Resistance Factor (LRFD Only) Explained:
Used in Sawn Lumber Design, Glu Lam Design, Round Timber/Poles Design?, etc, the resistance factor (ø) is used to help calculate the format conversion factor. By using LRFD in lieu of ASD design you are substituting three variables for one, therefore I normally recommend ASD as being the superior choice for wood design.
Note: It seems that the ø variable for the format conversion factor and the ø variable for the resistance factor would cancel one another out. But I haven't had the chance to look through the ASTM Standard D 5457-04[1] therefore I cannot be certain what the purpose of these factors are.
Resistance Factors (ø)[2]
| Table 1: Resistance Factors (ø) | |||
| Application | Property | Symbol | Value |
| Members: | Fb | øb | 0.85 |
| Ft | øt | 0.80 | |
| Fv, Frt, Fs | øv | 0.75 | |
| Fc, Fc-p | øc | 0.90 | |
| Emin | øs | 0.85 | |
| Connections: | (all types) | øz | 0.65 |
References:
- W. Conshohocken, "Standard Specification for Computing the Reference Resistance of Wood Based Materials and Structural Connections for Load Resistance Factor Design (ASTM Standard D 5457-04)," PA, 2004
- American Forest and Paper Association, "National Design Specification for Wood Construction", 2005
- Found in Appendix N.