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; f_pu=270 ksi.

Curves shown for partial development of strand near member end, where f_ps≈ f_se.

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, P_u.

Enter at bottom with applied magnified factored moment, ΦM_u.

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