BUILDING TECHNOLOGY 05

The steel tendons are tensioned before the concrete is cast in pre-tensioning. After the concrete has been laid and cured, the tendons are temporarily fixed to certain abutments and subsequently cut or freed. The connection throughout the length of the tendon transfers the pre-stressing force to this concrete. Pre-tensioning is often done on permanent beds at pre-casting factories that manufacture pre-tensioned precast concrete parts for the building industry. While, the steel tendons are tensioned after the concrete has been poured and hardened in post-tensioning. It is accomplished in two steps: tensioning the steel wires or strands with hydraulic jacks that stretch the strands while bearing on the ends of the member, and then replacing the jacks with permanent anchorages that bear on the member and keep the steel strands tensioned.