16
STEEL DETAILERS' MANUAL
cont
inuo
us site workshop
D yield of
moment
C beam section
B
simple
A
Figure 1.17 Locations of site connections.
rotation
Welding Ð Bolting
workshop
Ð site
For bridges continuous connections should be used to withstand vibration from vehicular loading and spans should usually be made continuous. This allows the numbers of deck expansion joints and bearings to be reduced thus minimising maintenance of these costly items which are vulnerable to traffic and external environment. black bolts
black bolts
HSFG bolts
HSFG bolts
For UK buildings, connection design is usually carried out
A
B
C
D
by the fabricator with the member sizes and end reac-
Figure 1.15 Typical moment : rotation behaviour of beam/column connections.
tions being specified on the engineer's drawings. It is important that all design assumptions are advised to the fabricator for him to design and detail the connections. If joints are continuous then bending moments and any axial loads must be specified in addition to end reactions.
‘continuous’
For simple connections the engineer must specify how stability is to be achieved, both during construction and finally when in service.
‘simple’
vertical loading
bracing required (or shear walls, etc.) lateral loading (e.g. wind)
Figure 1.16 Continuous and simple connections.
Connections to hollow sections are generally more costly and often demand butt welding rather than fillet welds. Bolted connections in hollow sections require extended end plates or gussets and sealing plates because internal access is not feasible for bolt tightening whereas channels or rolled steel angles (RSAs) can be connected by simple lap joints. Figure 1.18 compares typical welded or bolted
because assemblies cannot be turned to permit downhand
connections.
welding and erection costs arise for equipment in supporting/aligning connections, pre-heating/sheltering and non-destructive testing (NDT). The exception is a major
1.6 Interface to foundations
project where such costs can be absorbed within a larger
It is important to recognise whether the interface of
number of connections (say minimum 500). As a general
steelwork to foundations must rely on a moment (or rigid)
rule welding and bolting are used thus:
form of connection or not.