How does STRUDS® decide primary & secondary beams for analysis?
Relative stiffness and boundary conditions of the beams decide the primary and secondary beams. A beam having larger section will behave as primary section. However it does happen that neither of beam acts as primary and both of them support each other. For example, in waffle slab geometry, beams along both directions support each other. Also sometimes two cantilever beams are seen supporting each other. If the user wants to enforce his choice of primary and secondary beams, he can do so by changing the sections of beams or changing the support conditions. It is usual practice to provide discontinuity at the end supports of a beam, which the user wants to model as secondary beam.
