Reinforcing a Waffle Slab

[amgh]

I have an existing hospital that is trying to locate its radiological film storage. Building is a concrete building with waffle slab and drop panels at columns. I do have extensive exsiting drawings.

The original floor was designed for 500 psf for the film storage. The area they have picked to relocate the storage to was designed for 100 psf. I have verified that the slab is good for 150psf at most.

We do not have alot of experience reinforcing waffle slabs at my firm.

Is there anyone out there that has experience reinforcing waffle slabs?

 

[JAE]

The sledge hammer approach would be to add new steel beams in a grid and attached to the existing concrete columns. Design the beams to support 100% of the live load of the storage plus some consideration for creep in the two-way system, perhaps 20% to 30% of the dead load of the waffle system.

The beams can be installed with adhesive anchors into the column with a steel plate or other connection system to then attach to the steel beams. The beams should be grouted tight to the undersides of the waffle system.

Take care to align the anchors relative to the column reinforcing steel inside. You might want to detail the connection to allow some tolerance in the vertical positioning of the anchors due to uncertain column tie locations. Non-destructive testing prior to anchor drilling is preferred to locate ties and vertical bars.

Check for fireproofing the steel as well - probably is required.

 

[tincan]

The CRSI (Concrete Reinforcing Steel Institute)design handbooks based on the ACI code would be a starting point.
CRSI Chicago, Ill

Best Tincan

 

[DTGT2002]

I would suggest a consulting engineer that does have experience in the area of which you plan to design.

There are many options, on of which could be adding additional columns to levels below and topping the slab - with concrete or steel.

The problem is very dependent on the situation and the final answer that will do the least harm.

Good luck!

Daniel Toon