Design for Combined Forces
It is the strength calculation made by taking into account the combined stresses created in the elements under bending and axial force.
Design of Steel Members for Combined Forces Steel Beam Design
When purlins are included in the structural analysis system, they are designed by taking into account the axial force in the design under the combined effect, while if the purlins are not included in the structural analysis system, the axial force will be 0, so the design is made under the effect of bending moment.