Do you have any information on the performance of some of the early post-tensioned concrete bridges built in the United States?
One of the earliest, the Walnut Lane Memorial Bridge in Philadelphia, built in 1949, is still hale and hearty. There have been some problems with cracks in the bottom flanges of the thirteen 160-foot center-span girders, but these have been dealt with successfully by means of epoxy pressure injection. The cracks are believed to have resulted from the presence of water in the preformed tunnels which carry the post-tensioned strands. The tunnels were apparently grouted without pressure, allowing segregation and the accumulation of free water.