Thrie beam guardrail systems are used when enhanced Test Level 3 (TL-3) protection above what is typically provided with W-beam guardrail is necessary. Currently, a Manual for Assessing Safety Hardware (MASH) (1) compliant thrie-beam guardrail system for the roadside exists, but a median version has yet to be developed. Furthermore, the currently available roadside system incorporates components that are costly to fabricate and install. Therefore, the Roadside Safety Pooled Fund has prioritized a project to develop MASH-compliant cost-effective thrie-beam guardrail systems for both roadside and median applications.
The research objective is to develop cost-effective thrie beam guardrail systems for both roadside and median applications. These systems will be crash tested to MASH specifications. Lastly, a transition design from these newly developed systems to standard W-beam systems will be developed through computer simulation.
This project will benefit the members of the Roadside Safety Pooled Fund by providing designs for thrie beam guardrail systems which can be implemented on the roadside and in the median. These designs will be a valuable option for enhanced protection against roadside hazards which the members of the Roadside Safety Pooled Fund can implement when needed.
The TTI research team will prepare and submit a research report fully documenting all of the work completed within this project. Application documentation for FHWA Eligibility Letters will be provided for systems that meet FHWA Eligibility Letter requirements. For other systems, the research team will provide engineering justification explaining that the critical tests were performed.
With the tested thrie beam guardrail systems, the Roadside Safety Pooled Fund will have MASH-compliant methods to provide enhanced protection that can be implemented when required.
The research team will review the current literature and previous research related to thrie beam guardrail systems and transitions between W-beam and thrie beam sections. This includes reviewing the National Cooperative Highway Research Program (NCHRP) Report 350 (2) compliant systems and the current MASH compliant system. The research team will also complete a preliminary analysis of the roadside, median, and transition systems in preparation for the computer simulation.
The primary objective of Task 2 is to use computer simulation to develop designs for the following systems:
These designs not only need to be MASH-compliant, but should also be cost-efficient and enable simple installation. The TTI research team will use the results of these simulations to assess the probability of each design concept to meet MASH impact performance requirements and provide other desirable functional characteristics.
The TTI research team will use the explicit finite element code LS-DYNA to perform impact simulations using the developed barrier model and available vehicle models, as shown in Figure 1 (3, 4). These models include (a) Toyota Yaris model representing a 2420-lb (1100C) MASH small car test vehicle; and (b) Chevrolet Silverado model representing a 5000-lb (2270P) MASH pickup truck test vehicle. The impact simulations will be representing MASH Tests 3-10, 3-11, 3-20, and 3-21. Each of these tests requires an impact speed of 62 mph and an impact angle of 25°.
|(a) Toyota Yaris (2420-lb)||(b) Chevrolet Silverado (5000-lb)|
Figure 1. Available Finite Element Models (3, 4).
The TTI research team will use a combination of previous research, MASH guidelines, and computer simulations to determine the critical impact points for the MASH crash testing. Once the critical impact points have been determined, the TTI research team will consult the findings with the technical representative before beginning installation and crash testing.
The TTI research team will complete full-scale MASH crash tests on the roadside and median systems. The current budget allows for three full-scale crash tests, which include two on one system and one on the other system. Therefore, the results from the computer simulations will be used to identify the critical tests which will be completed. These three tests will either be MASH Test 3-11 or 3-10.
Depending on the computer simulation results to possibly identify the most critical two tests on the systems, the one remaining test can be used to test on the median transition. In this case, the three tests will be MASH 3-10, 3-11, and 3-21. These tests include the MASH 2270P (5000-lb) pickup truck and the MASH 1100C (2420-lb) small car.
The TTI research team will prepare a research report fully documenting all of the work completed in this project. The report will include detailed engineering drawings of the thrie beam systems. This draft report will follow the reporting recommendations of MASH and will be submitted to the technical representative of the Roadside Safety Pooled Fund for review and approval.
The TTI research team will prepare application documentation for FHWA Eligibility Letters for the systems that meet FHWA Eligibility Letter requirements. For the other systems, the research team will prepare engineering justification explaining that the critical tests were performed.
|TTI Research Supervisor:
Maysam Kiani, Ph.D.
Associate Transportation Researcher
Texas A&M Transportation Institute
College Station, Texas 77843-3135
|Pooled Fund Technical Representative:
Assistant State Traffic Engineer
Massachusetts Department of Transportation
10 Park Plaza, Room 7210
Boston, MA 02116