What is Post-Tensioning

Post-tensioning is a method of reinforcing (strengthening) concrete or other materials with high-strength steel strands or bars, typically referred to as tendons. Post-tensioning applications include office and apartment buildings, parking structures, slabs-on-ground, bridges, sports stadiums, rock and soil anchors, and water-tanks. In many cases, posttensioning allows construction that would otherwise be impossible due to either site constraints or architectural requirements.

Although post-tensioning systems require specialized knowledge and expertise to fabricate, assemble and install, the concept is easy to explain. Imagine a series of wooden blocks with holes drilled through them, into which a rubber band is threaded. If one holds the ends of the rubber band, the blocks will sag. Post-tensioning can be demonstrated by placing wing nuts on either end of the rubber band and winding the rubber band so that the blocks are pushed tightly together. If one holds the wing nuts after winding, the blocks will remain straight. The tightened rubber band is comparable to a post-tensioning tendon that has been stretched by hydraulic jacks and is held in place by wedge-type anchoring devices. (Post-Tensioning Institute 2000)

How Stressing Works 

The unique feature of the VSL Post-Tensioning System lies in its special wedge locking procedure. The wedges always remain in contact with the strands during the stressing operation. As the pressure in the jack is released, the wedges automatically seat into the conical holes of the anchor head.



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