In　corrosive　environments,　steel　bridges　demonstrate　time-dependent　seismic　performance　and　varied　directional　responses　to　bi-directional　excitation　at　different　life-cycle　stages.　However,　current　seismic　assessment　methods　for　bridges　have　not　adequately　addressed　the　time-dependent　effects　of　bi-directional　excitation　directionality　on　seismic　responses　throughout　their　entire　life　cycle.　Thus,　this　study　aims　to　investigate　the　time-varying　directional　effects　of　bi-directional　seismic　excitations　on　steel　bridges　with　multiple　parameters　and　to　propose　a　method　for　predicting　the　range　of　critical　incident　angles　while　considering　the　aging　effects　of　bridges.　Initially,　time-dependent　functions　that　characterize　steel　corrosion　are　integrated　into　multiscale　finite　element　models　of　the　steel　bridges　to　simulate　corrosion　progression　across　their　life-cycle　stages.　Subsequently,　a　quantitative　analysis　of　the　bi-directional　seismic　response　of　steel　bridges　is　conducted　throughout　their　life　cycle,　accounting　for　the　directionality　of　seismic　excitation.　Finally,　a　method　and　process　for　predicting　the　range　of　time-varying　bi-directional　critical　incident　angles　with　95　%　probability　are　derived　by　fitting　the　statistical　probability　distribution　boundary　values　of　the　critical　incident　angle　deviation　index.　The　study＇s　findings　indicate　that　the　aging　effects　of　steel　bridges　amplify　the　displacement　response　under　bi-directional　seismic　excitation,　with　the　maximum　displacement　response　difference　exceeds　40　%.　The　service　time　may　increase　the　sensitivity　of　steel　bridges　to　changes　in　incident　angles,　potentially　amplifying　the　displacement　response　by　a　factor　of　1.69.　The　study＇s　findings　highlight　the　importance　of　considering　aging　effects　and　bi-directional　excitation　directionality　in　bridge　seismic　assessments.　©　2024