Design Examples of Steel and Steel-Concrete Composite Bridges - Finite Element Analysis and Design of Steel and Steel-Concrete Composite Bridges - page 421

F Ed L ð maximum ¼ 28,991 : 3 1 : 3 + 3365 : 6 1 : 35

¼ 8302 : 3 kN Tension force ð Þ

F Ed L ð minimum ¼ 2891 : 3 1 : 3 119 : 4 1 : 35

¼ 3597 : 5 kN Tension force ð Þ

It should be noted that, from the equilibrium of joint J 8 (see Figure 4.182 ),
the force in lower chord truss member L 2 is equal to that of L 3 . It should also
be noted that, under the dead and live cases of loading, the force in the lower
chord member L 1 is zero.

4.6.3.4 Calculation of Force in the Upper Chord Member U 4
We can repeat the previous procedures now and change the pole where the
moment is calculated to determine the force in the upper chord member U 4 ,
as shown in Figure 4.183 . Hence, the forces due to the dead and live loads
can be calculated as follows:
F D : L : U ðÞ¼ 0 : 5 40 2 : 3475 77 : 1 ¼ 3614 : 1kN

F L : L : U ðÞ¼ 450 2 ð : 3475 + 2 : 23125 Þ 0 : 5 40 2 : 3475 45 : 65

¼ 4198 : 6kN

F Ed U ðÞ¼F D : L : g g + F L : L : g q

s

J 4

U 3 U 4

4 m

a

A

s

15 m 25 m

g vk = 77.1 kN/m

450 kN 450 kN

q vk = 45.65 kN/m

1.2 m

-

15 × 25/(40 × 4) = 2.34375 2.23125

Figure 4.183 Determination of the compressive force in upper chord member U 4 using
the influence line method.