Joints - The Behaviour and Design of Steel Structures to EC3 - page 392

Joints
9.1Introduction
Connections or joints are used to transfer the forces supported by a structural
member to other parts of the structure or to the supports. They are also used
to connect braces and other members which provide restraints to the structural
member.Although the terms connections and joints are often regarded as having
thesamemeaning,thedefinitionsofEC3-1-8[1]areslightlydifferent,asfollows.
A connection consists of fasteners such as bolts, pins, rivets, or welds, and the
local member elements connected by these fasteners, and may include additional
plates or cleats.A joint consists of the zone in which the members are connected,
and includes the connection as well as the portions of the member or members at
the joint needed to facilitate the action being transferred.
The arrangement of a joint is usually chosen to suit the type of action (force
and/or moment) being transferred and the type of member (tension or compres-
sion member, beam, or beam-column) being connected. The arrangement should
be chosen to avoid excessive costs, since the design, detailing, manufacture, and
assembly of a joint is usually time consuming; in particular the joint type has a
significantinfluenceoncosts.Forexample,itisoftenbettertouseaheaviermem-
ber rather than stiffeners since this will reduce the number of processes required
for its manufacture.
A joint is designed by first identifying the force transfers from the member
through the components of the joint to the other parts of the structure. Each com-
ponentisthenproportionedsothatithassufficientstrengthtoresisttheforcethat
it is required to transmit. General guidance on joints is given in [2-11].
9.2 Joint components
9.2.1 Bolts
Severaldifferenttypesofboltsmaybeusedinstructuraljoints,includingordinary
structural bolts (i.e. commercial or precision bolts and black bolts), and high-
strengthbolts.Turnedclosetoleranceboltsarenowrarelyused.Boltsmaytransfer