Determined uncertainty models of reference material properties and the en 338 strength class of Nigerian grown Terminalia ivorensis (black afara) timber

Abstract

The purpose of this paper was the determination of the uncertainty models of reference material properties and [1] strength class of Nigerian Grown Terminalia ivorensis timber, so that it can be used in structures designed based on the Eurocode 5. The test data were analysed using Easyfit® statistical package. The uncertainty models (Coefficients of Variation and Distribution models) of the reference material properties (density, bending strength and modulus of elasticity) were determined. The coefficient of variation of the density, modulus of elasticity and bending strength were found to be 15%, 21% and 16% respectively. The mean values of the density, modulus of elasticity and the bending strengths were determined at moisture contents of 17.93%. The values were adjusted to 12% moisture content for the determination of the strength class according to [1]. Five standard probability distribution models (Normal, Lognormal, Gumbel, Weibull and Frechet) were fitted to each of the three reference material properties using Kolmogorov Smirnov probability distribution fitting technique. The best fit theoretical distribution models were found to be Normal distribution for Density, Lognormal distribution for Modulus of Elasticity and Weibull for Bending Strength. The Terminalia ivorensis timber specie was also classified as D18 in accordance with [1] specification. The uncertainty models will facilitate the application of reliability based approach in the design of timber structures with Terminalia ivorensis. Also Terminalia ivorensis can now be used for construction of structural timber designed based on Eurocode 5 since its strength class is now established.

Keywords: Black Afara Timber, Terminalia Ivorensis, Uncertainty Models, Density, Modulus of Elasticity