Snow load on existing buildings 2

[donegalcol]

Section 3403.3.1 of IBC 2009 states that if the live load is not changed then the presumed live load at the time the building was constructed may be used in lieu of the new live load per IBC. Does anyone know if this applies to snow loads on roofs.
I have a condition whereby I am adding solar modules on a roof. The roof is adequate is I use the smaller snow load that existed when the building was constructed, however the roof is overstressed if I use the new snow load per IBC 2009.

 

[woodman88]

My copy of the 1944 NDS states in section 202 “...for permanent loading, i.e. long-time loading whether live or dead.” and section 203 “203—ALLOWABLE UNIT STRESSES FOR SNOW, WIND, EARTHQUAKE OR SHORT TIME LOADING” Though it does seem to equate the ALL the loads in section 203 as short time live loads. You can download a free copy of this from the attached website. Also some lumber values from 1922.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[MiketheEngineer]

Told you I was old

 

[JStephen]

In the AISC manual, 9th Edition, under A4.1, "The live load, including snow load if any, shall be that stipulated..."

 

[mbullism]

IBC 2009 1602.1 Definitions

"Live Load"...

Those loads produced by the use and occupancy of the building...and do not include...environmental loads such as wind load, snow load, rain load...

"Live Loads (Roof)"

Those loads produced (1) during maintenance...and (2) by moveable objects such as planters and by people. **commentary** "...This definition clarifies that roof loads, such as snow loads, are not live loads"

 

[msquared48]

OK. Until the definition is agreed upon by all the codes, just take the conservative approach and use the most stringent definition for the applicable code in your jurisdiction. That approach you can justify in court.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com