Concealed Beam

[ALK2415]

Dear Friends,
This question came through friend, asking for information about ACI (if any) related to slab concealed (hidden) beam ?
What's your professional opinion about its structural effectiveness ?
Are they widely used or only when its last resort ?

 

[HTURKAK]

-ACI specify flat slab without beams. Flat slabs (joist slab with infill material ) is common at some countries ( Eurozone etc)


I do not see that , it is effective . Atleast you will get unnecessary heavy slab . Designing flat slab without beams is better alternative for non seismic zones. What about seismicity ?


This method could be local practice . Apparently not efficient design. Will you post the full structural plan ? Apparently some beams curved at plan.



Use it up, wear it out;
Make it do, or do without.

NEW ENGLAND MAXIM

 

[ALK2415]

Thanks HTURKAK,
Iam on your side, not effective since the steel reinforcement couple ( C & T = As*d) which is very limited (8" = 200mm slab thickness ----> 160mm)
But some civil engineers (around my location), insist on adding them when they had brick wall (3m height with 24cm thick) on top of flat slab (without beams).
and sorry don't have the full house plan, it should be 6-7 meters max span length
the area has low seismic events.

 

[JAE]

I've seen many....uh, many...flat slabs with interior (hidden) beams over the years.
The added reinforcement is usually only longitudinal bars (not ties/stirrups like shown in the photos).
It's also part of ACI's two-way flat slab design methodology (column strips).

If the strength is then provided by the hidden beams, a remaining concern would be the stiffness of the slab/beam system with respect to deflection control.

Yes there's some added weight (more rebar per volume of concrete) but not that significant.