aslamwalekum to all, when we need semi rigid diaphragm , i normaly take rigid diaphram for beam slab system , i got a vetting project (model made on ETABS 2016) , in which flat slab are used and semi rigid diaphram is assign , A/c to IBC 2006 , concrete slab with thickness more than 1.5 in , not consider as flexible diaphram , here is the code refrence. ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 1613.6.1 Assumption of flexible diaph