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39 CHAPTER 9 Evaluation of Hole in Rail The objective of this evaluation was to determine the effect cessful containment of the pendulum mass. To represent worst of a hole in a rail on barrier crash performance through pen- case conditions, the hole was aligned with the impact loca- dulum testing (Figure 34). The performance of the barrier tion and in the upper fold of the w-beam section. Based on section with an artificially introduced hole was compared to the results of the test, the performance of the hole-damaged the performance of a similar barrier section with no flaw. The rail section was virtually identical to that of the undamaged pendulum test setup is described in an earlier chapter on the strong post barrier section tested at the 17.5 mph impact research approach. speed. As a result, the research team has recommended that Test 07-2 investigated the performance of a two-post section the repair be initiated if the hole exceeds 1 inch in height. of strong-post w-beam barrier with a 1.25-inch hole. For this Note that the limit on size of a non-manufactured hole has test, a hole in the rail was simulated by drilling through the rail. been specified in the vertical, rather than the horizontal, The location of the hole corresponded to the pendulum mass direction because the vertical direction is perpendicular to impact location and was on the upper fold of the w-beam. predominant (tension) loads, and is thus more likely to cause failures. A medium priority was assigned to smaller holes in the rail because of the possibility that holes may 9.1 Results serve as the initiation point for horizontal tearing on im- The barrier with a hole in the rail successfully contained the pact. The only exception would be if this hole was located pendulum mass impacting at 18.2 mph. Based on an analysis near the splice as described below. of the overhead high-speed video data, the maximum dynamic Multiple holes in a rail section or holes with a diameter deflection of the rail was 22 inches and occurred 120 ms after exceeding a height of 1 inch could lead to rail tearing as seen trigger. Based on an analysis of the overhead high speed video in the vertical tear pendulum tests. To avoid the possibility data, the maximum static deflection was 15.4 inches The rail of catastrophic rail failure, these modes were assigned a high was intact at the position of the hole (Figure 35). Figure 36 priority for repair. A special case was a hole of any size which shows time sequential snapshots of the test obtained from the intersects either the top or bottom edge of the rail. Because high speed camera positioned overhead. a hole which disrupts either the upper or lower surface of a rail has the characteristics of a vertical tear, this damage mode has the potential for the same catastrophic failure of 9.2 Recommendation the rail that was observed in the pendulum tests of vertical A pendulum test (18.2 mph impact speed) of a strong-post tears. This damage mode was given a high priority for repair w-beam barrier with a 1.25-inch diameter hole resulted in suc- (Exhibit 6.0).
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40 Field Example Pendulum Test Setup Figure 34. Hole damage evaluated in pendulum tests. Figure 35. Damage near a hole in Test 07-2.
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41 0.02 s 0.06 s 0.10 s 0.14 s 0.18 s 0.22 s 0.26 s 0.30 s Figure 36. Sequential photographs for 1.25-inch hole damage (Test 07-2): overhead view. Exhibit 6.0. Recommendations for hole in rail damage. Damage Mode Repair Threshold Relative Priority Non-Manufactured holes More than 2 holes less than 1 in. High in height in a 12.5-in. length of (such as crash-induced rail. holes, lug-nut damage, or holes rusted-through the Any holes greater than 1in. in rail) height. Any hole which intersects either the top or bottom edge of the rail. 1 or 2 holes less than 1 in. in height in Medium a 12.5-in length of rail.