EN 338 Strength characterization and grading of Igba (Rhizophora racemosa) and Adere (Syzgium Guineense) Timbers for Structural Applications

Abstract

The paper characterizes two potential timbers grown in Nigeria according to EN338 (2009) timber strength classification. The timbers namely Igba (Rhizophora racemosa) and Adere (Syzgium guineense) were obtained in Kwara state in the North-central part of Nigeria. Physical and Mechanical properties of timber species were obtained in accordance with EN 13183-1 (2002) and EN 408 (2003). Four point bending tests based on EN 408 (2003) with specimen size 50x50x1000 mm was carried out using a Universal testing machine (UTM) to determine the bending strength and Modulus of Elasticity of each timber specie. Characteristic values of Bending strength, Modulus of Rupture and Density were determined using EN 384(2004). Rhizophora racemosa and Syzgium guineense had equilibrium moisture content (EMC) of 10.59 % and 22.34 % respectively. This moisture content were adjusted to 12% using adjustment factors so as to satisfy EN338 (2009) requirements for strength grading of timber. Rhizophora racemosa and Syzgium guineense were assigned to strength class C14 and D24 respectively. The Kolmogorov Smirnov test of goodness of fit test at 95% level of significance (α = 0.05) for bending strength of the two timber species as obtained using Easyfit 5.6 software shows that the most fitted distribution model for bending strength of Rhizophora racemosa is the normal distribution, while Lognormal Distribution is the most fitted for Syzgium guineense.