Development of a connector element for steel hub joints with end-bearing and bolt-connected wood members

Steel hub joints featuring end-bearing and bolt-connected wood members (EBBC joints) are widely used in timber arches and reticulated domes, but their rotational behaviour is highly dependent on the axial force applied, which cannot be captured by general-purpose finite element analysis software. This paper proposes a two‑node connector element (UCEL‑EBBC) for use in space frame systems that properly reflects the axial-bending load coupling as well as the biaxial bending coupling effect on the joint behaviour. The element is based on a mechanical model with non-linear springs for tension and a fibre-based component for compression, and is implemented in ABAQUS via a UEL subroutine for real-time stiffness updating. Validation through tests on eccentrically compressed members showed that the UCEL‑EBBC accurately captured the compression-bending coupling effect. Based on results from a validated solid finite element joint model, the biaxial bending coupling characteristics were well reflected, whereas the computation time was reduced by 85%–90% by the UCEL-EBBC. Experimental validation of biaxial bending remains for future work. Within the scope of joint configurations and loading schemes studied in the current paper, the UCEL-EBBC element provides a robust and accurate tool for the global analysis of long-span timber structures.