Design Examples of Steel and Steel-Concrete Composite Bridges - Finite Element Analysis and Design of Steel and Steel-Concrete Composite Bridges - page 293

0 55 3 0 40 3 0 3 0 2 I y ¼ 3 : = 12 + 3 : = 12 + 2 45 2 : = 12 + 45 2 : 0 21 :

8cm 4 ¼ 137,033 :

r

I x
A

r

160,709 : 1

i x ¼ ¼ ¼ 18 : 59 cm

465

r

I y
A

r

137,033

: 8

i y ¼ ¼ ¼ 17 : 17 cm

465

l b x ¼ l b y ¼ 6000mm

L cr
i

1
l 1

l¼

l 1 ¼ 93 : 9 0 : 924 ¼ 86 : 7636

6000
171

1

l¼

7 7636 ¼ 0

: 4

: 86 :

The axial compressive force in the upper chord member U 3
( N Ed ¼ 9773.9 kN):

N Ed
N b , Rd 1

: 0

wAf y
g M1

where N b , Rd ¼

1
F +

w¼ p but w 1 : 0

l 2 F 2

h i

+ l 2

51+ a l 0 F¼ 0 : : 2

¼ 0

4 2 F¼ 0 : 51+0 : 34 0 ð : 4 0 : 2 Þ +0 : : 614

1

614 +

p

w¼ ¼ 0 : 926 but w 1 : 0

614 2 4 2

0 : 0 : 0 :

0 : 926 46,500 275

1

Then, N b , Rd ¼ ¼ 10,764,750N

:

1

N b , Rd ¼ 10,764 : 8kN > N Ed ¼ 9773 : 9 kN Then O ð : K : Þ

4.3.3.15 Design of the Compression Upper Chord Member U 2
The compression member U 2 , shown in Figure 4.69 , carrying a compressive
design force of 7449.1 kN can be designed as follows. To classify the cross
section chosen (see Figure 4.69 ) ,