shows the differences between the two. Figure 9-25 shows the differences in crew size due in large part to the heavier gauge steel required by the ABM 240.

Keep in mind that the information provided in this section on the K-SPAN building is basic. During the actual construction of this building, you must consult the manufacturer's complete set of manuals.

TOWERS AND BUNKERS

TOWERS are framework structures designed to provide vertical support. They may be used to support another structure, such as a bridge, or they may be used to support a piece of equipment, such as a communication antenna or for a lookout post or weapon mounts. Since the prime purpose of a tower is to provide vertical support for a load applied at the top, the compression members, providing this support, are the only ones that require high-structural strength. The rest of the structure is designed to stiffen the vertical members and to prevent bending under load. Primarily, the bracing members are designed to take loads in tension and are based on a series of diagonals. Atypical

Figure 9-25. - Chart for determining crew size for ABM 240.