Civil Engineering Reference
In-Depth Information
Supporting
member
Supporting
member
End plate
M
Ed
M
Ed
N
Ed
N
Ed
V
Ed
V
Ed
Beam
Beam
(a) Welded joint
(b) Bolted end plate
Figure 9.12
Common rigid end joints.
forces
N
xi
can be determined from
N
xi
=
M
y
A
i
z
i
−
M
z
A
i
y
i
A
i
z
i
A
i
y
i
(9.4)
in which
y
i
,
z
i
are the principal axis coordinates of the connector measured from
the centroid of the connector group.
Thisresultimpliesthatthecompressionforcesaretransmittedonlybythecon-
nectors, but in real bolted joints these are transmitted primarily through those
portions of the connection plates which remain in contact. Thus the connector
tensionforcesdeterminedfromequation9.4willbeinaccuratewhenthereisasig-
nificantdifferencebetweenthecentroidofthecontactareaandthatoftheassumed
compressionconnectors.Clause6.2.7ofEC3-1-8[1]correctsthisdefectbydefin-
ing the centres of compression for a number of bolted beam-column joints, and
by requiring the lever arms used in determining the bolt tensions to be measured
from these centres.
The result of equation 9.4 is also defective when prying forces are introduced
by flexure of any T-stubs (real or idealised) used to transfer bolt tensions, as
shown in Figure 9.13 [13-15]. This shows two T-stubs connected through their
flanges (or tables) by rows of bolts, which are used to model the tension zone of
boltedjointsinClause6.2.4ofEC3-1-8.IsolatingaT-stubsimplifiestheanalysis
of a joint. For example, the prying forces in the joint in Figure 9.13b that are
producedbyflexureoftheflangeoftheT-stubandwhichmustbeincludedinthe
tensileaction
N
t
,
Ed
ontheboltcanbedeterminedfrombendingtheory(Chapter5).
Examples of tension zones which include idealised T-stub assemblies are shown
in Figures 9.12 and 9.14.
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