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Dynamic Testing of MGS W6x8.5 Posts at Decreased Embedment




Tyler Schmidt, Mario Mongiardini, Bob Bielenberg, Karla Lechtenberg, John Reid, Ronald Faller




The objective of this study was to evaluate and compare the energy absorption characteristics of W6x8.5 (W152x12.6) posts at a reduced embedment depth of 36 in. (914 mm) to that of the standard 40-in. (1,016-mm) embedded W6x8.5 (W152x12.6) posts used in the original Midwest Guardrail System (MGS). A total of eight dynamic component tests were performed - two tests with the 40-in. (1,016-mm) embedment depth and six with a 36-in. (914-mm) embedment depth. For two of the six 36-in. (914-mm) embedment tests, the load height was increased from 24 7/8 in. (632 mm) to 28 7/8 (733 mm). The posts were embedded in a highly compacted, coarse, crushed limestone material. For each test, acceleration data was used to determine the force vs. deflection and energy vs. deflection characteristics of the various post installations. Post-soil interaction forces and energy dissipation characteristics of the steel posts with a 36-in. (914-mm) embedment depth were compared to those for the steel post used in the original design of the MGS in both moderately and highly compacted soil. From these comparisons, the post with a 36-in. (914-mm) embedment depth was found to provide similar strength to that of the W6x9 (W152x13.4) steel post with a 40-in. (1,016-mm) embedment depth and installed in moderately compacted soil. In highly compacted soil, the post with a 36-in. (914-mm) embedment depth exhibited less resistance than the post with a 40-in. (1,016-mm) embedment depth. Therefore, the dynamic resistance of the W6x8.5 (W152x12.6) post with a 36-in. (914-mm) embedment was determined to provide enough resistance to be used with the MGS, which may allow a potential increase in the maximum rail mounting height of the MGS.


Highway Safety, Crash Test, Roadside Appurtenances, MASH, MGS, W6x8.5 Posts, Decreased Embedment Depth, Bogie Test

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