5 ton forklift on 8" slab 3

[CDLD]

Good morning,

I am checking a 5-ton forklift on a 8” slab cast on a 3” metal deck (formwork only).

By a strict read of the code (ACI 318-19), concentrated loads located close to the support (<d) have a critical section located at the face of the support for one-way shear.

By locating the front axle directly adjacent to the support (ie. 2” to the center of wheel), I get a very small effective width (using “French distribution method”), which seems overly punishing.

Where should I locate the front axle relative to the support to achieve reasonable results?

I was reading these articles:Link Link, and it seems that the most critical position occurs when the front axle is clear from the support by 2*d (due to arching), however these articles are tailored to Eurocode and I’m not sure if its appropriate to use with ACI (cl. 7.4.3).

Thank you.

 

[CDLD]

Thanks Floatsam for the input.
When you check one way shear, where do you place your load relative to the support?

The load spreading method you mentioned is apparently called the "French Method" and it correlates well with test results when the load is close to a support.

 

[Flotsam7018]

Ha! Sorry CDLD, I see now that is really the question you've been asking throughout the whole thread. I have typically just considered the front edge of the tire "d" from the support which for standard truck loads and tire sizes often works out well for an 8" slab to work as others have mentioned. I see for your case, with a higher point load and smaller contact area you'd need a 12" slab give or take when considering this distance from the support. Now you'd have to judge whether further refining for 4" less of concrete is worth it for the particular project.

If it was worth it - I would likely dive down a strut and tie model to determine the maximum strut angle greater than the minimum 25° in which I could get those numbers to work and use that associated angle to determine the effective width.

 

[CDLD]

Thanks Flotsam, I think you are bang on with your approach.
I may push the load closer to 2*d clear from support and see how the numbers look (this is the approach in Europe). I suspect a thicker slab will be required as the shear capacity in ACI 318-19 has been reduced quite significantly from the previous code.

I think 2*d gives slightly shallower struts than 25 degrees, so I may bring the load in a little closer to comply with that if needed.

 

[Flotsam7018]

I'm seriously dreading the anticipated volume of complaints for every footing/slab/wall I'll get once my jurisdiction finally updates to IBC '21.