Sunday, 6 January 2008

Q: When is a Column not a Column? - Part 1

A: When it’s a Beam.

A quick explanation for the 37% of you, that visit this blog from the USA. In the UK we use steel sections called Universal Beams (UB) and Universal Columns (UC),

With Universal Beams the Height (h) or web depth of the section is larger than the breadth (b) or width of the flanges.

With Universal Columns the height (h) and breadth (b) are approximately the same.

Both UB’s and UC’s come in what is termed “serial sizes”

An example of serial size can be seen in the columns table extract shown above. There are three sections with serial size of 152x152 however to define the actual section specified, one uses the mass per metre, to more accurately define the section.

You will note that the actual depth of section and width of section are given and vary based on the increase in thickness of the Web and Flange and rolling tolerances etc..

One normal pre-computer design practice was to place the designation of UB or UC between the serial size and the weight to assist in avoiding any confusion between size and weight when specifying

i.e. 152x152UC23 = 152x152 serial size Universal Column 23 kg/m
203x133UB25 = 203x 133 serial size Universal Beam 25 kg/m

Another UK practice is to specify the section by placing the section designation after the serial size and weight i.e. 152x152x23UC. Yet another is to use the section designation in font of the serial size and weight i.e. UC152x152x23. This format lends itself to lookup tables for computer programs as it is easier to process information in a table if the section size is presented first in the information.

Now that being said there are occasions where a UK Engineer will use a column section horizontally as a beam, and a beam section vertically as a column, why? Because they can, and sometimes the nature of the situation lends itself to this, typical examples:

Beam sections are used as columns in portal frame structures because of the enhanced resistance to horizontal loads due to the section properties.

Column sections are used in domestic situations where the depth of the beam needs to be contained within a timber floor and the wide flange allows bearing of the timber

Universal Beams typically range from 127 x 76 x 13kg/m up to 1016 x 305 x 487kg/m. Universal Columns typically range from 152 x 152 x 23kg/m up to 356 x 406 x 1086kg/m.

Corus Construction & Industrial provides structural sections in accordance with the following specifications: BS4: part 1: 1993 and EN10056: 1999, ASTM A6/A6m, European narrow flange beams in accordance with Euronorm 89, European wide flange beams in accordance with Euronorm 53-62 and JIS.

From September 2006 the Corus Advance section range was developed to reflect current structural design practice and make it easier to specify Corus CE marked structural sections compliant with the EU Directive on Construction Products.

There are an additional 5 Column Sections and 24 Beam Sections in the Advance section range which are not given in BS 4-1:2005

Corus has trademarked new designations for use by the UK steel construction industry.

UB now becomes UKB
UC now becomes UKC

Asymmetric slimflor beams remain as ASB

Advance, UKA, UKB, UKBP, UKC, UKPFC and UKT are trademarks of Corus.

I’m suspicious that this was not only done to comply with the EU directive but also as a marketing ploy to specify the source of the steel specified by using the UKC and UKB etc designation which are Corus trademarks

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