Steel Buildings in Europe

Part 5: Detailed Design of Trusses 5 - 46 5.1.2 Convergence of the axes at the truss-column connection Another question to be asked when carrying out the connection of a truss on a post is that of convergence of the axes of the connected members and of its effect on the modelling. The choices are illustrated in Figure 5.2. Convergence of the axes column/chord/diagonal: solution to avoid Axis convergence of the axes chord/diagonal at the internal face of the column: recommended solution 1 1 : Rigid links Figure 5.2 Rigid truss-column connection In the first example, the actual physical connection and the model are not consistent: there is a risk of causing significant secondary moments in the diagonal and the chord. In the second example, the consistency is much greater; the eccentric moment is clearly supported by the post, which has a higher bending resistance than the chord or the diagonal, particularly when the truss is hinged at the post. Note that this not the case in the worked example in which the posts have their web perpendicular to the plane of the truss: the convergence of the three axes happens then without causing secondary moments. 5.1.3 Worked example: detailing a pinned joint The Figure 5.3 represents horizontal displacements of the lower and upper nodes of the two support sections, for cases of ULS gravity load combinations and for cases of ULS uplift load combinations. We can observe that, when the structure is symmetric or symmetrically loaded, each load case produces equal global rotations in the two support sections.