Anchorage of masonry wall to wood diaphragm
Anchorage of masonry wall to wood diaphragm
(OP)
Does anyone have a good solution for providing out-of-plane anchorage of the top of masonry walls to a wood trussed roof? It can easily be done when the masonry walls extend past the diaphragm (parapet) with a Simpson strap embedded into the CMU. The condition I am referring to is where the top of the masonry wall stops just below the truss bearing elevation and a wood sill plate is attached to the top of the masonry wall with anchor bolts and then the trusses bear on the wood sill plate. I haven't been able to find a Simpson strap that will work well in that condition. It would be preferable to have a strap attach to the side of the truss top chord (assuming the roof is pitched). In the past I have used a peice of steel angle that rests on top of the sill plate, parallel with the truss, and the vertical leg buts against the side of a truss. The angle is bolted down into the top of the masonry and then bolted into the side of the truss and through a Simpson sheet metal strap that is nailed to the side of the truss bottom chord.
I would like to hear if anyone has an better solution.
Thank you
I would like to hear if anyone has an better solution.
Thank you






RE: Anchorage of masonry wall to wood diaphragm
RE: Anchorage of masonry wall to wood diaphragm
RE: Anchorage of masonry wall to wood diaphragm
RE: Anchorage of masonry wall to wood diaphragm
RE: Anchorage of masonry wall to wood diaphragm
RE: Anchorage of masonry wall to wood diaphragm
RE: Anchorage of masonry wall to wood diaphragm
1. Resist up lift force as determined by truss supplier.
2. In plane load to transfer the roof diaphragm from decking to walls.
3. Out of plane wind load. This is important because I design my CMU wall as being pinned-pinned condition. Of course the tie beam will support the top of the wall along with the trusses.
For items 2 and 3, I compute these forces based on number of trusses and their spacing. I found lots of resistance from local contractors when they saw my criteria. They were used to providing straps for uplift only. However, this is not the case. Simpson and southeaster Metals in the southeast do provide straps that have the three capacities.
Regards,
Lutfi
RE: Anchorage of masonry wall to wood diaphragm
IMHO, I believe the "no cross grain bending" is to eliminate a ledger bolted to the side of the wall where the diaphragm would pull on the top of the ledger and the bolts would restrain it at mid-point causing "cross grain" bending. The plate on top of the wall would be loaded in bending parallel to the grain.
I use metal clips like your angles just making sure that they are long enough or installed in pairs such that regardless of the direction of the force, they are not causing tension perpendicular to the grain at the bolt. The edge distance requirement for the bolts may take care of that as well.