Reinforcing existing suspended floor for new equipment
Reinforcing existing suspended floor for new equipment
(OP)
I have an existing suspended 12” reinforced concrete ground floor slab (basement below) in an industrial building. This slab will need to support new equipment that will apply a uniform pressure on the floor exceeding the original floor design load of 250psf. These are large equipment with weights exceeding 50,000 lbs.
I am evaluating several options for reinforcing the existing floor. One option is to build a “drop panel” under the existing ground floor with a plan size to match the new equipment. The “drop panel” would be a 12” thick slab supported on steel beams that are supported on steel posts. The steel posts would be supported by micropiles at basement level.
The slab would be tight against the existing slab. There would be ties connecting the existing slab to the new slab and the surface between the two slabs would be roughened and a bonding agent would be applied. The effects of stress redistribution on the existing slab and girders would be considered.
Is this a practical approach to reinforcing the existing floor? What are some constructability issues that may arise? Any alternatives?
I am evaluating several options for reinforcing the existing floor. One option is to build a “drop panel” under the existing ground floor with a plan size to match the new equipment. The “drop panel” would be a 12” thick slab supported on steel beams that are supported on steel posts. The steel posts would be supported by micropiles at basement level.
The slab would be tight against the existing slab. There would be ties connecting the existing slab to the new slab and the surface between the two slabs would be roughened and a bonding agent would be applied. The effects of stress redistribution on the existing slab and girders would be considered.
Is this a practical approach to reinforcing the existing floor? What are some constructability issues that may arise? Any alternatives?






RE: Reinforcing existing suspended floor for new equipment
RE: Reinforcing existing suspended floor for new equipment
RE: Reinforcing existing suspended floor for new equipment
RE: Reinforcing existing suspended floor for new equipment
RE: Reinforcing existing suspended floor for new equipment
RE: Reinforcing existing suspended floor for new equipment
RE: Reinforcing existing suspended floor for new equipment
You can assure some load transfer by jacking the new steel system up into the existing slab. Further contact can be obtained by using short, simply supported spans for the new basement steel system. Does the existing slab have a decent amount of top reinforcement? If yes, you can jack the new supports up and put negative bending on the old slab. Trying to get a new system to uniformly support an old system is a balancing act that I'd shy away from. Full demo should still be on the table.
RE: Reinforcing existing suspended floor for new equipment
I don't think anyone is suggesting a steel plate under the entire footprint. But if you install new columns under the equipment, and possibly steel beams between these columns, I think it probable that a 12" slab originally designed for 250 PSF live load would be capable of distributing the loads to the new structural steel.
But have you actually checked the capacity of the slab for the new loading? If your slab is designed for 250 PSF, and you have some new areas above 350 PSF, that does not automatically mean the slab is not strong enough. It depends on how much of the area is loaded, and would require new analysis to determine adequacy or otherwise.