Page 155 - Handbook of Civil Engineering Calculations, Second Edition

1.138 STRUCTURAL STEEL ENGINEERING AND DESIGN

b b f
flange 9.9
t 2t f
h c
web 24.9
t w
(a) In A36 steel
flange p 10.8
See W6 15
web p 24.9

(a) Since flange (b/t 9.9) < ( p 10.8), and web (h c /t w 24.9) < ( p 106.7), a W12
65 beam is compact in A36 steel.
(b) However, if F y 50 ksi (344.5 MPa)
flange p 9.2
See W6 15
web p 90.5
(a) Because flange (b/t 9.9) > ( p 9.2), a W12 65 beam is noncompact if F y 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 classified 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, p .
Structural steel members with 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 W10 49 column, 10 ft (3 m) 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,
EA g