Veerapong Chotchuay, Buhnnum Kyokong, and Winai Ouypornprasert

pp. 649 - 657

Abstract

      This study was carried out to investigate engineering properties of one type of wood composites known as Oriented Strand Lumber (OSL). Heat-treated Parawood strands were used for producing OSL specimens (HOSL) and compared to a control one (nonheat-treated or NOSL). The structural application as beams was selected to determine the effect of sheared volume to longitudinal shear strength since shear failure is a critical mode of OSL. The reliability concept was then employed to analyze the data to ensure that OSL structural members can be used for construction safely and economically.
         The results indicated that mean values of strength of HOSL subjected to axial loading, i.e., compression (39 MPa) and tension (36 MPa) parallel to the grain as well as bending in the flatwise (59 MPa) and edgewise (61 MPa) directions were significantly higher than those of NOSL. However, the differences between HOSL and NOSL subjected to normal loading, i.e., compression perpendicular to the grain (26 vs 25 MPa), shear parallel to the grain (4 vs 3 MPa) and internal bonding (0.48 vs 0.47 MPa) were non-significant. The results of shear strength studies showed that the shear strength of HOSL beams was higher than that of NOSL beams and regression analysis revealed that the shear strength depended on sheared volume. It showed that shear strength decreased with increasing sheared volume. The results of the reliability analysis indicated that the fitted distribution of the flexural rigidity (EI) could be represented well as normal. The coefficient
of variation of the fitted EI distribution was found to be within the serviceability limit state required by the building codes. This implies that OSL beams can be used safely as an alternative structural material for wood construction. The safety factor and recommended allowable design stresses are also presented.