EN 338 Strength Characterization and Grading of Igba (Rhizophora Racemosa) and Adere (Syzgium Guineense) Timbers for Structural Applications

Document Type : Original Article


Department of Civil Engineering, University of Ilorin, Ilorin, Nigeria


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.


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[1]     Obasi FA, Agbo FU, Onyenekwe CS. Environmental and socio-economic effects of timber harvesting in Ebonyi State, Nigeria. African J Agric Res 2015;10:1233–8.
[2]     Saravanan V, Parthiban KT, Thiruneraiselvan S, Kumar P, Vennila S, Kanna SU. Comparative study of wood physical and mechanical properties of Melia dubia with Tectona grandis at different Age Gradation. Res J Recent Sci ISSN 2014;2277:2502.
[3]     Ajuwa JI. The Nigerian Timber Structures, Samaru Zaria, Ahmadu Bello University Press Limited Nigeria 2016.
[4]     EZEAGU CA, EROMOSELE AF, Okoro H, CHUKWUJEKWU UJ, EMETOMO TB. Flexural Strength of solid and glue-laminated timber beams. Am J Eng Sci Technol Res 2015;3:1–14.
[5]     Jimoh AA, Rahmon RO, Babatunde OY, Tazou OL. Characterization and Classification of Ayunre (Albizia zygia) Timber Specie grown in Kwara State Nigeria in accordance to bS 5268 nad NCP 2. Epistemics Sci Eng Technol 2017;7:549–57.
[6]     Aguwa JI. Reliability assessment of the Nigerian apa (afzelia bipindensis) timber bridge beam subjected to bending and deflection under the ultimate limit state of loading. Int J Eng Technol 2012;2:1076–88.
[7]     Appiah-Kubi E, Kankam CK, Adom-Asamoah M. Bending and modulus of elasticity properties of ten lesser-used timber species in Ghana using structural dimensions 2012.
[8]     EN 338, Structural timber - Strength Classes, European Committee for Standardization. Austrian Standards Institute Heinestrase 38, 1020 Wien, 2009 n.d.
[9]     EN 13153-1, Moisture Content of a Piece of Sawn Timber-Part 1, Determination by Oven Dry Method.ComiteEuropeen de Normalisation, Brussels, Belgium, 2002. n.d.
[10]   EN 408, European Standard: Timber structures - Structural Timber - Determination of some physical and mechanical properties,ComiteEuropeen de Normalisation, Brussels, Belgium, 2004. n.d.
[11]   EN 384, Timber Structures; Structural timber Determination of Characteristic Values of Mechanical Properties and Density, ComiteEuropeen de Normalisation, Brussels, Belgium, 2004. n.d.
[12]   Antwi K, Effah B, Adu G, Adu S. Strength and some physical properties of Allanblackia parviflora for furniture production in Ghana 2014.
[13]   Abubakar I, Nabade AM. Physical and Mechanical Properties of Some Common Nigerian Timber Species Based on Limit State Design Approach. Study Civ Eng Archit Vol 2013;2.
[14]   Zziwa A, Kambugu R, Kizito S, Mugisha A, Sseremba O, Syofuna A. Evaluation of Basic Strength Indicators of Mangifera Indica Timber to ascertain its Suitability For Furniture Construction. Int J Res Eng Adv Technol 2016;4.
[15]   Idris A, Muhammad NA. Bending Strength Classification of Some Common Nigerian Timber Species. Jordan J Civ Eng 2014;159:1–7.
[16]   Kaura J, Abubakar I, Aliyu I, Hassan U. EN 338 Strength Grade and Uncertainty Models of Material Properties for Nigerian Grown Terminalia Superba (White Afara) Timber Specie. Niger J Technol 2014;34:21. doi:10.4314/njt.v34i1.3.
[17]   DeCarlo LT. On the meaning and use of kurtosis. Psychol Methods 1997;2:292.