@article{ref1,
title="Pendulum tests using rigid and crushable bumpers",
journal="Transportation research record",
year="1976",
author="Bronstad, M. E. and Michie, J. D. and White, R. R.",
volume="566",
number="",
pages="56-64",
abstract="The test program discussed in this paper consisted of 19 tests of a breakaway sign support using a 2,000-lb (907-kb) pendulum mass impacting the support at 20 mph (32 km/h). Use of both rigid and crushable bumpers permitted examination of these techniques compared with current momentum change criterion. In addition, the effects of bolt-tightening torque on the slip-base release loads were investigated. Hi-Lok frangible nuts, which control tightening torque, were also evaluated for the design torque condition. Only in the crushable bumper tests were dramatically different results obtained for the various nut-tightening torques when momentum change was used as the criterion. Momentum change with the hard bumper was 65 plus minus 15 lbf-sec (289 plus minus 67 N-s) for all base-nut torque levels. Momentum change with the crushable bumper ranged from 88 lbf-sec (391 N-s) for design torque condition to 398 lbf-sec (1770 N-s) for the overtorqued condition. Repeatibility of slip-base loads was generally good when both a calibrated torque wrench and the Hi-Lok torque control nuts were used. It was concluded that momentum-change criterion is insufficient in evaluating results of pendulum tests using a rigid bumper. Use of a bumper with vehicle crush characteristics appears to provide a superior experimental evaluation.<p />",
language="en",
issn="0361-1981",
doi="",
url="http://dx.doi.org/"
}