PRG 320 Table A-2 and O86 8.4.3.1 - Bending Moment Resistance

The factored bending moment resistance for the major axis strength direction is

M’ = 0.85 C_D C_t (F_bS)_eff,f,0

and for the minor axis direction is

M’ = C_D C_t (F_bS)_eff,f,90,

where the values of (F_bS)_eff are those listed in table A-2 of the PRG 320. For custom CLT materials, and for fire design, (F_bS) _eff is calculated using O86 8.4.3.1:

(F_bS) _eff = α F_b S_eff

where

S_eff = 2 (EI)_eff / E h

and

• h is the panel depth for major axis loading, and the panel depth minus the thickness of the outermost layers for the minor axis.
• α is 0.85 for major axis loading and 1.0 for minor axis.
• F_b, (EI)_eff, and E are evaluated for the longitudinal layers when loading is along the major strength axis, and for the transverse layers when loading is along the minor axis. F_b and E are found in PRG 320 Table A1.
• (EI)_eff is given in CLT Handbook 3.3.1 and O86 8.4.3.2 - Effective Stiffness

Note that the CLT Handbook Chapter 3, Section 2.1, Equations 1 and 2 for transverse loading uses the full panel loading depth rather then the reduced depth, and the F_b of the outermost layer rather than the transverse layers. The CSA method was used because that is the approach used to generate (F_bS)_eff in the current PRG 320.

For fire reduced sections, refer to CLT Handbook 8, 4.1.4.1 - Bending Moment for FIre Reduced Sections