Wind Loads on Wood Gambrel Truss 1

[Deadblow]

Hello All,

I am tasked with calculating the wind loads on wood framed Gambrel roof trusses that span 65'-0". The slope on the lower portion of the truss is about 62 degrees and the slope on the upper portion of the truss is about 22 degrees. They are symmetrical about the center. I am using IBC 2009 and unfortunately, I don't think that ASCE 7 addresses this type of a roof. I thought about just using the Gable roof loads from ASCE but the figures max out at 45 degrees. My involvement with this project deals mostly with component and cladding pressures. I do not know how to accurately determine the pressures. Any suggestions?

EIT

 

[DETstru]

I've never done that before but how about treating the steep portion as wall pressure and the shallow as roof?

 

[SlideRuleEra]

On my website, check out "Design of Barns to Withstand Wind Loads".
This publication is based on c.1941 wind tunnel investigations of gambrel (and similar) roofs. May be the best data available. This style roof was more common (and important) in the past. Before mechanized farm machinery was widely available, large-roofed barns allowed ample storage of feed for the powerful draft horses used in agriculture.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[Deadblow]

Thank you for the responses! SRE, your references never cease to amaze me, thanks!

EIT

 

[gravityandinertia]

That document is a great piece of engineering history!