Prestressed

Load-bearing vertical structural component for one or more stories. Made with or without corbels.

Criteria
Minimum prestress = 225 psi.
Strand assumed 1/2 in. in diameter; fpu=270 ksi.
Curves shown for partial development of strand near member end, where fps≈ fse.
Horizontal portion of curve is the maximum for tied columns: 0.80ΦPo.
Varies linearly from 0.9 for tension-controlled section to 0.65 for compression-controlled sections in accordance with ACI 318-05, section 9.3.2.
Use of Curves
Enter at left with applied factors axial load, Pu.
Enter at bottom with applied magnified factored moment, ΦMu.
Intersection point must be to the left of the curve that indicates required concrete strength.

12 x 12

4 Strands

14 x 14

4 Strands

16 x 16

4 Strands

18 x 18

4 Strands

20 x 20

8 Strands

24 x 24

8 Strands