Experimental and numerical validation of a new design for three-dimensional semi-rigid composite joints

Semi-rigid composite joints not only have the advantage of optimizing the use of the material, but also of providing lateral stiffness for sway frames. By means of semi-rigid joints, the lateral stability of the structure may rely on the stiffness and ductility of the joints, thus avoiding bracing systems. These advantages may even increase when the joints are designed as semi-rigid in both axes. In this case, the joint behaves in a three-dimensional way that includes an interaction between the major and the minor axis of the column.In this paper, a new design for three-dimensional semi-rigid composite joint is proposed and tested in order to improve the behaviour and obtain the benefits of semi-rigidity when both the major and minor axis are included. Thus, the proposed design involves beams that are attached in a semi-rigid manner to both, the major and minor axes of the column.The experimental program consists in one 3D semi-rigid composite internal joint under proportional loads, another internal joint subjected to non-proportional loads and one facade joint. These tests provide information as to whether the joints satisfy the requirements of the Eurocodes 3 and 4 (EC3 and EC4) in terms of ductility, stiffness and resistance. Also the possible interactions between the major and minor axes of the proposed joint that are caused by the loads and/or the geometry are studied.Simultaneously, finite element modelling and analysis have been carried out and calibrated against the experimental results. These models have been performed with the aim of finding tools and ways to characterize and analyse the proposed joint design.Design guidelines are also provided for the use of this joint, and some additions and modifications to the Eurocode component method are proposed.

► A new design 3D semi-rigid composite joint is proposed and tested.
► These tests provide information about the ductility, stiffness and resistance.
► FEM and parametric study are carried out to analyze the interaction in both axis.
► Design guidelines and modifications to the EC4 component method are proposed.