Modeling Suspended floor slab w/ mid span beam supports 1

[Ben2]

I am attempting to model a suspended floor slab with edge supportes provided by walls, and also supported at mid spans with beams running on each direction. With out the beams the floor slab can be analyzed as the plate structure and I am facing no problem with that. FE software I am using is GTstrudl which can do the required FE analysis in no time. My focus of investigation is to find out how much of the deflections of the slab is controlled(reduced)because of introducing the beam elements.

While my focus is on deflections, I am also intrested looking into bending resultants for the plate(slab) and shear and bending of the beam elements.

Any hint as to how I should model it is appreciated.

 

[lenio]

In place of beam put plate with larger thickness equal to the bending stiffness of beam.
If all loads are perpendicular to the plate it should work.

 

[rapt]

Ben2,

The beams should only be modelled as thickened slabs if they are wide flat beams (band beams in some countries). If the beam depth is greater than half the width they should be modelled as beam elements.

Remember also that the deflections you are getting from most FE programs do not allow for cracking of the concrete or long term effects such as creep and shrinkage. So the deflections you are getting will be very low compared to the real figures. The real deflections could easily be 5 to 10 times higher.

Even using kcs factor for longterm effects for your comparison is not very good because kcs for beams and slabs is actually quite different because of the differentce in the creep and shrinkage for the different section shapes even though ACI318 does not differentiate.

 

[Ben2]

rapt,
I agree with you on the modeling issue. And thanks for your comment on long term deflection. It is true and that is something I will be looking at carefully.