The Impact of Different Shapes in Knockdown Construction Interlocking Systems on the Flexural Strength of Longitudinal Half-Lap Wooden Joints with Tongue-and-Groove

Wooden joints are considered as vulnerable parts that often lead to structural failure. One of the most widely used joints is the longitudinal half-lap joint. This is used to joint woods longitudinally and is frequently employed for joints in beam or column elements. Various types of joints are utilized, such as mortise and tenon joints, bolts, and nails. Jointing wood using a dowel joint tool, or known as ‘interlocking wooden joint’ allows woods material being joined to adapt. This way, the joint becomes more optimal in dealing with changes in temperature and humidity. Therefore, research related to wooden interlocking needs to be developed. This study aims to assess how various interlocking shapes affect the flexural strength of longitudinal half-lap joints. This is experimental research with a three-point load-bending test. The longitudinal half-lap joint was explored using four variations of the interlock system, namely circle, triangle, rhombus, and concave hexagon, each with three samples. Based on the test results, the interlocking shape with the highest values for Modulus of Rupture (MoR) and Modulus of Elasticity (MoE) is the concave hexagonal shape, with MoR = 21.12 MPa and MoE = 2087 MPa. The MoR value is 14% higher than the triangular shape, 37% higher than the rhombus shape, and 48% higher than the circular shape. The MoE value is 5% higher than the triangular shape, 20% higher than the rhombus shape, and 48% higher than the circular shape. Therefore, the concave hexagonal interlocking shape is stronger in resisting flexural strength among the variations.