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Re: ASCE 7-05: Ice Loads Due To Freezing Rain (Chapter 10)

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Bill,
 
        I have always treated ice load on grating or decks as you describe as being part of the live load.  Live load is generally an ALLOWANCE for a load that MIGHT be applied; if you have a 50 psf live load and you have 10 psf of ice you would have 40 psf left for other live load that could possibly be applied at the same time.  That said, ice loading on wall cladding could be a problem, I suppose; but I have never encountered (or heard of) problems from that source.
 
        Ice is definitely a problem for cables and wires which are designed to carry themselves. It's also a concern but not usually the governing criteria for designing guys providing structural support for other components in addition to holding themselves up.
 
Regards,
 
Daryl
----- Original Message -----
Sent: Tuesday, February 24, 2009 5:18 PM
Subject: ASCE 7-05: Ice Loads Due To Freezing Rain (Chapter 10)

I have been reading up on this, realizing that it is probably pertinent to all our industrial / refining stuff we do, since we've got a lot of bare steel frame structures sitting around outside.

My specific question is regarding bar grating.

Even in the South, Figure 10-2 shows between 0.25 and 0.75 in of "uniform ice thickness due to freezing rain." If you have the typical 1-1/4" x 3/16" bar grating with bars spaced at 1-3/6", the gap between the bars will just about be closed, completely filled with ice. That would be an additional dead load of something like 8 or 9 psf to the structure. For some extensive platforms that's gonna be a LOT of weight!

Am I looking at this right, or is there some other way I should consider it?

Thanks.