Ultimate behaviour of hybrid stainless steel cross-sections

Hybrid steel plate girders are used worldwide as primary structural members in steel and composite bridges, when there is a need for deeper sections with greater stiffness and bending resistance than rolled sections to carry heavy loads. With the increasing importance of sustainability and lifecycle (cost) analysis, design for maintenance has become an important consideration for infrastructure projects like bridges which have a design working life exceeding 100 years over which they need to be regularly inspected and maintained. Stainless steels are known for their excellent corrosion resistance and low maintenance costs and thus the application of hybrid plate girders in bridge designs could be explored. This paper reports a numerical study on stainless steel hybrid plate girders subjected to compression and to bending and assesses relevant recommendations for their design. Previously developed FE models validated against stub column and four-point bending tests are employed and a parametric study is conducted on hybrid I-sections over a wide range of cross-section slenderness and aspect ratios. Based on the obtained results, the EN 1993-1-4 design predictions for stainless steel cross-sections in compression and in bending are assessed and the accuracy of the codified slenderness limits for both homogeneous and hybrid stainless steel girders is discussed. Furthermore, the numerically obtained deformation capacity at ultimate load is plotted against the CSM base curve originally derived for homogeneous sections and the accuracy of the CSM predictions of the cross-section resistance is also assessed, demonstrating that the CSM can be employed to predict the cross-section resistance of hybrid girders.