offset shear walls 3

[AlpineEngineer]

I searched and saw a question like this has been asked before but I'm still a tad confused, so here it goes:

I have a rather large 2 story stick built home. I need some interior upper level shear walls (trusses parallel to these shear walls) to transfer roof Diaphragm loads. So I have 2 upper level interior shear walls w/ drag trusses on them. The problem is my lower level walls are about 10' horizontally away from the upper level walls. I have drawn details for shear transfer when the lower level walls were only 1' or so away but this is a differant animal.

Can I push the shear into the floor Diaphragm and then carry it out of the floor Diaphragm with my lower level walls which are offset? How do I resist the tension/compression on the upper level shear walls with the floor Diaphragm? Maybe tie the hold downs to an LVL in the floor which is strapped on its ends?

As always, thanks a ton for the help, you guys are the best.

 

[msquared48]

Yes, you can use the floor diaphragm below to transfer the forces back to the lower shear walls. You will have to check the diaphragm stresses and nail/block accordingly, and provide solid wood (PSL or GL ?) transfer beams for the upper shear walls to engage the shear and uplift forces, taking the overturning from these upper walls hopefully directly to the foundation. If things work out well, the lower walls will only see overturning from the floor above them.

Don't forget that this is an offset condition too and you will have to factor your results accordingly.

Mike McCann
MMC Engineering

 

[RARWOOD]

Buy or borrow a copy of Don Bryer's book "Design of Wood Framed Structures". His book has a chapter that covers both vertical and horizontal offsets in shear walls. msquared48 outlines the basic procedure. You apply the walls base shear as a concentrated load on the diaphragm. In addition you need beams and columns under the wall chords to carry the vertical load forces to the ground.