Simultaneous evaluation of bending and shear stiffness of wood I-joists by transverse vibration tests

Abstract

Prefabricated wood I-joists are widely used in lightweight wood constructions. Accurate and efficient measurements of their elastic properties are of great importance for predicting their mechanical behaviour during structural design. In this study, an alternative algorithm for simultaneous measurement of bending and shear stiffness of wood I-joists was developed for transverse vibration techniques based on Timoshenko beam theory. Sixty-five wood I-joists with thirteen configurations were tested by using the proposed modal testing method as well as traditional third-point bending tests. Based on the test results, the influences of section properties of wood I-joists on the shear rigidities were studied. It was found that the transverse vibration tests can be simply and efficiently implemented to determine the true and apparent bending stiffness of wood I-joists. In addition to the I-joist depth, the shear rigidities are also influenced by the web thickness and flange width. More importantly, shear deflection coefficients of tested wood I-joists are significantly larger than those theoretical values currently used by wood I-joist manufacturers.