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UBC Theses and Dissertations

Stresses in pitch-cambered glulam beams Thut, Walter K.


The stress distribution near the centerline apex of pitch-cambered glulam beams is analysed. The analysis is done with an orthotropic trapezoidal finite element utilizing the stiffness approach. The element is tested with various grid sizes against known solutions and shown to give an overall accuracy to within five percent. Radial tension stresses perpendicular to grain due to moment, were calculated for various geometries and plotted as a design aid. These stresses can be several times those found in a uniform curved beam. The effect of changing the elastic moduli of the whole beam or individual laminations was investigated and found to be unimportant. Radial stress due to shear forces was found to be unimportant. Radial stress for one typical geometry due to moisture change was investigated in detail. This showed that ten pounds per square inch tensile stress was generated for a one percent change in moisture content. Twenty two tests were performed on tension perpendicular to grain to indicate that the allowable stress would be near thirty five pounds per square inch. A numerical example and design recommendations are included.

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