Handbook of Civil Engineering Calculations

b bf

flange& - = -^ = 9.9

t 2tf

hc

web — = 24.9

tw

(a) In A3 6 steel

flange A= 10.8

See W6 x 15

web A^ = 24.9

Since flange (bit = 9.9) < (Ap = 10.8), and web (hjtw = 24.9) < (\p = 106.7), a W12 x

65 beam is compact in A3 6 steel.

(b) However, if Fy = 50 ksi (344.5 MPa)

flange A. = 9.2P

See W6 x 15

web A^ = 90.5

Because flange (bit = 9.9) > (\p = 9.2), a W12 x 65 beam is noncompact if Fy = 50 ksi

(344.5 MPa)

Related Calculations: The concept of compactness, states Abraham J. Rokach,
MSCE, AISC, relates to local buckling. Cross-sections of structural members are classi-
fied as compact, noncompact, or slender-element sections. A section is compact if the
flanges are continuously connected to the web, and the width-thickness ratios of all its
compression elements are equal to, or less than, A^.
Structural steel members tih compact sections can develop their full strength without
local instability. In design, the limit state of local buckling need not be considered for
compact members.
This procedure is the work of Abraham J. Rokach, MSCE, AISC, Associate Director
of Education, American Institute of Steel Construction. SI values were prepared by the
handbook editor.

DETERMINING COLUMN AXIAL

SHORTENING WITH A SPECIFIED LOAD

A WlO x 49 column, 10ft (3m) long, carries a service load of 250 kips (113.5 Mg). What
axial shortening will occur in this column with this load?

Calculation Procedure:

1. Choose a suitable axial displacement equation for this column
   The LRFD equation for axial shortening of a loaded column is

Pl

Shortening, A = —-

K