Design Examples of Steel and Steel-Concrete Composite Bridges - Finite Element Analysis and Design of Steel and Steel-Concrete Composite Bridges - page 232

4.2.3 Design of the Main Plate Girders
Let us now design the main plate girders supporting the cross girders as
shown in Figure 4.1 . We can estimate the dead and live loads acting on a
main plate girder as follows:

Dead Loads

5 30 ¼ 24 kNm 1
Track load ¼ 6kNm 1

Weight of steel structure ¼ 9+0 :

6kNm 1
The main plate girders are simply supported; hence, we can calculate the
maximum shear force and bending moment due to dead loads on a main
plate girder (see Figure 4.12 ) as follows:
Q D : L : ¼ g vk L

Total dead load ¼ g vk ¼ 1 : 8 24 = 2+6 ¼ 27 :

= 2 ¼ 27 : 6 30 = 2 ¼ 414 kN

M D : L : ¼ g vk L 2 =

8 ¼ 27

:

6 30 2

=

8 ¼ 3105 kNm

Live Loads
Considering the axle loads on the bridge components according to Load
Model 71 (see Figure 4.4 ), two cases of loading for the evaluation of maxi-
mum bending moment due to live loads on a main plate girder can be studied.

g vk = 27.6 kN/m

A

B

30.0 m

Y A = 414 kN Y B = 414 kN

414 kN

+

S.F.D.

-

414 kN

B.M.D.

+

3105 kN.m

Figure 4.12 Straining actions from dead loads acting on one main plate girder.