National Academies Press: OpenBook

Criteria for Restoration of Longitudinal Barriers (2010)

Chapter: Chapter 6 - Evaluation of Splice Damage

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Page 31
Suggested Citation:"Chapter 6 - Evaluation of Splice Damage." National Academies of Sciences, Engineering, and Medicine. 2010. Criteria for Restoration of Longitudinal Barriers. Washington, DC: The National Academies Press. doi: 10.17226/14374.
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Page 31
Page 32
Suggested Citation:"Chapter 6 - Evaluation of Splice Damage." National Academies of Sciences, Engineering, and Medicine. 2010. Criteria for Restoration of Longitudinal Barriers. Washington, DC: The National Academies Press. doi: 10.17226/14374.
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Page 32

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31 The objective of this evaluation was to determine the effect of splice damage on barrier crash performance by pendulum testing (Figure 23). The performance of the barrier section with splice damage was compared to the performance of a similar barrier section with no flaw. The pendulum test setup is described in an earlier chapter on the research approach. Splice damage was simulated by removing a rectangular block of material directly in line with a single splice bolt and having width equal to the diameter of the splice bolt. The intent was to simulate complete loss of bearing capacity for a single bolt (of 8 bolts total) in the splice connection. 6.1 Results In Test 07-4, the splice damaged barrier contained the pen- dulum mass impacting at 29.3 km/hr (18.2 mph), which was calculated using the overhead high-speed video footage. The maximum dynamic deflection of the test section was 574 mm (22.6 inches) at 130 ms after the initial impact. Both post-rail connections remained intact and no serious splice separation was observed in the splice damage created prior to the impact. There was approximately 13 mm (0.5 inches) of relative move- ment between the two w-beams at the splice location. A detailed view of the splice damage and the individual post damage is shown in Figure 24. Figure 25 shows time sequence snapshots of the test obtained from the overhead camera. 6.2 Recommendation A pendulum test of a strong-post w-beam barrier with splice damage resulted in successful containment of the pendulum mass. The splice damage consisted of extending the hole for a single splice bolt to the end of the rail (e.g., no bearing capac- ity for that particular bolt). Under a pendulum impact at 29.3 km/hr (18.2 mph), this barrier was able to contain the impacting pendulum mass with performance indistinguish- able from the undamaged barrier section. It is known how- ever from full-scale crash testing as well as the splice failures observed in the pendulum tests that the splice is a weak point in the guardrail system. Balancing these two observations, the research team recommends a repair threshold of 2 or more splice bolts with any guardrail material missing around the bolts with high priority. In the case of damage to a single splice bolt, the research team assigned the repair a medium priority (rather than a low priority) based on the fact that the splice is the weak point in the rail element (Exhibit 3.0). C H A P T E R 6 Evaluation of Splice Damage Figure 23. Splice damage evaluated in pendulum tests.

32 Figure 24. Test 07-4: Detail view of splice bolt damage after test (left) and post damage at splice (center) and non-splice location (right). 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 25. Sequential overhead photographs for splice damage, Test 07-4 (29.3 km/hr). Damage Mode Repair Threshold Relative Priority More than 1 splice bolt: Missing, Damaged, Visibly missing any underlying rail, and Torn through rail. High Damage at a rail splice 1 splice bolt: Missing, Damaged, Visibly missing any underlying rail, and Torn through rail. Medium Exhibit 3.0. Recommendations for splice damage repair.

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TRB’s National Cooperative Highway Research Program (NCHRP) Report 656: Criteria for Restoration of Longitudinal Barriers explores the identification of levels of damage and deterioration to longitudinal barriers that require repairs to restore operational performance.

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