Placing concrete slab over an existing Roof
Placing concrete slab over an existing Roof
(OP)
Hi,
Please guide me about the adverse effects of placing a slab on existing Roof Arrangement . Both top(250mm thk) & bottom (400mm thk) slabs are having 16 dia rebars @150 mm spacing. This modified slab will be used for crane access (operating load 300tons). The crane is of All terrain type with Outriggers.A bonding agent Concresive 1414 or equivalent shall be applied at the interface of two surfaces.
Please guide me about the adverse effects of placing a slab on existing Roof Arrangement . Both top(250mm thk) & bottom (400mm thk) slabs are having 16 dia rebars @150 mm spacing. This modified slab will be used for crane access (operating load 300tons). The crane is of All terrain type with Outriggers.A bonding agent Concresive 1414 or equivalent shall be applied at the interface of two surfaces.






RE: Placing concrete slab over an existing Roof
Seriously, your structural engineer should be evaluating this design. An internet forum is good for ideas, but not for evaluating a structural design sketchily described.
RE: Placing concrete slab over an existing Roof
RE: Placing concrete slab over an existing Roof
Proof that outrigger loads are not to be ignored.
Mike McCann, PE, SE (WA)
RE: Placing concrete slab over an existing Roof
1) Your existing slab will need to be able to handle the wet weight of the new slab in terms of both flexure and punching shear. Of course, a 400 thick slab is pretty darn sturdy.
2) If you need the two slabs to act compositely in order to make a go of things, take great care to convince yourself that what you're constructing will truly behave as a composite slab, for both bending and punching shear.
3) Obviously, columns and footings need to be able to handle the new load.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Placing concrete slab over an existing Roof
RE: Placing concrete slab over an existing Roof
That is still well short of the information needed by your structural engineer to assess the proposed structure.
RE: Placing concrete slab over an existing Roof
Basically we are checking span moment, shear & support moment, shear due to the self weight of crane, counter weight & lifting weight. Dead load of concrete & a live load of 13.5 kN/m2 is considered apart from this. 11m x 13m is the overall size of slab.
RE: Placing concrete slab over an existing Roof
The outrigger load is the load that matters, not so much the total weight of the crane and load being picked. You can estimate the outrigger load, or better yet get it from the crane provider.
RE: Placing concrete slab over an existing Roof