How to determine casted slab can take the vehicle load?
How to determine casted slab can take the vehicle load?
(OP)
Recently we are planning to park a mobile crane on the casted rc slab. But how we can check / determine if the rc slab can taking this load? I'm trying to check the deflection and punching shear on rc slab. Is these checking enought to determine the slab can taking the load? Thanks for advice.






RE: How to determine casted slab can take the vehicle load?
If the slab has been there awhile but unintended for crane loading, then you'll need to verify the compressive strength of the concrete and reinforcing. If it is a slab on grade you'll need the subgrade modulus too.
Then you'll need to verify the loading. Will the crane be supported by outriggers entirely or share loading with rubber tires. Or is the crane a track type?
Depending on your familiarity with various software you can develop a model of this or use theory of plates to solve. There are a lot of stress tables/charts for point loaded slabs (if you have outriggers) but the uniform line load may be a tad more difficult. I would think it's in Roarks Book of Stress/Strain.
If there are outriggers then chances are you will have quite a bit of dunnage under each rigger to distribute the load out over a larger area of concrete. This will help prevent punching shear. Deflection will be dependent on the subgrade, loading and flexural rigidity of the plate/slab.
Regards,
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Qshake
Eng-Tips Forums:Real Solutions for Real Problems Really Quick.
RE: How to determine casted slab can take the vehicle load?
If you are in doubt as to how to proceed, get an experienced engineer to check it for you. Note that there have been many failures of concrete slabs supporting mobile cranes.
BA
RE: How to determine casted slab can take the vehicle load?
BA
RE: How to determine casted slab can take the vehicle load?
Regards,
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Qshake
Eng-Tips Forums:Real Solutions for Real Problems Really Quick.
RE: How to determine casted slab can take the vehicle load?
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: How to determine casted slab can take the vehicle load?
Regards,
![[pipe] pipe](https://www.tipmaster.com/images/pipe.gif)
Qshake
Eng-Tips Forums:Real Solutions for Real Problems Really Quick.
RE: How to determine casted slab can take the vehicle load?
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BA
RE: How to determine casted slab can take the vehicle load?
The suspended slab was casted more then 3 months ago and had achieved the required concrete compressive strength.The crane have outriggers. But base on the crane loading i have check and assume the outriggers will park on the middle on span, then it must required at least 1700mm2 main reinforcement. So could i say that the slab have 2 layers main reinforcement T13-100 and the rebar provide is 1330mm2 x 2 = 2660 mm2? Enclosed the slab details.
Thanks.
RE: How to determine casted slab can take the vehicle load?
RE: How to determine casted slab can take the vehicle load?
RE: How to determine casted slab can take the vehicle load?
I come from an era where FEM was not the panacea and the design can be checked using by relatively simple analysis unless the column spacing is pretty wierd...
I didn't look at the info provided, but a 12" slab spanning 15', if there's any continuity, is pretty robust; you still have to 'do the sums...'
Dik
RE: How to determine casted slab can take the vehicle load?
The outrigger load is about 100KN each. I don't have any FE software to analysed.
RE: How to determine casted slab can take the vehicle load?
RE: How to determine casted slab can take the vehicle load?
RE: How to determine casted slab can take the vehicle load?
As noted previously you should not be assuming anything.
Any method, Roark's or FEA or even peer review should be used in tandem to provide a check on each method.
The outriggers typically are shored up using mats of 4x4 or 6x6 timbers specifically for spreading load out and avoiding punching shear failure.
Also contractors like to use larger safety factors to ensure they are not going to have a failure such as posted by BAretired. Short of that failure contractor's don't want to be liable for cracks in slabs either. So be conservative.
Regards,
![[pipe] pipe](https://www.tipmaster.com/images/pipe.gif)
Qshake
Eng-Tips Forums:Real Solutions for Real Problems Really Quick.
RE: How to determine casted slab can take the vehicle load?
RE: How to determine casted slab can take the vehicle load?
Wind forces can alter the crane reactions substantially. They can act in any direction and cannot be ignored. Here are a few links to the subject of wind on mobile cranes.
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If the slab thickness is 250 mm as shown on your sketch, it is 10", not 12" as earlier stated. I agree with hokie and Qshake that you cannot assume anything. This is not a job for amateurs, but if you decide to tackle it yourself, make sure that your professional liability is paid up.
BA
RE: How to determine casted slab can take the vehicle load?
Regards,
![[pipe] pipe](https://www.tipmaster.com/images/pipe.gif)
Qshake
Eng-Tips Forums:Real Solutions for Real Problems Really Quick.
RE: How to determine casted slab can take the vehicle load?
RE: How to determine casted slab can take the vehicle load?
RE: How to determine casted slab can take the vehicle load?
BA