Investigation of the Lateraltorsional Buckling Behaviour of Engineered Wood I-Joists with Varying End Conditions

Abstract

The need to include economical and yet environmentally friendly products in modern day structural systems has pushed the development of engineered wood products such as engineering wooden I-joists. These products are engineered to resist high transverse loads and use the wood material more efficiently. Beam members, specially those that are deep and have long spans, are prone to lateral-torsional buckling as a possible mode of failure. Laboratory testing rarely take into account actual end conditions and initial imperfection which might have a significant impact on the buckling behavior of beams. The current research project aims to investigate the lateral torsional buckling of wooden I-joists. A total of 41 joists were tested using various commercial joists hangers and enhanced connections to represent different support conditions. A numerical 3D model was also developed using commercially available finite element program ABAQUS to determine the buckling loads and associated mode shapes of joists similar to those tested. It was demonstrated that the lateral stiffness of the joists’ top flange support has a significant influence on the buckling load and that a stiffness variation of the bottom flange lateral support shows no significant impact on the buckling load. The results also suggest that an enhanced rotational connection can significantly increase the buckling load of a member. The verified FE model was capable of predicting the buckling load of wood I-joists with various end conditions and initial imperfections with reasonable accuracy.