridges that are potentially hazardous based on the two scales used to judge them.

Two spalls -- patches of deterioration of thin layers of concrete -- were visible during yesterday's inspection. They will be noted in the report for maintenance but were not enough to shut the bridge down.

In recent years, engineers have remedied this problem by applying a coat of epoxy over the steel to prevent spalls.

"This bridge, I think, is in very good condition," Miller said. "This one being 34 years old, looks very nice. We try to keep our interstate bridges in pristine shape."

nicole.fuller@baltsun.com

Baltimore Sun Articles
|
|
|
Please note the green-lined linked article text has been applied commercially without any involvement from our newsroom editors, reporters or any other editorial staff.