sparks wrote:
During the inspection, faster than expected deterioration was discovered and they closed the bridge before it failed.IMO, the inspection process worked exactly like it was supposed to. Since you claim to be knowledgeable about concrete structures, enlighten us on what you feel went wrong with the process.
Without the inspection report and not visiting the site firsthand, I can only assume the obvious. The concrete spalled away from the prestressed/post tensioned reinforcing, and exposed the cables. This is caused by many factors, including:
1. Insufficient coverage between the reinforcing and the concrete. Normally 2" of cover is specified, but 2 1/2" to 3" should have been utilized.
2. Insufficient concrete strength. Normally 5,000 psi is specified, but should have been 7,500 to even 10,000 psi @ 28 days.
3. IF the structural components were cast on site, in the open, contaminants may have been introduced when the concrete was poured, thereby weakening the concrete.
4. insufficient drainage design. Salt and other contaminants MAY have been allowed to pond on the surface, thereby corroding the structure from the top to the bottom.
Anything else?
Oh yeah:
5. The concrete MAY have not been sprayed with a sealer periodically...
And by the way, anybody other than myself, ever notice the cracking on the Homan Avenue overpass? From the guard rails to the sidewalk and transfered to the deck? Just an observation I made and asked Hammond Inspector (voter3) about, LAST YEAR...
The Cline Avenue bridge is what is known as a post-tensioned, concrete box girder bridge. It's poured-in-place girders are supported by thick cables stretched through ductwork within the concrete.
Concerns about such bridges was raised nine years ago when it was discovered cables had come apart in three major bridges in Florida due to corrosion, according to Michael Sprinkel, associate director of the Virginia Transportation Research Council.
A similar cable failure was found in 2007 in Virginia's Varina-Enon bridge. In response, the Virginia Department of Transportation stepped up inspections of all such bridges, Sprinkel said.
http://www.nwitimes.com/news/local/lake ... 11320.html