Investigation of Strength Parameters and Physical Properties of non-class Timber Species in Sri Lanka

Abstract

Timber is a commonly used construction material in Sri Lanka. But the strength parameters of locally available non-class timber are not available. In this study main objectives are to determine strength parameters and physical properties of selected local timber materials and to develop a strength class classification with their possible applications in the construction field. Different strength parameter tests are conducted in bending, compression (grain parallel and perpendicular), tension (parallel to grains), and shear perpendicular to grain. In addition, durability, fire resistance tests and physical properties such as dry density, bulk density, and water absorption were carried out. For those tests BS 373 (1957) and EURO CODE 5 were used as references. Average moisture contents of nonclass timber specimens were around 12%, modulus of elasticity varies 3200 MPa - 13,000 MPa, modulus of rupture varies 37 MPa – 85 MPa, dry density varies 600 kg/m3 - 900 kg/m3. Strength parameters at serviceability limit, mainly compressive strength at parallel to grains varies 13 MPa - 45 MPa, and compressive strength perpendicular to grains varies 3 MPa – 22 MPa in most of the non-class timber species. Shear capacity of perpendicular to graons of non-class timber materials varies 0.9 MPa - 5 MPa at serviceability limit. Tension capacities of timber materials vary 35 MPa - 100 MPa and charring rate of timber species varies 0.25 mm/min - 0.8 mm/min. Similarly other test parameters were investigated and presented in the paper. Finally identified non-class timber species were classified according to available strength classes and proposed suitable applications for each type.