Interactive Buckling of Q420 Welded Circular Tubes under Axial Compression

Finite element models (FE models) of high-strength steel Q420 (yield strength 420 MPa) circular tubes considering residual stresses and local and overall geometric imperfections were established and verified against existing test data. Based on parameter analysis, it was derived that the reduction of ultimate capacity resulting from residual stresses was up to 11.8%. When slenderness ratio was larger than 25, the effect of overall geometric imperfection played a major role compared with that of local geometric imperfection, which resulted in the reduction of the ultimate capacity of about 11.5%. Through tracking the failure process, it was found that, in the initial stage of loading, the deformation of columns mainly presents overall bending. When the load increased near the ultimate load, local buckling occurred and the bearing capacity decreased rapidly. The D/t limit value 27 was determined for preventing the local buckling, and the overall slenderness λl limit value 40 was proposed to distinguish whether local buckling occurs. Based on the FEM result and test data, the applicability of ASCE48-05 and AS4100 for local buckling resistance was evaluated. Continuing the result of stub columns, curve a in GB50017-2017 and in Eurocode 3 of the overall buckling factor φ was proposed to be used in EWM and DSM for estimating the interactive buckling resistance of circular tubes of Q420 under axial compression