Design Examples of Steel and Steel-Concrete Composite Bridges - Finite Element Analysis and Design of Steel and Steel-Concrete Composite Bridges - page 448

R A

R B

40 m

B

A

5 m

5 m

q WL = 5.73 kN/m

Figure 4.208 Loads on the lower wind bracing.

Similar to the upper wind bracing analysis, the forces in the members
of the lower wind bracing can be calculated with the loads acting on the
lower wind bracing as shown in Figure 4.208 . Thelowerwindbracing
carries the wind forces acting on the midspacing between the upper
and lower wind bracings. It should be noted that the level of the upper
wind bracing is taken at the bottom flange of the cross girders. Since
the cross girders are connected to the main upper chord member, there-
fore, it is assumed that the upper chord members are restrained to buckle
outside the plane of the main truss at the interactions with the cross
girders.

4.6.3.25 Design of Roller Steel Fabricated Bearings
Let us now design the roller steel fabricated bearings shown in Figure 4.162
and detailed in Figure 4.209 . The maximum vertical reaction at the supports
of the main truss was previously calculated under dead and live loads with
dynamic effect ( R D+L+ F ), which was 4433.9 kN. The material of construc-
tion for the bearings is cast iron steel (ISO 3755) 340-550 having a yield stress
of 340 MPa and an ultimate stress of 550 MPa.

Design of the Sole Plate
The reaction ( R D+L+ F ) can be assumed as two equal concentrated loads at
two points, which are the centers of gravity of half of the last vertical member
V 9 shown in Figure 4.209 . To determine the centers of gravity (distance e ), we
can take the first area moment around the axis z - z , shown in Figure 4.209 , as
follows:

2 4 13 6 : 5+28 1 : 5 0 : 75

e ¼ ¼ 4 : 85 cm

ð 2 4 13 + 28 1 : 5 Þ