Joints - The Behaviour and Design of Steel Structures to EC3 - page 396

areflexible, andallowtherelativerotationofthejointmembers, whiletheflange
plates and web stiffeners (Figure 9.3c) are stiff, and restrict the relative rotation.
Thesimplicityofweldedjointsandtheircomparativerigidityhasoftenresulted
intheomissionofstiffeningplateswhentheyarenotrequiredforstrengthpurposes.
Thus the rigid joint of Figure 9.3c can be greatly simplified by butt welding the
beam directly onto the column flange and by omitting the column web stiffeners.
However, this omission will make the joint more flexible since local distortions
of the column flange and web will no longer be prevented.
9.3 Arrangement of joints
9.3.1 Joints for force transmission
In many cases, a joint is only required to transmit a force, and there is no
moment acting on the group of connectors. While the joint may be capable of
also transmitting a moment, it will be referred to as a force joint.
Force joints are generally of two types. For the first, the force acts in the con-
nection plane formed by the interface between the two plates connected, and the
connectors between these plates act in shear, as in Figure 9.1a. For the second
type, the force acts out of the connection plane and the connectors act in tension,
as in Figure 9.1c.
Examples of force joints include splices in tension and compression members,
truss joints, and shear splices and joints in beams. A simple shear and bearing
bolted tension member splice is shown in Figure 9.1a, and a friction-grip bolted
splice in Figure 9.1b.These are simpler than the tension bolt joint of Figure 9.1c,
and are typical of site joints.
Ordinary structural and high-strength bolts are used in clearance holes (often
2 or 3mm oversize to provide erection tolerances) as shown in Figure 9.1a. The
hole clearances lead to slip under service loading, and when this is undesirable, a
preloadedfriction-gripjointsuchasthatshowninFigure9.1bmaybeused.Inthis
joint, the transverse clamping action produced by preloading the high-strength
bolts allows high frictional resistances to develop and transfer the longitudinal
force. Preloaded friction-grip joints are often used to make site joints which need
to be comparatively rigid.
ThebuttandfilletweldedsplicesofFigure9.2aandcaretypicalofshopjoints,
and are of high rigidity. While they are often simpler to manufacture under shop
conditions than the corresponding bolted joints of Figure 9.1, special care may
need to be taken during welding if these are critical joints.
The truss joint shown in Figure 9.4b uses a gusset plate in order to provide
sufficient room for the bolts. The use of a gusset plate is avoided in the joint of
Figure 9.4a, while end plates are used in the joint of Figure 9.4c to facilitate the
field-bolted connection of shop-welded assemblies.
The beam web shear splice of Figure 9.5a shows a typical shop-welded and
site-bolted arrangement. The common simple joint between a beam and column
shown in Figure 9.3a is often considered to transmit only shear from the beam to