One of the major advancements in bridge and deck construction in the world was the development and use of prestressed concrete. Made possible through the use of post-tensioned steel cables run through post-tension ducts, this construction method enables thinner concrete sections, longer spans between supports, stiffer walls to resist lateral loads, and stiffer concrete deck sections.
Post tension round and flat corrugated duct is roll formed by the GI steel strip, with its special corrugations and high radial stiffness. The corrugated tubes meet with structural design specifications for void former in concrete structures, used to reduce the cross section area and thus the weight of the structure. It is a very rigid but yet light weight sheet metal tubing that without excessive deforming, withstands existing forces during the pouring of the concrete. The spiral seam is tight and no water from the concrete will enter the tube. The low weight of the tubing makes it easy to handle.
On many construction projects like apartment buildings, parking garages, office buildings, industrial buildings, bridges and docks, schools and hospitals, the introduction of the prestressed protection tubes will make it possible to use very long spans. The reduction in weight allows large areas and fewer columns which in turn will give technical economical and esthetic advantage.