Safety Factor 1

[jjdavis]

Can anyone tell me if there is a recommended safety factor for design of mezzanines? It is a mezzanine for equipment, so people are not normally on top, but people will be working underneath.

We purchased the mezzanine as a part of a whole package of equipment. We are concerned with the structural integrity of the mezzanine and are trying to get the vendor to brace the structure. I would like to tell them a safety factor of 2, but I wanted to check if there was something better to reference that would back me up.

Thanks.

 

[ishvaaag]

If the dynamical effects are scarce you can go on 1.35 on Dead Load + Superimposed Dead Load and 1.6 times for the live loads. Or check suitable factors and procedures in the governing code, maybe AISC 360-10 or 05. If it seems flimsy check also if limits to deflection, both lateral and vertical look OK. Contemplate material and geometrical nonlinear efects. In any case should be rare not to to furnish something valid that goes with standard equipment, but who knows.

 

[JAE]

Mezzanines fall under the same design criteria that a typical floor would in terms of required live load capacity and design safety factors. If steel - then AISC would apply in the US, for example.

 

[JedClampett]

Factors of safety are somewhat nebulous. For instance, the standard F.S. for steel is 1.6 vs. yield. But yield is not failure, it's a deformation property. And everyone knows that the material properties usually exceed the design values used. Same with concrete, but with different numbers. So a factor of safety of 2 might be appropriate vs. a gradual failure that gives plenty of warning but not against a "Oh my god, the building is falling down.."
I would require that they design it to whatever code applies in your jurisdiction and not define a F. S.

 

[ishvaaag]

Not to forget that even if the stated safety factors above are what normal for buildings, for particular items or details -even in such codes- subject to fatigue, wear, dynamic action the apparent safety factor on the uncorrected basic capacities of the materials would show to be far bigger, i.e., only low working stresses (relative to the nominal capacity) would be permitted.

So this is why to find an appropriate guide or code for the contraption is paramount, since it will keep you tight to a path of safety, economy, and good practice.

 

[BAretired]

JAE is absolutely correct. The factor of safety is the same for a mezzanine floor as it would be for any other floor or roof. Guidance for analysis may be found in your local building code. A safety factor of 2 would seem to be conservative but not unreasonable, so go with it.

BA

 

[JAE]

The only problem with vendor created mezzanines is that many times they use very unique shapes and non-typical metals in their product. Makes it hard for the structural engineer (that you should hire) to evaluate.

 

[JLNJ]

If you are in the USA, determine the actual use live load and compare that to the code-required minimum live load. Once the vendor knows the live load and the State you are in he should be able to provide the appropriate mezzanine design.

If a vendor insists that you provide a "factor of safety" for a structural item like a mezzanine then go find yourself a different vendor. Machine designers might use "factor of safety" terminology but structural engineers (generally) do not.

Now, if you know your required minimum live load is 100 psf then it is you perogotive at that point to add a factor of safety if you wish and ask for the mezzanine to be designed for, say, 200 psf instead.

 

[BAretired]

Live load for equipment storage can be quite variable. Shelves with small parts like nuts and bolts stacked in racks can be extremely heavy and should be stored at ground level, not a mezzanine. If you have similar storage elsewhere in your shop, it would be prudent to check the actual weight of the stored items to get a rough idea of live load. The minimum live load you should consider is 100 psf but that may not be sufficient in your case.

BA

 

[jjdavis]

Thanks for all the info. Yes, in the US. I found a reference of IBC 2006, ASCE 7-05, and 9th Edition ASD AISC Steel Construction Manual that a co-worker found on a mezzanine vendor website. I'm guessing that this is correct?

A little more info. The equipment is already in house and there is already deflection in the support beams, so this is a situation where we are trying to get the vendor to correct the issue.

Calculating the load for one of the heavier pieces of equipment, it would be 182 psf.

 

[graybeach]

We recently dealt with Portafab, a fabricator of mezzanines and in-plant offices. They had engineers on staff who designed based on the loading criteria we provided, and they provided PE sealed drawings which we needed to get a certificate of occupancy. The engineers were very competent and easy to deal with.

It could be that your equipment vendor did not specify the correct loading to the mezzanine fabricator. You could probably find out what the mezzanine fabricator designed for and compare that to the weight of the equipment.