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1
Effective Length Factor - Real Conditions
The effective length factor (K) was introduced in
page (C-7) for six ideal conditions, these are
not encountered in practical field conditions.
LRFD commentary provides both real conditions and
standard ideal conditions (C-C2.2) (page 16.1-239
to 242)
Braced Frames
Unbraced Frames
No lateral movement is allowed (0.5 lt K lt 1.0)
(sideway prevented)
Lateral movement possible (1.0 lt K lt 20.0)
(sideway allowed)

• Diagonal
• bracing

b) Shear Walls (masonry,
reinforcement concrete or steel plate)
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2
Alignment Charts (LRFD P-16.1 - 241)
where A is top of column
where B is bottom of column
For fixed footing G 1.0 For pinned support
G 10.0
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3
Use of Alignment Charts
Example C 8 -
In the rigid frame shown below, Determine Kx for
columns (AB) (BC). Knowing that all columns
webs are in the plane.
Solution
Column (AB) Joint (A)
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4
For joint B,-
From the alignment chart for sideways
uninhibited, with GA 0.94 and GB 0.95, Kx
1.3 for column AB.
Column (BC)
For joint B, as before, G 0.95 For joint C, at
a pin connection the situation is analogous to
that of a very stiff column attached to
infinitely flexible girders that is, girders of
zero stiffness. The ratio of column stiffness to
girder stiffness would therefore be infinite for
a perfectly frictionless hinge. This end
condition is only be approximated in practice, so
the discussion accompanying the alignment chart
recommends that G be taken as 10.0. From the
alignment chart with GA 0.95 and GB 10.0, Kx
1.85 for column BC.
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