ABSTRACT
Wood used for structural purposes is generally referred to as lumber. Lumber may be cut and used directly from felled trees (logs), or may be manufactured in various ways from wood pieces and components. Lumber cut from natural wood is referred to as sawn, lumber that is manufactured is referred to as engineered.
The terminologies and general characteristics of sawn dimensional lumber and timbers are discussed, along with the design significance of wood species, grading, cellular structure, and grain orientation. The significance of wood being anisotropic (i.e., having different properties depending on grain orientation) is also explained.
The National Design Specification for Wood Construction (NDS) concepts of reference design values, adjustment factors, and adjusted design values (i.e., allowable stress) are introduced. Design considerations for beams and columns are presented, noting that horizontal shear is generally a more significant concern for wood beams than vertical shear.
A brief history of engineered wood is presented along with descriptions of commonly used engineered structural products such as I-joists, structural composite lumber (SCL), and glue laminated lumber (glulam). Products used for the emerging technology of mass timber design, such as cross laminated timber (CLT) and nail laminated timber (NLT), are also presented.
