wood truss modification
wood truss modification
(OP)
I have some existing pre-engineered wood trusses on a house that I would like to cut back because the bearing location is being moved in toward the ridge.The trusses have a 12:12 pitch and currently spans 25' the trusses would be trimmed back approx. 5' and new bearing support provided. I am planning to sheath both sides of the trusses in a 4 ft width from the new bearing location. The sheathing would be attached to the truss bottom & top chord and 2x4 blocking at the other two panel edges; the sheathing would be attached with a dense nailing pattern. Any thoughts on this approach or alternate solutions? Anyone of aware of any modification design guidance from SBCA or WTCA? thanks






RE: wood truss modification
Dik
RE: wood truss modification
RE: wood truss modification
You should have a diagonal web member going from the bottom support to one of the top panel points.
Dik
RE: wood truss modification
Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.
RE: wood truss modification
Sheathing the sides with plywood and nailing will seldom achieve a desirable end. I have seen this done and seen it result in very poor/disastrous results. You need to re-engineer the entire truss, with no shortcuts. Look at TPI 1, and use the NDS for wood and fastener values. You will probably find that 3/4" plywood and 1/2" bolts will work best, and be sure to maintain truss action. If the plywood is too large, you will end up fixing the members, changing the action of members, and introducing flexure into tension/compression members.
But, you will likely also find that for closely-spaced trusses on 20 foot spans, there isn't that much load anyway.
RE: wood truss modification
The easiest connection is plywood and bolts like TXStructural mentioned.
You can check it, but I don't think fixing the joint would have much effect. You are reducing the span of the trusses so the forces should be fairly low.