Local-flexural interactive buckling of S690 high strength steel slender welded I-section columns: Testing, modelling and design

The present paper reports a thorough experimental and numerical investigation into the local-flexural interactive buckling behaviour and resistances of S690 high strength steel slender welded I-section columns. A testing programme, adopting two S690 high strength steel slender welded I-sections, was firstly conducted and included initial geometric imperfection measurements and ten pin-ended column tests. The testing programme was accompanied by a numerical modelling programme, where finite element models were developed and validated against the test results and then employed to perform parametric studies to generate further numerical data over a wide range of cross-section dimensions and member effective lengths. On the basis of the test and numerical results, the interaction of local and flexural buckling of S690 high strength steel slender welded I-section columns was carefully analysed. Regarding the design of S690 high strength steel slender welded I-section columns failing by local-flexural interactive buckling, the existing European code, Australian standard and American specification adopt the same design concept of using effective width method to consider local buckling and buckling curves to consider flexural buckling. Evaluation of the three existing design standards generally indicated that both the European code and Australian standard yield conservative interactive buckling resistance predictions for S690 high strength steel slender welded I-section columns, owing mainly to the adoption of conservative design flexural buckling curves, while the American specification results in an overall good level of design accuracy, but with many over-predicted resistances. An improved approach was then developed through the use of a new design flexural buckling curve combined with the effective width method given in the European code, and shown to yield accurate, consistent and safe interactive buckling resistance predictions for S690 high strength steel slender welded I-section columns.