ASCE7 Fig 7-8 1

[msquared48]

Can't really find where "W" is defined other in section 7.1, and for a flat roof, this is nebulous at best.

I have a 3' high parapet that extends for 60 feet of the building width and saw a detail on the internet defining "W as 2/3 of the length of the parapet. This gives a drift length that seems unreasonable to me of 40 feet.

I have a structural problem in that with a uniform snow load, the steel joist girder panel point loads are at 4.3 kips, and I check that. But using the values above and ASCE7 chapter 7, I get panel point loads of about 4.7 kips. The depth of the drift seems reasonable to me at 2.5 feet, but the length of the drift to me is not for my region.

Does anyone have any further information? Unless I hear differently with more definitive information, I am going to revert to my 1998 version of the SEAW "Snow Loads for Washington". That is well defined.

Mike McCann
MMC Engineering

 

[OldPaperMaker]

Mike,
I assume that you are using ASCE7-10. The capital "W" shows in Figure 7-5 as the horizontal distamce from eave to ridge just like the defination called out in "symbols". Note that in Figure 7-8 the capital "W" is shown in error. The erreta notes that this should be small"w" which is the width of the snowdrift.

The Commentary, C7 expans of the stuff in this chapter.

I hope that this helps

 

[msquared48]

I was looking at 05. I'll check 10. Thanks.

Mike McCann
MMC Engineering