Local buckling behaviour of welded I-section steel stub columns with longitudinally profiled steel plates under axial compression: Testing, modelling and design

The use of welded I-section steel members with longitudinally profiled (LP) steel plates is becoming popular in structures, and such members are manufactured with variable thickness to accommodate the loading distributions in practical construction. Compared with the constant thickness steel plates, the use of LP steel plates is more susceptible to local buckling at the thinner end. However, there was no study that reported the local buckling behaviour of such members. Furthermore, existing design codes do not provide any design guidance for calculating the strength of such steel members. In this paper, a total of sixteen welded I-shaped section stub columns with LP and constant thickness steel plates under axial compression were tested to study the local buckling behaviour of such members. The initial geometric imperfections of all specimens were measured using 3D laser scanning technology prior to the axial compression experiments. A nonlinear finite element (FE) model was also established, and validated against the corresponding experimental results, which showed a good agreement both in terms of ultimate strength and failure modes. An extensive parametric study including 130 FE models was conducted using validated FE models. To evaluate the feasibility and reliability of the existing design provisions for steel members with constant thickness steel plates, the test and numerical results were compared against design strength predicted from the existing design provisions. Upon comparison, the existing design formulas in Chinese Standard (GB 50017-2017), American Specification (ANSI/AISC 360-10) and European Standard (BS EN 1993-1-5) are found to be generally conservative when calculating the strength of such members with LP steel plates. New design formulas are proposed, in which the modified normalized slenderness ratio and enhancement coefficient are applied to the existing design provisions.