Design Examples of Steel and Steel-Concrete Composite Bridges - Finite Element Analysis and Design of Steel and Steel-Concrete Composite Bridges - page 346

4.4.2 Design of the Composite Plate Girder Cross Section at
Mid- and Quarter-Span
After the evaluation of the straining actions acting on the composite bridge,
we can now design the critical cross sections of an intermediate composite
plate girder as follows.

Design of the Intermediate Composite Plate Girder Cross Section at Midspan
Following the design rules specified in EC4 [3.6], the effective width of the
concrete slab is 2.5 m and the cross-sectional dimensions are shown in
Figure 4.113 . Knowing that the design concrete strength f cd is equal to
f ck /

g c ( f cd ¼ 40/1.5 ¼ 26.67 MPa), we can calculate the forces acting on
the composite girder as shown in Figure 4.113 . The position of the plastic
neutral axis can be located from the equilibrium of these forces, assuming
an initial position in the top flange of the steel plate girder, as follows:
14,168 : 4 + 3173 : 7+ x 700 275 = 1000 ¼ 9405 + 7585 : 6

+ 700 38 x

ð Þ 275 =

1000

17,342 : 1 + 192 : 5 x¼ 16,990 : 6 192 : 5 x + 7315

2 192 : 5 x ¼ 6963 : 5

Then, x¼ 18.1 mm.

2500

250 14168.4 kN

3173.7 kN
3484.3 kN
3830.8 kN

200

18.1

x

38- x

19.9

700

7585.6 kN

1724 mm

16

38 9405 kN

900 mm

Figure 4.113 Calculation of bending resistance at the critical mid-span section of an
intermediate composite plate girder.