Adding new support (beam) under existing RC slab?

[mats12]

Greeting,

I'm dealing with an existing residental building with masonry walls and RC slabs.
I figured there is a bearing wall in the middle of the slab span - load from this wall acting on a slab is pretty large.
Slab is only 140 mm thick and is not sufficient for current standards.

What can be done there?
Putting a RC/steel beam under existing slab will change bending and shear moments in the slab since we go from simply supported to continous beam.
I'm not concerned about bottom reinforcement in the slab but there is no reinforcement in the middle of the slab (the top zone) where is needed if I add a beam.
There will be some cracking at the top of the slab resulting enlarged bending moments in left and right field.
I'm not sure whats the proper way to solve this.

Hoping for some suggestions.

Tnx

 

[Tomfh]

Why are you adding the beam? Is the structure being altered? Does the slab currently span across as you’ve shown?

 

[MIStructE_IRE]

Just allow the top of the slab to crack (or saw cut it to show it where to crack) and you have 2 simply supported spans. The bottom steel in each is surely adequate if it has been spanning the full length all this time.

I’d go for a steel beam. Light and easy to install. You’ll never pour insitu concrete in there anyway and precast would be unnecessarily heavy.

 

[mats12]

Tnx for help. But saw cuts have to be done on both sides of existing bearing wall since it cant be made in the middle?

 

[r13]

Turn the steel beam 90°, make continuous spans across the length of the building, then saw cut joint above the beams.

 

[LittleInch]

You haven't said why you're doing this. If there is no sign of distress, what's the point?

The wall look to be more like a weight - that top slab will flex the same amount as the bottom slab surely?

What's the other dimension? i.e. into the page.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[mats12]

I'm doing this because attic space wont be unused any longer plus screed on existing slabs,...
Therefore load on first existing RC slab will be increased and my calculations says that 140 mm thick slab is not sufficient.

This is the plane view:

 

[Tomfh]

That plan suggests the slab is spanning the other way?

140 slab can’t span 9m

 

[MSUK90]

Besides others views, how that steel beam is going to be supported?
The whole structure is bearing wall system?
I think the connection design and the ability of the connected members to carry the load from steel beam also plays a role here..

 

[MSUK90]

That plan suggests the slab is spanning the other way?

140 slab can’t span 9m

You are right. The reinforcing and its direction and location needs to be known..