Steel Buildings in Europe

Part 5: Detailed Design of Trusses 5 - 16 Once the scope of the model has been decided and adapted according to use to be made of the results, it is important to consider the nature of the internal connections. In current modelling of member structures, the selection is made between “a pin-jointed member at a node” and a “member rigidly connected to a node”; the possibility offered by EN 1993 to model connections as semi-rigid is rarely used for truss structures. For trusses, the model is commonly represented as either:  Continuous chords (and therefore chord members rigidly connected at both ends)  Truss members (diagonals and verticals) pin jointed to the chords. 3.3 Modelling the worked example In the worked example, the truss diagonals are pin jointed to the chords, although the connections are carried out using high strength bolts suitable for preloading with controlled tightening. This provides a rigid connection without slack between the diagonal and the connection gusset plates. The connection can be considered as pinned due to the fact that the vertical gusset plates are welded in the middle of the horizontal, not very stiff, IPE 330 web. The modelling is shown in Figure 3.1, with the numbering of the members. Left part Right part Figure 3.1 Computer model It is important for the model to be representative of the eccentricities which exist in the real structure. They can have a significant effect, as illustrated in Section 3.6.1. It is also important that modelling of the loads is representative of the real situation. In particular, the fact of applying to the truss nodes loads which, in reality, are applied between nodes, risks leading to neglect of the bending with quite significant outcomes. The main results of the analysis are given in Figure 3.2 for the left part of the truss.