Shear strength of Canadian softwood structural lumber

Abstract

An experimental study has been conducted to evaluate the longitudinal shear strength of nominal 38 × 185 mm and 38 × 285 mm Canadian softwood select structural lumber using a two-span five-point bending test procedure with test span to specimen depth ratios of 6 and 5. Based on American Society for Testing and Materials shear block test results of small clear specimens, finite element analyses coupled with Weibull weakest link theory have been used to predict the shear failure loads of the lumber. Good agreement between the predicted and measured median failure loads has been observed. This study has shown that the Weibull shape parameter is species dependent, which yields a higher unit volume shear strength under constant stresses; therefore, the characteristic shear strength values adopted in the current Canadian Code on Engineering Design in Wood might be conservative for select structural dimension lumber.