The cable-stayed stayed.
Standing up to the wrath of Hurricane Katrina, the Cochrane Africatown USA Bridge in Mobile, Ala., took a hit from an oil platform and lived to carry traffic another day. Sitting on a dry dock barge a few miles up the Mobile River, the platform broke loose during the storm of the century and rammed into the center span. Amazingly, the damage was relatively minor considering the storm’s fatal effect on the Gulf Coast. Alabama’s only cable-stayed bridge was spared.
“It certainly could have been much worse in terms of damage,” Tony Harris, chief spokesman for the Alabama DOT, told Roads & Bridges. “Part of the reason it sustained such minimal damage is that the top part of this platform had some equipment and rigging that sheared right off on impact. Had it struck center on one of the main towers it could have been much worse.”
Crews were certainly bracing for the worst when they were dispatched to the site shortly after the brunt of Hurricane Katrina left the region. With winds still reaching 75 mph, engineers surveyed the 1,500-ft-long bridge and found damage to three bearing assemblies and some cable insulation. Striking the bearing units also moved the main span, which is 780 ft long, 2 in. off center. Inspectors gathered volumes of information for a conference call with ADOT and the bridge designer, FIGG, Tallahassee, Fla. It was decided the bridge was strong enough to keep two of the four lanes open with weight restrictions.
The move kept a major artery open. The Cochrane bridge is a connector for U.S. 90/98 and is a route hazmat trucks take to bypass the Wallace Tunnels on I-10. Harris believes most, if not all, hazmat trucks could cross the injured bridge.
A temporary repair on cable insulation was executed almost immediately. Crews wrapped plastic and duct tape around exposed steel cables. The rest of the mending began at the end of September. ADOT was hoping to do much of the repair work under traffic. A schedule and cost was not determined at press time.
The only elevated structure Hurricane Katrina got her hands on in Alabama was a 250-ft bridge ramp off U.S. 98 along the Gulf Coast.
“The bridge deck lifted up with the tidal surge and washed off the piers,” said Harris. “We had several other bridge-deck segments along the causeway that displaced some, but we were able to lift and carry them back into place.”
There also were some washouts along the roadbed on U.S. 98 and flooding in the ventilation working area underneath the Wallace Tunnels. ADOT, however, had traffic running smoothly by the end of the week.
“We prepositioned a lot of people and we know what parts of our transportation system are vulnerable. Healthy measures of preparedness and advance planning allowed us to respond effectively,” said Harris.