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Title:

DEVELOPMENT AND TESTING OF A BREAKAWAY SUPPORT COUPLING FOR LIGHT POLES. ABRIDGMENT

Accession Number:

00196617

Record Type:

Component

Availability:

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Order URL: http://worldcat.org/issn/03611981

Abstract:

Each year numerous injuries and fatalities occur as a result of vehicles hitting light poles adjacent to U.S. highways. Until recently the widely used transformer base has been considered "breakaway". The 1975 AASHTO Standard Specifications for Structural Supports for Highway Signs, Luminaires and Traffic Signals has tightened design standards by calling for a improvement in the performance of the breakaway feature. Satisfactory dynamic performance is indicated when the maximum change in momentum for a standard 1020-kg (2250-lb) vehicle, or its equivalent--striking a breakaway support at speeds from 32 to 97 km/h (20 to 60 mph)--does not exceed 4895 nt,s (1100 lb's). A "preferable" maximum change of momentum of 3337 nt's (750 lb's) is also stated in the above specifications as a goal for the future. The Pole-Safe breakaway support coupling (longitudinally grooved) is a frangible coupling designed for use on light poles so that they will break away under impact within these criteria. The coupling (Figure 1) is made from die-cast aluminum, roughly cylindrical in shape with a 2.54-cm (1-in) 8UNC threaded hole at one end and a 2.54-cm (1-in) 8UNC 304 stainless steel stud protruding from the other end. The coupling thus provides a breakaway spacer between an existing light pole and its foundation. It fits over the anchor bolt, and the stud protrudes through the pole base plate. It eliminates fatigue problems in tension and bending loads that would be present with circumferentially notched couplings, shear pins, notched bolts, and so forth. Longitudinal notches provide high stress concentration for rapid fracture at relatively low impact force levels. Ratio of service-load capacity to failure load is higher than existing designs due to unique geometry. Ratios up to 6:1 are possible. Highest possible control of fracture mode ensures repeat impact performance for any design impact load. /Author/

Supplemental Notes:

Publication of this paper sponsored by Committee on Safety Appurtenances. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved.

Monograph Accession #:

01411518

Report/Paper Numbers:

HS-026 748

Authors:

Dinitz, Arthur M
Chisholm, Douglas B

Pagination:

pp 26-28

Publication Date:

1978

Serial:

Transportation Research Record

Issue Number: 679
Publisher: Transportation Research Board
ISSN: 0361-1981

Conference:

57th Annual Meeting of the Transportation Research Board

Location: Washington District of Columbia, United States
Date: 1978-1-16 to 1978-1-20

ISBN:

0309028248

Media Type:

Digital/other

Features:

Figures (6) ; Photos

Old TRIS Terms:

Subject Areas:

Design; Highways; Research; Safety and Human Factors

Files:

TRIS, TRB

Created Date:

Aug 28 1979 12:00AM

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