MASH guidelines contain recommended procedures for the testing and evaluation of roadside safety devices. Although significant progress has been made toward MASH implementation, many needs still remain unaddressed. Initial efforts at a national level focused on common types of longitudinal barrier systems such as solid concrete barrier systems and the Midwest Guardrail System (MGS). While WYDOT has benefited from these national efforts, there are some roadside safety systems that are specific to Wyoming or a smaller number of states. As an example, WYDOT uses a significant amount of box beam guardrail because its unique characteristics (e.g., narrow profile and larger ground clearance) help prevent snow drifting and facilitate snow clearing operations. For these same reasons, WYDOT has a need for open steel bridge rail systems instead of solid concrete bridge rail systems at some locations.
Several longitudinal barrier systems used by or of interest to WYDOT are MASH compliant. These include the MGS guardrail system and the Texas Department of Transportation (TxDOT) Type C2P bridge rail system. MASH evaluation of the box beam guardrail system will be completed soon under another WYDOT sponsored research project.
Having addressed WYDOT’s guardrail and bridge rail needs, the next priority is to develop MASH compliant approach transitions between the guardrail and bridge rail systems. Properly designed transition systems are required to transition the stiffness from the more flexible guardrail systems to the more rigid bridge rail system in a manner that is crashworthy and provides continuity of protection along the roadside.
Due to their nature, transition systems are specific to the guardrail and bridge rail systems they connect. For example, a transition designed for use with an MGS guardrail has unique components and characteristics that prevent it from being used with a box beam guardrail system. The transition systems that have been evaluated to MASH to date almost exclusively involve a transition from a W-beam guardrail to a solid concrete bridge rail or parapet end. Information on these MASH transition systems can be found in a MASH Crash Test Database sponsored by the Roadside Safety Pooled Fund Program and maintained by Texas A&M Transportation Institute (TTI). Review of this database confirms that there are no systems available that transition an MGS or box beam guardrail directly to an open steel bridge rail system such as needed by WYDOT.
Previous research has developed a MASH compliant TL-3 transition from MGS guardrail to a thrie beam transition section using a non-symmetric W-beam to thrie beam connector section and appropriate post spacing to transition both the stiffness and geometry between the two different rail shapes. Details of this transition can be found in FHWA Eligibility Letter B231 and Research Report TRP-03-210-10. Since the upstream end of the MGS guardrail to thrie beam transition system is MASH compliant, not further research is needed if the tested details are acceptable to WYDOT. The proposed project will, therefore, focus on the downstream end of the transition where it attaches directly to the Type C2P bridge rail. Results from testing of the thrie beam transition attached to a solid concrete parapet (see Research Report TRP-03-175-06)
will provide valuable information that can be utilized when developing transition details for attaching the thrie beam to the Type C2P bridge rail.
Currently there are no MASH compliant approach transition systems for box beam guardrail. A MASH TL-3 transition from box beam guardrail to Type C2P bridge rail will need to be developed and tested at both the upstream and downstream ends. The existing WYDOT box beam transition (ref. Standard Plan 606-6A) will be used as a starting point for the development of a MASH compliant box beam transition. The current box beam transition was tested under National Cooperative Highway Re
The research objective is to develop two non-proprietary approach guardrail transition systems from box beam and MGS guardrail that are MASH Test Level 3 (TL-3) compliant. The transitions will be designed to connect the guardrail systems to the Texas Department of Transportation (TxDOT) Type C2P TL-4 bridge rail system. Direct connection between the transition section and bridge rail is desired to avoid use of a solid concrete parapet end that could hinder snow clearing operations.
Scope of Work
The work plan for the proposed project consists of seven tasks that relate to the design, analysis, testing, evaluation, and documentation of two transition systems from approach guardrail to a bridge rail. Details of these tasks are described below:
1. Transition Design. The scope of the project involves developing and testing two, non-proprietary, MASH TL-3 guardrail approach transitions to the TxDOT Type CP2 bridge rail. Under this task, the research team will develop initial designs for both transition systems.
2. Finite Element Modeling and Simulation. The research team will model the approved transition designs for both the box beam and MGS guardrail systems for use in simulations to help assess impact performance and ability to meet MASH criteria.
3. test Installation Construction. Once the details of the transition systems have been finalized through simulation and approved by WYDOT, the research team will develop and submit the detailed construction drawings for the test installations for review and approval. After approval of the test installation drawings, the test installation will be constructed at the TTI Proving Ground. The test installation will include at least 17 ft. of bridge rail per MASH Section 126.96.36.199. The bridge rail section will be anchored to a moment slab. A transition, approach guardrail, and terminal will be attached to each end of the bridge rail section. This will reduce repair requirements and help expedite execution of the testing matrix.
4. Full Scale Crash Testin - Box Beam Transition. The full-scale crash testing will be performed at the Texas A&M Transportation Institute (TTI) Proving Ground facility, an International Standards Organization (ISO) 17025-accredited laboratory with American Association for Laboratory Accreditation (A2LA) Mechanical Testing Certificate 2821.01. The research team will perform the full-scale crash tests according to TTI Proving Ground quality procedures, and according to MASH guidelines and standards.
5. Full Scale Crash Testing - MGS Transition. After completing the testing on the box beam transition, the bridge rail section will be repaired as needed and the box beam transitions, approach guardrail, and end anchorage sections will be removed.
6. Final Report. At the conclusion of the full-scale crash testing, the research team will prepare and submit a final report to WYDOT.
Bridges, Other Structures, and Hydraulics and Hydrology
Planning and Administration
Safety and Human Performance