Design Examples of Steel and Steel-Concrete Composite Bridges - Finite Element Analysis and Design of Steel and Steel-Concrete Composite Bridges - page 250

Considering the structural analysis for the upper wind bracing system
shown in Figure 4.26 , the critical design wind force in the diagonal bracing
members can be calculated as follows:

Distributed wind loads ðq WL Þ¼ 522 : 6 5 ð : 5 = 7 Þ= 30 ¼ 13 : 69 kN = m

Factored distributed wind loads ¼ q WL g q ¼ 13 : 69 1 : 7 ¼ 23 : 27 kN = m

R A ¼ 100 + 23

: 27 15 ¼ 449 : 05 kN

a¼ tan 1 3 75

ð : 6 = 5 Þ 35 :

F D ¼ 349 : 05 = ð 2 sin35 : 75 Þ ¼ 298 : 7kN

The cross section of the bracing member (see Figure 4.28 ) can be deter-
mined as follows:

2mm
Choose two angles back-to-back 150 150 15, with 10 mm gusset plate
between them:

l b x ¼ 6160mm, l b y ¼ 1 : 2 6160 ¼ 739 :

4cm 2 , A¼ 2 43 : 2 ¼ 86 : i x ¼ 4 : 59 cm, e ¼ 4 : 26 cm,

q

4

2

i y ¼ :

59 2 +4

ð : = Þ ¼ 6 : 61 cm

26 + 1 2

r

235
275

e ¼ ¼ 0 : 924

L cr
i

1
l 1

l¼

e = 42.6 mm

y

x x

2 angles back-to-back
150 × 150 × 15

10 mm

y

Figure 4.28 Upper wind bracing cross section s-s.