Chord Forces- Roof Diaphram

[TimmyH76]

Where/How are the chord forces in wood roof diaphram taken care of? I've heard that you can use a bond beam (BB) for masonry walls or top plate(TP) for wood walls, but my question is....The tension is in the diaphram... How do you get the tension from the diaphram to the Bond Beam or top plate? In my mind you need blocking between the trusses or rafters and possibly a strap running along the top of the blocking and trusses, then connect the bottom of the blocking/trusses assemply to the TP or BB sufficently. Thanks for you input.

 

[JRESE]

TimmyH76:

Realize that the chord force varies from zero at the ends of the diaphragm to max at the center. Therefore, you need blocking, clips, nails, etc. between the diaphragm and chord to transfer that force (blocking in half of the chord length should transfer all of the force.) Make sure to design splices in wood chords. If you put a continuous strap over the blocking, that would be your chord. Usually, that is not necessary.

Jim Emanuel, S.E.