Structural Utilisation and Windows

In much of the work about embodied energy minimisation, we explore the structural utilisation of members in a building. This is usually defined as the ratio between an actual performance value and the maximum allowable performance value which is deemed limiting for a structural member. It allows us to explore how close to the limit state (be that serviceability or ultimate) a member is. In this post I raise two questions for further analysis.

1) How can design choice be captured in a utilisation ratio?

2) Can we define a "structural safety window"