Study On Lateral-torsional Buckling Of Q460High Strength Steel Welded I-section Beams In Ambient And Elevated Temperature

Lateral-torsional buckling of Q460high strength steel welded I-section beams inambient and elevated temperature is studyed in this article.First of all, the validity of the ANSYS model was verified by related theory andexperiment. On the premise of meet the requirements of local stability, the geometricaland material nonlinearities were taken into account. The influence of differentconstitutive relations and residual stress on overall stability of Q460high strength steelwelded I-section beams in ambient temperature was obtained. By comparing with thoseof the mild steel welded I-section beams, the different influences of the initialimperfections and strength grade of high strength steel welded I-section beams on theoverall stability in ambient temperature were getted. It is shown that the lateral-torsionalbuckling capacity of Q460high strength steel welded I-section beams increased ratherlargely in ambient temperature compared to that of mild steel welded I-section beams.therefore, Combination GB50017-201X（draft for approval）, a new formula oflateral-torsional buckling coefficient in ambient temperature for Q460high strengthsteel welded I-section beams was proposed, Confirmed by the FE analysis, the newformula is accurate and safe for practical use.Secondly, The overall stability of Q460high strength steel welded I-section beamsin elevated temperature was analysed. The distribution of temperature in beamsection under fire on three sides was obtained through thermal analysis. The influenceof initial geometric imperfection and the different constitutive relations of Q460highstrength steel welded I-section beams on overall stability in elevated temperature wasgiven through structural analysis. It is shown that the lateral-torsional buckling capacity of Q460high strength steel welded I-section beams in elevated temperature are quitedifferent from those of mild steel welded I-section beams. Therefore, Combination EN1993-1-2, a new formula of lateral-torsional buckling coefficient in elevatedtemperature for Q460high strength steel welded I-section beams was proposed.Confirmed by the FE analysis，the new formula is accurate and safe for practical use.