Applied Loads and Stability of Steel and Steel-Concrete Composite Bridges - Finite Element Analysis and Design of Steel and Steel-Concrete Composite Bridges - page 208

l e l e l

l tot

Figure 3.40 Calculation of weld forces for intermittent welds specified in EC3 (BS EN
1993-1-8) [2.13].

This applies specifically to the normal stress parallel to the axis of a weld.
Welded joints should be designed to have adequate deformation capacity.
However, ductility of the welds should not be relied upon. In joints where
plastic hinges may form, the welds should be designed to provide at least the
same design resistance as the weakest of the connected parts. In other joints
where deformation capacity for joint rotation is required due to the possi-
bility of excessive straining, the welds require sufficient strength not to rup-
ture before general yielding in the adjacent parent material. If the design
resistance of an intermittent weld is determined by using the total length l tot ,
the weld shear force per unit length F w,Ed should be multiplied by the factor
( e + l )/ l (see Figure 3.40 ).

3.11 DESIGN OF BRIDGE BEARINGS
3.11.1 General
This section provides a brief review for the types and design of bearings
commonly used in steel bridges. The bearings used in steel bridges can be
classified according to its main supply source to proprietary and steel-
fabricated bearings. Proprietary bearings are commonly made of elastomeric
material, which is either natural or synthetic rubber. Elastomeric materials
are flexible when subjected to shearing forces; however, they are very stiff
against volumetric change. On the other hand, steel-fabricated bearings are
made of designed steel parts preventing or allowing applied translations and
rotations. Proprietary bearings are efficiently used with most of steel bridges.
However, steel-fabricated bearings can be economic in uplift situations or
in situations where large rotations are expected to occur. Bearings used in
bridges can be also classified according to their restraint performance to
fixed, hinged, and expansion bearings. Fixed bearings prevent rotations
and translations of the supported structure at their locations, while hinged
bearings allow rotations and prevent translations of the supported structure