United States Department of Transportation
i
Effects of coupler height mismatch on the structural integrity of railroad tank car stub sills.
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2001-12-01
[PDF-1.76 MB]
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Abstract:This project evaluated the safety implications of coupler height mismatches on the integrity of railroad tank car stub sills, through a series of static and impact tests. The test car was a loaded tank car instrumented with strain gages at critical locations. Static tests consisted of squeeze tests and vertical load tests. Impact tests using the test car as the struck car, and a 263 kip hopper car as the hammer car, consisted of impacts at speeds ranging from 2 mph to 8.5 mph for three (3) coupler mismatch levels: a) coupler heights at the same level, b) test car coupler 2" higher, and c) test car coupler 2" lower. The static tests showed that a 50,000 lb vertical force generated as much stress as a 680,000 lb longitudinal force, on average. This implies that moderately high longitudinal forces, in conjunction with moderately high vertical forces can cause significantly high stresses. The impact results indicate that significant coupler vertical forces are generated even in the absence of any coupler height mismatch. However, vertical forces and stresses in critical areas were generally higher when the struck car was 2" lower. Vertical forces induce 50 % of the maximum stresses seen at the tank head, and about 44 % of the maximum stresses seen at the head pad extension, under impact conditions. Therefore, ignoring the effects of vertical force will lead to an under-estimation of stress levels and fatigue levels in tank cars.
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