Design Examples of Steel and Steel-Concrete Composite Bridges - Finite Element Analysis and Design of Steel and Steel-Concrete Composite Bridges - page 446

F w

Figure 4.206 Design height for the calculation of wind forces on the upper and lower
wind bracings.

A ref , x ¼ 6 40 ¼ 240m 2

1
2 1

25 26 2 F w ¼ : 5 : 7 240 ¼ 578,000N ¼ 578 kN

Consider the structural analysis for the upper wind bracing system shown
in Figure 4.207 . Assume that the upper wind bracing carries wind forces on
the moving traffic, upper part of truss, and forces on the midspacing between
upper and lower wind bracings. The critical design wind force in the diag-
onal bracing members can be calculated as follows:
Distributed wind loads q WL

ð Þ¼ 578 4 ð : 6 = 6 Þ= 40 ¼ 11 : 1kN = m

Factored distributed wind loads ¼ q WL g q ¼ 11 : 1 1 : 7 ¼ 18 : 9kN = m

R A ¼ 18 9 20 ¼ 378 kN

a¼ tan 1 6

:

ðÞ¼ 45 =

F D ¼ 378 = ð 2 sin45 Þ ¼ 267 : 3kN

R A

R B

40 m

A

B

α

5 m

Fsin α

5 m

q WL = 18.9 kN/m

Figure 4.207 Loads on the upper wind bracing.