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Live Load Reduction based on common sense

Live Load Reduction based on common sense

Live Load Reduction based on common sense

(OP)
I have a 10'x33' platform for pipeline valve. This valve will only be maintained once a year by most likely 3 people.
I was thinking of using 10 people x 200 lbs + another 10 x 200 for whatever they will be carrying for maintenance = 4000 lbs.

As opposed to 100 psf x 10 x 33 = 33000 lbs x reduction factor (20%?) = 26400 lbs.

I don't have issues with the platform structure design. I can use full 100psf for that.
But the timber pile/foundation, I want to use "common sense" live load.
Is there anywhere in ASCE/IBC I can do this for industrial platform?

RE: Live Load Reduction based on common sense

Neither ASCE nor IBC allows "common sense." There are several reasons:
- "Common sense" is not common
- You can't check calculations for compliance with "common sense"
- Local building officials need to be able to review your design
- If something fails or gets abused, you will have to convince lawyers that you used "common sense" while another "expert" is telling everyone that you didn't use "common sense."

PS - this was meant to be somewhat "tongue in cheek", but I'm pretty sure you want to keep to the minimum Live Loads listed. Maybe consider this a catwalk and sharpen your pencil regarding the equipment load.

If you want to talk this over with your client, the building official and post a load restriction on the platform, that might be a workable solution.

RE: Live Load Reduction based on common sense

Industrial structures that are not open to the public are not generally required to be designed to the same live loading standard that buildings and ASCE-7 would specify.

That being said, I have a couple of quick / additional thoughts:
a) What happens when those three workers bring up equipment with them? How much does their equipment weigh?
b) What happens when valves or sections of the pipe need to be replaced or repaired. You can have heavy sections of pipe resting of the platform for long periods of time. Akin to roof live load where the load you're concerned about is often a re-roofing construction load rather than a true live load.
c) It's not just the total load that's important, it's the concentration of load. Yes, the structure doesn't need to be designed for 26000 lbs. But, the 100psf would be much more reasonable design load over a smaller sub-section of the platform.

Personally, I might not use the 100psf that you'd have for a public corridor (because it's not open to the public). But, I would definitely design it for more than the 12 psf that you're talking about.

Large industrial companies will often have their own company standards for things of this nature. Looking through an old project of mine I found the following spec for live load:

Platform Framing = 100 psf
for column or foundations = 50 psf
Personnel Access Platforms and walkways = 60 psf
Stairs and Ramps = 100psf

RE: Live Load Reduction based on common sense

Wouldn't this be considered "Walkways and Elevated Platforms?" Therefore LL = 60 PSF?

DaveAtkins

RE: Live Load Reduction based on common sense

(OP)
Pipe and valve weight are dead load. I will include that without reduction.

RE: Live Load Reduction based on common sense

You could shrink the platform, 10x33 is awfully big for valve access. But if it's there, they will use it for something, and probably that something weighs a lot more than 12 psf.

RE: Live Load Reduction based on common sense

I wouldn't be using building code provisions for this. The issue isn't really even people, it's that as soon as you put a platform in an industrial location someone is going to try and use it for storage or will throw a bunch of equipment on it while doing maintenance or something else similar.

Personally, except in one absolutely ridiculously oversized platform, I've never done a live load reduction on an industrial platform. If anything, you're more likely to see the full rating on a column because when it's full a bunch of the load could be from a pile of equipment that they could put anywhere. I've seen too many piles of pipes on platforms to get cute about it. The cost is usually negligible, as well. Also, your influence zone is normally pretty small on a platform... are you sure you even have the area required to do live load reduction?

100psf is typical for industrial platforms for most major industrial companies I've done work for. 50psf is used on occasion. PIP suggests 75psf (and also specifically allows live load reduction as per ASCE 7). If the client has standards, look at those. Also check your local OHS requirements for an absolute minimum.

ASCE allows 40psf for "Catwalks for maintenance access," but somewhere where a person would actually stand to do significant work would not, in my opinion, usually be considered a catwalk for maintenance access in an industrial scenario.

To be more helpful, consider the fact that if your foundation is something that would fail via settlement, you have a lot of leeway for judgement. You're talking short term loads and even if you assume a reasonably high area loading on the platform, it's probably actually pretty small soil pressures. You also may not really be sensitive to settlement. Maybe talk to your geotech.

Check with the company's standards first, then have a conversation with the client about how you want to build this thing and what they expect from it. Record whatever decision you come to. Communicate it in terms of what types of operations that can perform on the platform and what type of robustness they have, not a quantified load rating. Help them with this conversation, because at first go you'll often have people say "yeah, it's just two dudes," but then you go into more depth and realize there are other things that could be happening up there. You don't necessarily have to follow the building code, but it is good practice and /could/ be considered the standard of care. You definitely do have to follow any workplace safety regs or legislation, along with any client standards. You also have to record whatever your design basis actually is and, if you're concerned about misuse, post a notice on the platform itself.

Personally, if it's not a pretty significant cost impact I'd stick with a conventional loading. You rarely go wrong by designing industrial structures for robustness.

RE: Live Load Reduction based on common sense

ASCE 37 would use 75psf for working surfaces for heavy duty construction. 100 psf is also not uncommon in bridge construction. Reductions only after 400ft^2.

We also have cases in construction where the live load can be limited to a certain number of workers at 250lbs/ea (with tools, not including materials) if that limit is posted with signs at all entrances to the limited region. I'd also include some uniform load with that condition.

RE: Live Load Reduction based on common sense

Talk to the operations people at the client who will actually use this platform - not just the project team.

As a user of such things, anything that has a 'special' restriction on it will make you unpopular. A one-off saving would have to be fairly spectacular to justify the long term inconvenience of a 'No more than 10 people on the platform restriction' for the lifetime of the pipeline.
  • Want to erect a scaffold? No, that's X's platform, you can't.
  • Valve leaking and Furmanite are on site to save the day with their magic box of tricks? Not allowed because no-one can figure out the loading at 3am on a weekend, blame X.
  • Or, the ultimate career killer, a 10' x 33' platform looks like a great place to take a project completion photo for the visiting big boss and the whole team, so one of us has to tell him that the platform isn't designed for the weight of the number of people who can fit on it.
Matt

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