shear blocking trusses

[Skicat]

We are in the process of re-vamping our shearwall details. The detailing of shear blocking trusses used when floor trusses are perpendicular to the shearwall on both sides is causing a discussion in our office. Can anyone elaborate on how you detail shear blocking trusses, and how you fasten them to the truss? Thank you.

 

[msquared48]

I assume you are talking about the situation where the trusses cannot bear on the shearwall, i.e., the shear wall is not a bearing wall.

In that situation, I run the wall double top plate about 1/4" or so below the bottom chord of the trusses (depending on the max deflection of the trusses) and use Simpson DTC clips to transfer the shear from the blocking to a 3X flat nailer attached to the floor/roof diaphragm above. The DTC clips allow vertical movement, but not lateral, so lateral load is able to be transmitted.

All connection frequencies and nailing will obviously depend on the load seen.

Mike McCann
McCann Engineering

 

[MiketheEngineer]

Usually on a shear and bearing wall - I just install blocking the same size as the top chord of the truss between the trusses. Anchor w/nails or Simpson clip based on load.

Sometimes - in smaller apps - the Simpson H10 or similiar will suffice w/o blocking.

In seismic areas - 2x blocking is usually required.

 

[JAE]

It is difficult to attempt to extend the sheathing up between floor trusses. But that is what we generally do.

Alternatively, what you can do is create a collector element (like what MiketheEngineer suggests) and identify a few areas along the shearwall to create a blocking system or panel that can take all the shear instead of sheathing up between each and every truss.

 

[MiketheEngineer]

Sorry - I missed the point about them being floor trusses. Typically you need to use some sort of "rim" board. This may be 2x10's, 2x12's or a TJI rimjoist.

I have also seen short sections of floor truss between floor trusses when they were very tall - say 24'' and then sheathed with plywood.

You need to develope a "chord" of some sort on the edges of the floor or roof diaphragm. Don't forget to detail the splices.

 

[Skicat]

Thanks for all of your help. We've been consulting with a truss manufacturer and a truss engineer to help resolve our dilema. Based on information we obtained from them, we have essentially decided to install discontinuous shear blocking trusses between every perpendicular floor truss and nail the whole assembly together. It seems to be the most economical and easiest to install solution we came up with. Thanks again.