Local-Overall Interactive Buckling of High Strength Steel Welded Circular Tubes under Axial Compression

In the present study, an investigation into the interactive buckling performance of high strength steel circular tubes was performed using finite element (FE) models verified against existing test data. The parametrical analysis of overall geometric imperfection, local geometric imperfection, and residual stresses incorporated in the FE models was performed. The result revealed that (i) the normalized member slenderness ( λ nl ) of HSS circular tube columns significantly affected by overall geometric imperfection was in the range from 0.2 to 1.6, and the reduction of ultimate capacity was 5.05%, 5.35% and 3.23% with 460 MPa, 690 MPa and 960 MPa on average, respectively; (ii) the local geometric imperfection led to the ultimate capacity to be reduced by 2% on average, which can be ignored when λ nl higher than 1.4; (iii) the reduction of ultimate capacity resulted from residual stresses was 11.39%, 8.93% and 6.54% with 460 MPa, 690 MPa and 960 MPa columns, and the pronouncedly influenced λ nl varying from 0.4 to 1.6. Subsequently, overall slenderness limit used to identify failure modes was discussed. On the basis of numerical program, codified design rules for local buckling load of stub columns were re-examined for HSS circular tubes. Finally, the overall buckling factor of HSS columns was distinguished in conjunction with the local buckling resistance prediction formulas to evaluate the interactive buckling resistance of HSS circular tube columns.