Dented Tubular Members

Hi all,

I've been looking into a model that another engineering firm has done for an offshore platform that my firm is currently working on, and they used the dented tubular member to model a brace they requested to be filled with grout.  I have been able to reproduce the section properties and stresses for the member from discussions found in this forum and through AISC 14th Ed., Chapter I "Design of Composite Members".  However, I cannot seem to replicate the allowable stresses SACS generates when I review the member in its post view model.

As a little side study I made a simple model using the dented tubular member card and changed several inputs.  I found that the allowable stresses were proportional to the compressive strength of the grout f'c and inversely proportional to the modulus of elasticity of concrete Ec.

Can someone shed some light on how the allowable stresses are calculated in SACS for the dented tubular member checks? 

Please and thank you for your time,