Influence of moisture content and reinforcement on load-carrying capacity of housings in solid timber beams

Timber construction is a sustainable solution to address the increasing global demand for housing. Timber framing currently uses mostly mechanical fasteners, which are made from metals with high carbon footprint, and – depending on the type of fasteners– provide poor aesthetics. These challenges can be addressed by using traditional joints such as timber housings. However, there are no design guidelines available that account for the joint geometric parameters, the wood moisture content during fabrication and when loaded as well as the impact of mechanical reinforcements. This thesis extends on previous research to investigate the influence of wood moisture and reinforcement on the load-carrying capacity of solid timber beams with housings. A total of 60 beams with single housings and 30 beams with double housings were prepared and tested while varying the moisture condition (either wet or dry) at the time of cutting the housings and at the time of testing the beams. Along with 32 test data from previous research, statistical analysis was conducted to evaluate the statistical significance of the investigated parameters. In addition, 198 small-scale specimens were tested for shear, tension and compression to evaluate the impact of small clear specimen material strength on the beam load-carrying capacity. The tests confirmed that larger depth below the mortise and the use of self-tapping screws as reinforcement lead to increase of load-carrying capacity; however, the moisture condition during cutting and testing was only shown to have a significant impact on the load-carrying capacity of double housings, but not single housings. The correlation between the material strength tests and load-carrying capacities demonstrated that the strength of small clear specimens from the same beam had no influence on the load-carrying capacity of the housings.