Page 329 - Civil Engineering Formulas

262 CHAPTER TEN

At points of maximum positive moments, P is the smaller of P and P ,
1
2
computed from
(10.49)
P 1 A s F y
P 2 0.85 f c A c (10.50)
2
2
where A effective concrete area, in (mm )
c
f 28-day compressive strength of concrete, ksi (MPa)
c
2
2
A total area of steel section, in (mm )
s
F steel yield strength, ksi (MPa)
y
The number of connectors required between points of maximum positive
moment and points of adjacent maximum negative moment should equal or
exceed N , given by
2
N 2 P P 3 (10.51)
S u
At points of maximum negative moments, the force in the slab P , is com-
3
puted from
P 3 A sr F yr (10.52)
2
2
where A area of longitudinal reinforcing within effective flange, in (mm );
sr
and F reinforcing steel yield strength, ksi (MPa).
yr
Ultimate Shear Strength of Connectors in Bridges
For channels,
t
S u 17.4 h w f c (10.53)
2
where h average channel-flange thickness, in (mm)
t channel-web thickness, in (mm)
w channel length, in (mm)
For welded studs (H/d 4 in (101.6 mm),
2
S u 0.4d 2 f c E c (10.54)

ALLOWABLE-STRESS DESIGN FOR SHEAR IN BRIDGES

Based on the AASHTO specification for highway bridges, the allowable shear
stress, ksi (MPa), may be computed from
F y F y
F v C (10.55)
3 3