Lateral Torsional Buckling of Wood I-Joist

Abstract

Engineered wood I-joists have grown in popularity as flooring and roofing structural systems in the past 30 years, replacing solid sawn lumber joists. Typical wood I-joists are manufactured with a very slender section, which is desirable to achieve higher flexural capacities and longer spans; however, this makes them susceptible to lateral torsional buckling failure. Continuous beam spans and uplift forces on roof uplift are potential scenarios where lateral instability can occur and reflects the need to investigate the lateral torsional buckling behavior of wood I-joists. Within this context, the present study conducts an experimental investigation on the material properties and the critical buckling load of 42 wood I-joist specimens. A 3D finite element model is built using the experimentally determined material parameters to effectively predict the observed buckling behavior of the specimens while also accounting for initial imperfections in the joists. The adequacy of other analytical models to predict the critical buckling load of wood I-joists are also investigated. It is demonstrated that the American design standard underestimates the critical buckling load of wood I-joists while the classical theory provides an adequate estimate of the buckling capacity. Furthermore, the effects of initial imperfections on the lateral torsional buckling behavior are discussed. The developed and verified FE model is used to reproduce the nonlinear buckling behavior of the wood I-joist and also to provide an accurate estimate of the lateral torsional buckling capacity using the linear buckling analysis.