The Olmsted Locks and Dam Approach Walls Project represents one of the largest civil projects undertaken by the US Army Corps of Engineers. The project consisted of a set of locks, tainter gates, a boat-operated wicket navigable pass and a fixed weir. The goal of the project was to meet the significant shipping demands on the Ohio River, which can no longer be efficiently met by the existing locks and dams 52 & 53 which were constructed in 1929.
VSL provided post-tensioning for the construction of the approach walls which “guide” the barges and other river traffic to and from the locks. These walls are made up of 11 floating post-tensioned pontoons that were cast in a graving yard further up the river in Paducah, Kentucky. The pontoons vary in length from 158 feet to 389.5 feet. They are up to 52 feet wide and are typically 15 feet high. The pontoons are post-tensioned longitudinally in the keel, deck and walls using 5-31 bonded tendons and PT-PLUS™ corrugated duct. There are over 700 tons of post-tensioning in the pontoons. Upon completion of construction of the pontoons, the area was flooded and the pontoons were floated down to the lock site where they were “integrated” to the adjacent pontoons with 2.5” diameter post-tensioned bars. The ends of the pontoons are held in place with a connection to fixed nose piers.
The decision to construct post-tensioned floating pontoons was based on a significant reduction in cost, weight and maintenance as compared to other alternatives. The construction of the pontoons in a casting yard also helped to reduce disruption to navigation on the river.
Post-tensioned concrete floating structures have proven to be cost efficient and durable solutions for structures such as oil platforms, bridges and docks. Building the structures in an on-shore environment such as a casting yard can help improve quality and schedule. At the same time, the structures remain both buoyant and heavy enough to withstand significant ship and marine loads. Some of the other advantages of post-tensioned floating structures include fatigue resistance, crack mitigation, fire resistance, and low maintenance.