The　research　on　the　retrofitting　method　using　the　concept　of　integral　abutment　bridge　to　solve　the　durability　problems　of　simply　supported　bridges　was　carried　out.　The　general　retrofitting　process　adopted　by　real　projects　and　the　mechanical　properties　increment　after　retrofitting　were　summarized.　A　simply　supported　bridge　in　Italy　was　analyzed　numerically　using　finite　element　model　built　by　SAP2000　with　inclusion　of　soil-structure　interaction.　The　influence　of　old　and　new　Italian　codes　on　the　mechanical　properties　of　different　static　schemes,　including　simply　supported,　semi-integral　and　fully　integral,　was　investigated.