Mass　optimization　of　crane　box　girder　considering　both　ribs　and　diaphragms　is　a　crucial　aspect　of　crane　structural　design　in　mechanical　engineering.　However,　two　common　challenges　often　obscure　this　process:　the　sizing　of　stiffeners　such　as　diaphragms　and　ribs,　and　the　selection　of　constraints　on　state　variables　related　to　stresses　and　deformations　for　various　load　cases.　In　response,　this　paper　focuses　on　optimizing　the　dimensions,　number,　and　placement　of　stiffeners,　including　ribs　and　diaphragms,　in　a　two-girder　overhead　crane　structure.　The　paper　begins　by　establishing　criteria　for　the　initial　height　of　the　box　girder　through　a　comparative　analysis　of　structural　strength　and　stiffness.　Subsequently,　dimensional　relationships　between　stiffeners　and　the　girder　section　are　built　in　accordance　with　the　principles　of　local　plate　stability.　Following　this,　the　ANSYS　Parametric　Design　Language　(APDL)　program　is　coded　and　executed　to　optimize　the　crane　mass　using　three　methods:　sub-problem　approximation,　sweep,　and　first-order　methods　via　Module　Design　OPT　for　four　chosen　sets　of　state　variables.　A　comparative　analysis　of　the　optimum　crane　mass,　based　on　the　rounded-up　design　variables,　reveals　that　constraints　on　stresses　and　deformations　from　both　vertical　and　transversal　impact　cases,　as　well　as　the　vertical　frequency　from　dynamic　vibration　cases,　yield　the　best　results.　Furthermore,　the　proposed　APDL　method　is　compared　and　validated　against　Grey　Wolf　Optimizer,　Whale　Optimization　Algorithm,　Particle　Swarm　Optimization,　and　Genetic　Algorithm.　Finally,　a　parametric　study　is　conducted　using　curves　and　tables　to　explore　the　influence　of　structural　stiffness　and　material　property　on　the　optimized　dimensions　of　the　girder　and　stiffeners,　as　well　as　the　overall　mass　and　mechanical　performance.　©　Korean　Society　of　Steel　Construction　2024.