ABSTRACT
The size factor accounts for the effect of the structural member size on the strength of the sawn wood member. There are two moduli of elasticity design values tabulated in National Design Specification (NDS-S) for sawn lumber. There are two design methods in the NDS that can be used for the design of wood structures: the allowable stress design (ASD) method and the load and resistance factor design (LRFD) method. Several proprietary engineered wood products have been developed for use in wood structures that require longer clear spans and higher load-carrying capacity than can be sustained by sawn lumber products. Structural composite lumber (SCL) are proprietary that include laminated veneer lumber (LVL) and parallel strand lumber (PSL) and they have higher strength and stiffness compared to sawn lumber. Glulam is the acronym for glued-laminated timber, which is made from gluing together under pressure thin laminations of kiln-dried sawn lumber where the direction of grains in all the laminations is parallel.
