New Insights into the Behavior of Curved Glued-Laminated Timber Beams during Fabrication and Structural Testing Using Distributed Fiber-Optic Strain Sensors

Abstract

Curved glued-laminated (glulam) timber beams have been used in practice as structural components in roof systems and bridges, capitalizing on the architectural freedom of using wood as a building material. Despite their use in practice, there is limited experimental data on the structural behavior of curved glulam beams, both during fabrication and at their ultimate limit state. To address this gap, this study examines the structural behavior of curved glulam beams both during fabrication and under mechanical loading to failure through a series of experimental tests. A total of 13 beam tests are described, which varied in their radius to better understand the influence of beam curvature on the residual strain distribution and the beam stiffness, strength, and failure mode at ultimate limit states. The beams were instrumented with distributed fiber-optic sensors to generate high-resolution strain measurements along the length and over the depth of the beams for the first time. Results of the study demonstrate that a complex state of strain, and thus stress, exists in a curved glulam beam after fabrication through mechanical bending of the laminations. Under structural loading, the studied beams exhibited a range of failure modes, which depended on the beam radius, including flexural failure in tension, shear failure, and radial tension failure. The experimental results are also compared with North American wood design standards, and the results suggest that these standards can predict the strength of the curved glulam beams tested in this study to within 5% of their ultimate load-carrying capacity.