Civil Engineering Reference
In-Depth Information
tendons are generally made up of 7 mm wires, while bars range from 16 mm up to
75 mm diameter.
The tendon anchors consist of steel fabrications or cast iron forgings which are
sized to apply acceptable pressure to the concrete. Figure 5.9 (a) shows a CCL anchor
for six strands designed to fi t into a thin slab, Figure 5.9 (b) shows a CCL anchor for
a typical bridge deck tendon with 19 No 15.7 mm strands and Figure 5.9 (c) shows
one of the most powerful CCL anchors available, with 37 No 15.7 mm strands and an
ultimate force of 10,323 kN.
A stressed anchor is known as 'live', while unstressed anchors are known as 'dead'.
Each strand is locked to a live anchor by hardened steel wedges that fi t into conical
holes. Strand at dead anchors may also be locked by wedges that are pushed home
before the tendon is stressed, or by metal sleeves that are swaged onto the individual
strands. Wires are locked to the anchorage by button heads forged onto each wire,
while the anchorage body is threaded to take up the extension of the tendon. Bars are
Figure 5.10
Prestressing jack (Photo: Benaim)
