Evaluation of Compressive Strength Characteristics of Structural-sized Apa ( Afzelia bipindensis  ) and Opon ( Lannea schimperi  ) Timber species columns found in Nigeria

The work centers on the compressive strength characteristics of Nigerian Apa (Afzelia bipindensis) and Opon (Lannea schimperi) timber species columns of nominal lengths 200, 400, 600 and 800mm and a nominal width and thickness of 50mm by 50mm. The data revealed that, Apa and Opon have an average density of 652.74 and 472.60kg/m³ respectively. The mean moisture content (MC) of both species were less than the fibre saturation point (FSP) recommended value of 25-30% and the average strength at yield of Apa and Opon are 35.65 and 14.00N/mm². The derived continuous equations for design of Apa column and Opon column are σ = 47.882^-0.009λ and σ = 17.211^-0.007λ respectively. The results of the reliability analysis show that Apa and Opon timber species have reliability index of 0.64 and 0.65 respectively for a service life of 50 years, assuming other serviceability conditions are met. This design procedure is distinct and more effective than the usual procedure of classifying compression members as short, intermediate and long using their slenderness ratios. The paper therefore recommends the adoption of these equations for the design of compression members from these timber species in Nigeria.