A new approach to reinforce glulam timber beams has been developed by using compressed wood (CW) which is made of a lower grade wood through densification processes. In the reinforcing practice, compressed wood blocks are inserted into pre-cut holes on the top of glulam beams to produce pre-camber and to generate initial tensile and compressive stresses on the top and the bottom extreme fibre of the glulam beam. In order to optimize the size, the number and the location of CW blocks, 3-D finite element models have been developed. 3D non-linear finite element models have been developed to simulate the pre-camber of Glulam beams locally reinforced by compressed wood blocks. The models developed have also produced the initial tensile and compressive stresses at the top and bottom extreme fibres with building-up moisture-dependent swelling on the CW blocks. With the pre-camber and the initial stress state that cancel out proportions of working deflection and stresses.
In this study, glulam beams were strengthened by inserting compressed wood (CW) blocks into the precut rectangular holes with one-thirds of the beam depth from the top of the beams. This practice was to make use of moisture-dependent swelling nature of the compressed wood which was conditioned with the moisture content significantly lower than the ambient one. The test results showed that a pre-camber was produced in the mid-span of the beam reinforced due to expansion of the compressed wood blocks on the top part of the beam. As a result, significant initial tensile and compressive stresses were generated on both the top and the bottom extreme fibres of the beam, respectively. Subsequent bending tests revealed that the initial stiffness and load carrying capacity of the pre-stressed beams were increased significantly in comparison to the beam without pre-stressing.
