AISC Design Guide 13..

under panel-zone web shear per LRFD Specification Sec- Note that Equation 2.2-7 is in a form that has been adapted
tion F2. For Fy
50 ksi, these two shapes exceed the from that which appears in the AISC Seismic Provisions.
limit on ht / w by 1.9 and 1.5 percent, respectively. Thus,
for all practical purposes, in wind and low-seismic applications,
shear buckling of the column web need not be
2.2.2 Local Flange Bending
F
4 When a directly welded flange or flange-plated moment
checked for columns with y equal to or less than 50 ksi.
connection is used, differential stiffness across the width
In high-seismic applications involving Special Moment
of an unstiffened column flange results in a stress concen-
Frames (SMF) or Intermediate Moment Frames (IMF), the
tration in the weld adjacent to the column web as illuseffect
of inelastic panel-zone deformation on frame stabiltrated
in Figure 2-5 that must be limited for tensile flange
ity must be considered in the analysis. The design shear
forces. The design local flange bending strength Rn
strength of the panel-zone Rv
given in Equations 2.2-5
given in Equation 2.2-8 is determined from LRFD Speciand
2.2-6 is determined from AISC Seismic Provisions
fication Equation K1.1 with consideration of the proximity
Section 9.3a:
of the concentrated flange force to the end of the column:
Fr o P u 075 . Py,
2
R n 0. 9 6. 25 tf
Fy Ct
(2.2-8)
3b t2
f f
R v 0. 75 0. 6Fydctw
1 (2.2-5) When an extended end-plate moment connection is used,
ddt b cw
flange bending must be limited to
prevent yielding of the
column flange under tensile flange forces. The design local
Fr o P u 075 . Py,
flange bending strength Rn
given in Equation 2.2-9 is
b t
2
determined from Murray (1990) with consideration of the
3 f f 12 . Pu
R v 075 . 06 . Fydct w 1
19 .
proximity of the concentrated flange force tothe end of the
ddt b cw Py
column as:
(2.2-6)
bs
2
R n 0. 9
t F C
p f y t (2.2-9)
These provisions are identical to those in LRFD Specification
Equations K1-11 and K1-12, except that a lower re-
m e
sistance factor is used to provide an added margin against
where
excessive panel-zone yielding. Additionally, to prevent t f column flange thickness, in.
shear buckling under the higher inelastic demand associ-
Fy
column specified minimum yield strength, ksi.
ated with high-seismic loading, the minimum thickness of
Note that Equation 2.2-9 was developed from rethe
unreinforced column web given in Equation 2.2-7 is
search that considered only ASTM A36 material
determined from AISC Seismic Provisions Section 9.3b:
(Curtis and Murray, 1989). If column material
d d t
with higher yield strength is used, it is recom-
m c 2 f
tw
min
(2.2-7)
mended that Fy
be taken conservatively as 36 ksi
90
in Equation 2.2-9.
where
tw
column web thickness, in.
b f column flange width, in.
t f column flange thickness, in.
db
beam depth, in.
dc
column depth, in.
Fy
column minimum specified yield strength, ksi
Pu
column required axial strength, in.
Py
FyA, column axial yield strength, in.
A column cross-sectional area, in.
2
dm
moment arm between concentrated flange forces,
in.
4If using allowable stress design, the shear buckling limit is slightly
more conservative and the following W-shapes must be checked
for shear buckling: W44230, W40215, W40199, W40183,
W40174, W40167, W40149, W36150, W36135, W33130,
W33118, W3099, W3090, W2784, W2468, W2455,
W2144, W1835, W1631, W1626, W1422, and W1214.
Figure 2-5 Concentration
of stress in flange or
flange-plate weld for a
column with thin flanges
and no transverse
stiffeners.
8
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