Design of Wood Truss 2

[MIK5837]

Dear all..
i am designing roof truss in timber ( wood) for a span length of 32 feet. I need help from the experts in wood truss design. any documents, design example or and other helping material
professional drawings ..
Thanks in advance

 

[charliealphabravo]

If you are talking about metal plate connected wood trusses then those are all proprietary and designed by the plate manufacturer (Miitek, Alpine). If you are talking about custom timber trusses then the truss analysis is pretty conventional. Connection detailing is the tricky part. Split rings and shear plates are a bit old school but there was a supplier in Cleveland (TECO) last time I needed some. A more typical alternative would be custom cut steel plates and self tapping screws.

 

[oldestguy]

I've built many a truss and the joints were all 1/2" plywood nailed. I used a guide I received from the US Forest Products lab in Madison, WI. Which I think is free. It was very complete. I used ring shank nails on the latest with a nailer gun. Look them up on the Internet. I'd then call. Earlier I did a lot of hand nailing years ago.

Here is one of their articles on line.

https://www.fpl.fs.fed.us/documnts/pdf1982/ander82a.pdf

I note that it shows those ring joints and bolts. If I were using them, I'd need that device for cutting the ring for the metal. For plywood gussets, I used the holding power of the nails (think it was 100 lb) and then thew in a few more for good measure. Not much of a job when it comes to doing it.


Here is an older paper from FloridaU. It deals with gluing or nailing the gussets.

http://ufdc.ufl.edu/AA00020505/00001/5j

For design of the trusses I used the graphic method and a big sheet of paper. More likely you will find 2 x 4's will do the job for all members. Nail length went thru both gussets, but I neglected the help from the other side.

 

[oldestguy]

OG once more. In trying to verify that a design shear load of 100 pounds per nail shear strength was OK, I did some looking via Google. A lot of equations and tests, but ultimate for a nail at pounds per inch of penetration shows roughly a 2 to three times better hold for the ring shanks than smooth nails. For a nail of 0.139 diam. smooth show about 100 to 145 lb/inch as compared to ring shanks at 337 to 448 lb/inch. These are withdrawal test results. For a working value for shear of 100 lbs they look plenty safe at this level of shear pounds since the 2 x 4's are holding at much over these lb/in numbers.

 

[MIK5837]

Thank you for the help.