2.3.1 Live anchorages
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The non-jacking end of the strand may be bonded in concrete, or it may be
fitted with a pre-locked anchorage which has also been cast in the concrete. The
anchorage at the jacking end is called a live anchorage whereas the one at the
non-jacking end is termed a dead anchorage.
Protection to an anchorage is required only at the live end, the dead end is cast
in the concrete. The live anchorage is housed in a recess, or pocket, which is wide
enough for the stressing jack and deep enough so that there would be adequate
concrete cover to the assembly when the recess is made good. After stressing, the
strand is cut off close to the face of the wedge using a disc cutter and the whole
assembly is sprayed with a corrosion inhibitant. The assembly is then covered
with a grease-filled cap and the recess made good with mortar containing a
non-shrinking agent.
A few decades ago most manufacturers had their own patent devices for
anchoring tendons. They included bars with threaded ends, enlarged ends of wire
which passed through holes in thick plates such that the button sat on the plate,
wedges, concrete male and female cones gripping a number of wires arranged in a
circle, and a toothed conical wedge in a barrel. The cone and barrel system is now
the most commonly employed device for post-tensioning floors and it is available
from most manufacturers.
Figure 2.9 .shows a typical section at the end of a post-tensioned member
containing a monostrand anchorage assembly, complete including the corrosion
protection and Figure 2.10 shows a typical multistrand anchorage. Their
representative dimensions are given in Tables 2.10 and 2.11.