Platform Live Load Vs Dead Load Calculations
Platform Live Load Vs Dead Load Calculations
(OP)
I would like to pick the brains of you experts out there about the proper calculation method of a support structure for platform.
For discussion purposes, let's say that I have a platform 3' wide x 10' long (19W4, 1" x 1/8" grating) that is simply supported by tube steel at the ends. (Think coffee table)The grating span is reinforced by 5"x3"x1/4" angle, toe-up.
If I was interested in the values of the reaction at each support for base plate design, it would be a simple statics calculation based on the dead weight of all the steel involved.
Now here is where I need clarification:
If the platform is required to handle 100psf of live load, am I supposed to ensure that I factor the additional total 3,000 lbs into the reaction for base plate calculations?
What is the proper method of such calculations to ensure that the live load capacity is always met?
The reason I ask is because in many facilities with platform grating, I noticed that even though the platforms are rated for 100psf or 125psf, the support steel are nowhere close to what they should be if the total live load is factored into the calculations for each base plate.
Thank you in advance for your comments and insight.
For discussion purposes, let's say that I have a platform 3' wide x 10' long (19W4, 1" x 1/8" grating) that is simply supported by tube steel at the ends. (Think coffee table)The grating span is reinforced by 5"x3"x1/4" angle, toe-up.
If I was interested in the values of the reaction at each support for base plate design, it would be a simple statics calculation based on the dead weight of all the steel involved.
Now here is where I need clarification:
If the platform is required to handle 100psf of live load, am I supposed to ensure that I factor the additional total 3,000 lbs into the reaction for base plate calculations?
What is the proper method of such calculations to ensure that the live load capacity is always met?
The reason I ask is because in many facilities with platform grating, I noticed that even though the platforms are rated for 100psf or 125psf, the support steel are nowhere close to what they should be if the total live load is factored into the calculations for each base plate.
Thank you in advance for your comments and insight.






RE: Platform Live Load Vs Dead Load Calculations
You could, however, have grating which is capable of resisting a greater load than required, and in that case the supporting structure need only carry the required load. The selection of grating is often controlled by deflection rather than strength.
RE: Platform Live Load Vs Dead Load Calculations
Does the BOCA National Building Code or IBC contain information showing when and how much to reduce live load reactions?
Thanks for the clarification about the deflection of the grating.
RE: Platform Live Load Vs Dead Load Calculations
RE: Platform Live Load Vs Dead Load Calculations
RE: Platform Live Load Vs Dead Load Calculations
Yes. The reason I'm sure is because the installations are based on customer specifications that require either 100 psf or 125 psf ratings on platforms. Most of these setups are typically for elevated equipment structures or equipment mezzanines if you will. We have concentrated load requirements too and normally that is approached by deflection of L/240 or L/360, etc.
With that said, we normally calculate and size for the dead load but that's what is confusing. Live loads of 100 psf and 125 psf to be used accross the board for platform erection does not make sense because the reactions to the supports would be astronomical especially when the platforms are normally like 30'-0" wide be 60'-0" long.
RE: Platform Live Load Vs Dead Load Calculations
I don't have it on front of me, but it's based on trib area of the member in question and what type of member it is. For example, interior vs. exterior columns are reduced at a different rate.
Be aware that per code you may not reduce the live load if it is over 100 PSF.
I do not know what type of loading is likely on this platform, but I would suggest using your judgment on whether it should be reduced. Remember that a reduction is allowed, not required.
RE: Platform Live Load Vs Dead Load Calculations
I assume you're a mechanical engineer. I strongly suggest that a structural engineer supervise you in the design of your platform. The structural engineer should be proficient in the building code that the platform needs to be designed for.
You don't just design a platform for dead load and live load. You also design them for other applicable loads like wind, earthquake, snow loads, etc. After determining all the applicable loads, you need to apply them in load combinations and load factors as specified in the applicable building code. You then design your platform and other structural components based on the worst load.
RE: Platform Live Load Vs Dead Load Calculations
You're correct. My area is mechanical. However I find my scope spanning across structural issues quite a bit lately.
We normally have a structural engineer to sign off on such designs prior to erection but I normally have to do a preliminary design layout for R.O.M. purposes.
BTW, all these platforms in question are indoors. Therefore, the only other "external" forces other than dead and live loads to consider are earthquake loads.
Thanks for the feedback.
RE: Platform Live Load Vs Dead Load Calculations
RE: Platform Live Load Vs Dead Load Calculations
RE: Platform Live Load Vs Dead Load Calculations
That makes sense as most of these platforms we deal with are strictly for maintenance personnel only.
IFTs - Thanks for your viewpoint. However, in our profession, it's not the point of trying to weasle out of things but taking the best approaches to solutions both from a safety and economical point of view. Besides, based on what I noted before, if it was a 30'-0"W x 120'-0"L platform rated at 125psf, many of the courier commercial buildings do not have concrete slabs that can withstand 22.5kips per reaction assuming I'm using 20 supports over the whole platform. They would either have to add more supports or increase the base plate sizes and both would prove undesirable under normal forklift traffic operations.
Last but not least, I think IFRs has brought up a good point. I think this discussion has gone a little too long but thank you everyone for your very helpful comments.
RE: Platform Live Load Vs Dead Load Calculations