End-colloquium Nick Meinsma
Investigation of the mechanical behavior of a large finger joint in veneer-based panels
A Finger joint (FJ) is commonly used in timber structures to establish timber connections. A FJ is used to extend two pieces of timber by gluing the end grain face together. This can be used in multiple structural applications, in this study the aim is a rafter for a roof structure. When using a FJ in a structure bending could occur in the FJ. However, when a FJ is applied in timber, the FJ geometry weakens the bending strength, compared to a full cross-section. This is also conventionally described in the NEN-EN 1995 Eurocode 5, where a reduction of 20% is applied to the bending strength of a full-size finger joint.
Nevertheless, in this study, a new design (made by Spantenfabriek.nl) of a large finger joint (LFJ) is studied as shown in this previewed Figure. This LFJ is significantly larger compared with a common finger joint. The LFJ is composed of two types of plywood (ply), one ply cross-layered, and one ply mainly parallel-layered. The LFJ will be loaded in-plane (loaded edge-wise). To understand the mechanical behavior of this new design of the LFJ, in bending, the following research question will be answered:
"What is the mechanical behavior of the large finger joint (LFJ), in bending, designed by Spantenfabriek.nl made in veneer-based panels and how will different heights of the connection influence the mechanical behavior?"
This question will be answered by conducting literature research which forms the basis for creating an analytical model. The analytical model describes the strains and stresses in the large finger joint in bending, which predicts the bending strength and stiffness. Additionally, several experimental tests were executed based on EN 408 and EN 789, to obtain the material properties (tension, compression, and bending) as input for the analytical model. Finally, four-point bending tests were performed, according to EN 408, to make a comparison with the generated analytical model. And to study the behavior of the LFJ in bending.
