WELDS-STATIC AND FATIGUE STRENGTH-II
31
WELDS- STATIC AND FATIGUE STRENGTH – II
1.0
INTRODUCTION
In the previous chapter, a detailed account of various welding processes, types of welds,
advantages of welded connections etc. were presented. It was seen that welded
connections are continuous and more rigid when compared to bolted connections. It was
also pointed out that fillet welds and butt welds constitute respectively 80% and 15% of
all welds in the construction industry; the balance 5% is made up by plug, slot and spot
resistance welds.
In this chapter, the behaviour and design of welded connections under various static
loading conditions is considered. A typical connection design process is initiated with the
design, which is followed by the welding operation and, concludes with inspection.
2.0
CONNECTION DESIGN
In the design of connections, due attention must be paid to the flow of the force through
the connection. The transfer of forces should occur smoothly, without causing any stress
concentration or cracks. The connections can be either concentric or eccentric. In
concentric connections, the forces acting on the connections will essentially be axial in
nature, whereas in eccentric connections, the axial forces will be coupled with bending or
torsion. These types of connections are described in the following.
2.1
Concentric connections
Static strength of a welded joint depends upon the following factors
•
Type and size of the weld
•
Manner of welding, and
•
Type of electrode used.
A primary responsibility of a designer is to select the type and size of the weld. A number
of varieties of welds are available. When it is properly chosen with the correct electrode,
it develops full strength of the parent material. The chosen type of weld should develop
minimal residual stresses and distortions.
As stated in the introduction, butt and fillet welds are the usual forms of welds in
practical building construction. Butt welds are used at an edge-to-edge junction or a tee
junction. A butt weld connection is made by bringing the plates to be joined face to face
edgewise and then filling the cavity formed by edge preparation or by just penetrating the
unprepared junction. Butt welds can be either full penetration or partial penetration.
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