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For sawn lumber, glulam, and SCL members, is possible to enter an oblique angle between 0 and 90 degrees to model a beam or joist rotated with respect to the load. This most often represents an oblique purlin, a secondary framing member used in curved or pitched roofs that are subjected to two-way bending moments when the roof sheathing cannot effectively transfer tangential loads to the member ends.
Oblique loading is not available for CLT panels or I-joists.
Bending Moment Design
Two-way bending is created by the action of the tangential and normal components of the vertical load. Sizer calculates the x-axis (strong axis) and y-axis ( weak axis) resistance separately and compares the resistances to the load components in each direction. It shows both sets of results in the Design Check report.
Design for Shear
It is not sufficient in this situation to resolve the shear stress into components perpendicular and parallel to the member sides, and compare these with the strengths in these directions, because in the longitudinal direction, the material is subject to the full shear stress regardless of the rotational angle.
For anisotropic members materials such as glulam and SCL the equation
fvx/Fvx' + fvy/Fvy' <= 1
is used, where the actual stress fv and factored allowable stress Fv' are given in NDS 3.4 - Bending Members - Shear. It was suggested by AITC, the former authority for glulam design.
In the absence of other guidance for sawn lumber, which is isotropic, the same equation is used, reduced to
(fvx + fvy )/Fv' <= 1
= fv ( cos q + sin q ) / Fv' <= 1
where fv is calculated as in 3.4-1 as if V was applied orthogonally to either the b or d face. Note that the maximum shear stress in a square section rotated 45 degrees and loaded at the tip of the diamond-shaped section is 9/8 V / A as opposed to the 3/2 V / A for the same section loaded at the side, so this formula is undoubtedly conservative.
Design for Bearing
For members rotated less than 90 degrees, bearing design assumes that all load is applied to the b face and resistance to that load calculated using the bearing are from the b face (member width).. For members rotated through a small angle, results are conservative for both bearing design and in terms of calculating the design span using minimum required bearing. For members rotated more than 45 degrees, it is not realistic and results should be disregarded. For members rotated 90 degrees, i.e. planks, the bearing area from the d face (member depth) is used, giving accurate bearing design.
Deflection
The deflection of a rotated member is the vector sum of deflections from x-axis and y-axis bending,