TPF-5(193) Supplement 63

This project is a supplement to an existing project originated from the Year 23 Midwest States Pooled Fund Program titled “Dynamic Testing and Evaluation of Curb and Gutter Placed Under Asymmetrical Section of MGS Thrie Beam Transition.” Its project No. is TPF-5(193) Supplement #58, or Pooled Fund Project RPFP-13-AGT-1.

This research supplement is required to finish the project noted above due to the unforeseen system failure experienced during the first full-scale crash test of the project, MWTC-1. The system was subsequently redesigned with nested W-beam rail leading into the W-to-thrie transition segment. Following the redesign, both small car and pickup truck MASH crash tests needed to be conducted. After conducting a successful small car re-test, test no MWTC-2, a letter was sent out to Pooled Fund members explaining that the remaining funds would not be sufficient to finish the project. However, the remaining funds could be used to rebuild the system and start to plan for the pickup truck test. Additional funding would be needed to conduct the data analysis and write the summary report.

Through an e-mail chain of questions and comments in December 2012, members of the Midwest States Pooled Fund agreed to use the remaining funds to conduct the remaining 2270P pickup truck test and support a supplemental project in the Year 24 funds to complete the research project. This proposal has been formulated as a result of the selected plan of action and is necessary to complete the goals of the research project.

Previously, MASH test no. 3-20 was conducted on the MGS upstream stiffness transition placed over a 4” curb. Test no. MWTC-1 resulted in the guardrail tearing near the upstream end of the W-to-thrie transition segment. This small car test was to be performed to evaluate the tendency for the small car vehicle to become wedged under the asymmetrical W-beam to thrie beam transition element with a 4-in. tall concrete curb placed under the entire barrier system. During the crash test, components of the small car vehicle penetrated under the W-beam rail while the wheel overrode and/or climbed up the curb. The combination of these events led to heavy upward and lateral vehicle loading on the lower region of the W-beam rail in advance of the splice between the W-beam and asymmetrical segment. Shortly thereafter, the W-beam rail ruptured at the splice location, gave way, thus allowing the vehicle to snag on a stiff rail element in combination with several exposed transition posts. Due to this W-beam rail rupture, MwRSF researchers were unable to evaluate the potential for the small car vehicle to become severely snagged under and on the lower sloped region of the asymmetric section with a curb in place. Subsequently, the system was modified to include 12'-6" of nested W-beam rail upstream of the W-to-thrie transition segment. Test no. MWTC-2 (an originally unfunded re-test of MASH test no. 3-20) was conducted on this modified system and satisfied all of the MASH performance criteria.

Since the December 2012 plan of action agreement, the test installation was rebuilt and is ready for MASH test no. 3-21. Weather conditions have resulted in testing delays as the ground has remained saturated thus far in 2013.

The objective of this research effort is to evaluate the upstream end of the MGS approach guardrail stiffness transition with an asymmetric transition element and configured with a lower concrete curb. The safety performance evaluation is to be conducted according to the TL-3 impact safety standards published in MASH.

The original proposed research plan included the preparation of 3-D CAD details for a simulated bridge end, thrie beam approach guardrail transition, MGS stiffness transition, and MGS approach rail with a lower, continuous 4-in. high concrete curb.

Two full-scale crash tests were to be conducted according to the TL-3 MASH impact safety standards using both 1100C and 2270P passenger vehicles. As noted above, the need to repeat test no. MWTC-1 with a modified design means that additional test was added to the project. Thus, three full-scale crash test are planned to complete the research project.

Following the research effort, MwRSF will prepare and submit a final research report which documents the crash test results.

The successful development of the MGS stiffness transition with asymmetric transition element and lower curb will allow state department of transportation personnel to provide continuous hydraulic runoff control between approach guardrail transitions and W-beam approach rails. The use of continuous concrete curb will help to mitigate soil erosion near bridge ends as well as its costly maintenance and repair.

RPFP-15-AGT-1 Standardized Parapet for AGTs - Progress Report - 1Q 2015.pdf
RPFP-14-AGT-1 Transition with Curb - Progress Report - 3Q 2015.pdf