Characterization of the halved undersquinted scarf joint and stop-splayed and tabled scarf with key joint (Jupiter joint)

Abstract

Historical timber frame structures constitute a huge part of the cultural heritage. The preservation of such structures requires a good understanding of both the original constructional methods and of the load-bearing principles of the structure. Carpentry connections are crucial for the behaviour of the structures, and a good understanding of them is of basic importance to lead a correct structural analysis. The present work introduces the basic load-bearing principles of the stop-splayed and tabled scarf joint with key (Jupiter joint) and the halved undersquinted joint; two among the basic types of lengthening joints used in traditional half-timbered and frame structures. The halved joint was used as a reference for developing an overview on the general structural behaviour. Therefore, the problem was examined in depth with the experimental and numerical analysis of the halved undersquinted scarf. Basic analytical linear-elastic models were developed. Tests were conducted under static loads in order to describe the maximum load, failure mechanisms, position of the forces along the loading process, rotational stiffness, friction mechanisms and the influence of the geometry on the load-bearing behaviour. The analytical model, based on the initial assumptions was calibrated on the experimental results. The influence and function of both the sloped surfaces and the wedge is investigated through some intermediate geometries. Finally, in order to give general remarks about the behaviour of the splayed and tabled scarf with key joint (Jupiter joint) along the strong and weak axis, a small series of specimens were tested, in order to describe the interaction between normal force (N) and bending moment (M) in a N-M interaction diagram and to record the failure modes along the strong and weak axis. The experimental outputs were compared with the numerical results obtained from the structural analysis of the dome of Santiago de Cuba’s cathedral to verify the reliability of the analytical model and the experimental results. The case study was chosen because the inner timber framed structure of the building demonstrated reliability against earthquakes and hurricane along the centuries. Here, the Jupiter joint was employed in the dome’s structure. The description of such carpentry connections through a static model is of importance for the structural analysis of old timber structures with the aim of restoration and reinforcement of them.