Casting New Slab in Existing Building

[Zizoui10]

Hello, my fellow engineers

I have questions

I am dealing with an issue of casting a concrete slab (22cm thick) in an existing building (attached picture for explanation)

I proposed to add a steel system, but the client refused and insisted on making the whole system as concrete

the old slab thickness is 22cm as well.
I am thinking of adding dowels to connect the slabs together (how to calculate the embedment depth of the dowels?)
Also how to make dowels in beams knowing that the beam is just 20cm in width (I don't think there is enough length of embedment)

Notes:
1- This is a multi-story building, and the slab is to be casted in all floors above.
2- There are existing beams all around except for the bottom left corner
3- The slab dimension is 4m x 6m
4- The load to be applied is (7.5 kN/m2 as DL + own weight) and 3.5 kN/m2 as LL)

Thank you

 

[Zizoui10]

in case the picture not shown

 

[jhnblgr]

What’s the point of the new slab, that’s a lot of dead load

 

[Zizoui10]

What’s the point of the new slab, that’s a lot of dead load

if you mean the purpose, it is a family hall and used to hold parties and gatherings
it is a cultural thing.

 

[XR250]

Sounds like a youtube video in the making. That is a lot of weight/mass to add to a building.

 

[jhnblgr]

I think there is a language barrier here.

The building is existing and there is an existing floor slab on each level?

You are adding a floor slab on top of each level? Or are you demolishing the existing floor slab and floor beams prior and replacing them?

Why is there a new floor slab being added? Is the existing one failing?

 

[HTURKAK]

I proposed to add a steel system,

-Are the RHS's 80X40X4 and IPE 100 beams the proposed steel system?
- If the existing one is RC slab having thk .22 cm, what is the reason to add alot of weight with new 22 cm slab overlay?
This is alot of weight and you need to do structural calculation for the slab and overall structure.

 

[Zizoui10]

I think there is a language barrier here.

The building is existing and there is an existing floor slab on each level?

You are adding a floor slab on top of each level? Or are you demolishing the existing floor slab and floor beams prior and replacing them?

Why is there a new floor slab being added? Is the existing one failing?

English is not my first language, so I apologize if I am not being clear, but I will do my best.

the building is multi-story with the clouded area as a void in all levels (the attached is a part of the full plan)

the clouded area is originally a void, and the client wants to fill this void with a concrete slab

I proposed a steel system to support, but the client rejected the proposal

 

[jhnblgr]

So this is just an open shaft currently that you are designing a floor for. The adjacent rooms have concrete slab that you plan to match elevations. So the issue is the load transfer from the slab to the existing beams. Could you though bolt a steel angle for a ledge for the slab and transfer the load that way.

 

[jayrod12]

Still feels like you're double counting dead loads. 7.5 kN/m^2 is more than the weight of the 220mm thick concrete slab. I'd be inclined to think that the 7.5 should be inclusive of self weight of slab, plus finishes on top, plus M&E hanging allowance. The slab itself weighs around 5.5 kN/m^2, the additional 2 kN/m^2 is a hefty allowance for finishes and M&E in a typical building. I've only seen that level of additional allowance on manufacturing facilities.

 

[Greenalleycat]

Still feels like you're double counting dead loads. 7.5 kN/m^2 is more than the weight of the 220mm thick concrete slab. I'd be inclined to think that the 7.5 should be inclusive of self weight of slab, plus finishes on top, plus M&E hanging allowance. The slab itself weighs around 5.5 kN/m^2, the additional 2 kN/m^2 is a hefty allowance for finishes and M&E in a typical building. I've only seen that level of additional allowance on manufacturing facilities.

The loads are strange, 3.5kPa seems low for a dancing/party area - it's 5kPa in our code

 

[jayrod12]

The loads are strange, 3.5kPa seems low for a dancing/party area - it's 5kPa in our code

Agreed, they're the same here.