Repair of the Androscoggin River Bridge in Maine
The Maine Turnpike, Interstate 95 in Maine in northeastern USA, also known as the Gold Star Memorial Highway, crosses the Androscoggin River on two separate bridge structures − one for northbound traffic and one for southbound.
Built in 1955, the bridges had to be repaired and strengthened due to their age, condition and the increased traffic volume. For this purpose, the longitudinal main girders of both bridges were strengthened using a multistrand post-tensioning system consisting of Type 7-0.6", 1,862 MPa (270 ksi) DYWIDAG Strand Tendons with epoxy-coated post tensioning strands. At the mid spans, the post-tensioning tendons were installed along the bottom of the girders. Above the piers, the tendons are installed along the top of the girders.
DSI USA supplied tendons to strengthen eleven locations on each bridge. The epoxy-coated DYWIDAG Tendons were approx. 15.2m (50ft) long and protected by HDPE ducts. DSI designed and developed the anchor brackets consisting of galvanized high strength steel.
The work above the piers proved to be especially difficult due to very low clearance between the girders and the bridge deck. DSI therefore developed a special stressing plan for the DYWIDAG Tendons which allowed for proper stressing in these tight conditions.
In addition, DSI designed eight special anchor bracket mounting plates that had to match up with existing rivet locations on the girders. For structural reasons, the drilling of new holes into the girders was not permitted.
Work for phase one of this project was difficult because it was carried out in late fall and the severe winter of 2013/14. The second phase of this project was successfully completed in the first quarter of 2014.