Prestressed
Loadbearing 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 tensioncontrolled section to 0.65 for compressioncontrolled sections in accordance with ACI 31805, 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
