Engineers are expediting repairs on the Sarah Mildred Long Bridge, which sustained $2.5 million in damages in April when an oil tanker broke loose from a state pier and smashed into the structure's center lift span.
Covered by insurance, this temporary repair will last until work on a $160-million bridge replacement begins in 2015, says Bill Boynton, New Hampshire Dept. of Transportation spokesman.
The 2,000-ft-long, lift-span structure, co-owned by the New Hampshire and Maine DOTs, crosses the Piscataqua River on U.S. Route 1. One of three bridges linking Portsmouth, N.H., and Kittery, Maine, the 73-year-old span carries an average of 14,000 vehicles per day and is considered critical as a backup for I-95. It also supports a rail line serving the Portsmouth Navy Shipyard.
Since Memorial Bridge is still under construction and scheduled to open in July, only the I-95 High Level Bridge, carrying 86,000 vehicles daily, is left to absorb the Sarah Mildred Long Bridge traffic, Boynton says. "We had to repair the bridge since summer peak traffic would exacerbate problems," he says.
"Repairing the vertical and diagonal elements was straightforward, replacing one for one," says Alan Fisher, construction structures manager at Pittsfield, Maine-based general contractor Cianbro and lead engineer on the project.
The team opted to hire International Straightening Inc., Bismarck, N.D., as a consultant to assist with repairing the bottom-chord element. "I've never seen [heat straightening] used on anything assembled like this with a complex member. The bottom chord has 3.4-inch plates on each side of the member," Fisher says.
Repair work has progressed smoothly, and the team is ahead of schedule, Fisher says. Erecting the falsework support system in the water and gathering materials took most of the time, he adds. Work is scheduled for completion by May 2.
Cianbro is lead contractor on the replacement bridge, with Figg Engineering, Tallahassee, Fla., and Hardesty and Hanover, New York City, on design.