Experimental mechanical characterisation of selected Sri Lankan hardwood timber species for local structural timber design applications with reference to EN 338

Abstract

Timber is a renewable structural material, but Sri Lankan design practice often relies on properties developed for foreign species and strength classes. This study established a preliminary local dataset for Hora, Jak, Mahogany and Teak and compared their behavior with values commonly adopted from EN 338. Fifty-three small clear specimens were tested in four-point bending, tension parallel to grain, compression parallel to grain and compression perpendicular to grain. Moisture content and density were also measured. Clear differences occurred between species and loading directions. Teak had the highest density and bending stiffness, Hora the greatest bending strength, Mahogany the highest tensile strength, and Jak the highest moisture-normalised compression strength parallel to grain. Compression perpendicular to grain was far lower than longitudinal compression for all species tested in that mode, confirming the need for separate bearing and support zone checks. The measured mean properties showed different relationships with EN 338 benchmarks across the loading modes, indicating that a single reference class does not consistently represent all measured properties of these local hardwoods. The reported values are preliminary sample means rather than characteristic design values. The dataset supports the development of a nationally verified timber property database, although larger samples and full-size graded-member testing are required before formal strength classes can be proposed.