Wood - Lumber Stress Grade & Design

Course Summary:

This course briefly discusses the U.S. Department of Commerce American Softwood Lumber Standard PS20 (1994) sorting criteria for two stress-grading methods, and the philosophy of how properties for engineering design are derived. The derived properties are then used in one of two design formats: (a) the load and resistance factor design (LRFD), which is based on a reference strength at the 5th percentile 5-min bending stress (AF&PA 1996), or (b) the allowable stress design (ASD), which is based on a design stress at the lower 5th percentile 10-year bending stress. The properties depend on the particular sorting criteria and on additional factors that are independent of the sorting criteria.

Learning Objective:

• Responsibilities and Standards for Stress Grading
• National Grading Rule
• Visually Graded Structural Lumber
• Visual Sorting Criteria
• Procedures for Deriving Design Properties
• Machine-Graded Structural Lumber
• Machine Sorting Criteria
• Procedures for Deriving Design Properties
• Quality Control
• Adjustment of Properties for Design Use
• Shrinkage
• Moisture Adjustments
• Treatment Effects
• Temperature Effects

Review the quiz before studying the course.

Course Content

Course Author: US Forest Services