Civil Engineering Reference
In-Depth Information
the chapter provides readers with sufficient background needed for future
studies. It should be noted that the design examples are presented for specific
bridges; however, the design procedures can be adopted for different steel
and steel-concrete composite bridges. It should also be noted that the author
purposely avoided complex bridge geometries, supports, and long spans to
use hand calculations, which make it easy for readers to apply the design rules
highlighted in
Chapter 3
. Finally, the author hopes that the presented design
examples in this Chapter provide all the basic fundamentals for students
interested in the structural analysis and design of steel and steel-concrete
composite bridges.
4.2 DESIGN EXAMPLE OF A DOUBLE-TRACK PLATE GIRDER
DECK RAILWAY STEEL BRIDGE
Let us start by presenting the first design example, which is for a double-
track open-timber floor plate girder deck railway steel bridge. The general
layout of the double-track railway bridge is shown in
Figures 4.1
and
4.2
,
with a brief introduction of the bridge components previously highlighted
in Figure 1.20. The bridge has simply supported ends, a length between
supports of 30 m and an overall length of 31 m. The width of the bridge
(spacing between main plate girders) is 7.2 m as shown in
Figure 4.1
.Itis
required to design the bridge components adopting the design rules spec-
ified in EC3 [1.27]. The steel material of construction of the double-track
railway bridge conformed to standard steel grade EN 10025-2 (S 275) hav-
ing a yield stress of 275 MPa and an ultimate strength of 430 MPa. The
bridge has upper and lower wind bracings of K-shaped truss members as
well as cross bracings of X-shaped truss members as shown in
Figure 4.1
.
In addition, the bridge has lateral shock (nosing force) bracing for the
stringers as well as braking force bracing at the level of upper wind bracing
as shown in
Figure 4.2
. The lateral shock bracing eliminates bending
moments around the vertical axis of the stringers, while the braking force
bracing eliminates bending moments around the vertical axis of the cross
girder. The plate girder web is stiffened by vertical stiffeners, to safeguard
against shear stresses and web buckling, spaced at a constant distance of
1.667 m. The expected live loads on the bridge conform to Load Model
71, which represents the static effect of vertical loading due to normal rail
traffic as specified in EC1 [3.1]. The bolts used in connections and field
splices are M27 high-strength pretensioned bolts of grade 8.8.
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