Design Examples of Steel and Steel-Concrete Composite Bridges - Finite Element Analysis and Design of Steel and Steel-Concrete Composite Bridges - page 224

g vk = 4.8 kN/m

5 m

12 kN

+

S.F.D.

-

12 kN

B.M.D.

+

15 kN.m
Figure 4.3 Straining actions from dead loads acting on a stringer.

250 250 250 250 kN

q vk = 80 kN/m

q vk = 80 kN/m

1600 1600

800
Figure 4.4 Axle live loads on the bridge conforming to Load Model 71 specified in
EC1 [3.1].

800 800 800

rail traffic as specified in EC1 [3.1] (see Figure 4.4 ) , three cases of loading for
the evaluation of maximum bending moment due to the live loads on a
stringer can be studied. The first case of loading is that the centerline at mid-
span of a stringer divides the spacing between the resultant of the concen-
trated live loads and the closest load, with maximum bending moment
located at the closest load (point a in Figure 4.5 ) , while the second case
of loading is that the centerline of the stringer is located under one of
the intermediate concentrated loads, with maximum bending moment
located at the midspan, and finally, the third case of loading is that the
stringer span is covered by the distributed live loads, with maximum bending
moment located at the midspan. The three cases of loading are shown in
Figure 4.5 :
M L : L :

ð case of loading 1 Þ ¼ 217 : 5 2 : 1 125 1 : 6 ¼ 256 : 75 kNm

M L : L : ð case of loading 2 Þ ¼ 187 : 5 2 : 5 125 1 : 6 ¼ 268 : 75 kNm

Þ ¼ 40 5 2 M L : L : ð case of loading 3 = 8 ¼ 125 kNm