ERECTION OF GUYED TOWERS

The following paragraphs present methods that have been successfully used to erect guyed towers. '1he most practical method for any particular tower

Table 8-2.-Bolt Torques (foot-pounds)

Figure 8-32.-Triangular tower foundation.

will be determined by the size, the weight, and the construction characteristics of the tower and by the hoisting equipment.

Davit Method

Lightweight guyed towers are frequently erected with a davit hoist that is anchored to the previously erected section, providing a pivoted hoisting arm. The davit arm is swung away from the tower in hoisting the added section and swung centrally over the tower in depositing the section before bolting up the splice plates. Figure 8-33 shows a ground assembled unit being hoisted for connection to a previously erected tower section. A snatch block, secured to the tower base, transmits the hoisting line to a source of power

Figure 8-33.-Typical davit installation.

or hand winch. A tag line, secured to the base of section being hoisted, avoids possible contact with the erected portion of the tower.

Gin Pole Method

Light triangular guyed towers, furnished with a pivoted base, may be completely assembled on the ground and then raised to a vertical position with the aid of a gin pole. Figure 8-34 shows the lower section

Figure 8-34.-Pivoted tower-hoisting preparation.

Figure 8-35.-Erection plan for a pivoted tower.

of a tower that has an attached pivoted base in a horizontal position preparatory to hoisting. The thrust sling shown counteracts the thrust on the base foundation from hoisting operations. Rigging operations and location of personnel essential to the raising of a pivoted base tower are detailed in figures 8-35 and 8-36. Light towers in lengths of approximately 80 feet may be raised with a single attachment of the winch line. However, longer towers frequently are too flexible for a single attachment, and, in this case, a hoisting sling, furnished with a snatch block, allows for two points of attachment. The gin pole is mounted close to a concrete tower base and is provided with atop sheave to take the winch line. Permanent guys, attached to the tower at three elevations, are handled by personnel during hoisting operations, as shown in figure 8-35. Temporary rope guys, provided with a snatch block anchored to deadmen, furnish the necessary lateral

Figure 8-36.-Erection of a pivoted guyed tower.

stability As the mast approaches a vertical position, the permanent guys are fastened to the guy anchors installed before erection.

Hand Assembly

Erection, without a davit or gin pole, may be accomplished by the assembly of the individual members piece by piece, as the tower is erected. As assembler, you climb inside the tower and work with the lower half of your body inside the previously assembled construction. You then build the web of the tower section around you, as you progress upward. As each member is bolted in place, you should tighten all of the connections immediately so that at no time are you standing on or being supported by any loose member.

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