Development and Test of 26F-E Hem-Fir Glulam Beams

To make Hem-fir glulam beams to a new Canadian specification, E-rated and visually graded lumber was arranged by stiffness, after proof loading the outer tension laminations. Bending strength tests are described in detail for MOR, MOE, and failure modes. An unadjusted mean MOR of 6,900 pounds per square inch (47.6 MPa) was developed with a fifth-percentile point estimate of about 5,400 pounds per square inch (37.2 MPa). The unadjusted mean MOE was 1.92×106 pounds per square inch (13 200 MPa). Comparison is made with parallel work by Johnson in 1971. A key difference between this and Johnson’s study was the placement in this study of end joints in the highest stressed region of the outer tension lamination. Outer tension and compression laminations were almost balanced in strength in some specimens that showed distress in the outer compression lamination before collapse occurred owing to tension failure. This observation confirmed earlier conclusions that, with lumber distributed by stiffness, lower visual requirements may be used in the compression zones.

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