When are you obliged to perform a second order calculation for steel structures according EN 1993-1-1? And how can this be verified in SCIA Engineer?
The criterion to be obliged to execute a second order analysis is mentioned in article 5.2.1(3) of EN1993-1-1. This can be verified via the factor alpha_critical mentioned in formula 5.1 of EN1993-1-1
Alpha_critical can be obtained if you execute a stability calculation in SCIA Engineer. Once that has been done you will find in the result menu ‘Critical load coefficients’. The critical load coefficient with the lowest value is the alpha_critical mentioned in formula 5.1 of EN1993-1-1.