A Sustainable Solution for Strengthening Mass Timber Using Shape Memory Alloys

The use of reinforcement and prestress for strengthening mass timber glulam beams is not new and has been previously used to increase the beams' capacity, stiffness, and ductility. Different reinforcing and prestressing techniques using cables, curved tendons, slotted steel bars, strips, plates, and fiber-reinforced polymer (FRP) bars, strips, and sheets were previously studied by gluing and anchoring with timber. However, the complexity associated with the reinforcing/prestressing technique such as anchoring devices, mechanical jacking system, geometric limitations, prestress loss, and slotting preparation makes the conventional strengthening technique challenging. Shape memory alloys (SMAs) have been studied extensively for prestressing steel and concrete members, but using SMAs for prestressing glulam beams was not given any attention so far which can be an emerging trend in strengthening mass timber. Therefore, in this study, an innovative localized prestressing technique for mass timber using SMA was studied through numerical analyses, which was compared with the conventional FRP strengthening. The new prestressing technique showed promising results with a significant improvement in the beam bending stiffness.