Tenon connections: Consideration of brittle failure by fracture mechanics approach

Since timber constructions have been extensively planned and fabricated using digital processes, new connection types were developed for engineered timber construc- tions. One possibility to make more out of the precision of automated machinery is to multiply the contact surfaces in one connection. Enders-Comberg (2016) investigated the multiple-step joint and Claus & Seim (2018) conducted experimental and numerical tests on multiple tenon connections. In this context, tenons and notches are gaining new attention. The current design formulation for laterally loaded tenon connections in the second generation of Eurocode 5 (2025) is an extension of Gustafsson’s (1988) approach to end-notched beams based on empirically provided factors. However, the formulation is restricted due to the limited number of experimental tests carried out in the 1980s. Consequently, modern beam geometries, materials and CNC-fabricated joint geometries have not been adequately addressed. The following study tries to transfer the knowledge of the widely investigated end- notched beam (N) to tenon connections (T) and, finally, to multiple tenon joints (MT) with several contact surfaces and possible crack layers (Fig. 1). Additionally, the energy- based approach will be compared to experimental tests results and the results of a numerical J-integral model. Finally, a design formulation will be proposed for tenon and multiple tenon connections.