Full-Scale Impact Test of Four Traffic Barriers on Top of an Instrumented MSE Wall
Publication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 136, Issue 3
Abstract
This paper presents the results of four full-scale impact tests against barriers placed on top of an instrumented mechanically stabilized earth (MSE) wall. The impact was created by a head-on collision of a 2,268-kg bogie going at about 32.2 km/h. The barriers were New Jersey and vertical wall barriers with a 1.37-m-wide moment slab in 9.14-m-long sections. The wall was 1.52 m high with one panel and two layers of reinforcement. The reinforcement was 2.44-m-long strips, 4.88-m-long strips, and 2.44-m-long bar mats. The backfill was crushed rock. The instrumentation consisted of accelerometers, strain gauges, contact switch, displacement targets, string lines, and high-speed cameras. The test was designed to represent a commonly used installation in current practice including an impact load on the barrier at least equal to 240 kN. Most of the barriers sustained significant damage but overall the behavior of the wall was satisfactory since the displacements of the panels were minimal (less than 25 mm) and the panel damage was acceptable except possibly in the case of the 4.88-m-long strips. The loads measured in the reinforcement indicate that the reinforcement was brought to its ultimate capacity for the duration of the impact but since the impact duration was so short and since the displacements of the panels were within tolerable limits of 25 mm, this is considered acceptable. The use of the longer strips (4.88-m-long strips) leads to slightly smaller panel displacements and higher panel stresses as evidenced by a bending crack in the panel. The 2.44-m-long strips permitted more displacement of the wall panels, but the magnitude of the displacement was considered to be tolerable. The measured maximum dynamic loads in the strips were found to be 3–5 times higher than the calculated maximum static loads by AASHTO guidelines.
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Acknowledgments
The content of this paper is the partial result of a project sponsored by the National Cooperative Highway Research Program (Grant No. UNSPECIFIEDNCHRP 22-20). The opinions expressed in the paper are those of the writers and not necessarily those of NCHRP. The writers thank the NCHRP panel members for their input and in particular Mark McClelland, chair of the panel. The writers also thank the Reinforced Earth Company (Pete Anderson, John Sankey) for providing components for construction of the test wall, sharing data, and answering many questions. The writers also thank Foster Geotechnical (William Neely) for sharing their experience on MSE walls. A special note of thanks to Geotesting Express in Atlanta for conducting the rate effect study on pull-out resistance of the wall reinforcement.
The precast barrier-coping sections, concrete wall panels, and steel strip wall reinforcement were provided by RECO at no cost to the project. RECO also provided supervision of the construction of the wall. The bar mat reinforcement that was used in one of the tests was provided by Foster Geotechnical at no cost to the project.
References
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Information & Authors
Information
Published In
Journal of Geotechnical and Geoenvironmental Engineering
Volume 136 • Issue 3 • March 2010
Pages: 431 - 438
Copyright
© 2010 ASCE.
History
Received: May 4, 2009
Accepted: Aug 24, 2009
Published online: Aug 28, 2009
Published in print: Mar 2010
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