While we would prefer a bridge to be constructed of mostly curved steel, steel can still add value in the construction of a concrete bridge. Post-tensioning is a form of “prestressing”, meaning that the steel is stressed (pulled or tensioned) before the concrete has to support the service loads. A typical steel strand used for post-tensioning has a diameter of 15.7mm and a tensile strength around four times higher than an average non-prestressed piece of rebar. Albina completed a recent project consisting of 300,000# of 3-1/2″-5″ OD pipe bent, cut, trimmed, weld marked and galvanized for thousands of pieces for a post tensioning piping (conduit) for a local bridge project. Our bent steel is then placed in a sheath or duct. This allows it to move as necessary when the tensioning force is applied after the concrete cures. The steel stretches as it is tensioned and it is locked into place, thus maintaining the force in the strand for the life of the structure.
Please reference the following article written by BBR VT International LTD. to learn more about the benefits of post-tensioning, the different types of post-tensioning and how it is installed. You can also reference concretenetwork.com or the Post Tensioning Institute for more information.