NDS C3.7.1 - Alternative Stability Factor for CLT Wall Panels

The Stability Factor C_P for CLT Wall panels is given in NDS Commentary C3.7.1.4, Equations C3.7.1-1 to -4. This equation is also in the CLT Handbook, Chapter 8, Section 4.1.4.1, Equation 16.

where

• P_c^* = F_c^* A_eff = axial compressive resistance
• F_c ^* = F_c factored with all adjustment factors except C_P
• c = 0.9 for CLT
• P_cE = π² (EI)_app-min’ / l_e²

l_e is the effective length between lateral supports, which is K_e l for wall panels, l being the unsupported distance, which in most cases is the panel height L, and (EI)_app-min is described in NDS 10.4.1 - CLT Stiffness .

The column buckling resistance P_cE is also required for for CLT combined axial and bending design.

Continuously Supported Panels

For the unusual case that the CLT panel would be continuously supported, placing the equation for (EI)_app-min’ in the expression for P_cE and setting l = 0 yields P_cE = (GA)_eff E_min / κ E . This results in a C_P less than 1.0 despite the continuous support. However, the derivation of Euler buckling factor involves some simplifying assumptions that break down at very small unsupported lengths, so that this result is unrealistic. For continuously supported members, we assume that C_P = 1.0.