Fire Rating of Concrete Walls AS3600.2018

[Seb_]

Hi All,

i would like your interpretation of the following clause from AS3600.2018 - Clause 5.7.2

"For walls where the lateral support at the top of the wall is provided on one side only by a member not required by the relevant authority to have FRL, the structural adequacy shall be deemed to have been achieved by satisfying the requirements of clause 5.7.1."

From the above, what is defined as lateral support.

My understanding is that when a wall is connected to the slab, the slab is the lateral support. The slabs requires FRL, therefore i need to reefer to table 5.7.2.

Thanks in advance.
Seb

 

[Just Some Nerd]

A slab would work provided it's braced in that direction against lateral loads. Similarly any other flooring system may be able to do the job, e.g. a steel truss roof) but conceivably any system that restrains the top of the wall against lateral movement will work. Often yes, whatever is bracing the wall will require an FRL so this exception doesn't help there. One example of a niche scenario where the clause helps would be for example a warehouse with precast wall panels (perimeter panels supported one side only) and a lightweight roof that isn't required to have any FRL, which allows to minimize the thickness of the wall. I don't quite like this exception but have had to rely on it when doing some additions to warehouses, and it becomes clear that's how the original design thickness of the wall was justified as without it the panels would be clearly below the minimum thickness for structural adequacy

 

[Retrograde]

I agree with Just Some Nerd that that particular clause in the code is meant to apply to industrial warehouse type buildings with tilt-up precast walls.