Fire Resistance of Bare Steel - NBCC

[murphy89]

Hi,

I'm in Canada and trying to get more familiar with fire resistance and have been doing some reading about UL designs, BXUL7. The question I'm trying to answer for myself is: Can bare steel be used to achieve any kind of fire resistance, or does it have to be combined with a fireproofing coating like spray foam, special paint, gypsum board, ect? Is there a UL design that covers bare steel (columns and/or beams)? The only ones I can find always use a minimum thickness of sprayfoam. Thanks!

 

[Canuck65]

To achieve a fire rating on structural steel, it needs to be protected. I typically have specified intumescent paint or boxed out with fire rated drywall. Without protection I believe the fire resistance of bare steel is zero.

 

[Jimbio7]

I've never seen a UL steel assembly that didn't have some kind of protection for the steel. The closest thing I know of is a procedure in NBCC for concrete filled HSS columns that don't need to be protected on the exterior. This is the last hope for an architect that doesn't like the colour or look of intumescent paint.
There are a bunch of special rules that result in its application being pretty limited.

 

[murphy89]

Thanks for your answers

 

[dik]

Canuck... unless it's concrete filled HSS, the rating is 0...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[mgmc]

You will generally only get ~15mins performance completely unprotected, at least under an ISO Fire Curve.

You can get up to 60 mins with partially exposed beams/columns (Beams with shelf angles/columns with block infill etc.).

It is however far more starightforward to apply intumescent paint or boarding as the latter relies upon the specific tested sections/materials/dimensions or an FEA analysis to simulate temperatures.

 

[HTURKAK]

As far as i know, unprotected steel sections have fire resistance of some 15-30 minutes , depending on the shape, thickness.

I would like to remind some facts regarding the fire resistance of steel ,

- The strength reduction of carbon steel is 50% at 500 C.

- The burning temperature of CS is around 1500 C. So, the CS is combustible material and burns with exotermic reaction. Pls look to the following video

https://www.youtube.com/watch?v=TsnLmgWXw-E

- The fire resistance can be increased with intumescent coatings, concrete encasement up to 120 min. rating. But can be unlimited with water filled sections . A good reference ( Baulicher Brandschutz durch wassergefüllte Stützen in Rahmentragwerken (By, Hönig, O., Klingsch, W.).

- I searched the forum for (Burning temperature of steel ) and found this thread330-346740 which is very useful.

 

[dik]

thanks

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[murphy89]

Thanks everyone!