Re: Post tension concrete - how does it work (GoLowDrew)
After the concrete is placed and has reached its required
strength, usually between 3000 and 3500 psi (“pounds per
square inch”), the tendons are stressed and anchored. The
tendons, like rubber bands, want to return to their original
length but are prevented from doing so by the anchorages.
The fact the tendons are kept in a permanently stressed
(elongated) state causes a compressive force to act on the
concrete. The compression that results from the posttensioning
counteracts the tensile forces created by
subsequent applied loading (cars, people, the weight of the
beam itself when the shoring is removed). This significantly
increases the load-carrying capacity of the concrete.
Since post-tensioned concrete is cast in place at the job site,
there is almost no limit to the shapes that can be formed.
Curved facades, arches and complicated slab edge layouts are
often a trademark of post-tensioned concrete structures.
Post-tensioning has been used to advantage in a number of
very aesthetically designed bridges.
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