Hi Erik, thank you for the quick response.
I should have mentioned that the geometry is already shared (as far as I understand it, anyway; both the plate and stiffener are already combined as one part with two bodies and have shared nodes at the point they meet). We've also been strongly advised against adding fillets as we're aiming to defeature the part as much as possible. Do you know if there is any other way of mitigating the influence of the stress singularity such that we can perform an optimisation that targets minimal stress? Thank you.