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For Ishaped beams and similar flexural members with thin webs, only
the web area between flange plates should be used in calculating Aw.
Table 9 gives equations for support shears, V, for beams for several
particular load and support conditions.
(5) Local Buckling. To insure that a steel beam will attain fully
plastic behavior and possess the assumed ductility at plastic hinge
locations, the elements of the beam section must meet the minimum thickness
requirements sufficient to prevent a local buckling failure. Adopting the
plastic design requirements of the AISC Specification, the widththickness
ratio for flanges of rolled I and Wshapes, and similar builtup single web
shapes that would be subjected to compression involving plastic hinge
rotation, shall not exceed the following values:
Fy(ksi)
bf/2tf
36
8.5
42
8.0
45
7.4
50
7.0
55
6.6
60
6.3
65
6.0
where,
Fy = specific minimum static yield stress for steel
bf = flange width
tf = flange thickness.
(a) The widththickness ratio of similarly compressed flange
plates in box sections and cover plates shall not exceed 19O/(Fy)1/2.
For this purpose, the width of a cover plate shall be taken as the distance
between longitudinal lines of connecting rivets, highstrength bolts or
welds.
(b) The depththickness ratio of webs subjected to plastic
bending shall not exceed the value given by Equations (93a) or (93b)
depending on the value of P/Py. When P/Py is less than 0.27:
EQUATION:
d/tw = [412/(Fy)1/2][l  l.4P/Py]
(93a)
When P/Py is greater than 0.27:
EQUATION:
d/tw = 257/(Fy)1/2
(93b)
where,
P = applied compressive load
Py = plastic axial load equal to the crosssectional area
times the specified minimum static yield stress, Fy.
2.08134


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