Reliability-Based Investigation on Compressive Strength Characteristics of Structural-Sized Iroko (Meliceae Excelsa) and Mahogany (Khaya Ivorensis) Timber Column Found in Nigeria

Abstract

This research work examined the reliability of the Nigerian grown Iroko and Mahogany timber species as column materials. The strength and physical properties of these timber species were determined to predict the suitability of the species as structural material. Forty lengths of timber species of 50mm x 50mm cross-section were purchased from timber market in Ilorin, Nigeria. The prevailing environmental conditions during the test were 31oC and 64% relative humidity. The properties tested included; air dry density, moisture content and compressive strength parallel to grain of forty test specimens each of lengths, 200, 400, 600 and 800mm done in accordance with the British Standard BS 373(1957). Mean air-dried moisture content for Iroko and Mahogany were 12.09 and 14.81% respectively. Mean density of Iroko and Mahogany were 500.8 and 830.1kg/m3 respectively. The derived continuous equations for design of Iroko column and Mahogany column are σ=〖37.552e〗^(-0.005λ) and σ=〖37.125e〗^(-0.007λ) respectively. The results of the reliability analysis show that Iroko and Mahogany timber species have reliability index of 0.64 and 0.65 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.

Keywords

• compressive strength
• iroko
• mahogany
• regression analysis
• reliability