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Loading Tables for Roof

Loading Tables for Roof

Loading Tables for Roof

(OP)
Loading Table for Roof (PSF)
Purlin Spacing 2' 3.5' 4'
Due to Stress 800 368 280
Due to L/360 1700 500 340
Due to L/240 1900 560 380

I need help on how to understand this loading tables.
Thanks

RE: Loading Tables for Roof

Source? What you're posting looks like huge capacities... Is this an old (unfactored) asd table?

RE: Loading Tables for Roof

For an infinite span? odd that from 2' o.c. to 3.5 the capacity drops so much given the span (presumably) is maintained. they are probably factored loads like one would see in open-web bar joists ASD.

RE: Loading Tables for Roof

The load numbers make no sense since the load is a linear function in the formulas and the loads shown are decreased non-linearly.

Throw your reference away!

Mike McCann
MMC Engineering

RE: Loading Tables for Roof

(OP)
Thanks for your prompt response.

This source came from roof supplier not from ASD table.

I think I just got what I need. So, these load numbers are capacity or maximum allowable psf the roof can carry at a given purlin spacing. Pls correct me if I'm wrong.

I also recheck the technical properties and I dont know why there is a sudden drop of values from 2' to 3.5' purlin spacing.

Anyway many thanks to all!

RE: Loading Tables for Roof

Post a copy of the whole table, like others have said those loads make no sense. For most purposes 20psf is your max roof live load (not including snow).

RE: Loading Tables for Roof

Yes, the "sudden drop of values from 2' to 3.5' " is likely do to the purlin breaking. As msquared said above, the table does not make any sense.

Your statement "these load numbers are capacity or maximum allowable psf the roof can carry at a given purlin spacing " makes even less sense if that is possible. So if the first made no sense and this makes less sense the, we have negative sense going on here.

"Pls correct me if I'm wrong." You are wrong.

The only thing making any sense here is "This source came from roof supplier not from ASD table." Some one is trying to sell you something. Don't buy it until you have an engineers review as a2mfk said.

RE: Loading Tables for Roof

Who is the supplier? I could use some of the those purlins with the 1900psf rating for my bomb shelter.

RE: Loading Tables for Roof

Patrich27,
See below the posting window..... "Or upload your file to engineering.com" please try uploading there. I, for one, am unable to see you document at the location you provided.

RE: Loading Tables for Roof

Likewise, I am not a member of googledrive and I want as little to do with them as I can.

Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin

RE: Loading Tables for Roof

Strange. Who is the manufacturer?

RE: Loading Tables for Roof

Patrich27

from your post above "So, these load numbers are capacity or maximum allowable psf the roof can carry at a given purlin spacing."

i'd pretty much bet the bank that this is not allowable psf, particularly for light gauge steel members. But until you give fuller information, i don't think i can be of much more help.

Good Luck!!

RE: Loading Tables for Roof

flash!
is this metal deck?

RE: Loading Tables for Roof

This is only about the flooring between supports, the deflection controls are pretty much irrelevant, deflection limits will be controlled by the supporting members.

Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin

RE: Loading Tables for Roof

(OP)
Triangled,

This is a high rib metal roof. I will send more details next week.

Thanks

RE: Loading Tables for Roof

Patrich27:
That looks like a load table for some kind of metal decking. That is, the metal deck can carry those loads, at the listed purlin spacings, without being over stressed, or without exceeding the listed deflections. That should all be explained someplace in the footnotes of those tables. But, the purlins and the rest of the roof structure must also be designed to carry those same loads, or a reduced loading in lbs./sq.ft., in which case the decking won’t be the controlling design element. If you don’t know where this table came from (what product and manufacturer) or how to read/interpret the table, maybe you shouldn’t be doing this kind of work. You could hurt someone. I don’t see the loads you first posted in what you’ve posted now. Why not attach more of the table so we can see what your actually looking at?

RE: Loading Tables for Roof

I agree this is a metal deck table; however, it appears that the loads are given in lbs/ft of deck width not psf. Odd way to present the data. Have seen this in specialty aluminum decking, but this doesn't appear to be that.

RE: Loading Tables for Roof

That table shows the load in lbs/sqft. It shows the capacity of the deck with the purlins at the purlin spacing shown, I assume, but you should check, that this is based on interior spans of decking continuous over the supports. What it doesn't show is the reduced end span value that would follow if this were true.

You don't have to calculate reactions of the deck on the purlins, design them for the same uniform load as the deck with the addition of allowances for self weight and MEP over the tributary width (the purlin spacing).

Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin

RE: Loading Tables for Roof

(OP)
Thanks to all!

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