Steel Buildings in Europe

Part 5: Detailed Design of Trusses 5 - 8 The intended use of the internal space can lead either to the choice of a horizontal bottom chord (e.g. where conveyors must be hung under the chord), or to an inclined internal chord, to allow maximum space to be freed up (see the final example in Table 1.1). To get an efficient layout of the truss members between the chords, the following is advisable:  The inclination of the diagonal members in relation to the chords should be between 35° and 55°  Point loads should only be applied at nodes  The orientation of the diagonal members should be such that the longest members are subject to tension (the shorter ones being subject to compression). 1.4.3 Section of the members Many solutions are available. The main criteria are:  Sections should be symmetrical for bending out of the vertical plane of the truss  For members in compression, the buckling resistance in the vertical plane of the truss should be similar to that out of the plane. A very popular solution, especially for industrial buildings, is to use sections composed of two angles bolted on vertical gusset plates and intermediately battened, for both chords and internal members. It is a very simple and efficient solution. For large member forces, it is a good solution to use:  Chords having IPE, HEA or HEB sections, or a section made up of two channels (UPE)  Diagonals formed from two battened angles. The web of the IPE / HEA / HEB chord section is oriented either vertically or horizontally. As it is easier to increase the resistance to in-plane buckling of the chords (by adding secondary diagonal members) than to increase their to out- of-plane resistance, it is more efficient to have the web horizontal, for chords in compression. On the other hand, it is easier to connect purlins to the top chord if it has a vertical web. It could be a good solution to have the top chord with a vertical web, and the bottom chord with a horizontal web. Another range of solutions is given by the use of hollow sections, for chords and/or for internals. 1.4.4 Types of connections For all the types of member sections, it is possible to design either bolted connections or welded connections. Generally, bolted connections are preferred on site. Where bolted connections are used with bolts loaded perpendicular to their shank, it is necessary to evaluate the consequences of slack in