Frequently Asked Questions
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?
The short answer to this question is that, in general, engineered wood products and assemblies do not exhibit well-defined plastic characteristics. While some material properties show nonlinear stress-strain behavior (e.g., compression perpendicular to grain) as do many types of dowel-type wood connections, they do not exhibit the extended plastic region exhibited by mild steel. Neither do engineered wood products generally exhibit "transition" failure modes such as those of reinforced concrete (i.e., concrete cracking, load redistribution, etc.). As new engineered wood and non-wood composite products are developed and marketed that DO exhibit well-defined plastic characteristics, we hope to extend some of the classical plastic analysis techniques to these products in our LRFD documents.
Wood Products
- Why are the wind speeds in Minimum Design Loads for Buildings and Other Structures, ASCE 7-10 so much higher than those in ASCE 7-05?
- 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 is the difference between 2012 NDS 3.5 and 2012 IBC Table 1604.3 Footnote d for adjusting long-term deflection of wood members?
- 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?
- For structural composite lumber (SCL), should the volume factor, CV, be applied to Fb* in calculation of the beam stability factor, CL, or is it intended that CV be applied following calculation of CL?
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