Does anyone know if there is a reduction in capacity for a steel girder bridge that has had the bottom flange heat straightened after a traffic collision?
There are a couple of resources on this. First try the FHWA and author Krishna Verma, he is probably the leading authority on heat straightening of girders. Should be some documents available. If not call him, he's generally very responsive.
Second Peter Xanthakos treats this subject matter in his text on bridge strengthening and rehabilitation. It is old and it certainly is not all encompassing but will offer some insight.
Also I recall that Verma teamed with LSU professor for research into Heat Straightening.
larsacious - as Qshake points out there's no clear cut answer. You have to do some research because there are a lot of opinions on the subject. I think a strength reduction could be prudent if the affected area has fatigue prone details. A lot depends on how badly damaged the flange was and how much heat and jacking was needed for the repair. The FHWA does have excellent resources.
I've dealt with three fire damage bridges. Each time we proposed heat straightening. In one case the owner agreed. In the other two cases they owners wanted the safe route. one bridge was a century old single span riveted plate girder bridge the owner decided to replace the superstructure. It was a matter of practicality rather than money because the bridge is over Amtrak with catenary lines.
The other project was a three span continuous superstructure. We did a partial superstructure replacement of the damaged stringers. The person we were dealing with at DOT had no confidence in heat straightening, for good or bad he was a metallurgist.
Qshake - The professor you're thinking of is Richard Avent. He consulted on two of our projects.
Thanks for the responses. The project that I am working on has (2) identical bridges. The bridge with the traffic collision has an existing inventory and operating rating of HS11 and HS26, respectively. The non-impacted bridge has an inventory and operating rating of HS18 and HS29, respectively. I am attaching photos of the damaged area at the point of collision. There does not appear to be any deep cuts that would require a loss of section in the rating calcs. Also, the level of corrosion/deterioration appears to similar for both bridges based on my field visit yesterday. Any thoughts?
Is this a welded plate girder or a rolled beam with a cover plate? I see a butt weld to the left of the splice but then further to the left the flange has the appearance of having a cover plate - anyway not important, I was just curious.
What's above the fascia - a sidewalk? traffic lane? I've seen much worse. If it's a sidewalk above, you probably don't need to do anything. If traffic is directly above, you may want to consider grinding smooth any deep nicks or cuts.
This is a rolled section that is reinforced with top and bottom plates at the longest span. This was the original detail back in the day when labor was cheap and materials were expensive.
The bridge is a 3 lane highway with shoulders. Our project is a re-deck and will include repainting the girders. Part of our contract includes re-rating the bridge with the new deck.
Perhaps I can request the current rating calculations from the DOT to see how and why the rating is so much lower on the collision bridge.
You should ask for the rating. At the least, I imagine they would want you to bring the bridge up to HS-20 or 25. Sometimes, one small area of section loss could be the cause of the low rating.
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