Steel Buildings in Europe

Part 5: Detailed Design of Trusses 5 - 30 1 1 2 A A A-A 1 Batten 2 Gusset Figure 4.1 Members composed of two angles The maximum spacing of the connections between members is limited by EN 1993-1-1 to 15 times the minimum radius of gyration of the isolated component. Otherwise a more complex verification needs to be carried out, by taking into account the shear stiffness of the composed member. This limitation is very restrictive. By way of example, in order to link two 50 × 50 × 5 angles by respecting the spacing limit, it would be necessary to provide a batten every 15 cm. In order to illustrate the different principles stated above, justifying calculations are developed in the following sections for the different types of compressed members in the worked example truss structure. The results are taken from the basic worked example:  IPE 330 chords with horizontal web  Web members are assumed to be hinged at both ends  Chords are assumed to be continuous. 4.1.1 Upper chord in compression The verifications set out below, concern the upper chord member adjacent to mid span (element B107 in Figure 3.1), in which the normal compression force calculated under gravity ULS loads is greatest and equal to: N Ed = − 1477 kN The checks take into account the coincident bending moments. Note that the verification should also be carried out on the first member from the mid span, which is not restrained by the secondary truss: axial force of lesser compression, but with increased buckling length in the plane of the truss. Since the calculation is identical, it is not set out formally below. If this verification indicated a lack of resistance, the reinforcement solution would of course consist of extending the installation of the secondary truss. The shear force and the bending moments are given in Figure 4.2.