Civil Engineering Reference
In-Depth Information
Initial stiffness
S
j
,
ini
M
j
,
Rd
M
j
,
Ed
Stiffness
S
j
f
Cd
Joint rotation
f
j
Figure 9.10
Characteristics of a moment joint.
characteristics theoretically, owing to the uncertainties in modelling the various
components of the joint, even though a significant body of experimental data is
available.
EC3-1-8usesa
component method
ofmomentjointdesign,inwhichthecharac-
teristics of a joint can be determined from the properties of its basic components,
including the fasteners or connectors, beam end plates acting in bending, col-
umnwebpanelsinshear(Section4.3),orcolumnwebsintransversecompression
causedbybearing(Section4.6).Theuseofthismethodformomentjointsbetween
I-sectionmembersisgiveninSection6ofEC3-1-8anddiscussedinthefollowing
subsections,whilethemethodformomentjointsbetweenhollowsectionmembers
is given in Section 7 of EC3-1-8.
9.4.2.2 Design moment resistance
Each component of a joint must have sufficient resistance to transmit the actions
acting on it. Thus the design moment resistance of the joint is governed by the
component which has the highest value of its design action to resistance. It is
therefore necessary to analyse the joint under its design moment to determine the
distribution of the design actions on the joint components.
Jointswherethemomentactsintheplaneoftheconnectors(asinFigure9.11a)
sothatthemomentistransferredbyconnectorshearareoftenanalysedelastically
[12], by assuming that all the connectors fit perfectly and that each plate acts
as if rigid, so that the relative rotation between them is
δθ
x
. In this case, each
connector transfers a shear force
V
vi
from one plate to the other. This shear force
actsperpendiculartotheradius
r
i
totheaxisofrotation,andisproportionaltothe
relative displacement
r
i
δθ
x
of the two plates at the connector, whence
V
vi
=
k
v
A
i
r
i
δθ
x
,
(9.1)
where
A
i
istheshearareaoftheconnector,andtheconstant
k
v
dependsontheshear
stiffness of that type of connector. It is shown in Section 9.9.1 by considering the
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