Force distribution in bolted cover plate splices, part 1

This article helps understand the distribution of different loads acting on a bolted cover plate splice. It can be even said that a similar distribution concerns the distribution of forces within a section in general element design. Some comments could be only extended on torsional effects for I-section beams, but this can be easily found in other technical publications.

There are two different elements to be considered when dealing with bolted cover plate splices: flange plates and web plates. All loads act on these elements in a different way and the illustrations of this fact are presented below.

Figure 1 shows a vertical load which is transmitted fully to the web of the section.

Figure 1.

Horizontal shear force is split into two flange forces as shown in Figure 2.

Figure 2.

The issue of torsional moment acting on beams is a more difficult topic, especially for I-sections where there are two types of torsion: St Venant torsion and warping torsion. Without going into too much detail, as a general rule of thumb, we can replace a torsional moment with two parallel and opposite forces as shown in Figure 3 below.

Figure 3.

Axial force in the section is spread over the two flanges and web taking into account the percentage of their areas. This will be described in the next part of this series. Figure 4 depicts these forces.

Figure 4.

Major bending moment is transferred mostly to the flanges, but it should be noted that some part of that moment is also taken by the web. There are cases when we can neglect the force taken by the web and assume that all forces are taken by the flanges. Figure 5 presents the real distribution of the moment within a section.