PROBABILITY-BASED DESIGN OF GLUED THIN-WEBBED TIMBER BEAMS

Probabilistic design methods are very attractive as they allow a systematic treatment of uncertainties and to set performance requirements in terms of explicit safety targets. The design of thin-webbed timber beams involves appreciable structural analysis of the load effect because of the various stress levels to be checked at different points of a cross-section. The presence of uncertainties in the response or the structural capacity of such beams may significantly alter the conjectured performance. This paper considers varying degrees of variability (measured by the coefficients of variation) in some selected design variables to derive appropriate safe design values for all relevant design variables at predefined performance levels for a typical cross-section of an I-beam. The design point concept of the First-Order Reliability Method (FORM) is employed to facilitate the needed solution. Design tables for typical cross-sections composed of glulam flanges and different species of plywood for the web are provided.