Structural products made of beech wood: quality assessment of the raw material

Hardwood timber is becoming increasingly important in Europe for its use as structural material, both as solid wood and engineered structural products. In Italy, the great abundance of beech forests has recently led to a research project to investigate the use of this species in construction. A first step is the characterization of the raw material for the production of structural glued products. This requires developing the strength grading of beech boards, both by visual and machine methods. To the aim, four provenances were collected across the distribution of beech in Italy. The main strength reducing characteristics were measured visually, and the dynamic modulus of elasticity was determined before performing the destructive bending tests of sampled boards. Correlations between properties were similar to what is usually observed for softwoods with the exception of density, which did not correlate with any other property. Several visual rules and machine settings were developed and compared, showing the effectiveness of both methods for the strength grading of beech. The grading yields for the high strength classes were very similar for machine and visual grading, while the machine permitted to reduce the number of rejected elements when two grades were selected at the same time.