D4.A.3 Slenderness Effects and Analysis Considerations
The second method by which STAAD allows the user to account for the slenderness effect is through user supplied moment magnification factors (see the parameter MMAG in D4.A.4 Design Parameters). Here the user approximates the additional moment by supplying a factor by which moments will be multiplied before beginning member design. This second procedure allows slenderness to be considered in accordance with Clause 10.14 of the code.
While performing a P-Delta analysis, all load cases must be defined as primary load cases. If the effects of separate load cases are to be combined, it should be done either by using the REPEAT LOAD command or by specifying the load information of these individual loading cases under one single load case. Usage of the LOAD COMBINATION command will yield incorrect results for P-Delta Analysis in STAAD.Pro.