In the design of single-layer structures, the hypothesis of pinned joints leads to structures with low capacity in terms of stability and resistance. Therefore, one of the main concerns of structural designers in recent years has been to find an appropriate joint design which would endow the joint with sufficient stiffness. In this paper, the results of experimental tests conducted with the aim of establishing geometrical parameters for a semi-rigid joint that may be used in single-layer structures are presented. They showed how the combination of different parameters can improve the stiffness of the joint and its rotational capacity. At the same time, the experimental tests provided the initial rotational stiffness of the tested joints which is to be introduced into the analysis of the structure. The paper presents an analytical method for the determination of the initial rotational stiffness of the joint. The method follows a technique similar to the component method of Eurocode 3 part 1.8, although it has been adapted to the geometry of this particular joint. (C) 2010 Elsevier Ltd. All rights reserved.