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Frequently Asked Questions

What is LRFD?

Load and Resistance Factor Design (LRFD) Manual for Engineered Wood Construction is now out of print and LRFD is incorporated in the 2005 NDS.

The AF&PA/ASCE 16-95 Standard for Load and Resistance Factor Design (LRFD) for Engineered Wood Construction was approved in November 1995 as a consensus standard through the ASCE standards development process. It has been replaced by the 2005 NDS.

What's the difference between LRFD and ASD?

Load and Resistance Factor Design (LRFD) and Allowable Stress Design (ASD) are two separate methods for proportioning structural components. Applicable load combinations and resistance values differ between LRFD and ASD. Both LRFD and ASD methods for structural design of wood members and their connections are provided in the 2005 National Design Specification (NDS) for Wood Construction.

For more details, see the following papers:
LRFD versus ASD for Wood Design (4 pages pdf, 32 KB) July 1998
Designing with LRFD for Wood (5 pages pdf, 660 KB) July 2001

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