Homogenous verus orthotropic floor

[lkj-17]

Hi Guys,

I have a podium slab that to support 5 stories steel containers that is part of the building. The slab is commerical tray deck with concrete topping that land on heavy steel beams and columns (gridline like). 

I initially modelled the slab as a homogenous plate with a constant thickness, then apply exaggerated area loads to the slab and point loads to the steel beams. In this case, I got about combined deflection 18mm in my transverse beams, which is fine by SLS deflection checking (8.5m span/400=21mm).

However, after I start to try orthotropic floor with trapezium tray deck, the analysis come out about near 30mm deflections on my heavy beams.

I did tried to verify the results by other software as below,

• apply equivalent loadings to a transeverse beam and I got 11mm deflection.
• then one longitudinal beam will pick up two transeverse beam in equal distance.
• after I import two reactions to longitudinal beam I got 12mm deflection for the longi beam.

Therefore, my combined deflection for mid point of transeverse beam is 11+12/3=15mm

This simple analysis suggest previous model was correct.

Is any one can tell me should I trust homogeous plate more or orthotropic floor more?

If the orthotropic floor is correct then both trans and long floor beam have to upgrated to a deeper member.

Right now i got 600mm deep long beam with 40mm flange and 32mm web. Can't really go 800mm as floor height restrictions.

Cheers 

[t.sautierr]

model please