STEEL TOWERS

Airfield observation towers, harbor shipping control towers, and radio towers are all erected by Steelworkers. These towers are manufactured and packaged according to military specifications. They are shipped with all parts and with plans and specifications.

The framework of the tower is made up of fabricated structural shapes that are bolted together. Anchor angles with baseplates are furnished for setting in the concrete foundation, as shown in figure 8-26. In most cases, the foundation will be built by the Builders. The manufacturer also furnishes square head bolts, lock washers, and nuts. Spud wrenches and driftpins are suppfied for each size of bolt. Field bolts and shipping lists are prepared and packaged with each shipment of a tower.

The tower members are bundled in the most compact manner possible to keep shipping space to a minimum. Erection identification marks and stock list

Figure 8-26. - Anchor angles in a concrete foundation.

numbers are painted on all of the pieces. All of the nuts, the bolts, and the washers are boxed and identified by painted marks.

A check must be made of all of the parts and packages received in a tower shipment. Check them against the shipping list to be sure that no boxes or bundles have been lost, stolen, or misplaced. Also, check to see that none have been damaged When all are accounted for, sort the materials. The drawings tell you what is needed for each section. It is smart planning to lay out all of the materials for each section from the foundation to the top before any erection is started. This will save a lot of time later.

ASSEMBLY AND ERECTION OF SECTIONS

The first section of the tower is assembled on the ground alongside the foundation. Start by assembling the two-column legs on one side of the tower and bolt them loosely, with one bolt each, to two foundation stubs (anchor angle irons); these will act as pivot points. Next, loosely join the angle and the cross braces. Then lift the entire side. A crane or gin pole can be used to rotate it into a vertical position or, if necessary, it can be lifted by hand. Two people can start by lifting the far end and start walking it up. The two others, with handlines, can complete the upward journey.

As the column legs fall into position, use driftpins or spud wrenches to line up the holes with the holes in the anchor angle irons. Then insert the bolts and tighten them. Use spud wrenches for this job. Place lock washers under each nut. When one side is standing in the upright position, repeat the process for the opposite legs. Finally, connect the cross braces on the open sides, and add the cross braces on the inside. When the whole first section, or bay, is in place, tighten the bolts. Figure 8-27 shows the correct connection of diagonal and center horizontal members; notice the alternate connections of the diagonal members at all points,

Use a snatch block and line to lift each piece for the next section. Do not tighten the bolts until the entire section is in place. Then start lifting the pieces for the next section, shifting the snatch block as necessary. When the whole section is in place, tighten the bolts. Repeat this process until the whole framework of the tower is erected. Bolts should be hoisted by handlines in buckets or leather-bottom bolt bags. Figure 8-28 shows a partially completed tower.