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Re: roof truss daiphragm forces

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This is normally done on Blue houses only :-)

THis is for in-plane drag forces along the top chords of the trusses? A 2kip transfer via metal plates seems pretty high for a single truss, but I usually dbl up drag trusses.

Internal Diaphragm Stresses to me is a strange statement. Usually the ridges are at the lowest shears of the diaphragm (perp. to the trusses) and placing straps over the top does nothing. If the shears are high @ the ridges due to an internal shear resistance line, you need to create mini-shearwalls blockings between the trusses to get the load to the wall below...


On 5/17/07, Pinyon Engineering <Pinyonengineering(--nospam--at)> wrote:
I just went thru a plan check for a garage with roof trusses (the house color is sand)  The plan check engineer wanted me to install straps across the ridges of the trusses to account for internal diaphragm stresses.  I designed the chords of the diaphragm.  I added a note for the truss mgf to add an additional 2000 lbs tension capacity to the ridge plate connection(I calced this) (for all the trusses) instead of the straps.  I have never had this comment before.  is this commonly done? or is this guy super conservative?
Tim Rudolph
Pinyon Engineering
Bishop CA