Design of stainless steel structural systems by GMNIA with strain limits

Design by GMNIA (Geometrically and Materially Nonlinear Analysis with Imperfections) allows the key behavioural features of structures to be directly captured in the analysis, improving accuracy and dramatically reducing the need for subsequent design checks. Since the analysis of frames typically employs beam elements, in which local buckling of cross-sections cannot be explicitly simulated, cross-section classification and capacity checks remain necessary. However, the step-wise and overly conservative nature of these traditional checks restricts accuracy. To resolve this, the use of strain limits, defined using the Continuous Strength Method, in place of these cross-section checks has been proposed. This design method is extended to indeterminate stainless steel structural systems herein. Ultimate load-carrying capacity predictions from the proposed design approach are compared against results obtained from benchmark shell finite element models as well as predictions using traditional stainless steel design methods. The new design framework allows for element interaction at the cross-section level, the influence of local moment gradients, the partial spread of plasticity, moment redistribution, strain hardening and the visualisation of the structural failure mechanism, resulting in more accurate and consistent resistance predictions. The method is included in AISC 370 and prEN 1993-1-14 offering a step change in efficiency for the future direction of structural stainless steel design.