Reinforcing wood trusses

[structural01]

When reinforcing a wood truss member, what I've seen is people nail the member at whatever inch on center only. I don't think this is correct. When the member is nailed at some even spacing, it is only nailed in for shear flow. The member must be nailed in for the full axial force first at each end of the member before it can be nailed in for shear flow (to make the reinforcing member and the existing member composite).

Do you agree with what I think?

Thanks.

Structural01

 

[jike]

If a member needs to be reinforced to prevent buckling, obviously right at the end connections, a higher stress can be allowed. With equally spaced nails, the load will bleed into the other member. There must be a sufficient nails to fully transfer this load in some distance "x". The question is really: what should the distance "x" be?
L/4, L/3? Certainly, it cannot be greater than L/2.

 

[IFRs]

The NDS design specification has tables on the strength of nails, screws, bolts, etc. Determine the load, then the number of nails then the spacing.

 

[structural01]

Jike,
I think you seem to agree with what I say.

I believe the way to nail in for compression member is to cluster nails at each end per NDS minimum spacings. But, of course there's a limit to how many nails you can cluster.

For tension member, it is not necessary to cluster in nails, like you said. Nails can be evenly spaced per NDS along the length of the member.

IFRs,

Yes. NDS gives you the load values for each fasterner type. But, you have to know how to use them. NDS does not tell you how to make connection for what I've mentioned above.

I welcome any more inputs.

Structural01

 

[FSS]

Why are you reinforcing the member? Is it a repair? Truss plate manufacturers have standard web reinforcing details on their web sites (Alpine, Mitek, etc.) when trying to reduce Kl/r. They also have details for common truss repairs when they get damaged during delivery.

 

[structural01]

FSS,
The way most of these truss manufacturers repair or reinforce wood trusses is by only nailing the member in tension/compression at some distance on center along the length of the member.

I don't think this is the correct way to reinforce or repair.

structural01