Steel-pipe posts are frequently used in urban areas and have the advantage of being readily available. They require special fastening hardware, and an earth plate when directly embedded, to prevent the post from rotating from its intended position. Standard steel pipe, schedule 40, galvanized, is readily available from plumbing supply wholesalers. The maximum sign panel areas that can be mounted on the 2-in — and 2.5-ininternal-diameter (51-mm and 64-mm) standard steel pipe are listed in Table 7.6.
Round steel supports, made from standard schedule 40 pipe, that have an internal diameter (ID) of less than 2 in (50 mm) can be embedded directly into the ground to a depth of at least 42 in (1070 mm) and provide acceptable performance upon impact. A steel earth plate measuring 4 in X 12 in X 0.25 in (100 mm X 310 mm X 6 mm) should be welded or bolted to the pipe to prevent support rotation due to the wind.
Standard schedule 40 pipe, 2-in (50-mm) ID and larger, is no longer approved for direct burial installation and must be installed with a weakening device [31]. A breakaway collar assembly is required for standard schedule 40 pipe sizes, equal to or greater than 2-in (50-mm) ID, and also for smaller pipe sizes when the device is likely to be hit. A regular pipe coupling or reducing coupling will provide acceptable breakaway performance. The use of a pipe coupling will, however, frequently result in damage to the anchor piece. Therefore the reducing coupling is the preferred breakaway device. The anchor assembly consists of a concrete footing, usually 30 in (760 mm) deep by 12 in (300 mm) in diameter and a 24-in-long (610-mm) piece of anchor pipe. The anchor pipe is usually one size larger than the signpost to prevent damage to the anchor and to allow use of the reducing coupling. The possibility of damage to the anchor post can be further reduced by embedding the reducing coupling halfway into the concrete footing.
Round steel tube, in wall thicknesses of 12 gauge or less, can be used with anchor systems instead of standard schedule 40 pipe. These tubes are available from a number of manufacturers. Southwestern Pipe Inc. is one tubing manufacturer that also markets the Poz-Loc anchor system. This system consists of a tubular anchor socket with 2.5-in (64-mm) ID and 27 in (686 mm) long constructed of 12 gauge steel. The socket is pointed to facilitate driving into the ground and accepts a 2-in-ID (50-mm) steel round tube as the sign support. The sign support is held in place by driving a post wedge between the socket
TABLE 7.6 Maximum Sign Area for Standard Steel-Pipe Single-Support Posts
a. Area in U. S. Customary units for 70-mi/h wind, ft2
Internal diameter post size, in Maximum sign area, ft2
2.0 6.5
2.5 11.8
b. Area in SI units for 113-km/h wind, m2
Internal diameter post size, mm Maximum sign area, m2
0.6
1.1
