Composite column - Fire protection 2 hours - Big diameter D=900mm

[daranguiz]

Hello,

I have a composite column CHS900x40 that needs to be protected for 2 hours.
The calculation method exposed on Eurocode is not applicable for columns with D>400mm. The solution proposed by the EC is either protect the steel for T=350°C or do a thermal calculation (fancy software). I've been told by some fire experts that the behavior of a composite column under fire is such as the increase in the steel is slower and maybe won't activate the chemical reaction when needed on the intumescent paint.

Do you know an intumescent paint for composite columns that is able protect for 350°C?
Does AISC or other codes give some guidance on this subject?

Thank you very much

 

[daranguiz]

Well, I talked to 2 fire design experts and I learned 2 things:

- It's unsafe to calculate the resistance of the column under fire by ignoring the concrete. Because the loads under fire are less important, I though than maybe I could check for steel only, but it's an unsafe approach because of "the unequal temperature field creates a rather inhomogenous distribution" and "the unequal temperature field leads to strong internal stresses" ( see Technical note #55 of ECCS)

- In eurocode, for big columns (diameter>400mm) I have to check with a lab or run a thermal calculation

 

[Lomarandil]

Thanks for the follow up!