Design Examples of Steel and Steel-Concrete Composite Bridges - Finite Element Analysis and Design of Steel and Steel-Concrete Composite Bridges - page 248

The axial compressive force in the diagonal bracing member

( N Ed ¼ 90.9 kN):

N Ed
N b , Rd 1

: 0

wAf y
g M1

where N b , Rd ¼

6cm 2 A¼ 2 12 : 3 ¼ 24 :

1
F +

w¼ p but w 1 : 0

l 2 F 2

h i

+ l 2

51+ a l 0 F¼ 0 : : 2

¼ 1

163 2 F¼ 0 : 51+0 : 34 1 ð : 163 0 : 2 Þ +1 : : 34

1

34 +

p

w¼ ¼ 0 : 499 but w 1 : 0

34 2 163 2

1 : 1 : 1 :

:

499 24

:

6 100 275
1 : 1

0

Then, N b , Rd ¼ ¼ 306,885N

N b , Rd ¼ 306 : > N Ed ¼ 90 : ð : : Þ

9kN 9 kN Then O K

4.2.9 Design of Wind Bracings
Wind forces acting on the double-track railway bridge (see Figure 4.25 ) as
well as any other lateral forces directly applied to the bridge are transmitted
to the bearings by systems of upper and lower wind bracings as well as cross
bracings. The upper wind bracing carries wind forces on the moving train,

4 m

F w

1.5 m

1.5 m

7200 mm

Figure 4.25 Design heights for upper and lower wind bracings.