Thousands　of　multi-span,　simply　supported　beam　bridges　with　short　or　medium　spans　have　been　built　in　China.　They　often　suffer　from　problems　of　cracks　in　the　link　slabs　over　piers,　and　the　deterioration　and　damage　of　deck　expansion　joints　at　abutments.　To　address　these　problems,　one　approach　is　to　retrofit　them　by　converting　the　simply　supported　box　beams　into　continuous　structures　over　the　piers　and　jointless　bridges　over　the　abutments.　This　paper　discusses　the　design　methodology　and　details　for　retrofitting　the　Jinpu　Bridge　in　Zhangzhou,　Fujian,　China,　from　a　simply　supported　bridge　into　a　semi-integral　bridge,　in　which　semi-fixed　dowel　joints　are　used　to　connect　the　superstructure　and　the　substructure,　including　piers　and　abutments.　Simultaneously,　the　finite　element　software　is　used　to　calculate　the　internal　forces　and　displacements　of　the　structure.　The　analysis　reveals　an　11.1%　reduction　in　the　maximum　positive　moment　at　the　midspan　of　the　main　beam　in　the　semi-integral　bridge　compared　to　the　simply　supported　bridge.　However,　the　shear　forces　at　the　interior　pier　increase　by　6.4%.　According　to　the　response　spectrum　analysis,　the　maximum　longitudinal　displacement　of　the　semi-integral　bridge’s　main　beam　is　11.6　mm,　reduced　by　80.1%　compared　to　the　simply　supported　bridge　under　a　dead　load　and　earthquake　effects.　The　maximum　bending　moment　and　shear　force　on　the　pier　of　the　semi-integral　bridge　are　984.7　kN·m　and　312.6　kN,　respectively,　both　below　their　ultimate　bearing　capacities.　The　maximum　displacement　at　the　top　of　the　pier　is　7.7　mm,　which　is　below　the　allowable　52.4　mm　displacement.　The　calculated　results　conform　to　the　design　requirements　specified　by　the　code.　©　2025　by　the　authors.