Q: When we use area object as membrane we get higher moments in beam in comparison to the model where area object is modelled as shell and meshed into finer elements? Please comment why it is like that?
*A: *In membrane objects the load from floor is transferred directly to beams/walls as a distributed load, like a triangular or a trapezoidal load and beam carries 100% of out-of-plane shear. When the floor is modelled as shell object with finite element mesh then slab’s bending stiffness is also taken into account. Hence as a result part of the moment goes to beam and remaining to the slab. This is the reason a smaller moment develops in beams. However it should be noted that when a slab is modelled as a shell object and its stiffness is taken into account then the design of slab should be carried out based on the same finite element results so that the design and analysis are consistent with each other.