Civil Engineering Reference
In-Depth Information
Q
Q/n
Q/n
n
connectors
Q
(a) Shear joint
(b) Assumed shear
(c) Actual shear
distribution
distribution
(rigid plates)
(elastic plates)
Figure 9.9
Shear distribution in a force connection.
Due to the great differences in the stiffnesses of joints using different types of
connectors, it is usual not to allow the joint force to be shared between slip and
non-slip connectors, and instead, the non-slip connectors are required to transfer
alltheforce.Forexample,whenordinarysite-boltingisusedtoholdtwomembers
in place at a joint which is subsequently site welded, the bolts are designed for
theerectionconditionsonly,whiletheweldsaredesignedforthefinaltotalforce.
However, it is rational and generally permissible to share the joint force between
welds and preloaded friction-grip bolts which are designed against slip, and this
is allowed in EC3-1-8 [1].
On the other hand, it is always satisfactory to use one type of connector to
transfer the complete force at one part of a joint and a different type at another
part.ExamplesofthisareshowninFigure9.5aandb,whereshopweldsareused
to join each connection plate to one member and field bolts to join it to the other.
9.4.2 Joints for moment transmission
9.4.2.1 General
Although a real connection is rarely required to transmit only a moment, the
behaviour of a moment joint may usefully be discussed as an introduction to the
considerationofjointswhichtransmitbothforceandmomentandtothecomponent
method of joint design used in EC3-1-8 [1].
TheidealisedbehaviourofamomentjointisshowninFigure9.10,whichignores
any initial slip or taking up of clearances. The characteristics of the joint are the
designmomentresistance
M
j
,
Rd
,thedesignrotationalstiffness
S
j
,andtherotation
capacity
φ
Cd
. These characteristics are related to those of the individual compo-
nentsofthejoint.Formostjoints,itisdifficulttodeterminetheirmoment-rotation
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