The　out-of-phase　vibration　between　neighboring　structures　owing　to　their　different　vibration　characteristics　and　spatially　varying　seismic　excitations　may　result　in　strong　impact　between　the　adjacent　structural　components,　which　might　result　in　detrimental　damage　to　the　structures.　To　preclude　such　damage,　the　gap　size　of　the　expansion　joint　and　the　vibration　period　ratio　between　the　adjacent　structures　should　be　carefully　selected.　Herein,　the　framework　of　performance-based　seismic　design　(PBSD)　is　extended　to　optimize　the　gap　size　and　period　ratio　between　the　cable-stayed　bridge　and　its　approach　spans　under　the　spatially　varying　ground　motions.　Considering　the　computational　burden,　an　equivalent　cable-stayed　bridge　model　is　proposed　and　verified,　and　then　adopted　in　the　optimization　process.　Based　on　the　multi-stripe　analysis　(MSA)　method,　the　component　fragility　curves　(pylons,　bearings,　and　local　damage)　for　the　typical　cable-stayed　bridge　are　derived,　and　then　the　corresponding　structural　fragility　functions,　namely,　repair　cost　ratios　(RCRs)　are　derived.　The　optimal　gap　size　and　period　ratio　between　main　bridge　and　approach　spans　could　be　identified　by　the　proposed　optimization　framework　under　both　uniform　and　spatially　varying　excitations.　The　analytical　results　demonstrated　that　the　optimal　gap　size　and　period　ratio　depend　on　the　earthquake　characteristics　and　the　excitation　methods.　The　optimized　RCR　values　of　the　bridge　subjected　to　the　spatial　varying　ground　motions　are　much　larger　than　those　of　bridge　under　the　uniform　excitation.