Re: Subject: Re: roof truss daiphragm forces

Are you saying that the plan checker want you to design each truss for the shear force diagram at it's corresponding location along the diaphragm?

That's certainly not necessary.

It may mean heavier nailing zones and blocked diaphragms at the areas of high shear, but not straps across the joints in the trusses. If so, every tilt-up building would need a strap from sub-purlin to sub-purlin using that logic.

-g

On 5/17/07, Pinyon Engineering <Pinyonengineering@hughes.net> wrote:

Yes, the comment was on Internal Diaphragm Stresses.  I have the chord designed on the gable end wall(and shed roof side).  I aways understood that that was sufficient.  the 2kip was figured based on the resulting shear diagram of the forces and simplified for all common trusses(way over designed for the center of the building). no drag trusses or internal shear walls it doesn't get simpler the building is a rectangle no popouts or architect stuff. The shears are not very high either.  - seems like this is one of thoes wood design things that works and shouldn't be thought about too much - like how variable in quality wood is

 

Tim

 

 

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...

-g

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-gm