Effects of Sawn Splits on Buckling, Bending, and Shearing Properties in Full-Size Squared Lumber of Hinoki (Chamaecyparis obtusa)

Effects of depth (30 and 50% of lumber width) and inclination to the loaded face of sawn splits on buckling, bending, and shearing properties were investigated for full-size squared lumber (10.5 by 10.5 cm in cross section) of hinoki (Chamaecyparis obtusa Sieb. et Zucc.). No significant differences in buckling properties, and modulus of elasticity and proportional limit ratio in static bending were found between lumber without or with a sawn split. On the other hand, when load was applied to the side opposite to the sawn split, modulus of rupture in static bending was significantly decreased for all depths of sawn split. In addition, shearing strength determined by an asymmetric four-point loading method largely decreased when the load was applied to the side perpendicular to the sawn split. However, modulus of rupture in static bending and shearing strength of lumber with a sawn split with depth 50% of width exceeded the design strength requirement values of ungraded hinoki lumber listed in Bulletin No.1452 of the Ministry of Construction, Japan. The obtained values of buckling strength in all specimens tested here were higher than the buckling strength of ungraded hinoki lumber estimated by compression design strength based on “Standard for Structural Design of Timber Structures” of the Architectural Institute of Japan.