Shear Deflection of Composite Wood Beams

Shear deflection of wood beams usually is not included in design calculations. Ignoring shear deflection could lead to significant errors in total beam deflection predictions, especially for composite wood beams that have less and/or lower quality material in the core (or web) as compared to the outer zones (flanges).A generalized shear deflection equation was developed for layered composite beams. The model can accommodate variable numbers of laminations, nonprismatic shapes, and variable elastic properties between laminations and along the beam length. The model was validated using full-sized glued-laminated timber beam test data. Sensitivity analyses were conducted on numerical integration step sizes, ratio of modulus of elasticity to shear modulus, and span-to-depth ratio (L/d). One important finding was that the common engineering design practice of not including shear deflection for solid-sawn wood beams with L/d ratios of 15 to 25 could lead to significant errors for composite wood beams