DEVELOPMENT OF DESIGN STRESSES FOR GLULAM TIMBER IN THE UNITED STATES

In North America, glued-laminated (glulam) timber beams are used as major structural elements in many buildings and bridges. The engineering design of these important structural members requires a knowledge of their engineering properties on which to base design stresses. A changing timber resource base demands a better characterization of strength properties for glulam timber. Consequently, reviews of established design stresses are necessary. procedures, incorporating reliability-based design methodologies, will also require the establishment of strength and stiffness distributions. This paper presents an overview of the current method of assigning design stresses for glulam beams and the research underway that is directed towards characterizing the engineering properties of glulam beams. Research is summarized in the areas of (1) reanalysis of allowable clear wood stresses for design. (2) formulation of equations to represent the volume effect in glulam bending members, and (3) the use of mathematical models for strength and stiffness predictions. New and emerging desig