Characterisation of the behaviour of beam-to-column steel joints up to failure

The design of steel joints is currently dealt with in Eurocode 3 through the well-known “component method”. In particular, Part 1-8 of this standard provides guidance on how to apply the method to a wide range of joint configurations allowing to assess the latter’s initial rotational stiffness and resistance. Nonetheless, whenever a global structural plastic analysis is contemplated, provisions of Eurocode 3 are insufficient since no clear guidance on how to determine the ultimate resistance and the ultimate rotation capacity of joints is provided. In this paper, the full-range behaviour of beam-to-column steel joints is investigated using experimental, analytical, and numerical methods. A new analytical approach based on the component method is proposed and validated against five physical experiments. Through additional analytical expressions for the characterisation of basic components of steel joints, the proposed approach extends the applicability of the component method such that strain-hardening and ductility of components are accounted for. The results show a good agreement between the analytical prediction and the experimental results and also highlight specific limitations of the classical component method. Three-dimensional finite element (FE) models are also employed to simulate the behaviour of the tested beam-to-column joints. The results prove the accuracy of numerical models to simulate the non-linear response of steel joints emphasizing, however, the importance of proper modelling assumptions.