| TTI Research Supervisor: Roger Bligh Senior Research Engineer Texas A&M Transportation Institute Texas A&M University System TAMU 3135, College Station, Texas, 77843-3135 [email protected] | Pooled Fund Technical Representative: Jeff C. Jeffers, P.E. Statewide Standard Specifications Alaska Department of Transportation & Public Facilities 3132 Channel Drive P.O. Box 112500 Juneau, AK 99811-2500 (907) 465-8962 [email protected] |
The American Association of State Highway and Transportation Officials (AASHTO) recently published an updated 2016 edition of the Manual for Assessing Safety Hardware (MASH) document. Along with this, the Federal Highway Administration (FHWA) and AASHTO developed a revised joint implementation agreement which establishes dates for discontinuing the use of safety hardware that has met earlier crash testing criteria for new installations and full replacements on the National Highway System (NHS). While some of roadside safety apparatuses were tested and evaluated according to MASH 16, there is a need to evaluate the remaining widely used roadside safety features using the safety-performance evaluation guidelines included in MASH 2016. In additions, providing various MASH compliant roadside safety systems gives the designers within the DOTs more flexible options to opt to promote the safety of the NHS.
The TTI research team will center this research on evaluating and developing guidelines using engineering analysis, and/or simulation for attachment of prioritized MASH compliant TL-3 thrie beam transition(s) to various rigid concrete barriers. The TTI research team will determine the barrier types, profiles, and heights evaluated as part of this project on a case by case basis that will be prioritized based on frequency of usage and/or interest in usage by participating member agencies. Considerations will be given, but not limited to, 32-inch or 42-inch Vertical Wall, Fshape, NJ shape, single slope Concrete Bridge Barriers with/without flare.
The purpose of this research is to evaluate and develop guidelines for connecting MASH-compliant thrie beam transitions to rigid barriers other than the tested rigid barrier. Determine whether MASH compliant transitions, in general, may be connected to rigid barriers other than those tested. If so, determine what factors must be considered before connecting a different rigid barrier than tested. The information compiled from this research will provide design solutions to adapt connection of MASH tested thrie beam transition to a rigid barrier having different material, slope, or snagging potential than the tested rigid barrier. Guidance should address opposite direction hits at the connection.
The research objective centers on developing guidelines for connecting MASH-compliant thrie beam transitions to rigid barriers other than the tested rigid barrier. The first step will be to determine whether MASH-compliant transitions, in general, may be connected to rigid barriers other than those tested. If yes, the second step will be to determine what factors must be considered before connecting a different rigid barrier than tested.
The compiled research information will provide the FHWA and State DOTs with guidelines for connecting existing MASH compliant transitions to rigid barriers other than those tested. These guidelines will reduce development cost of multiple options and give states flexibility by adapting tested transitions to various needs on the highway system.
The TTI research team will produce a report and a standalone guidance document. The details of the report and the guidelines are presented in Task 3 of the Work Plan.
The TTI research team will perform a literature review of thrie beam transitions to evaluate various current thrie beam transition designs from states and to determine which designs (i.e., vertical wall, F-Shape, Single Slope, etc…) are commonly used by states, and which represent critical conditions for analysis and simulation. In addition, the TTI research team will determine the critical transitions design. Since a MASH TL-4 thrie beam transition has not yet been developed, the TTI research team will limit the analysis of the thrie beam transition system to MASH TL-3 compliance only. The TTI research team will propose the evaluation plan for MASH compliance for different aspects of the transition system through professional opinion, or computer simulation.
Within the outcomes of Task 1, the TTI research team will work closely with the project Technical Representative and, if necessary, will coordinate with the Pooled Fund DOTs members to prioritize
the most critical transitions that will be evaluated through the project. The TTI research team will work on the prioritized systems to prepare baseline models for evaluation through the computer simulation. For each prioritized system, the TTI research team will conduct the computer simulation to investigate the crashworthiness of the base-line design. For each prioritized system, the TTI research team will conduct computer simulations parametrically to replicate the real-world installations by varying a single parameter each time. The TTI research team anticipates that the total number of combinations that will be investigated by computer simulation could be 5-10.
The TTI research team will generate a final report from the research findings, and computer simulation study. This report will describe the transition(s) considered and included in the analysis, the results of engineering analysis and simulation, and the determination whether other MASH-compliant transitions can be treated in the same manner as the analyzed transition(s). The Guidance Document will provide design solutions to adapt connection of MASH tested thrie beam transition to a rigid barrier having different material, slope, or snagging potential than the tested rigid barrier. This document should address opposite direction hits at the connection. The TTI research team will introduce recommendations regarding conducting the real crash tests to satisfy MASH requirements for some critical cases for the second phase (new Problem Statement).
Design solutions and guidance may include or address:
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2022-03-03