Rolling Shear Resistance

For CLT design, rolling shear in the transverse layers is assumed to govern over longitudinal shear. Refer to O86 Figure 8.1 for a depiction of rolling shear.

From O86 8.4.4.2, rolling shear resistance V_r is

V_r = 2 f F_s A_g/3

where

• f = 0.9.
• F_s is the factored bending resistance in the transverse layers for major-axis design and for the longitudunal layers for minor-axis design. The unfactored fs is given in Table 8.2 and it is factored by the load duration factor and possibly a fire-retardant factor.
• A_g is the gross cross-sectional area of the panel for loading on the major axis, and for the minor axis it is the cross-sectional area minus the area of the outermost layers. For the case of design in the transverse direction with double outermost layers, both layers at the top and the bottom of the panel are omitted from the calculation of A.

Note that for simplicity, the subscripts "f" for flatwise and 0 or 90 indicating panel direction that are used in the O86 have been dropped here.

This method conservatively assumes that the maximum shear in the member cross section occurs in a transverse layer, where rolling shear governs, as rolling shear strength F_s is typically much lower than shear strength F_v. For custom CLT materials with higher F_s than F_v, it is recommended to enter the F_v value in the database as F_s.

This method yields the same shear resistance values V_r given in APA PRG 320 Table A-2.

Fire Design

The full residual section is used in the calculation of the gross cross-sectional area, except that it does not include final partially charred layer if is transverse to the axis of loading.