change of bending moments in RC slab 2

[kjG87]

hi, this is really not my area but i want to know about this one...
PICTURE 1 - slab is supported on 4 masonry walls.
PICTURE 2 - we remove one wall under existing slab and we made RC beam instead.

my question - do bending moments in existing slab change because we remove a bearing wall even tho we replaced it with a RC beam?

are bending moments of slab depending on a stiffness of a RC beam?

Since masonry wall is far more stiff in vertical direction than a RC beam (deflection) I think there might be larger bending moments (tension in lower zone of a slab) because of this? Or am I wrong?

 

[JAE]

If the beam is a wet noodle, moments in the slab will change.
If the beam is infinitely rigid, moments in the slab will change very little.

You are probably somewhere in between these two. So yes, it does depend on the rigidity of the beam...and also to some extent the relative beam-slab values of rigidity.

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[atrizzy]

CSA has a definition of 'stiff beam' that it allows to use, if (beam width)*(beam depth)^3 / (beam span)*(slab depth)^3 >+ 2.0, it counts as 'stiff'. If it's less than 2, consider more moment in your slab than currently exists. Or just design the depth of your beam to meet the above criteria.

 

[dik]

JAE: and the beam will be stiffer than the wall...

About 35 years ago, my wife and I were looking at a new stove and were 'pounced upon' by a salesguy... We were informed that the stove had infinite temperature control... to which I replied that if I were to live forever, I would never be able to appreciate that function... I think the guy is still scratching his head...

Dik