I have done a buckling analysis and can see the buckling factors. However when I attempt to do a steel design, all members fail. Why?
Buckling analysis is only to be used for finding out the buckling factor. The purpose of the analysis is to find out the load at which the structure starts to buckle. This load is obtained by multiplying the applied loading by a buckling factor that is reported by the analysis. The displacement/support reactions/ member forces reported by the STAAD.Pro basic solver from a buckling analysis, represents the values at the near buckling load. One should not attempt to design the structure based on these forces. For member design, one should always use a PERFORM ANALYSIS or any form of second order analysis like PDELTA.