The development of a strength grading system for small diameter roundwood

Roundwood as a construction material is becoming more and more interesting to users. Using this wood in construction will increase the value of the material and may open new opportunities for construction design. In order to use roundwood for this application, suitable connectors and/or joints have to be developed, but before all, the strength characteristics of roundwood must be determined and grading systems should be established. This investigation deals with the determination of the modulus of elasticity and the bending strength. The wood species concerned are Larch, grown in The Netherlands, and Douglas fir, grown in France, with diameters between 80 mm and 140 mm. The modulus of elasticity is determined by static and dynamic test methods. The data were included in a multiple regression model in order to predict the bending strength. The resulting model is compared with models for sawn timber that are nowadays used in practice