Strength Evaluation of Connectors for Intermodal Containers.
Strength Evaluation of Connectors for Intermodal
Containers.
(21230 K)
Lew, H. S.; Sadek, F.; Anderson, E. D.
NISTIR 6557; 41 p. August 2000.
Sponsor:
Occupational Safety and Health Administration,
Washington, DC
Available from:
National Technical Information Service
(NTIS), Technology Administration, U.S. Department of
Commerce, Springfield, VA 22161.
Telephone:
1-800-553-6847 or 703-605-6000;
Fax: 703-605-6900; Rush
Service (Telephone Orders Only) 800-553-6847;
Website:
http://www.ntis.gov
Order number: PB2000-108102
Keywords:
connectors; containers; evaluation; corner fittings;
interbox connectors; latch locks; twistlocks; vertical
tandem lifts; test methods
Abstract:
Intermodal containers are used widely in marine cargo
handling. In order to facilitate unloading of empty
containers from ship to shore, two containers are
frequently lifted in tandem. This operation is referred
to as "vertical tandem lifting." In this lifting
process, the lower container is attached to the upper
container by means of interbox connectors at the four
comers of the container. During the vertical tandem
lifting operation, if one or more connectors are
disengaged, the bottom container may be separated from
the upper container, thereby creating an unsafe
condition to workers below. This safety concern prompted
the Occupational Safety and Health Administration (OSHA)
to request the National Institute of Standards and
Technology (NIST) to study the suitability of interbox
connectors for vertical tandem lifting. The NIST study
included site visits to port facilities and laboratory
tests of interbox connectors. Test specimens included
semi-automatic twistlocks and latch locks. The
experimental program included testing of twistlocks in
tension, twistlock and latch lock assemblies with corner
fittings in tension and compression, and shafts of
twistlocks in tension to obtain the stress-strain
relationship. In addition, measurements were made of the
bearing area of the top and bottom cones of twistlocks
and the latch on the inner surface of the corner
fitting. The study indicated that the tensile capacity
of the connection is governed by the strength of the
corner fitting. The study also shows that the bearing
area of latch locks on the comer fitting is less than
that required by the IS0 standards.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899