Building Design and Construction Handbook - Merritt - Ventech!

COLD-FORMED STEEL CONSTRUCTION 8.11
FIGURE 8.3 Cold-formed stainless steel sections. (The
International Nickel Co., Inc.)
thickness, make it possible to consider, in computing structural properties (moment
of inertia, section modulus, etc.) that such properties vary directly as the first power
of the thickness. So, in most cases, section properties can be approximated by first
assuming that the section is made up of a series of line elements, omitting the
thickness dimension. Then, final values can be obtained by multiplying the lineelement
result by the thickness.
With this method, the final multiplier is always the first power of the thickness,
and first-power quantities such as radius of gyration and those locating the centroid
of the section do not involve the thickness dimension. The assumption that the area,
moment of inertia, and section modulus vary directly as the first power of the
thickness is particularly useful in determining the required thickness of a section
after the widths of the various elements composing the section have been fixed.
This method is sufficiently accurate for most practical purposes. It is advisable,
however, particularly when a section is fairly thick compared to the widths of the
elements, to check the final result through an exact method of computation.
Properties of thin elements are given in Table 8.4.
Various Failure Modes. One of the distinguishing characteristics of lightweight
cold-formed sections is that they are usually composed of elements that are relatively
wide and thin. As a result, attention must be given to certain modes of
structural behavior ordinarily neglected in dealing with heavier sections, such as
hot-rolled structural shapes.