CIVIL ENGINEERING FORMULAS

CHAPTER 10

249

BRIDGE AND

SUSPENSION-

CABLE FORMULAS

SHEAR STRENGTH DESIGN FOR BRIDGES

Based on the American Association of State Highway and Transportation Offi-
cials(AASHTO) specifications for load-factor design(LFD), the shear capacity,
kip (kN), may be computed from

(10.1)

for flexural members with unstiffened webs with h/tw150 or for girders with
stiffened webs but a/hexceeding 3 or 67,600(h/tw)^2 :

For girders with transverse stiffeners and a/hless than 3 and 67,600(h/tw)^2 , the
shear capacity is given by

(10.2)

Stiffeners are required when the shear exceeds Vu.
Refer to Chap. 9, “Building and Structures Formulas,” for symbols used in
the preceding equations.

Vu0.58FydtwC

1 C

1.15 1 (a/h)^2 



45,000k

Fy(h/tw)^2

when

h

tw

1.25





h/tw

when 

h

tw

1.25

C1.0 when

h

tw



Vu0.58FyhtwC