Timber Beam in Torsion
Timber Beam in Torsion
(OP)
Hey.
I have attached an image of my query. I have timber beams that support decking that is tied into the beams using lag screws that provide lateral restraint. Attached to the left support beam is a post at approx 1m c/c along the length of the beam. The design code requires me to check the post for a horizontal load at the top of the rail which is equivalent to 1kN. I know wood is weak in torsion as the force acts against the grain which is the weak section of wood. Would the attached decking provide adequate restraint to resist the torsion? Would I still need to design the beam to resist the torsion?
Thanks
I have attached an image of my query. I have timber beams that support decking that is tied into the beams using lag screws that provide lateral restraint. Attached to the left support beam is a post at approx 1m c/c along the length of the beam. The design code requires me to check the post for a horizontal load at the top of the rail which is equivalent to 1kN. I know wood is weak in torsion as the force acts against the grain which is the weak section of wood. Would the attached decking provide adequate restraint to resist the torsion? Would I still need to design the beam to resist the torsion?
Thanks






RE: Timber Beam in Torsion
Depends on it's flexural stiffness.
RE: Timber Beam in Torsion
RE: Timber Beam in Torsion
Therefore, my tendency would be to connect the decking directly to the post as well. That way, the moment is taken out as a force couple. Beam gets a weak axis shear opposed by similar load going into the decking.The Simpson detail looks pretty good to me. Plus the blocking seems to be the key to avoiding the cross grain bending.
RE: Timber Beam in Torsion
See Attached PDF.
RE: Timber Beam in Torsion
Cheers
RE: Timber Beam in Torsion
That isn't the way I see it. It almost certainly would try to (as drawn) bend the decking (as the whole section tried to rotate).
I like jayrod12's suggestion about blocking. (Lots of it too.)
RE: Timber Beam in Torsion
The AWC has a free document that has prescriptive code compliant setups for residential decks and posts. Even if your deck is for commercial loads; I would still start with their setup and then just tweak it.
Here's a link:
http://www.awc.org/codes-standards/publications/dc...
Also, attached is another article with connections (Structure Magazine July 2007)