Regardless of the type of support that is being used, there are three general rules that must be followed: (1) the top of the sign should be 9 ft (2750 mm) above ground level to reduce the possibility of intrusion into the passenger compartment upon impact, (2) the retaining bolts must be snug but not so tight as to distort the sign face, and (3) the bolts must be of the proper size and length to prevent the sign blank from separating from the support.
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FIGURE 7.37 Improper installation of slip base anchor piece. |
Fastening to a U-Channel. Signs are normally mounted on the front face of the U-channel. This is the widest face of the U-channel. Signs can also be mounted on the narrow face, as in back-to-back sign installations, for example, but the decreased surface contact with the sign can result in damage to the sign face due to environmental loads. Side mounting on a U-channel requires channel brackets, and brackets for mounting street name signs to the top of the post are available. Typical sign blank installations for a U-channel are presented in Fig. 7.38.
Fastening to Wood Supports. Sign installation on wood supports requires a bolt completely through the post and fastened with a nut. Lag bolts are not recommended for fastening sign blanks to the posts. Fastening with lag bolts is unpredictable upon impact because of the size of the bore hole, possible postsplitting, the presence of knots, and variable characteristics of the wood.
Fastening to Square Tubes. Sign installations on square tubes can be accomplished by %s-in (8-mm) bolts and nuts or by the use of rivets. Figure 7.39 presents typical sign panel fastening details for shaped wooden and square-tube sign supports.
Fastening to Round Steel Shapes. Signs should not be fastened directly to standard steel pipe or to light standards. The contact area between the back of the sign and the support due to the round support shape is too small to withstand the wind and other environmental loads. A number of different fastening methods can be used, including B-clamps, U-bolts, and stainless steel band clamps. Figure 7.40 presents the configuration of the B and stainless steel band clamps. The dimensions shown for the B-clamp are typical and vary slightly by manufacturer. The B-clamp is also available in other sizes than shown in Fig. 7.40.
FLAT WASHER
ND LOCK WASHER
50 MIN
FIGURE 7.38 Typical sign blank fastening to U-channel. Dimensions shown as mm: 50 mm = 1 in.
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FIGURE 7.40 Typical design of B and stainless band clamps for round sign supports. (a) B-type clamp. (b) Stainless steel band clamps for round sign supports. Dimensions shown as mm. Conversions: 8 mm = % in, 9 mm = /8 in, 50 mm = 2 in, 100 mm = 4 in, 125 mm = 5 in. |
U-bolts can also be used to fasten signs to round supports. The U-bolt is attached to the sign by the use of Z-bar aluminum channel or pieces of U-channel. The U-bolt is purchased with an anchor chair to grip the post. Fastening details for U-bolts with aluminum Z-bar are presented in Fig. 7.41 and with aluminum channel or U-channel in Fig. 7.42.
Fastening to Structural Steel Shapes. Fastening signs to S — or W-shaped beam posts, often used with slip base designs, should be accomplished by using a stiffener. Clamps are used to fasten the stiffeners to the support, eliminating the need to drill into the support itself. Fastening details using aluminum Z-bar as the stiffener are presented in
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FIGURE 7.41 Fastening details for aluminum Z-bar and channel. (a) Z-bar. (b) Aluminum channel. Dimensions shown as mm. Conversions: 8 mm = ife in, 205 mm = 8 in, 355 mm = 14 in, 460 mm = 18 in, 760 mm = /0 in. |
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FIGURE 7.42 Typical variations for installing signs on round posts. (a) With formed channel. (b) With clamps or bolts. |
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FIGURE 7.43 Aluminum Z-bar for attaching sign panels to beam post. (a) Top view. (b) Side view. Dimensions shown as mm. Conversions: 8 mm = %5 in, 10 mm = % in, 20 mm = %in, 153 mm = 6 in. |
Fig. 7.43. Figures 7.44 and 7.45 present fastening details for commercially available
aluminum stiffeners specifically designed for mounting signs to beam supports.
