Constant Bending Method for Determining Modulus of Elasticity of Lumber in Structural Size


  • Marcel Samson
  • J. R. Sotomayor-Castellanos


Structural lumber, bending modulus of elasticity, shear modulus of elasticity


The objective of this study was to develop a method to determine modulus of elasticity of full-length lumber members loaded on edge in pure bending. This was achieved by loading the members by moments applied at each end of span using specially designed levers and a cable. To validate this approach, 38 x 89-mm (2 x 4-in.) spruce members of varying grades were instrumented with strain gauges and tested over a span/depth ratio of 17. Strain data revealed that the method developed was capable of subjecting members to pure bending except when a member twisted during loading due to the presence of large knots or spiral grain. A procedure is also presented to obtain shear modulus of elasticity of the members from a complementary test in center-point loading. Advantages of constant bending over standard test methods are discussed.


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