Design Examples of Steel and Steel-Concrete Composite Bridges - Finite Element Analysis and Design of Steel and Steel-Concrete Composite Bridges - page 243

z

56

3

y y

1.6

60

z
Figure 4.21 Check of lateral torsional buckling of plate girder.

torsional buckling ( M cr ). Considering the cross section at midspan shown
in Figure 4.21 , wecancalculate M cr as follows:

s

pE y
kl b

2

M cr ¼C b p
kl b

C w I z + E z I z GJ

Given: C b ¼ 1.13, E¼ 210 GPa, G ¼ 81 GPa, l b ¼ 5000 mm, and k¼ 1
Inertia about z - zIðÞ¼ 2 3 60 3

12 + 2 3 56 2 6 3

= = 12 + 300 1 : = 12

¼ 195,910 cm 4

h 2 3120 2 195,910 10 4

4

I z
4 ¼

76766576 10 15 mm 6

C w ¼ ¼ 4 :

¼ 25,139,840mm 2

1
3

2 600 30 3 +2 560 30 3 + 3120 16 3 j ¼