Supervision Of Prestressing

Introducing Pre-stressing is creation for known permanent stresses in a member of structure before the full dead and live loads are applied. These stresses are created by means of high tensile steels tendons, which are tensioned and then anchored mechanically to the member being pre-stressed. This offset or counter reacts the stress, which the subsequent loading will produce. This also modifies the behavior of the material of which the member or structure is composed. For example ,concrete those have relatively low tensile strength ,after pre-stressing it will behave as if it were ductile and as if it had high tensile strength.

SAI Post Tensioning Anchorage system used to transfer the pre-stressing force to the concrete comprise of a Tube Unit, Bearing plate and conical shaped wedge. The Bearing plate is a medium carbon steel material having drilled holes with conical shape for holding the strand with the conical shaped three-piece wedges. The Bearing plate is also named as Anchor head. The Tube unit is a cast iron material placed at the ends, and is set into the concrete structure. The Tube Units allowed for strands spreading out for anchoring. A tapped hole is provided to the tube Unit for grout injection.

The Tube Unit is also named as Guide Cone. The wedges holding strands are in three segments with serration inside for holding the required meter of strands. The three segments are held together in wire circlips.

Pre-Tensioning Anchorage system does not have a Tube Unit or a Bearing plate, dead barrels & wedges are used for holding the strands.