Ice Plus Snow Load Combinations ASCE7-05

[cgstrucg]

Hello,

I was going through load Combination 3 mentioned in ASCE 7-05 page 5 which is D+S+0.7Di+0.7Wi when we consider atmospheric ice load. My senior engineer and I were discussing now that if we have snow drift and snow balanced then we should put snow balanced only in this load combination as snow drift + ice is like an extreme case.

So something like D+S Balanced+0.7Di+0.7Wi and not D+S Balanced+S Drift+0.7Di+0.7Wi

The thing is I can't find anywhere in codes specifying this. Can someone please guide me to a proper resource I can look into regarding this anomaly.

Thanks

 

[JAE]

By the letter of the code, S is defined as the required Snow load in all its manifestations (Pf, Pf plus drift, Pmin, etc.)
So picking and choosing what part of S you would use to combine with Di and Wi isn't directly codified or allowed...by the direct code logic.

However, read through the commentary in C2.3.4 for a discussion of the combinations of S and Di and you can perhaps justify a rationale for not including drifts.
One relevant quote from that commentary: [blue]"The snow loads defined in Chapter 7 ....includes snow, ice due to freezing rain, and rain that falls onto snow and later freezes..."[/blue]



Check out Eng-Tips Forum's Policies here:
faq731-376

 

[cgstrucg]

Commentary actually helped. Never used to read it before. Thank You JAE

 

[dik]

Codes often exclude commentaries and appendices from being part of the code.

Dik