An assessment of common test methods to evaluate the mechanical properties of structural end-jointed lumber

This paper presents the results from a study assessing four different test standards used for qualification and ongoing quality control of structural end-jointed lumber in the United States and Canada: AITC 200-92 T119 (AITC 1992), SPS 1 (NLGA 2000), ASTM D 4761 (ASTM 1999), and the Southern Pine Inspection Bureau (SPIB 2000) Glued-Lumber Procedures. The purpose of this paper is to demonstrate the various test methods and to determine relationships between failure stresses and characteristics of the different test methods. End-jointed samples having fingers with a vertical joint profile were produced by a glulam manufacturer from 12.4 GPa (1.8E) machine stress-rated Douglas-fir lumber, with no visual over-ride. The population of end-jointed specimens was ordered by bending stiffness and assigned to groups such that the stiffness distributions of the groups were equivalent. The inferences regarding specific mechanical properties are limited, but the relationships between mechanical properties from the various test methods are useful. It was shown that failure mode was affected by test method. The strength data of each test group were fitted with normal, lognormal, and Weibull distributions. The Anderson-Darling goodness-of-fit test showed that normality could not be rejected for any group. A method for the purpose of converting mean strength and variance between test methods of future tests was presented and demonstrated.

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