Analytical study of the dimensional stability of tropical brazilian wood species

Estudo analítico da estabilidade dimensional longitudinal das espécies de madeira tropicais brasileiras

ABSTRACT

Brazil owns a large vegetal covering and the best utilization of these materials requires physical and mechanical characterization procedures. Equations found in the literature make easier the wood properties determination. At this context, well known authors developed the equation β_l = β_t/23, being β_l and β_t the longitudinal and tangential shrinkage percentages, for β_l estimation based on the β_t value specially for wood species from the Northern hemisphere. This paper aims to investigate the accuracy of this equation for fifteen tropical Brazilian wood species covering the entire range of hardwood strength classes according to the Brazilian Normative ABNT NBR7190. The average experimental values of β_l and β_t were 7.71% (CV = 26,71%) and 0.73% (CV = 38,76%), respectively. The non-parametric Kruskal-Wallis ANOVA refuted the hypothesis of equivalence between theoretical and experimental β_l values (p-value = 0.0000). A linear regression model fitted to experimental values provided β_l = β_t/9,84 as optimal solution (p-value = 0.0000, R² = 47,23%). According to results it is possible to conclude that the value of longitudinal shrinkage percentage of tropical Brazilian wood species is statistically 2,34 times greater than the value found in the literature, which impacts the design of timber structures procedures increasing the internal stresses in timber structural elements.

Keywords
Longitudinal shrinkage; Tangential shrinkage; Tropical Brazilian wood