Structural Concrete - Hassoun

912 Chapter 22 Prestressed Concrete Bridge Design
on the safe side, or can be obtained from the following equation:
ε s =
(|M| u )
d v
+ 0.5N u + |V u − V p | − A ps f po
(E c A cf + E s A s + E p A ps )
where A cf is the area of the section on the flexural tension side of the member.
22.7.6 Nominal Shear Resistance (AASHTO 5.8.3.3)
> −0.0004 (22.23)
The nominal shear resistance, V n , at a given section for the sectional design model is expressed as
the sum of contribution from the concrete, the transverse reinforcement, and the transverse component
of the prestressing force and shall be determined as the lesser of
V n = V c + V s + V p (22.24)
in which
where
V n = 0.25f ′ cb v d v + V p (22.25)
V c = 0.0316β √ f cb ′ v d v (22.26)
V s = A vf y d v (cot θ + cot α)
s
(22.27)
b v = effective web width taken as minimum web width within depth d v (in.)
d v = effective shear depth (in.)
s = spacing of stirrups (in.)
β = factor indicating ability of diagonal compressive stresses
α = angle of inclination of transverse reinforcement to longitudinal axis in degree
A v = area of shear reinforcement within distance s (in. 2 )
V p = component in direction of applied shear of effective prestressing force: positive if resisting
applied shear (kip)
V p = F sin α (22.28)
where α is the angle of inclination of the prestressing force with respect to the longitudinal axis of
the beam.
22.7.7 Regions Requiring Transverse Reinforcement (AASHTO 5.8.2.4)
Except for slabs, footings, and culverts, transverse reinforcement shall be provided where
22.7.8 Minimum Transverse Reinforcement (AASHTO 5.8.2.5)
V u >φ0.5(V c + V p ) (22.29)
Except for segmental posttensioned concrete box girder bridges, the area of steel shall satisfy
A v > 0.0316 √ f c
′ b v s
(22.30)
f y