Plywood Truss Plates 1

[ChrisMFG]

Hello all,

I am new to this forum and I am a manufacturer and builder of various building products.
As a builder in Florida we are having an extremely difficult time acquiring trusses. I have projects currently on hold as trusses have been delayed by months and it does not look to be getting better.
I am looking to construct trusses in my facility using plywood gussets in place of press in metal plates. I am looking to do this on both a short term basis (to get me back on track for my delayed projects) and a longer term basis (to help with other home builders in the same position until things go back to "normal" lead times).
I am looking to use 1/2" ply with adhesive and nails (every 3" oc 1" from each edge of the member). I have read some studies, although they were conducted in the mid 90's that shows plywood with adhesive is a strong alternative to metal press in plates.
Am I on the right path here as I can't seem to find a structural engineer to want to help with this?
I understand that purchasing pre-engineered trusses would be easier, but that is not an option right now.
Please let me know if I am way off basis with wanting to construct trusses using plywood plates or if it is a viable option.
Many thanks

 

[phamENG]

There were also several studies done further back into the 1950's. It can be done. The issue is that it's very unlikely that you'll get them to span as far as modern truss assembly methods. You also need a structural engineer to sign off on it. If you can't find one, don't build these. They'll fall under the section of the code that requires engineering, so the people you sell them to will be in trouble when the inspector comes out.

 

[XR250]

Probably be easier and cheaper to just design the houses as stick framed - even with the added expense of LVL's or steel beams.

 

[dauwerda]

medeek used to be a fairly active member on this site. I know he went down the path of designing these. It might be worth reaching out to him,

http://design.medeek.com/support/

 

[StrucPatholgst]

Anybody can design a plywood-gusseted truss. It's the product liability that everyone avoids.

 

[ChrisMFG]

Thank you for the responses thus far.
I have been in contact with Simpson Strong-tie and it looks like I will be setting up a truss plant using standard press-in truss plates.
This is how bad it's gotten here in Florida for us to acquire certain products.
It would still be my preference to use plywood plates but, as some have noted it seems to be the liability. I don't understand why as I manufacture unique products which are engineered for me (I have a pre-fab steel and concrete panel and I am also involved in a 3D concrete printer operation). I carry a large liability policy and would have thought that the insurances would go through the chain of command. So long as the engineer designed it right, if any failure occurred because of my fabrication it would fall on my liability???

Trusses have become so difficult to obtain for smaller builders like myself (5 - 10 homes a year) as they are only catering to the national builders that it warrants me setting up a small plant to service my business piers that have companies about my size.

Thanks for the recommendations

 

[EdStainless]

My former boss (now retired) used to design these. But as I recall they had a boat load of nails in them.
I think that it was staggered rows on 3/4" spacing. I remember that the nail heads nearly touched each other.
There used to be a lot of these used in Ag buildings (pole barns).
The other option are perforated metal nailing plates.
Finding sealed plans for either may be a stretch these days.

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P.E. Metallurgy, consulting work welcomed

 

[human909]

Good luck ChrisMFG.

And well done on the perfect approach to asking the question on this forum. Most of us can be pretty curt in our response when non engineers come seeking answers. It isn't that we aren't friendly, it is just then most non engineers approach this forum expecting engineering advice for free and supplying far too little information for sensible response. Answering non engineer's questions can cause more harm than good in many cases.

You managed not follow this path and got some constructive answers.

 

[XR250]

Did not realize Simpson manufactured and tested pressed-in truss plates. I thought they were proprietary and basically owned by the software companies.

 

[phamENG]

Other way around. MiTek is by far the biggest around here - but they started as a truss and component manufacturer and developed software as it became possible to keep their manufacturing business at the fore.

Simpson has been getting into it recently, and even more into the software game. They have a really wide variety of online tools for product selection, and they've developed a full inventory and manufacturing suite for companies that build trusses, panelized walls, etc.

 

[kipfoot]

Here are a couple thoughts on how to get an engineer to help you:
1) limit of liability. Engineers haven't done this and there aren't any industry wide standards on how to design plywood gussets, so most folks would nope out.
2) consider steel plates? I think engineers would be more comfortable with the transfer of forces through, say, 1/8" steel. It's a more straight forward design for connections, I think.
3) bill hourly..at least at first. Connections are a sometimes time consuming endeavor and you probably haven't found someone who has enough experience to give you a fixed fee.
4) build a mockup and test it before putting it in a house. This would be a chance for the engineer to a) assess the time involved for design, and b) to verify predicted deflections. It also will give you confidence that you and the engineer are creating something that works. You'll also get a sense of the time and fee involved and maybe you'll have invented a process that gives you a competitive advantage in your market.
5) you could also turn it around to pique the curiosity of an engineer: "hey I built these mockup trusses with SYP No. 2 and using plates and simpson screws and I'm about to load it up with sandbags. Can you do an analysis of this truss and tell me what you think will fail first?"

 

[XR250]

@Pham,

Thanks for the info. Glad to see another player in the market.

 

[dik]

https://www.tpinst.org/

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[dik]

When I first started engineering, we did dozens of northern stores in Canada and we used to design wood trusses and plywood gusset plates. We drew 'Cremona' diagrams to graphically get truss member forces. Stelco made a hardened fastener called 'Truss Gusset Nails'. We drew out the gussets and pieced them together to fit sheets of plywood. We used these trusses when we constructed my parents home at the lake.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[EdStainless]

When I load tested trusses we did it laying them flat on the floor.
We had steel blocks pinned into the floor for the support locations.
Then we could apply various point loads with hydraulic rams.
For uniform load the rams had large shoes on them to distribute the load.
It was easy to get load vs deflection data and then push them to failure.
You could contact these guys;

http://www.sheppardengineering.com/index.php

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[ChrisMFG]

Thanks again for the responses.

I am trying to put this together quickly and while I would prefer to build trusses using plywood plates, it looks as though I will be approaching it in a more common way using press in plates.

@Human909 Thanks. I spend a lot of time with engineers as most of what I build is not conventional. I am currently helping develop a 3D concrete printer for example. I would never look for "free" engineering as we all have worked too hard to achieve our qualifications.

Yes, Mitek is the biggest supplier in this area but Simpson have been very supportive and helpful in setting me up. They seem to have a great program to join. I am very familiar with Simpson as I use a ton of their products in my wall panel system.

@Kipfoot Thanks for the idea of building a sample, I will definitely do this before the end of the week. My original idea was to offer trusses up to about 40' long so I will look at an old set of truss drawings and use one of those trusses as an example.

Here was my thought process on my operation, had I been able to use plywood for the plates.
I was going to set up a vertical framing jig (a T-slot table) and secure the timber using clamps to frame the truss to its final shape. The table was going to be vertical because of space and easier on your back.
I was going to use my CNC router to pre-cut the plywood plates to fit the exact shape of the outside edges of the members (cut it to fit a 6/12 roof for example) and use the router to indicate the exact locations of the nail placement as the engineer specified. I figured a plate cut to fit exactly to the outer edges would be stronger than a smaller rectangular plate placed into a triangular shape. (See attached my very simple sketch as a starting point. Hopefully I uploaded it correctly.)
We would glue and nail all plates onto one side of the truss then roll it to some supports to nail the plates on the other side (think a V shaped jig).
Space is hard to come by and expensive in this market, so a flat operation would cost more. I may not have been able to produce trusses on a mass scale, but I'm only looking to make about a set of trusses per day.

I will keep moving forward but most likely with press in plates.

Thanks again.

 

[bones206]

Just to follow up on dauwerda’s reference to Medeek. Here is a link to his truss calculator, which has plywood gusset plates as a design option:

http://design.medeek.com/calculator/calculator.pl

 

[EdStainless]

If you go ply you want the full triangular, spreads the stresses better.
Don't overlook perforated metal nail plates. They were the standard before press plates came along.
Yes working on the floor is uncomfortable, but they are easy to align and brace, and it is a good solid surface to nail against.


= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[ThorenO2]

Agree that medeek would be a great resource.