Page 330 - Civil Engineering Formulas

BRIDGE AND SUSPENSION-CABLE FORMULAS 263

for flexural members with unstiffened webs with h/t 150 or for girders with
w
2
stiffened webs with a/h exceeding 3 and 67,600(h/t ) :
w
C 1.0 when h
t w
h
when 1.25
h/t w t w
45,000k when h
1.25
F y (h/t w ) 2 t w
a h 2
k 5 if exceeds 3 or 67,600
h t w
or stiffeners are not required
5 2
5 otherwise
(a/h)

k
190
BF y
2
For girders with transverse stiffeners and a/h less than 3 and 67,600(h/t ) , the
w
allowable shear stress is given by
F y 1 C 2
F v C (10.56)
3 1.15 1 (a/h)
Stiffeners are required when the shear exceeds F .
v

MAXIMUM WIDTH/THICKNESS RATIOS
FOR COMPRESSION ELEMENTS FOR HIGHWAY BRIDGES

Table 10.6 gives a number of formulas for maximum width/thickness ratios for
compression elements for highway bridges. These formulas are valuable for
highway bridge design.

SUSPENSION CABLES

Parabolic Cable Tension and Length
Steel cables are often used in suspension bridges to support the horizon-
tal roadway load (Fig. 10.2). With a uniformly distributed load along the