I've made the slab base (with the required thickness), attached it to the roof slab with 4 columns.. i've manually calculated all the loadings possible, and assigned them to the roof slab (as a floor load), and the self weight for all members.. but i get an error which says the structure is unstable.... please give me ur suggestions on how to move about with the model..
thanks in advance
Would you attach your staad file?
heres the file