Performance of finger jointed timber boards with different joint configurations

Abstract

Timber is one of the construction materials commonly used in Sri Lanka. When using timber for construction purpose waste timber is also produced. This is being used in a useful manner with finger jointed system. But in Sri Lanka still there is a lack of knowledge in using finger joint in an efficient way. Main objective of this study is to find the most suitable finger joint length and type of adhesive through experimental results to have better efficient structural performance. Tests such as bending, compression (grain parallel and perpendicular), tension (parallel to grain) and shear perpendicular to grain were conducted. For these tests BS 373:1957 and EURO CODE 5 were used as standards for tests. In Sri Lanka Hardwood class timber waste is generated in more than other classes. Therefore, Hardwood class timber Teak has been used for all test carried out. Ultimate limit compressive stress grain parallel Finger jointed timber variation was obtained between 24.17 MPa - 36.09 MPa. At the same time the serviceability limit compressive stress grain perpendicular value variation was between 22.02 MPa - 26.15 MPa. Here the highest value was obtained for the finger length of value 14mm.Similarly, the Ultimate limit compressive stress of Grain perpendicular varies between 5.69MPa - 9.6MPa and the serviceability limit compressive stress of grin perpendicular varies in between 1.91Mpa-5.59 MPa. Here highest value was obtained for the finger length of 25mm. Also the shear stress values showed the variation between 2.5 MPa -3.14 MPa. The Modulus of elasticity varies between 1.249GPa - 2.889Gpa. Here the highest value was attained when the finger length was at 14mm. And also the Ultimate modulus of Rupture differs within the range of 12.44MPa - 27.37Mpa where the highest value was gained for the finger length of 25mm. Ultimate limit of tensile stress varies between 12.54 MPa -18.5 MPa here highest value attained when the finger length was at 25mm also Favicol SWR adhesive shows high Tensile stress value 18Mpa finally The Strength properties show a non-linear variation with the finger length. Therefore, based on structural strength requirement finger length should be decided.