Snow loads

[Struct1206]

With regards to sliding snow, ASCE 7-05 gives a simple formula for calculating a load and states that sliding snow shall be applied uniformly over 15' on the lower roof. Does anyone have any idea why you would just blindly apply the load this way? Wouldn't snow falling from a roof tend to pile up, especially if the distance from one roof to the next is small?

On a similar note, if you have sliding snow as well as drifting snow, would you apply them both together? The code states that they should each be superimposed over the balanced load but doesn't state whether or not you apply them both at the same time. We were having these discussions at the office today and I am just looking for some other opinions. How would you do it?

Any thoughts or input would be appreciated.

 

[vandede427]

I cant find where it specifically states to apply the balanced load with the drift load with the sliding load all together.

But I think it's entirely possible for a drift to accumulate then the higher roof slide off onto the lower drift.

One would almost want to ask if an impact factor is needed for the sliding portion of the load.

 

[DaveAtkins]

It makes sense to me that the sliding snow drops onto the lower roof and then "smears" out across 15'.

I thought the Code says something about drifting and sliding snow not being simultaneous, but I can't remember for sure.

DaveAtkins

 

[DaveAtkins]

ASCE 7-05, Section 7.9: "Sliding loads shall be superimposed on the balanced snow load."

DaveAtkins

 

[SteveGregory]

The code mentions a combination with balanced snow which would seem to exclude unbalanced snow but does not exclude drift.

 

[DaveAtkins]

Maybe you are right, Steve, but the Code is certainly not clear on this point.

DaveAtkins