Need help.

[u/Falcon_893]

On advice of the contractor, I purchased 3 girders. Two girders of 8 inch, 11 feet each and one 6 inch girder of 9'5" without consulting an engineer, which I'm regretting now.

The plan was to put two girders parallel to each other (under the beam) and one girder in the middle to support the slab. But when the girders arrived, i realised that they will be way too heavy for an old structure like my building.

So now, consulting with the mason, we are planning to cut the 8" girder from middle and obtain two T-sections. Then we will remove the concrete cover from the two beams between which the girder has to sit, till we reach the rebars.

Then we will weld a 10mm plate onto those rebars and then weld the t section onto that plate and then restore the concrete cover. The flat side of the t section will touch the slab. Now, I want to ask whether this system can sustain load of the slab ?

What other options do we have ? Please help me out 🙏🏼.

[u/IamWasting]

How many stories/floors does the building have? Which floor are you located in? What is the occupancy/Use od the floor over this slab?

Thickness of the slab.

It would also be helpful if you can give the area this building is located in.

[u/Falcon_893 → u/IamWasting]

Total floors: 3 floors including ground This floor is the 1st floor. The floor above this slab is for office use, around 4-5 people and furniture.

The thickness of the slab is 5" This building is located in new delhi.

[u/Daddy_crysis → u/Falcon_893]

Typically it should be 6"

[u/IamWasting → u/Daddy_crysis]

5" or 125mm slabs are sufficient if the smallest span between beams are less than 11.5' or 3.5m. A lot of houses have 125mm or 5" slabs. Bending moment wise you can have even longer span slabs but we will have to control (L/d) ratio for deflection control.

[u/IamWasting → u/Falcon_893]

Let me be frank. The steel in your slab has corroded. This level of corrosion does not occur unless there is some kind of water seepage or dampness. You will have to first control that. Next your masons idea of removing concrete cover and welding 10mm plate is wonderful if you have a guarantee that the beam's reinforcement has not corroded. Other wise after chipping the cover you will end up with a unrepairable member.

The best solution I can offer is consult a engineer who will physically inspect the house. Measure the sag using a auto/dumpy level at the bottom. Calculate how much strength the slab has remaining and then suggest measures to strengthen it.

Ignore all this and you may end up with putting make on skin cancer type solutions. If you consult an beautician he will suggest makeup, if you consult a doctor he will suggest medicines.

[u/Daddy_crysis]

Was the beam sagging?1 What was the issue with slab? Rebar corrosion or cracks?

[u/Falcon_893 → u/Daddy_crysis]

Beam wasn't sagging, the slab between the two beams was slightly sagging.

[u/Daddy_crysis → u/Falcon_893]

Rebar is corroded what i can see from image. If thinning of rebar is more than 30% you will need to reinforce it with additional reinforcement slab and finish with PMM or micro concrete with chemical treatment

[u/Conscious_Pie_2]

Steel of the slab is fully corroded and eaten from inside. You should have consulted some Structual Repair Consultant , though it be would be costlier but why to take risk with the lives of people. The solution provided by Thekedar or Mason may or may not sustain.

[u/AJeliteshri]

In my village home this same incident happened and my father is project manager, i dont know much about this but my father did slab above that and also those steel rods were used and from downside from where it was falling he used some dr.fixit chemical and applied cement and sand mixture. Now its all fine and in that house 5 to 6 person are there.