Concept and application of member-based linear and system-based nonlinear analysis in steel structure design

The term "Advanced Analysis" and "Second-order Analysis" appear in code and other documents for decades but they still remain basically a check for the effect of sway moment or a tool for academic research. In practical design, engineers only use the method for checking of the magnitude of sway moments in slender frames. In fact, the direct design application of the method provides a valuable tool for practical design. Their underlying principle also carries a very different philosophy to the conventional design approach. This paper outlines the similarities and differences between the two design concepts, namely the linear effective length method and the second-order elastic or plastic analysis and design method. The era for re-thinking our design philosophy seems to be approaching. In this paper, the experience and theory on using the new design concept and method are also described with worked example demonstrated.