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According to BS5950, a beam section can be classified as plastic, semi-compact, compact or slender. For the same section area, a H-beam can take axial compression (without buckling) better than an I-beam, and as such, uses a different strut curve in the code:

enter image description here

Now, I understand that a H-beam has a wider flange compared to an I-beam, but at what point, precisely, does this transition from I- to H- occurs? For example, is a 400x300 (depth x width) beam considered a H- or an I-beam?

Update:

Extracted from BS5950 guide, the following table shows H-beams (also known as universal columns, some of which with depth greater than width. This is the reason why I don't believe the differentiation is so straight forward.

Section Property Table

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  • $\begingroup$ I'm probably wrong, but I'd say the only difference between these two is orientation at which they should be used... $\endgroup$
    – Slovakov
    Commented Feb 21, 2015 at 11:36
  • $\begingroup$ @AndyT, please refer to Table 23 above to understand why this H- or I-beam distinction needs to be clear. Also, from the SCI guide to BS5950, it is quite clear that Universal Column refers to H-beam and Universal Beam refers to I-beam. $\endgroup$
    – Question Overflow
    Commented Feb 28, 2015 at 12:31

1 Answer 1

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BS5950-1:2000 Clause 1.3.23 defines an H-section as having "an overall depth not greater than 1.2 times its overall width", and Clause 1.3.25 defines an I section as having "an overall depth greater than 1.2 times its overall width".

Note that at exactly a ratio of 1.2, it would be an H section not an I section.

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  • $\begingroup$ Wow, I can't believe it is actually right at the front. Thank you! $\endgroup$
    – Question Overflow
    Commented Mar 3, 2015 at 15:12
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    $\begingroup$ lol. Don't worry, yours isn't the only question on here where the answer is "read the design code you quoted" - I had one too! $\endgroup$
    – AndyT
    Commented Mar 3, 2015 at 16:51
  • $\begingroup$ Is this a case of RTFS where S represents 'Standard'? :-) $\endgroup$
    – Paul Uszak
    Commented Apr 30, 2017 at 21:09

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