Regularity and optimisation practice in steel structural frames in real design cases

We find that neither the regularity of the structure nor the cost, independent of the measure used, correlate with the mean utilisation ratio (ur). Conversely, we observe an apparent reluctance to design beams above a 0.8 capacity ur. This reluctance explains most of the unused mass in buildings. The rest of unused mass consists in cores, trimmers and ties (6%), some of which bear loads not captured in this analysis but are otherwise necessary for stability reasons, and in edge secondary beams (3%) which design is constrained, and should not necessarily be considered as 'unused' mass.