Modelling charring in CLT in abaqus

Hi,

I’m struggling to model charring of timber in abaqus as a 3d shell. I have applied the iso 834 heat curve, with eurocode 5 heat properties. Then applied an interaction of convection to both the top and bottom of the slab and then a radiation on the bottom of the slab where the slab is exposed to fire. But I do t seem to get a charring when modelling the temperature gradient. Does anyone know why this is? And how it could be solved?

I would be greatly appreciative of any help received

Cheers

 

Edu ABAQUS