In　order　to　study　the　interaction　mechanism　of　fatigue　damage　and　size　effect　of　prestressed　concrete　beams　under　fatigue　load,　multi-stage　variable　amplitude　fatigue　tests　of　three　groups　of　prestressed　concrete　beams　with　different　sizes　were　carried　out.　Through　the　research　and　analysis　of　the　test　data　of　prestressed　concrete　beams　under　fatigue　load,　it　is　found　that　due　to　the　action　of　fatigue　cyclic　load,　there　is　a　size　effect　in　the　residual　bearing　capacity　of　prestressed　concrete　beams,　that　is,　the　increase　of　residual　bearing　capacity　of　prestressed　concrete　beams　decreases　with　the　increase　of　section　size.　Considering　the　influence　of　size　and　the　degree　of　fatigue　damage,　the　coefficient　of　the　original　formula　is　modified,　and　the　new　calculation　formula　of　residual　bearing　capacity　is　basically　consistent　with　the　change　of　the　measured　results　of　the　specimen.　©　2025　Ernst　&　Sohn　GmbH.