Eurocode 1993-1-1 Chapter 5.2:
“Factor by which the design loading would have to be increased to cause elastic instability in global mode”
The solver requires Linear Elastic and Second Order P-Delta solvers to be run subsequently. * this is to get the linear elastic stiffness modulus and nonlinear stiffness modulus.
For design purposes, checking is normally done under SLS (Serviceability Limit State) condition. Therefore user should run in “Unfactored Load Combination”.