Intumescent paint protection of structural steelwork

[kurnal]

Working on a project in an existing 2 storey CLASP building used as a shop and offices.
The developers want to remove the existing fire resisting suspended ceiling in the ground floor shop and expose the void, and to remove the cladding from the steel columns. They are proposing intumescent paint treatment to the steelwork. I dont generally have a problem with this but some of the beams are of trussed design - wide top and narrow bottom flange with two wriggly bars forming the web of the truss. Obvoiously parts of this are in tension and other parts in compression and I wonder if such a beam is suitable for intumescent treatment or whether encasement will remain the best solution for these parts? All the fire tests on paints that I have so far found have been on RSJs.

Does anybody have any experience of this?

[wee brian]

You may struggle to get any valid info for paint on these things. The industry has been arguing about it on castellated beams for ages.

Get something from the manufacturer. - also make sure that they do it properly. Somebody needs to check that the right thickness of paint is applied.

[Peter Wilkinson]

I would agree with Wee Brian regarding information from manufactuer is the best route.  Also, it is worth specifying a FIRAS accredited applicator to give your client a fighting chance of success.

[kurnal]

Thanks for the advice. Theres also some good information in the UMIST website for which I attach the following link, and on the basis of this I have recommended that these trussed beams be protected by encasement, because the light gauge steelwork forming the truss is likely to heat up in an uneven and unpredictable way in a fire compared to a solid beam.

http://www.mace.manchester.ac.uk/project/research/structures/strucfire/DataBase/References/defaultSteel.htm

[wee brian]

you may find more practical info on the ASFP website - in the yellow book