Design Examples of Steel and Steel-Concrete Composite Bridges - Finite Element Analysis and Design of Steel and Steel-Concrete Composite Bridges - page 352

1
2 1

25 26 2

F w ¼ : 5 : 7 208 : 25 ¼ 501,518N ¼ 501 : 5kN

Considering the structural analysis for the upper wind bracing system
shown in Figure 4.118 , the critical design wind force in the diagonal bracing
members can be calculated as follows:
Distributed wind loads q WL ð Þ¼ 501 : 5 0 : 5 = 48 ¼ 5 : 22 kN = m

Factored distributed wind loads ¼ q WL g q ¼ 5 : 22 1 : 7 ¼ 8 : 87 kN = m

R A ¼ 8 : 87 24 ¼ 212 : 9kN

a¼ tan 1 2 8 ð : 5 = 3 Þ 39 :

6kN
The cross section of the bracing member (see Figure 4.119 ) can be deter-
mined as follows:
l b x ¼ 3910mm,

F D ¼ 212 : 9 = ð sin30 : 8 Þ 332 :

2 3910 ¼ 4690mm
Choose two angles back-to-back 100 100 10, with 10 mm gusset
plate between them:
A¼ 2 19

l b y ¼ 1 :

4cm 2 , : 2 ¼ 38 : i x ¼ 3 : 05 cm, e ¼ 2 : 83 cm,

q

3

2

05 2 +2

i y ¼ : ð : 83 + 0 : 5 Þ ¼ 4 : 52 cm

r

235
275

e ¼ ¼ 0 : 924

L cr
i

1
l 1

l¼

l 1 ¼ 93 : 9 0 : 924 ¼ 86 : 7636

3910
30

1

l¼

7636 ¼ 1

: 478

: 5 86 :

e = 28.3 mm

y

x x

2 angles back-to-back
100 × 100 × 10

10 mm

y

Figure 4.119 Lower wind bracing cross section.