Phase I Ponderosa Pine Round Post Equivalency Study
Ronald Faller, Scott Rosenbaugh, Karla Lechtenberg, Brad Winkelbauer, Craig Price
The primary research objective was to determine the appropriate size and embedment depth of a round Ponderosa Pine (PP) post for serving as a surrogate for the standard 6-in. x 8-in. x 64-in. (152-mm x 203-mm x 1,626-mm) Southern Yellow Pine (SYP) post used in Arizona Department of Transportation (AzDOT) guardrail systems. A total of seventeen dynamic component tests were performed. Three baseline tests were conducted on 6-in. x 8-in. x 72-in. (152-mm x 203-mm x 1,829-mm) SYP posts with a 43¼-in. (1,099-mm) embedment depth for comparison with standard U.S. guardrail systems in a follow-on Phase II continuation effort. Three baseline tests were conducted on the standard 6-in. x 8-in. (152-mm x 203-mm) AzDOT SYP post at an embedment depth of 35 in. (889 mm). Eleven tests were conducted on round PP posts. The first three PP tests were conducted with a 37-in. (940-mm) embedment depth, and the remaining eight tests used a 35-in. (889-mm) embedment depth. The posts were fabricated with various targeted diameters: 8¼ in. (210 mm), 8½ in. (216 mm), and 8¾ in. (222 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 post-soil behavior. Post-soil interaction forces and energy dissipation characteristics of the PP posts were compared to those behaviors obtained for the SYP posts. From these comparisons, an 8½-in. (216-mm) diameter by 64-in. (1,626-mm) long graded PP post with an embedment depth of 35 in. (889 mm) provided similar post-soil behavior to that obtained for 6-in. x 8-in. x 64-in. (152-mm x 203-mm x 1,626-mm) SYP rectangular posts used by the AzDOT. Therefore, the AzDOT standard G4(2W) W-beam guardrail system would be expected to provide acceptable safety performance when configured with round PP posts with a minimum ground line diameter of 8½ in. (216 mm) as well as the current rectangular SYP posts.
Highway Safety, Roadside Safety, Guardrail, MGS, Dynamic Test, Bogie, Wood Post, Round Post, Southern Yellow Pine, Ponderosa Pine, and Equivalency
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