STRUCTURAL CHARACTERIZATION OF TIMBER SPECIES FOR ENGINEERING APPLICATIONS IN KENYA

Abstract

Timber has been a key material in construction for centuries, offering strength, durability, and versatility. In Kakamega County, Kenya, both indigenous and exotic timber species are used in construction, with cypress and eucalyptus being the most commonly utilized due to their superior strength. The selection of these species for engineering applications is influenced by factors such as availability, growth rate, and cost. However, no characterization of these timber species has been conducted.This study investigated the structural characterization of timber for engineering applications, specifically focusing on the engineering properties of cypress and eucalyptus from Kakamega County. It aimed to determine the types of species predominantly used in construction, evaluate their strength properties, and classify them into specific grades based on EC 5 standards. Field visits to forests, timber yards, construction sites, and the Kenya Forest Research Institute (KEFRI) revealed that cypress and eucalyptus were favored for construction due to their strength, with eucalyptus being more common because of its faster growth and lower cost. In contrast, Grevillea was less used due to its susceptibility to insect infestation.Logs from the two species were tested for mechanical properties, with 720 samples subjected to compression, bending, and tensile strength tests. The results classified cypress as a softwood (strength class C20), suitable for high-strength applications such as roof trusses, while eucalyptus was classified as a hardwood (strength class D24), commonly used in structural products such as railway ties and mine timbers. Understanding these properties helped optimize the use of timber in construction and ensured that the appropriate species were selected for the correct engineering applications in compliance with Eurocode 5.