SLAB ON GRADE

[AKRAMCRANE]

I HAVE A JIB CRANE, 1 TON, SPAN 16 FT THE CUSTOMER WOULD LIKE TO PLACE IT ON A SLAB ON GRADE 10" ANY ONE HAS IDEA OF A DESIGN PROCEDURE ON VERIFYING THAT THE CONCRETE WILL TAKE THAT LOAD

 

[fattdad]

step 1: Hire an engineer.

f-d

¡papá gordo ain’t no madre flaca!

 

[fattdad]

(o.k. I could try to help, eh?)

You really need the subgrade modulus. Typically, I correlate subgrade modulus to soaked CBR value. So, I'd eitehr do a CBR test (compacted to 95 percent Standard Proctor) or use local knowledge to estimate subgrade modulus and then I'd turn the project over to our structural engineer. It seems you have the loading figured out, so now it's just a straightforward slab-on-grade design, it seems to me. Then again, I'm a geotechnical engineer. . .

f-d

¡papá gordo ain’t no madre flaca!

 

[hokie66]

Sorry to disagree slightly with my friend and fellow Hokie, but this is about the slab, not the subgrade. A 10" slab may or may not be an adequate footing for the jib crane described. It all depends on the reinforcement in the slab. I would not consider it unless the slab is reinforced top and bottom, and further that I had confidence that the reinforcement was placed as designed. This being the case, the slab could be analyzed for the load case, primarily the bending moment imposed by the loaded jib. So back to fattdad's Step 1: Hire a structural engineer.

 

[oneintheeye]

use appropriate steps that any structural engineer would use to verify or not. If you dont know how to do this find someone who does or ask for help from an suitably qualified collegue. To ask such a general question on here is not the way forward as there are so many things to consider. To consider them needs a lot more facts than you have provided.

 

[bimr]

The manufacturer of your jib crane should have provided you with an installation manual. Your installation manual for the jib crane will have installation details.

A link for a typical manual is listed below:

https://www.gorbel.com/resources/products/jibcranes/workstation/documents/workstationjib.pdf

One would expect that you would have to replace the floor with a foundation.

Consult a structural engineer if you deviate from the recommended installation guidelines.

Test the crane after installation and periodically afterward per the manufacturer's instructions.

 

[neaveyoung]

May be you can consider the original live load on this slab. Then suggest you to place the steel plate at least 16mm thick on your working crane and this will spread the loading on the rc slab. But be sure spreading of the loading must same or smaller than the original live load.

 

[hokie66]

neaveyoung,
When you contribute to an old thread, you should at least have something constructive to add. The original design live load has very little to do with this problem. The bending of the slab is the issue.

 

[parrot77]

hokie 66 what neaveyoung was suggesting was the origional live load could be examined to see if the new crane loading exceeds the design value. unless the floor is designed for large industrail raking/ forklift loading it is likely that the design load will be exceeded. Hokie66 who made you forum king who decides what is constructive? Ground bearing slabs can be designed as unreinforced, utilising the charactoristic tensile stenght of the concrete. for a point load the slab may be designed using yield line theory for point/patch loads as set out by Westergaard or Meyerhof

 

[parrot77]

I have successfully designed (but never checked existing slab) using similar methods as per the method attached.

 

[parrot77]

pg2

 

[parrot77]

pg1

 

[hokie66]

parrot77,
The problem with your (and neaveyoung's) suggestion is that this a jib crane which does not just impose a point load, but also more importantly a concentrated bending moment. The 1 ton load is hung at the end of a 16' jib boom, so imposes a sizeable bending moment. Whether or not the slab will tolerate this bending has little to do with the live load capacity of the slab.

 

[BAretired]

So what we have is a point load and moment on a slab on an elastic foundation. We need the subgrade modulus as stated earlier by fattdad. The analysis is not going to be a piece of cake either.

BA

 

[BAretired]

Do we all get to vote for forum king?

BA

 

[hokie66]

If the OP is still interested, this same problem has been debated in:
thread507-275056.