A　shell-supported　footbridge　was　designed　by　shaping　an　anticlastic　membrane　in　compression　between　deck　and　foundations.　Since　it　would　be　subject　to　biaxial　compression,　it　was　appropriate　to　be　made　of　concrete　because　concrete　strength　could　be　exploited　and　crack　propagation　prevented.　With　reference　to　Musmeci＇s　work,　a　form-finding　algorithm　shaped　the　shell　as　a　tension　structure　with　same　loads,　restraint　reactions　and　internal　normal　forces,　but　with　the　opposite　sign.　Using　a　finite　element　(FE)　model　of　the　shell,　unwished　bending　moments　(and　therefore　tensile　stresses)　were,　however,　found,　because　of　second　order　displacements　and　(contrary　to　a　tension　structure)　because　of　the　bending　stiffness　of　the　reinforced　concrete　(RC)　shell.　Tensile　stresses　were　progressively　eliminated　by　removing　material　from　the　shell　regions　where　unwished　bending　moments　occurred.　For　this　purpose,　topology　optimization　with　the　Solid　Isotropic　Material　with　Penalization　(SIMP)　method　was　used,　and　different　shell　structures　with　cavities　for　different　values　of　given　volume　reduction　were　obtained.　Appropriate　indexes　for　structural　response　were　defined,　and　an　optimization　index　was　finally　used　to　identify　the　most　suitable　pattern　of　cavities　along　the　shell.