Design Formula at Ultimate Stresses for Ekki (Lophira Alata) Timber Beam

Document Type : Original Article


Civil Engineering


The global pursuance of design method for economic utilization of building material is the basis of this study. The ultimate stress design method proposed in this study is in line with this pursuit as it encourages full utilization of material section and thus brings in economy in material application. This is the focus of this study on appropriate design procedure for Ekki (Lophira alata ) timber beam. This new method can replace the conventional design which is based only on modulus of rupture that has been reported not a rational method because it relies only on the extreme thin fibre tensile strength of the beam in flexure, whereas, for such a beam, it is subjected to both tension stress (below the neutral axis ) and compression stress (above the neutral axis). Based on this fact, the method generated two stress expressions, one for axial tension and the other for axial compression, represented by their typical stress-strain equations for loaded Ekki specimens. To develop the beam design equations, the axial typical stress-strain equations were converted to bending expressions of the stress-neutral axis depth relationships for the Ekki beam section. These relationships were further simplified and tested to give theoretical results that compare well with the experimental values.


Google Scholar


[1] Federal Department of Forest Research Institute, Nigerian Standard Code of Practice on Wood for Building and Construction Part 2 (NCP2) , 1973 , Ibadan, Nigeria , pp. 13-24.
[2] J.M.. Dinwoodie (1991), Timber, its nature, properties, and utilization, Van nostrand reinhold company, New York, pp 127.
[3] R.W.J Keay, C.F.A., Onoche, and D.P. Stanfield, D.P., (1964) Nigerian Trees, Vol. II, Department of Forest Research Institute Ibadan , 1964.
[4] B. Jozsef, and A.J. Benjamin, (1982) Mechanics of wood and wood composites, Van Nostrand Reinhold Company , New York.
[5] S.J. Mazur (1965), Ultimate Strength Theory for Rectangular Wooden Beans Symposium on Timber and Timber Structures, Transactions of the Engineering Institute of Canada, Paper No. EIC-65-Br & Str 13 Bridge and Structural, Vol 8 and 1 – 16
[6] B.D. Zakic (1973), In Elastic Bending of Wood Beams , Journal of Structural Division, Proceeding of the American Society of Civil Engineers, Vol. 99, No St10, pp. 2079-2095.
[7] A.A. Jimoh (2008) , Design equation for Ayin (Anogeissus leiocarpus) timber beam at ultimate loading capacity. Journal of Applied Science and Technology (JAST). 13(1 &2); 76-78, International Centre for Materials Science & Technology Ghana & Material Research Society of Ghana.
[8] W.H. Mosley and J.H. Bungey (1990);. Reinforced Concrete Design, Fourth Edition, Macmillan, London.
[9]K.A. Stroud (1980) , Engineering Mathematics , Programmes and Problems ,Macmillan Press Ltd, , London.
[10] BS 5268-2 (2002) , Structural use of timbers, British Standard Institution, London, United Kingdom.
[11] BS 373 (1957), Method of testing small clear specimen of timbers, British Standard Institution London, United Kingdom.
[12] BS 812-2 (1995) Methods for determination of density, British Standard Institution, London, United Kingdom.
[13] EN 384:( 2004) Structural timber- Determination of characteristic values of mechanical properties and density, British Standards institute, London, United Kingdom.
[14] William A.N and Sturgess C.E.N (1977); Schaum’s outline of Theory and Problems of Strength of Materials, Second Edition, Schaum’s Outline Series Mcgraw-Hill Book Company, New York
[15] American Institute of Timber Construction (2005), Timber Construction Manual, Fifth Edition, John Miley & Sons, INC., New Jercy, pp 19-297.
[16]   Deschi, H.E (1991).; Timber Properties, 6th Edition; Macmillan Education Ltd, London, pp 200-202.