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Testing of M203x9.7 (M8x6.5) and S76x8.5 (S3x5.7) Steel Posts-Post Comparison Study for the Cable Median Barrier




Beau Kuipers, John Reid




Dynamic impact testing of M203x9.7 (M8x6.5) and S76x8.5 (S3x5.7) steel posts with various embedment conditions and impact angles has been detailed and the results stated. The results provided the basis for a comparison of the two posts. The soil used conformed to AASHTO M 147-65 Gradation "B" specifications. Post type and embedment depth played an important role in the amount of energy dissipated during the impacts. For both angled and head-on impacts of similar nature, in soil and in a concrete sleeve, the M203x9.7 (M8x6.5) steel post was able to dissipate more energy than the S76x8.5 (S3x5.7) steel post with soil plate attached. Based on the results presented herein, the M203x9.7 (M8x6.5) with a 106.68 cm (42 in.) embedment depth should be considered for new cable guardrail systems. The force levels and energy absorbed at an embedment depth of 106.68 (42 in.) were greater than the current S76.8.5 (S3x5.7) post with standard embedment depth of 76.20 cm (30 in.). The M-post is stronger in the strong axis and weaker in the weak axis compared to the S-post, both believed desirable attributes for this application.


Highway Safety, Weak Steel Posts, Roadside Appurtenances, Bogie Crash Testing

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