The　tied-arched　steel　bridges　represent　an　advantageous　structural　typology　commonly　used　to　build　bridges　of　medium　span　length　(around　100　and　200　m).　The　design　concept　with　which　modern　steel　arch　bridges　are　built　nowadays　is　a　compromise　between　structural　optimization　and　robustness.　Structural　optimization　of　the　structure　leads　to　the　creation　of　increasingly　lighter　structures　to　minimize　the　use　of　the　material.　The　structural　robustness　instead　tends　to　design　＂redundant＂　structures　that　have　sufficient　resilience　in　dealing　with　extreme　actions　to　avoid　the　progressive　collapse　of　the　structure.　With　the　study　made　is　possible　to　make　interesting　considerations　on　the　concept　of　robustness　and　structural　optimization　of　the　bridge　considered　as　case　study　and　led　to　interesting　ideas　for　increasingly　cutting-edge　designs　that　can　pursue　the　objectives　that　are　imposed　on　us　by　today＇s　society.