Calculating the FRLs for masonry walls with AS 3700

Hi There,

The new schedule 5 in BCA 2019 - Fire Resistance of Building Elements means that building elements required to have an FRL need there fire resistance calculated in accordance with this schedule.

One way to achieve a calculation is in accordance with the masonry standard AS 3700 for masonry walls.

I've tried to calculate it myself for cavity walls but I am not an engineer so i've run into a bit of difficulty.

Clause 6.3.2.1 (a) states that for cavity walls:

Where both leaves have superimposed axial force, with values within 10% of each other, including the case of no superimposed axial force on either leaf, the slenderness ratio shall be based on two-thirds of the sum of the thickness of the two leaves and the fixity of the leaf not exposed to the fire.

I understand the majority of the above, but not the fixity of the exposed leaf, what is that? and how do I calculate it? I understand that calculating the slenderness ratio for a masonry member will allow me to calculate the fire resistance for structural adequecy.

Also is it possible for someone to go through the calculation for a masonry wall under 6.3.2.2 (b)?

Thanks in advance.