Bending Strength of Curved Glued Laminated Timber

An ultimate load theory for curved glued laminated beams in bending is developed which is based on a simplified model of timber behavior. The bending strength of curved laminated beams compared with that of straight beams of identical cross section is shown to be dependent on the type of loading, the ratio of lamination thickness to radius of curvature, stress relaxation, the number of laminations and the ratio of maximum tensile stress to maximum compressive stress in the timber. Stress relaxation tests are reported and the data used to determine one of the parameters required by the theory. It is shown that the predicted strength results are in satisfactory agreement with test data obtained from the work of previous investigators. After a consideration of current recommendations for the design of curved laminated timber beams new proposals are made which should lead to more satisfactory designs.