Mechanical Behavior of Timber Joists with Large Holes

In wood construction, to optimize the space and the floor height, the feasibility of large holes in timber beams, due to constraints imposed by ventilation or plumbing networks, are more and more studied. Their presence strongly influences the stress flow within the beam, which can cause early failures in comparison to unaltered beam. A non-exhaustive literature review highlights that peak stress in a rectangular hole is situated at the corners and, for circular hole, at approximately 45° ± 180° or 30° ± 120° with respect to the neutral axis for pure shear stress or pure bending moment, respectively. Nevertheless, dowel and plane type reinforcements enable to restore the load bearing capacity of the beam without hole. Experimental tests on glulam beams, monitoring by Digital Image Correlation, show that the stiffness is not affected by a single hole at mid-span in a four-points bending loading. To authorize the use of a wider range of configurations, the design of timber beam with large holes need to be investigate, yet. Moreover, further works will focus on the impact of large holes in timber-concrete floors.