IBC2009 MWFRS loads or C&C for Hurricane Ties

[cmatthews]

I am designing a wood trussed roof system for a building located in Boston Harbor. According to IBC2009 Section 2308.10.1, the rafter to truss ties to the wall below shall comply with Tables 2304.9.1 and 2308.10.1. I have confirmed that the uplift forces in the table are based upon Figure 6-2 of ASCE7-05 for a roof slope of 25degrees (MWFRS-Method 1). Footnote "c" states that the values in the table include an allowance for 10lbs of dead load. I believe there has been no allowance for dead load.

Is it appropriate to subtract 60% of the roof dead load to determine the NET uplift for the hurricane clip?

I have read through the commentary of ASCE7 and I cannot determine if the hurricane clip connection should be designed for MWFRS loads or Component and Cladding loads. Roof trusses are listed in both definitions. If someone could provide some clarity I would greatly appreciate your help.

Thanks

 

[brudgers]

Same as before: http://www.inspectpa.com/forum/showthread.php?7492-IBC2009-MWFRS-loads-or-C-amp-C-for-Hurricane-Ties&p=71860&viewfull=1#post71860

 

[Architect1281]

what note c says is use ONLY 10 # DL not 15 not 20 not what you think it could be but 10 and no more

 

[JPotter04210]

You need to use whichever force value is greater. I expect that you will find that, for an individual truss the C&C value will govern. The idea of the MWFRS values is for use on the building as a whole; for use on building sections such as the whole roof system or the shear wall system.