|
|
|
|
|
Despite the fact that CSA O86 6.5.3.2.3 and 7.5.6.3.1 say that members with a depth to width ratio greater than 2.5:1 must be laterally supported at points of bearing, users have indicated that they would like to design beams that are either not laterally braced at interior points of bearing or that are insufficiently laterally supported, in their engineering judgment, and therefore consider the full beam length as the unsupported length Lu for the calculation of the beam stability factor.
Noting that mechanics of the buckling equations used to derive the KL factor require only that the beam be fixed against rotation at two points, and that the American Wood Council Technical Report 14 includes a multi-span beam example with unsupported length as the entire length of the beam, Sizer allows the choice of whether a beam with is laterally supported at interior supports. This is specified for each support via a check box in the Supports for bearing and notch design data group.
Note that when multiple supports are selected and some are supported and some are not, Windows shows a black square in the box, which some users mistake for a positive indication of lateral support at all supports. Only when a check mark appears there are all lateral supports supported.