ORIGINAL Effect of moisture content on the flexural properties and dynamic modulus of elasticity of dimension chestnut timber Michela Nocetti • Michele Brunetti • Martin Bacher Received: 23 June 2014 / Published online: 4 November 2014 Ó Springer-Verlag Berlin Heidelberg 2014 Abstract Moisture content (MC) has an important influence on the physical and mechanical properties of wood. This has to be taken into account when using timber for structural purposes; in particular, a correct estimation of the modulus of elasticity (E) is not only important for the key role that this parameter plays in design calculations, but also because it is a property that can be measured non- destructively and used to predict the quality of the material and, thus, to strength grade it. Hence, moisture content adjustment factors between MC 12 % and green state for density, static and stress vibration dynamic E were devel- oped based on linear constant percentage model for dimension chestnut timber. The experiment was conducted on 200 ungraded pieces of 80 9 80 m 2 cross section. For density, the adjustment suggested by the European standard EN 384 is appropriate below fibre saturation point (FSP), however, a more suitable equation is reported for pieces above FSP. Concerning E, the recommendation of EN 384 results in an overestimation, when the adjustment is applied to pieces with MC between 12 and 18 %, and an under- estimation if applied to green timber. An appropriate adjustment equation is suggested for chestnut timber, tak- ing into account the proper balance between accuracy and simplicity in the model usage and the desirable safety when performing an MC adjustment for structural use. An increment of 27.7 % in bending strength from green to dry state was also calculated. Finally, the feasibility of strength grading of chestnut green timber was investigated, con- cluding that the same efficiency can be expected if the grading is performed on dry or on freshly cut timber. 1 Introduction It is well known that moisture content (MC) has an important influence on the physical and mechanical prop- erties of wood. This has to be taken into account when using timber for structural purposes and the relationship between timber properties and MC is something that has to be considered when designing timber structures. Among others, the flexural properties of wood are influenced by its moisture content. Generally, an increase in strength and stiffness due to the reduction in moisture content below fibre saturation point (FSP) is assumed and no fundamental changes above FSP (Skaar 1988). In the past, numerous studies analysed the relationship between bending properties and moisture content, both on clear specimens and dimension lumber, describing the effects of several factors. McLain et al. (1984) on Southern pine and Aplin et al. (1986) on Douglas fir, studying the effects of moisture content on the flexural properties of dimension lumber, found that the relationship was depen- dent upon both timber size and quality, but it was noted that bending strength (f m ) was much more sensitive than modulus of elasticity (E), which, at a practical level, could be considered independent of both size and quality. The effect of size on timber strength was also described for sugi (Cryptomeria japonica) by Ido et al. (2013), comparing small clear specimens, boards, square lumber and round timber. In general, the change in strength in response to M. Nocetti (&)  M. Brunetti CNR, IVALSA, Istituto per la Valorizzazione del Legno e delle Specie Arboree, Via Madonna del Piano 10, 50019 Sesto Fiorentino (FI), Italy e-mail: nocetti@ivalsa.cnr.it M. Bacher MiCROTEC Srl, Via Julius Durst Straße 98, 39042 Bressanone, Italy 123 Eur. J. Wood Prod. (2015) 73:51–60 DOI 10.1007/s00107-014-0861-1