ABSTRACT
In this research work, structural grade properties of some selected Nigerian timber species namely: Chlorophoral excelsa (Iroko), Khaya senegalensis (Mahogany), Daniellia oliveri (Maje) and Ceiba pentandra (Araba) were carried out after classifying the species to international strength classification system using EN338 (2008) with the aid of statistical package Easyfit (2010). This was done after establishing the physical and mechanical properties of the species in the laboratory using ASTM D193 (2000) and EN408 (2003). Chlorophoral excelsa was assigned to strength Class D70 with characteristic density of 474.95 kg/ , bending strength of 74.76 N/ and modulus of elasticity of 9,899.32 . Khaya senegalensis was assigned to strength Class D70 with characteristic density of 800.21 kg/ , bending strength of 80.64 N/ and modulus of elasticity of 8,944.0 . Daniellia oliveri was assigned to strength Class D50 with characteristic density of 509.01 kg/ , bending strength of 57.6 N/ and modulus of elasticity of 6,865.87 N/ and Ceiba pentandra was assigned to strength Class C40 with characteristic density of 300.78 kg/ bending strength of 41.16 N/ and modulus of elasticity of 4,423.64 N/ . Also, the distribution models were established for Chlorophoral exelsa, Khaya senegalensis, Daniellia oliveri and Ceiba pentandra to be normal, lognormal ,gumbel and weibull respectively.