R.P. Bligh, H.E. Ross, D.L. Bullard
A study was undertaken to evaluate the impact performance of ADOT's slip-away base luimaire support. For purposes of this evaluation, three full-scale crash tests were conducted in accordance with the requirements of NCHRP Report 350. During this test program, ADOT's 13.7-m (45-ft) constant tapered luminaire support was found to exhibit unacceptable impact performance. Although the slip base activated readily and the occupant impact velocity was within recommended limits, a secondary impact of the pole with the roof of the vehicle resulted in substantial deformation of the roof structure. A subsequent test of ADOT's standard 12.2-m (40-ft) luminaire system was judged to be marginally acceptable. Although the luminaire support readily yielded to the vehicle and the occupant risk criteria were well within the recommended limits established by "NCHRP Report 350," the test vehicle once again sustained substantial deformation to the roof structure from a secondary impact with the luminaire pole.|Several candidate systems were identified which provide a mounting height of 13.7 m (45 ft) or greater and which could serve as replacements for ADOT's deficient 13.7-m (45-ft) poles. The most promising of these is a steel 4-bolt slip-base design developed by the Utah Department of Transportation (UDOT) which has a mounting height of 15.8 m (52 ft) and was successfully crash tested. As an alternative to adopting a new design, it is also recommended that the current design requirements be carefully reviewed and options for reducing the weight of the existing system be considered.|Maintenance practices related to slip-bolt torque were also reviewed. Although no specific post-installation inspection procedure for slip-base bolt torques is offered at this time, periodic visual inspections of slip-base poles should be considered to determine if debris, soil, corrosion, erosion, or other hindrances that could compromise proper actuation of the slip-base are present. It was also noted that although proper performance of slip-base supports depends on the clamping force in the slip-base bolt, crash tests and analytical studies indicate that the performance is not overly sensitive to the clamping force.
Bolt Torque, crash test, Highway safety, Luminaire Support, slip base
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