Analytical study of the dimensional stability of tropical brazilian wood species

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 beta l= [3t / 23, being beta l and beta t the longitudinal and tangential shrinkage percentages, for beta lestimation based on the beta 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 beta l and beta 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 beta l values (p-value = 0.0000). A linear regression model fitted to experimental values provided beta l = [3t / 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.