State of the Art: Shear Deflection Theory and Design for Wood Products

Shear deflection is caused by warping within the beam cross section because of the application of loads. Excluding very deep beams, most metallic and cement-based structural materials experience little to no shear deflection. However, wood and wood composites exhibit greater shear compliance, making shear deflection calculation important for the assessment of overall deflection. The study of shear deflection in wood materials began in the early 20th century, and continues with the development of cross-laminated timber (CLT) and other mass timber products. This paper discusses the theoretical basis of shear deflection, applications of shear deflection, current measurement procedures, and wood design approaches for solid-sawn lumber, glued laminated timber, structural composite lumber, wood composite I-joists, and CLT. Different wood composites exhibit different responses to shear deflection. CLT in particular can experience higher percentages of shear deflection, especially under fixed end conditions, which necessitates the inclusion of shear deflection in serviceability calculations.