Criteria for Restoration of Longitudinal Barriers, Phase II (2021) / Chapter Skim
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303 CHAPTER 12 – EFFECTS OF SOIL EROSION AT GUARDRAIL POSTS FOR THE G4(2W) The effects of various levels of soil loss around a guardrail post were evaluated for the G4(2W)
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304 Figure 245. Example of severe soil erosion at multiple posts.
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305 properties, as shown in Table 67. The target soil conditions included a dry density of 138 pcf, a moisture content of 3.4 percent, and a soil compaction of 92 percent.
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306 Table 67. Dry density of soil for each test case measured at 6-inch lifts.
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307 Equipment and Instrumentation Pendulum Device The striker for the tests was a 2,372-lb concrete pendulum with a semi-rigid nose, which was the same striker used to evaluate the effects of post deterioration in Chapter 8 (see Chapter 8 for more details)
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308 Photography Cameras The tests were also recorded using four high-speed cameras with an operating speed of 500 frames per second and a digital video camera (∼30 fps)
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309 Results The x-channel accelerometer data was processed to obtain the accelerations of the pendulum during impact with the posts. The data was filtered using an SAE Class 60 filter with cutoff frequency of 100 Hz.
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310 Figure 250. Repair to the pendulum head included adding a steel "slide Plate" underneath the head.
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311 Table 69. Summary of results for Test Series 14003.
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312 Figure 251. Force vs.
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313 Figure 253. Energy vs.
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314 Figure 255. Peak "impulse" force in Test Series 14003.
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315 Figure 257. Total energy vs.
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316 Figure 258. Finite element model used for validating/calibrating soil-spring stiffness corresponding to various levels of soil erosion.
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317 Figure 259. Force vs.
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318 Figure 261. Sequential views of Test 14003F and FE analysis on baseline post-soil case, DL0.
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319 Figure 262. Force vs.
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320 The total energy absorbed at 12 inches displacement in the analysis was 99 kip-in, which was the same as that measured in Test 14003A; the total energy absorbed at 20 inches displacement in the analysis was 146 kip-in compared to 147 kip-in in Test 14003A; and the total energy absorbed at 40 inches displacement in the analysis was 199 kip-in compared to 203 kip-in in Test 14003A. Figure 264 shows sequential views comparing analysis results to dynamic impact test 14003A.
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321 14003C. Figure 267 shows sequential views comparing analysis results to dynamic impact Test14003C.
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322 Figure 267. Sequential views of Test 14003C and FE analysis for 6-inch erosion case.
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323 Figure 268. Force vs.
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324 Figure 270. Sequential views of Test 14003D and FE analysis for 9-inch erosion case.
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325 Figure 271. Force vs.
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326 Figure 273. Sequential views of Test 14003E and FE analysis for 12-inch erosion case.
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327 using FE analysis to be 45 inches (1.16 m) upstream of the w-beam rail splice connection at Post 14.
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328 Table 71. Summary of barrier damage evaluation from analyses of undamaged G4(2W)
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329 Figure 276. Summary of anchor displacement at rail height from analyses of undamaged G4(2W)
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330 Table 72. Summary of occupant risk measures from evaluation of undamaged G4(2W)
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331 Figure 278. Summary of maximum occupant ridedown accelerations for undamaged G4(2W)
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332 Figure 280. Summary of maximum effective plastic strains occurring at the splice-bolt locations at Post 16.
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333 Table 73. Summary of barrier damage evaluation from analyses of undamaged G4(2W)
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334 Figure 282. Summary of anchor displacement at rail height from analyses of undamaged G4(2W)
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335 Table 74. Summary of occupant risk measures from evaluation of undamaged G4(2W)
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336 Figure 284. Summary of maximum occupant ridedown accelerations for undamaged G4(2W)
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337 Figure 286. Summary of maximum effective plastic strains occurring at the splice-bolt locations at Post 16.
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338 Finite element models for the various soil erosion cases were then developed and validated based on comparison to the physical tests. In each soil-erosion case, the characterization of the soil model was exactly the same; that is, the same model was used in each case.
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339 not include erosion depths less than 6 inches. The upper bound was based on the high magnitude of strain in the splice-bolt holes for the 6-inch erosion analysis case, which was considered borderline regarding high potential for rail rupture.
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