Truss-to-wall connection 1

[ZXLeung]

For wood roof diaphragms with wood trusses supported on masonry walls and subject to lateral wind load,how to calculate the shear load F1(parallel to the supporting wall) and F2(normal to the supporting wall) for the truss-to-wall connector design?

P.S. In fact, this topic was posted before, but no solution yet.
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[jayrod12]

You need to trace your diaphragm loading to get the load parallel to the wall. Your diaphragm force needs to be transferred from the roof sheathing to the masonry wall somehow, usually it's through the connection of your roof framing to the wall combined with some blocking to prevent truss/rafter rollover. This is when the wind/seismic load is parallel to the roof ridge.

For the perpendicular to wall loads, those often come directly from the truss supplier in their shop drawings, however if this is preliminary so you don't have that number yet, it would be for wind loading perpendicular to the ridge on each truss. Technically the diaphragm also performs this function, but belts and suspenders prevent your pants from falling.

 

[ZXLeung]

Thanks a lot Jay for quick reply and helpful comments!

To understand this procedure corretly, I simplified an assumption below:

Assume truss spans from front to rear walls, then

Perpendicular to Truss Force, F1 equals:
Wind pressure to side wall * Width of side wall * Tributed height (inluding eave to mean roof height + eave to mid height of wall below) / 2 （here means front/rear 2 walls perpendicular to side wall) / Length of front or rear wall * Spacing of truss

Parallel to Truss Force, F2 equals:
Wind pressure to front wall * Tributed height (inluding eave to mean roof height + eave to mid height of wall below) * Spacing of truss

Please correct me if any wrong. Thanks again!

 

[jayrod12]

Those seem to be correct. Or at least how I'd calculate them.

 

[ZXLeung]

Thank you a lot Jay!!!