Relationship between stiffness properties for different mechanical demands in timber structures design projects

Abstract

In Brazil, the Brazilian Standard NBR 7190 (ABNT, 1997) establishes testing methods to obtaining the physical and mechanical properties wood. With the impossibility of determining the experimental results, the Brazilian Code establishes relations among the properties. However, the relations between the stiffness properties are based on the older normative standard MB-26: 1940 (Brazilian Standard NBR 6230), which condisidered another calculation model rather than the one used by the Brazilian standard. This research aimed to investigate the equivalence between the conventional modulus of elasticity in static bending tests (E_M), with compression parallel to the fibres (E_c0) and tension parallel to the fibres (E_t0) of ten species of tropical wood, as well as to establish relations between these properties, in case they are not equivalent. The ANOVA results showed that E_c0 and E_t0 were statistically equivalent, and the relation between E_M and 0.90∙E_c0 was not statistically equivalent, implying the determination of an ideal coefficient equal to 0.98 by the least squares method. This coefficient was 8.89% higher than the Brazilian standard.

Keywords:
Relations between properties; Hardwood; Stiffness; Beams theory