Experimental characterization of longitudinal mechanical properties of clear timber: Random spatial variability and size effects

Abstract

In this study, an experimental campaign was conducted to characterize the length effect on the elasticity and tensile strength of clear spruce wood parallel to the grain direction. Four groups of specimens of different lengths, cut from the same log, were tested under the same conditions under longitudinal tensile loading. The cross-sectional area of the specimens was selected as being constant and sufficiently small to exclude the effect of variations of the properties in the transverse direction. Local deformations along the lengths of the specimens were recorded during the tests in order to characterize the spatial variability of the elastic modulus. A connection between the mesostructure of the clear wood and its local elastic modulus was observed. Statistics concerning the elastic modulus, strength and strain to failure and the effect of length change on these properties were extracted. The strength statistics were also used to examine the accuracy of the classical Weibull size effect law. The correlations between the strength, the elasticity and the density were obtained. The results show a variability of approximately 20% in the local elastic modulus. Also, the variability of the effective elastic modulus decreases with increasing length. The mean value of the strength has an upper bound when the length approaches zero, in contrast to the Weibull law, while its variability remains virtually unchanged for different lengths.

Prediction of withdrawal resistance for a screw in hybrid cross-laminated timber

“…The small size screw specimens, Solid wood-6.5 and Plywood-6.5, are located to the right side of the Ø8.0 × 100 mm screw specimens, Solid wood-8.0 and Plywood-8.0, indicating their withdrawal strength value. This result seems to display the same phenomenon as the size effect of timber: the strength decreases as the size of the timber increases [42]. Figure 9 shows the distribution of the withdrawal capacity of screws for Ply-lam.…”

Mechanical properties of a balsa wood veneer structural sandwich core material

“…The above-mentioned studies were all conducted using balsa blocks or lumbers. Similar to other wood types [14], the mechanical properties of balsa wood exhibit significant variations in the radial direction of the tree's cross sections and thus considerable scattering, which causes difficulties in the design of sandwich panels incorporating a balsa core. In order to reduce this scatter, a new balsa product was developed for the deck of the above-mentioned Avançon bridge [8].…”

Anatomical, physical, and mechanical parameters of clone plantation tree, Cunninghamia lanceolata

“…"Cunninghamia lanceolata parameters," BioResources 16(2), 3494-3519. 3496 is usually referred to as "random spatial variability", which is most likely to influence the response of structural elements made of clear timber (Moshtaghin et al 2016). To analyze the spatial variability of above-ground biomass (AGB), stocks of managed forests, linear (LM), generalized additive (GAM), and Random Forest (RF) empirical models, with variables related to forest management, stand structure, topography, and climate, are developed to derive spatially explicit estimates and their uncertainty, and compared (Soriano-Luna et al 2018).…”