Frequently Asked Questions

1. MONOSYMMETRIC SECTIONS 
In Table 1 and 2 of CAN/CSA-S16-01, the criteria for the stems of T-Sections are based on (b/t).  Would it be (h/w) for the stem’s slenderness?  In BS5950 and ANSI/AISC-360-05, (h/w) are also used instead. In CAN/CSA-S16-01, I could not find the clauses for the bending of shapes other than doubly symmetric sections.  Would it be in another reference? - K.M. 

You could not find them because they do not exist in CAN/CSA-S16-01. With respect to stems of T-Sections, according to S16-01 Clause 11.3.1(b), the width “b” is the full nominal dimension. Also see Figure 2-8 of the CISC Commentary on CAN/CSA-S16-01 (S16S1-05) - page 2-28 of the Handbook (9th Edition). With respect to the bending of singly symmetric (or monosymmetric) sections, this specialized topic is not covered by S16. However, Clause 13.6(e) refers to the Guide to Stability Design Criteria for Metal Structures for providing a rational method of analysis of such sections. This publication has detailed information on the bending of monosymmetric sections, on top of being an excellent reference document for your library. You can order it from us at www.cisc-icca.ca/publications/technical/design/stability

It is a bit pricey but well worth it (I don’t know how many times I provided this book as a reference for topics not covered in S16, for engineers “seeking reliable, in-depth coverage of stability problems and research”). The first version was edited in 1960. Theodore (Ted)  V. Galambos, a very famous professor emeritus in civil engineering at the University of Minnesota, is the editor. Still hesitating? Glance at the table of contents: www.stabilitycouncil.org/html/guide.htm

2. BUILT-UP SECTIONS 
I’m trying to calculate the basic geometric properties of an older-type built-up section built in the 1940’s using a W or S shape, and a channel placed on top.  Do these formulas exist or do I have to start from scratch? - R.S. 

The section properties of this particular built-up section do exist in Part Six of the Handbook, entitled Properties and Dimensions. Check out page 6-140 of the 9th Edition for the equations  enabling you to calculate the moment of inertia (Ixx, Iyy, IyT), the section modulus (Sx1, Sz, Syy) and the radius of gyration (rxxand ryy). Here’s the bonus. You will also find over a dozen different built-up section configurations such as boxes (6 types), built-up I-shapes (5 types) with unequal flanges (unequal flange thicknesses or widths, plate or channel or W-shape with reinforced top and/or bottom flanges, flanges made of channels rather than plates), monosymmetric sections made of channels and/or angles (2 types) and a star-shaped section (1 type). If you don’t have the most recent version, go to: www.cisc-icca.ca/publications/technical/design/handbook

And for the grand finale, there is a table (pages 6-136 and 6-137) that provides a longer list of properties and sections for several configurations of W shapes and channels which includes values for mass, shear centre (Y), torsional constant (J) and warping constant (Cw). Hopefully, you will be lucky enough to find your configuration in this list. And if all else fails, get the Stability Guide (see previous question).

Incidentally, if you want to get the equations that can help you calculate shear centres, torsional constants and warping constants for several steel members (open and closed cross-sections; mono-and doubly-symmetric), download the following document from the Technical Resources on our website:
www.cisc-icca.ca/files/technical/techdocs/updates/torsionprop.pdf

3. TAPERED BEAM AND COLUMN SECTIONS 
We are checking the adequacy of an existing rigid-frame building that has tapered beam and column sections with rigid connections.  Do you know of any reference that could help us with the analysis of this type of structure? For example, what kL/r would you use for checking the tapered column? The “r” at mid-height? - J.L. 

I haven’t found anything “nice and quick”. Either you perform a 2nd order analysis in SAP or a similar analysis program, or you do something more empirical.

There is a very useful discussion in the all too famous Guide to Stability Design Criteria for Metal Structures (Section 3.3 TAPERED COLUMNS, pp 80-87 + Section 3.4 BUILT-UP COLUMNS pp 87-91). I believe I’ve already mentioned this Guide! www.cisc-icca.ca/publications/technical/design/stability/

I’ve found several research projects that suggest a methodology for obtaining an equivalent “k” factor, but nothing definitive. Since this type of column is more common in pre-engineered buildings or SBS (Steel Building Systems), you might consider getting information from CSSBI (Canadian Steel Sheet Building Institute): www.cssbi.ca

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This question appeared in the "Ask Dr. Sylvie" column of Advantage Steel no. 32, Fall 2008.