Hollow sections - warning!
Hollow sections can be hot finished or cold formed. HF hollow section calculations are only applicable to hot-finished sections. On more recent releases we print 'HF' next to the section name to emphasise this. Cold-formed sections have lower capacities and should not be substituted for hot-finished sections without explicitly checking their adequacy.
Tata supply two grades of cold-formed section, Strongbox; 235 and Hybox; 355. The Steel Construction Institute Advisory Desk note AD271 states "... it is strongly recommended that Strongbox 235 sections should not be used in structural applications, in particular where designs must comply with building regulations and/or design codes"
What's a PFC?
What's an IPE?
What's an ASB?
What's an SFB?
PFC stands for Parallel Flange Channel, a channel section in which the inner and outer faces of the flanges are parallel. See SCI Publication 210: Parallel Flange Channels - Section Properties and Member Capacities, 1996. IPE and HE are Euronorm I sections. A SFB (Slimflor Fabricated Beam) former comprises a UC section with a plate projecting 100mm either side welded on to the lower flange. An ASB (Asymmetric Beam) section is a rolled I section with the bottom flange 110mm wider than the top flange.
Column base plate sizing
A query has been raised re base plate sizing. ProSteel calculates the base plate thickness using the minimum base plate size, which is a function of the section size and concrete strength. If you make the base larger, the additional area is ignored. This is all in accordance with BS5950, but one user has pointed out that when designing mezzanine floors the base area is often determined by the permissible load on the subgrade below the slab, less an allowance for load dispersal through the slab. In such cases the base plate thickness should be calculated by using the actual size and actual stress under the whole plate which will give a greater plate thickness than ProSteel indicates. In such cases you will need to calculate the base plate thickness manually.
Mezzanine floor column effective lengths
Please note that the effective lengths for columns supporting internal platform (mezzanine) floors are given in Annex D Table D1. The factors rang from 0.70L to 4.00L. The ProSteel design dialog lets you type in your own effective length factor as well as selecting the standard values from the drop-down list. If you are involved in mezzanine floor design we would strongly advise you to obtain a copy of BRE Digest 437 - available from BRE Bookshop