Steel Designers Manual - TheBestFriend.org

This material is copyright - all rights reserved. Reproduced under licence from The Steel Construction Institute on 12/2/2007
To buy a hardcopy version of this document call 01344 872775 or go to http://shop.steelbiz.org/
Steel Designers' Manual - 6th Edition (2003)
1152 Notes on section dimensions and properties
Z =
y
1
where y is the distance to the extreme fibre of the section from the elastic neutral
axis.
For castellated sections, the elastic moduli given are those at the net section. The
elastic moduli of the tee are calculated at the outer face of the flange and toe of the
tee formed at the net section.
For parallel flange channels, the elastic modulus about the minor (y–y) axis is
given at the toe of the section, i.e.
y = B - c y
where B is the width of the section
cy is the distance from the back of the web to the centroidal axis.
For angles, the elastic moduli about both axes are given at the toes of the section,
i.e.
y x = A - c x
y y = B - c y
Where A is the leg length perpendicular to the x–x axis
B is the leg length perpendicular to the y–y axis
Cx is the distance from the back of the angle to the centre of gravity,
referred to as the x–x axis
Cy is the distance from the back of the angle to the centre of gravity,
referred to as the y–y axis.
3.2.4 Buckling parameter (u) and torsional index (x)
The buckling parameter and torsional index used in buckling calculations are
derived as follows:
(1) For bi-symmetric flanged sections and flanged sections symmetrical about the
minor axis only:
= [ ( 2 ) ( 2 2)
]
= [
12
]
u 4SxgA
h
x 0. 566h
A J
(2) For flanged sections symmetric about the major axis only:
= [ ( ) ( ) ]
u 2 IySxg2 A H
x = 1. 132 ( AH) ( I J)
[ ]
y
14
14
12