What is the purpose of the NDS Format Conversion Factor, KF?


The NDS Format Conversion Factor, KF, converts reference design values (allowable stress design values based on normal load duration) to LRFD reference resistances as described in ASTM D5457 Standard Specification for Computing Reference Resistance of Wood-Based Materials and Structural Connections for Load and Resistance Factor Design. The expression for KF is a constant divided by the resistance factor, Φ, and includes the following:

  1. a conversion factor to adjust an allowable design value to a strength level design value (embedded in the constant), 
  2. a conversion factor to adjust from a 10 year (long-term) load duration to a 10 minute (short-term) load duration basis (embedded in the constant), and 
  3. a conversion factor to adjust for a specified resistance factor, Φ (expressed independently in the denominator)