Residual Stresses in Curved Laminated Wood Beams

Radial tension separations of large curved laminated beams have been observed in the United States for the past dozen or more years. They occur even in members whose design and manufacture follow the best engineering practice. Their cause is still unknown. This report examines two kinds of residual stress found in such beams. One of these is due to bending of the laminations to curvature during manufacture. The other is due to the variations in shrinkage of individual laminations that occurs subsequent to manufacture. No account is taken of stress relaxation or any other time-related effect. Equations of elasticity are derived for a curvilinear-orthotropic material in polar coordinates. Estimates of residual stresses are presented graphically and their possible relation to radial tension separations is analyzed.