Experimental study on the effects of holes on bending strain distribution of wood beams

To analyze the deformation and strain distribution of wood beams which contained holes during loading, in this paper, four-point bending tests were performed on clear wood beams and wood beams containing holes using digital image correlation technique. The influence of three various locations of holes (a hole located at center, located at compression zone, and located at tension zone, respectively) on bending strain distributions of wood beams was analyzed, and the movement of the neutral axis during loading was discussed. The experiment results showed that strain distributions and neutral axis locations were significantly different for three various locations of holes. When beams were at the ultimate load, for beams containing holes at various locations, the compressive strain region was larger than the tensile strain region. Among three various locations of holes, wood beams containing a hole in the compression zone had the largest compressive strain region, beams containing a hole at center come second, and beams containing a hole in the tension zone had the smallest compressive strain region. Additionally, the neutral axis moved towards the bottom of the beam as the load increased during loading. The movement of neutral axis was largest when the hole located at the compression zone, secondly when the hole located at center, and smallest when the hole located at the tension zone. Based on plane-section assumption and Hoffman yield criterion in elastic-plastic theory, the theoretical analysis of strain distribution and movement of neutral axis was studied on wood beams which contained holes. The results provide proofs for further theoretical study on bending properties of wood beams containing holes.