PRETENSIONED ANCHORAGE ZONE [LRFD ART. 5.10.10]

Design of the anchorage zone reinforcement is computed using the force in the strands just before release.

Force in strands before release, Fpi is = [(27)(0.153)] (202.5) = 836.53 kips

The bursting resistance, Pr, should not be less than 4.0% of the prestressing force at transfer. [LRFD Arts. 5.10.10.1 and C3.4.3]

P_{r} = f_{s} A_{s} \geq 0.04 F_{p i} = 0.04 \times 836.53 = 33.46 k i p s

Where:

A_s = total area of vertical reinforcement located within the distance h/4 from the end of the beam, in²

f_s = stress in steel, but not taken greater than 20 ksi.

Solving for the required area of steel, therefore, A_s, is

A_{s} = \frac{33.46}{20} = 1.67 {i n}^{2}

At least 1.67 in² of vertical transverse reinforcement should be provided within a distance equal to one fifth of the precast beam depth $(\frac{h}{4} = \frac{42}{4} = 10.5 i n)$ , of the end of the beam.

A_{p s}^{*} =

=27(0.153)= 4.131 in² reduced for development length

= 1.648 in²