Citation

Mauer F, Bullard D, Alberson D, Menges W. Transp. Res. Rec. 1997; 1599: 57-63.

Copyright

(Copyright © 1997, Transportation Research Board, National Research Council, National Academy of Sciences USA, Publisher SAGE Publishing)

DOI

10.3141/1599-07

PMID

unavailable

Abstract

Researchers at Texas Transportation Institute designed a Slip Safe connection for use with steel U-channel sign-support structures within the highway right-of-way. The Slip Safe connection has two design configurations: a small Slip Safe design for single U-channel posts and a larger Slip Safe for back-to-back U-channel posts. Both configurations utilize Rib-Bak U-channel posts weighing up to 5.9 kg/m manufactured from 552-MPa yield billet steel. The Slip Safe is designed for use in a range of soil types with up to three supports per installation. There are two advantages of this Slip Safe design. First, the Slip Safe eliminates the dependency on material properties to achieve acceptable breakaway performance. In the past, all direct-driven and the majority of current breakaway designs for steel U-channel, square tube, wood, and round pipe sign supports have depended upon this. Second, the Slip Safe is omnidirectional and both hardware and supports are highly reusable due to the low energy required to activate the system. The Slip Safe designs are unlike most types of highway safety appurtenances in which performance is critically dependent on the failure of a bolt or bolts, the support material properties, or a combination of both. The Slip Safe has two advantages over other current U-channel connections. First, activation of the Slip Safe occurs with approximately one-third of the force needed to activate fracture-type connections. Second, the only disposable component in the Slip Safe connection is the keeper plate. All casting, bolts, and U-channel supports were undamaged, yielding economic advantages in high-frequency impact locations.

Language: en