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

Document Type: Original Article

Authors

Civil Engineering Department, Faculty of Engineering and Technology, University of Ilorin, Ilorin, 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.

Highlights

Google Scholar

Keywords

Main Subjects


[1]       Kermani A, Porteous J. Structural Timber Design to Eurocode 5 2007.

[2]       Apu SS. Wood Structure and Construction Method for Low-cost Housing. Int. Semin. Build. Mater. Low-Cost Housing, Sept. 7, vol. 28, 2003.

[3]       material RF-W handbook: wood as an engineering, 2010  undefined. Wood as a sustainable building material. FsUsdaGov n.d.

[4]       Gere JM. Mechanics of Materials. Thomson Learning Inc 2004.

[5]       Trahair NS. Flexural-torsional buckling of structures. Routledge; 2017.

[6]       Ajamu SO. Optimal design of cement-lime plastered straw bale masonry under vertical load and thermal insulation for a residential building 2014.

[7]       Nowak AS, Collins KR. Reliability of structures. CRC Press; 2012.

[8]       Ozelton EC, Baird JA. Timber designers’ manual. John Wiley & Sons; 2008.

[9]       Nowak AS. Survey of textbooks on reliability and structure. Rep Spec Proj Spons by Struct Eng Inst ASCE 2004.

[10]     Ghasemi SH, Nowak AS. Target reliability for bridges with consideration of ultimate limit state. Eng Struct 2017;152:226–37. doi:10.1016/J.ENGSTRUCT.2017.09.012.

[11]     Thelandersson S, Larsen HJ. Timber engineering. John Wiley & Sons; 2003.

[12]     Aguwa JI, Sadiku S. Reliability studies on the Nigerian Ekki timber as bridge beam in bending under the ultimate limit state of loading. J Civ Eng Constr Technol 2011;2:253–9. doi:https://doi.org/10.5897/JCECT11.052.

[13]     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.

[14]     Aguwa JI. Reliability studies on the nigerian timber as an orthotropic, elastic structural material. Unpubl Ph D Thesis Submitt to Post Grad Sch Fed Univ Technol Minna, Niger 2010.

[15]     Ghasemi SH, Nowak AS. Reliability index for non-normal distributions of limit state functions. Struct Eng Mech 2017;62:365–72.

[16]     Norge S. Timber structures—structural timber and glued laminated timber—determination of some physical and mechanical properties. Nor Stand NS-EN 2010;408.

[17]     Standard B. BS 373: Methods of Testing Small Clear Specimens of Timber. Br Stand Institution, London 1957.

[18]     Adedeji AA. Reliability-Based Probability Analysis for Predicting Failure of Earth Brick Wall in Compression 2008.