Posted 3/3/2009 15:34 (#630407 - in reply to #630321) Subject: Re: Pole buildings
The truss with the same sized top and bottom is stronger on a 5/12 than a 4/12 but the rafters have to be a little longer and the roof tin has more area. There's more height to the middle of the truss where the bending moment is greatest and the taller truss has a wider moment to stand that bending. In a uniform solid timber, the bending strength varies as the cube of the height. That probably applies to a truss, so a 5/12 truss with a given size materials would 125 over 64 times as strong as the 4/12 truss. Just about twice as strong.
Pole buildings
