Variability of engineering strength properties of Kenya pines

Abstract

An investigation into the high variability of engineering strength properties of Kenya pine timbers has been carried out. Pine timbers from ten sawmills throughout the country and from the main timber growing regions were sampled and tested for the strength properties. The theoretical part of the study covered the review of strength testing and results obtained by others (7. II) and the properties of wood and timber as an engmeenng material. Various strength properties were studied together with the effects of strength educing defects. Grading standards were also looked at. The following engineering strength properties of timber were calculated in accordance with BS 373: • Bending parallel to grains • Compression parallel to grains • Tension parallel to grains • Shear parallel to grains • Modulus of elasticity The raw data was used to obtain two other sets of data, one through data trimming r and the other through logarithmic data transformation. Each set of data was then statistically analysed. The logarithmic transformation yielded the best results and led to increase in the derived basic stresses for the timber. Identification of compression wood proved difficult and though the variability is chiefly as a result of this wood, adequate measures to identify it or deal with its effect on strength were not addressed