20.3 Prestressing Strands, Wires, and Bars
(a) ASTM A416 — strand
(b) ASTM A421 — wire
(c) ASTM A421 — low-relaxation wire including Supplementary Requirement S1, "Low-Relaxation Wire and Relaxation Testing"
(d) ASTM A722 — high-strength bar
Table 220.127.116.11—Prestressing strands, wires, and bars
|Type||Maximum value of fpu permitted for design calculations, psi||Applicable ASTM Specification|
|Strand (stress-relieved and low-relaxation)||270,000||A416|
|Wire (stress-relieved and low-relaxation)||250,000||A421|
|A421, including Supplementary Requirement S1 "Low-Relaxation Wire and Relaxation Testing"|
where γp is in accordance with Table 18.104.22.168.1.
If compression reinforcement is considered for the calculation of fps by Eq. (22.214.171.124.1), (a) and (b) shall be satisfied.
(a) If d' exceeds 0.15dp, the compression reinforcement shall be neglected in Eq. (126.96.36.199.1).
(b) If compression reinforcement is included in Eq. (188.8.131.52.1), the term
shall not be taken less than 0.17.
Table 184.108.40.206.1—Values of γp for use in Eq. (220.127.116.11.1)
|≤ 35||The least of:||fse + 10,000 + fc'/(100ρp)|
|fse + 60,000|
|> 35||The least of:||fse + 10,000 + fc'/(300ρp)|
|fse + 30,000|
|Stage||Location||Maximum tensile stress|
|During stressing||At jacking end||Least of:||0.94fpy|
|Maximum jacking force recommended by the supplier of anchorage device|
|Immediately after force transfer||At post-tensioning anchorage devices and couplers||0.70fpu|
(b) Elastic shortening of concrete
(c) Creep of concrete
(d) Shrinkage of concrete
(e) Relaxation of prestressed reinforcement