Wood truss connections

[raceyENG]

This is my first time on the forum, so I am seeing how this works. I am in the process of re-designing a truss. It is a truss over a garage that previously had a 10' span in the middle with a room, that is now being expanded to 12'. I need to spec connector plates (nailed) for the new connections that are a result of moving the interior truss members. I have already found all resulting forces, but I need to design the connection plates.
Which manufacturers sell these plates?
I know Simpson has some, but not load rated.

 

[ERV]

raceyENG,
Is this a floor or roof truss? What type of "connection plates"? What type of forces (lateral, axial)?

 

[raceyENG]

ERV: It is a roof truss. I was planning on using some kind of nailed metal plate, but if you have other suggestions I would like to hear. I am running like a max 2100lb axial load in the members themselves. I am not designing for lateral. Do you need anything else?

 

[ERV]

It sounds to me that you are designing connections for the truss members (such as webs and cords) themselves. Is this the case?

 

[raceyENG]

Yes, that is the case. I am trying to find out what manufacturers supply these plates, and where I might find a design guideline. Sorry for the confusion I am causing.

 

[ERV]

Mitek Industries. Try this link:

http://www.mitekinc.com

 

[raceyENG]

Thanks. The only problem is that I cannot use pressure plates (contractor does not have a hydraulic press). I need to use some kind of a nailed plate, and the Mitek ones are just the toothed pressure type. Is it possible to just use OSB and nail it to the members? I have never done one of these. Thank you for your help.

 

[unclesyd]

They have essentially done away with nailed plates or plywood in the manufacturing of engineered trusses. In Florida neither is allowed, but are regularly used for repair when no one is looking. Prior to introduction of metal connector plates 3,4,5, Ply plywood was commonly used as a connector plate when a truss was fabricated. It was very common to use a box nail to avoid splitting the wood SYP. When metal truss connector plates come on the seen they were originally nailed. The toothed truss plate took a long time for acceptance around here.

I would rather use plywood than OSB though the better grades of OSB seem to hold up very well. I would use 1/2" plywood with box nails.

There is demo at

http://www.achroneng.com

that will let you look at one or two type trusses. The whole program is only $40.00 and is downloadable

 

[raceyENG]

This is an existing truss that is being field modified to expand the attic space to make way for a bedroom. It is essentially not a truss in terms of design anymore, but the connections still need to be there. Thanks for the suggestion.

 

[pbonarrigo]

If I understand the problem correctly, You have a truss which was originally designed to span 10', now the span has changed to 12'. You want to use the existing truss, by adding 2' to it with some type of connection.
First, if this truss is the some type I am used to, wood 2x4, NE USA, they are specifly designed to the exact load and location where they are expected to go. With very little (NO) extra margin included. The only acceptiable way to modify one of these type of trusses is to contact the truss maunfacturer and obtain their written permission to approve a proposed modification.
Having said all that, since this is a forum for engineers, I would use 3/8" Plywood on both faces of the existing truss to bridge the connection between the the new and old truss. Since you are in an area of low bending check the nails for shear(NDS-Anerican Wood Council) and check the new combined section for the bending moment. Review the existing truss at it midspan for the new additional bending moment.
Or just save yourself a lot of time and plywood both faces the entire lenght.

 

[ERV]

Plywood gussets should generally be 16" X 16", APA Rated Sheathing, minimum thickness 7/16", nailed with 8d nails, however, these are not reliable for tension loads. If tension loads are involved, it may be best to call the truss manufacturer and have them sent out a field crew for the modifications. I can e-mail the details I have for gussets and allowable loads if that will help.