Question 2: Briefly describe what is meant by the terms “visually graded sawn lumber” and “machine stress-rated (MSR) lumber”. Answer: Visually graded sawn lumber is lumber which has been graded by eye by a certified lumber grader. The grader uses grading rules that evaluate the stress grade of the lumber based on size, location and number of strength-reducing characteristics in any piece. A grade stamp is then assigned based on the visual evaluation. Machine stress-rated (MSR) lumber is lumber which is also graded by a nondestructive test machine. The lumber is fed through the machine and bent about its weak axis. From force and displacement measurements, Modulus of Elasticity (MOE) is calculated. The bending strength of the piece is determined through correlation with the calculated MOE. Because of this extra grading step, MSR lumber is more reliable than visually graded lumber; it costs more and is therefore used in applications where the entire cross section of the member is highly stressed.

Peggi Clouston

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From the 6th edition textbook

1.25

(1.25) 1062.5

(1.25) 590.6

187.5

1462.5

(1.25)

(1.25)

Peggi Clouston

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From the the 5th edition textbook