Frequently Asked Questions
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).
Wood Products
- Where can I find information on federal specifications and standards for lumber and wood products?
- What are the design manuals for wood construction in high wind areas?
- What resources are available for wood construction in high seismic areas and why build with wood in earthquake-prone areas?
NDS
- What do the column headers for bolt design value tables 11 A-K in the NDS mean?
- Where can I find background on In-Grade Testing for the NDS supplement?
- Where can I find more information on all of the NDS references?
- What are the safety factors (factor of safety) that are used to derive allowable design values for wood fasteners, lumber design values, etc. referenced in the NDS?
- Why did shear parallel to grain (horizontal shear) design values increase in the 2001 NDS?
- If there's an existing structure where the MC<19% for southern pine timbers, could the designer back out the wet service adjustment from the NDS published design values in table 4D?
LRFD
- What is LRFD?
- What is the purpose of the NDS Format Conversion Factor, KF?
- For LRFD in the 2005 NDS®, why does the φ factor cancel out when adjusting nominal resistances using the LRFD Format Conversion Factor, KF , and the resistance factor, φ?
- For Load and Resistance Factor Designs (LRFD), many of the design examples and much of the discussion focuses on elastic stress analysis. I thought that one of the benefits of LRFD was its ability to accommodate plastic (non-linear) analysis. Why don't you cover plastic design considerations in your standards?
WFCM