Criteria for Restoration of Longitudinal Barriers (2010) / Chapter Skim
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Pages 11-22
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From page 11... ...
The candidate set of guidelines and quantitative criteria to gauge minor barrier damage were based on current metrics employed by transportation agencies and supplemented as needed to address specific damage modes. The final set of candidate repair guidelines to be evaluated was presented to and approved by the project Panel prior to commencement of Phase II: Evaluation of Candidate Repair Guidelines.
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Repair thresholds to be determined for w-beam barriers. Component Damage Description Rail Element Rail Element not Aligned Properly in Impactor Head*
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In addition to being based upon a strong analytical foundation, the guidelines must be easily understood and implemented. The repair threshold guidelines were presented in a graphical format that clarified how damage to w-beam barriers should be measured and repair priority assessed.
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between the existing rigid posts on either side of the FOIL pendulum. Using standard 1905 mm (6.25 feet)
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Impact Conditions and Relevance to Full-Scale Crash Testing. As the FOIL pendulum is not capable of reproducing an oblique impact characteristic of NCHRP Report 350 longitudinal barrier test procedures, the tests were designed to mimic the lateral forces experienced in a NCHRP Report 350 redirectional test (Figure 6)
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into a damaged strong-post w-beam barrier at NCHRP Report 350 test level 3 conditions (Test 3-11)
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17 Damage Mode Field Example Pendulum Test Setup Vertical Tear Horizontal Tear Splice Damage Twisted Blockout Missing Blockout Hole in Rail Table 12. Barrier damage modes evaluated in pendulum tests.
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Running the simulations on the system described previously, each simulation took approximately one day of real time to calculate 1,000 ms of simulated time. 3.4.1 The Vehicle-Guardrail Model A full-scale finite element model was created from two parts: (1)
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The three crash tests that were used for this study had drastically different bumper heights, as shown in Table 13. A modified version of the original finite element vehicle was developed to match these alternate dimensions.
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Damage Mode Field Example FE Model Rail and Post Deflection Missing Post Separated Rail / Post Rail Flattening Table 14. Barrier damage modes evaluated through finite element modeling.
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Detailed validation results are contained in the appendices. 3.5.2 Damaged Barrier Full-Scale Crash Test Validation This research program also conducted an NCHRP Report 350-type crash test of a vehicle colliding with a damaged section of strong-post w-beam barrier.
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From page 22... ...
• Weak Post W-Beam Systems -- Weak post w-beam guidelines were not evaluated independently of strong-post w-beam guidelines. Crash tests have shown that a primary failure mechanism of weak post w-beam barrier is rail rupture (Ray et al., 2001a; 2001b)
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