ASCE7-10 Ice Dam Loads

[medeek]

I am quite familiar with ASCE 7-10 Sec. 7.4.5 where a 2p_f load is applied at the eaves for essentially warm roofs. What I don't understand is why every truss document I have ever looked at with overhangs shows the overhang load as 1.00 times the flat roof live load. Where is the 1.0p_f coming from?

A confused student is a good student.
Nathaniel P. Wilkerson, PE

http://www.medeek.com

 

[msquared48]

Snow by code is not considered to be a "live load", it is a snow load, so the statement is not valid.

1.0 X the minimum construction "live load" would be 1.0 X 20psf = 20 psf or about 4" of ice to put it in perspective.

2.0 times the minimum snow load where I live is 50 psf, or about 10" of ice.

I do not know where they get the 1.0 factor.

All I have seen is 2.0.

Mike McCann, PE, SE (WA)

 

[medeek]

Nope, I just checked another truss package from Truss Components (Tumwater, WA), they use Mitek and the exact wording is: "This truss has been designed for greater of min. roof live load of 16.0 psf or 1.00 times flat roof load of 25.0 psf on overhangs non-concurrent with other live loads."

The roof snow load is 25 psf in this particular case.

I don't know where they get the 1.00 factor from either. The ASCE 7-10 specifies a 2.00 factor.

A confused student is a good student.
Nathaniel P. Wilkerson, PE

http://www.medeek.com

 

[gravityandinertia]

Have you tried calling them the manufacturer and asking?

 

[medeek]

This seems to be common practice around here. I'm not sure if this is coming from Mitek's software or the truss companies. Further investigation required.

A confused student is a good student.
Nathaniel P. Wilkerson, PE

http://www.medeek.com