A cooling-water intake structure in Louisiana which provides cooling water for a coal-powered generating plant was built using the sinking caisson method. Hence, all but the first pour of the 94x148-foot structure was cast above grade and lowered into the ground. This was done by casting a structural steel cutting edge in place at the base of the first 7-foot lift. Next, two 5-foot lifts and a 10-foot lift were placed. Inside excavation was then begun to sink the structure 10 feet, making it ready for the next lift. After each lift, excavation was resumed and the structure lowered 10 feet.


An important requirement of the project was that there be no reinforcing bars protruding from the exterior walls into the inside area. Specifications called for a system in which couplers are preswaged (pressed on with great force) to reinforcing bars. These couplers can be set flush with the inside surfaces of the exterior walls to avoid any protrusion into the relatively confined work area. Removable plastic caps keep concrete out of the couplers.

Reinforcing bars for interior partitions also had threaded couplers swaged on at the end. They were joined to bars in the walls by means of a high-tensile-strength steel stud threaded on each end. This permitted the two reinforcing bars to be positively connected by turning with a wrench. A main advantage of swaged threaded couplers is that they eliminate threading the rebars. Threaded rebars have to be carefully transported and handled to protect the threads against damage. The only exposed threads in this system are on the small steel connecting studs, and the studs are packed into cardboard cartons for safe and easy handling.