Joints - The Behaviour and Design of Steel Structures to EC3 - page 393

Bolt forces Plate forces Bolt forces

Bearing

Friction Bearing Bearing

Bearing

Bearing

Shear

Bearing
Shear

Friction

Tension

Bearing

Bearing

Friction

(a) Shear and bearing
joint

(b) Preloaded
friction-grip joint

(c) Tension joint

Figure 9.1 Use of bolts in joints.

loads by shear and bearing, as shown in Figure 9.1a, by friction between plates
clamped together as shown in the preloaded friction-grip joint of Figure 9.1b, or
by tension as shown in Figure 9.1c. The shear, bearing, and tension capacities
of bolts and the slip capacities of preloaded friction-grip joints are discussed in
Section 9.6.
Theuseofboltsoftenfacilitatestheassemblyofastructure,asonlyverysimple
tools are required. This is important in the completion of site joints, especially
where the accessibility of a joint is limited, or where it is difficult to provide
thespecialisedequipmentrequiredforothertypesoffasteners.Ontheotherhand,
boltingusuallyinvolvesasignificantfabricationefforttoproducetheboltholesand
the associated plates or cleats. In addition, special but not excessively expensive
proceduresarerequiredtoensurethattheclampingactionsrequiredforpreloaded
friction-gripjointsareachieved.Precautionsmayneedtobetakentoensurethatthe
bolts do not become undone, especially in situations where fluctuating or impact
loads may loosen them. Such precautions may involve the provision of special
locking devices or the use of preloaded high-strength bolts. Guidance on bolted
(and on riveted) joints is given in [2-11].

9.2.2 Pins

Pin joints used to be provided in some triangulated frames where it was thought
to be important to try to realise the common design assumption that these frames
are pin-jointed. The cost of making a pin joint is high because of the machining
requiredforthepinanditsholes,andalsobecauseofdifficultiesinassembly.Pins