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83 Table 34. Proposed revisions to original FHWA W-beam damage classification. Damage Category Damage Attributes (1) Non-Functional A. Rail element is no longer continuous. B. 1 or more posts are broken off or severely bent. C. Deflection of rail element is more than 10 in. D. Top of rail is less than 26 in. E. Rail element is torn. (2) Damaged but A. Rail element is continuous (can be bent or crushed may still work significantly). B. Deflection of the rail element is less than 10 in. research team recommends that the items below be consid- that these additional damage modes be given first priority ered in future evaluations of repair guidelines: for evaluation in a future follow-up phase to NCHRP Proj- ect 22-23. Additional damage modes for which repair guide- Conduct deeper sensitivity analyses for other impact con- lines should be developed in a follow-up phase to the current ditions. Examples would be alternate impact speeds, impact project include the following: angles, and impact points. The finite element modeling was applied to only some of the damage types, and if extended Wood post systems: This project has evaluated steel post to other damage modes could yield further insight into the systems--the most common variety of strong-post w-beam crash performance of damaged barriers. barrier systems. Wood post systems are heavily used in many Conduct additional full-scale crash tests of damaged longitu- installations however, and because these systems fail in a very dinal barriers both as a means to evaluate the crash perfor- different manner than steel post systems, there is a need to mance of these systems, and to provide an additional source determine repair criteria which are unique to wood posts. of finite element model validation data. Overlapping damage modes: Longitudinal barrier dam- Assess the implications of "damage" under MASH criteria. age often consists of overlapping damage modes, e.g., rail The MASH criteria use a larger pickup truck than the stan- deflection with flattening. There is a need to better under- dard 2000P vehicle used in NCHRP Report 350. stand the interaction between overlapping damage types. The approach in this project to focus on worst case scenarios Generic end treatments: The current guidelines are based led to the decision to evaluate impacts with larger vehicles. on engineering judgment and would benefit from quanti- However, there can also be significant issues associated with tative assessment. It would also be useful to extend the impacts with smaller vehicles. A follow-up project should guidelines for generic end treatments to proprietary end assess the risk of smaller vehicle impacts with damaged lon- treatments. gitudinal barriers. Damage to barriers near end terminals: A previously Rail tensions in the finite element simulations were examined deflected rail element within the first 50 feet of rail in an to determine the risk of rupture occurring in the guardrail energy absorbing terminal may not properly activate the end system as a whole. While localized tearing is possible in terminal in a head-on crash. If these rails are not straight, the vehicle-guardrail impacts, this guardrail model did not in- rail may lose column strength and be unable to resist buck- clude failure criteria for the steel components and was not ling when impacted end-on. configured to look for element tearing due to localized Transitions: It would be useful to broaden the guidance to stress concentrations. full systems by addressing damage to transitions. 15.3.6 Recommendations for Additional 15.4 Guideline Format for Damaged Barrier Repair Guidelines Maintenance Personnel This project has evaluated the crash performance of a num- The end customer for these repair guidelines are highway ber of the most commonly encountered damage modes maintenance personnel. In addition to being based upon a incurred by longitudinal barriers. The research team's eval- strong analytical foundation, the guidelines must be easily uation has not however been exhaustive. There is a continu- understood and implemented. Chapter 16 presents the repair ing need for development of repair guidelines for a number threshold guidelines in a graphical format that clarifies how of additional damage modes beyond those which could be damage to w-beam barriers should be measured and repair evaluated under this contract. The research team recommends priority assessed.