EVALUATION OF AN EXISTING STEEL POST ALTERNATIVE FOR THE THRIE BEAM BULLNOSE GUARDRAIL SYSTEM

Recently, the Minnesota Department of Transportation (MnDOT) funded a research project through the Midwest States Regional Pooled Fund to evaluate an existing steel post alternative for the thrie beam bullnose barrier system previously developed at the Midwest Roadside Safety Facility (MwRSF). MnDOT had an interest in the replacement of the wooden breakaway posts used in the current bullnose system with proprietary breakaway steel posts. The research project consisted of evaluation of current breakaway steel post designs, investigation and selection of a candidate post design, and full-scale testing of the bullnose system with a steel post alternative. The full-scale testing was to consist of two tests conducted according to the evaluation criteria of NCHRP Report 350: 1) Test 3-38, an impact of a 2000P vehicle on the Critical Impact Point (CIP) of the system at a speed of 100 km/h and an angle of 20 degrees, and 2) Test 3-31, an impact of a 2000P vehicle with the center of the vehicle aligned with the center of the nose of the system at a speed of 100 km/h and an angle of 0 degrees. The evaluation of the steel post alternative for the bullnose system project has been completed. A steel post alternative was selected followed by two full-scale crash tests. Unfortunately, both crash tests failed as the vehicle in each test ramped up the guardrail and vaulted the system. This letter summarizes the work completed

PERFORMANCE EVALUATION OF THE MIDWEST GUARDRAIL SYSTEM – UPDATE TO NCHRP 350 TEST NO. 3-11 WITH 28 C.G. HEIGHT (2214MG-2)

Based on the proposed changes to the National Cooperative Highway Research Program (NCHRP) Report No. 350 guidelines, NCHRP Project 22-14(2) researchers deemed it appropriate to evaluate a strong-post W-beam guardrail systems prior to finalizing the new crash testing procedures and guidelines. For this effort, the Midwest Guardrail System (MGS) was selected for evaluation. One full-scale vehicle crash test was performed on the longitudinal barrier system in accordance with the Test Level 3 (TL-3) requirements presented in the Update to NCHRP Report No. 350. For this test, a 2270P pickup truck vehicle, which was a 1⁄2-ton, four-door vehicle with a 711 mm (28 in.) c.g. height, was used. The MGS system, mounted at the metric top rail height of 787 mm (31.0 in.), provided an acceptable safety performance when impacted by the 1⁄2-ton, four-door pickup truck, thus meeting the proposed TL-3 requirements presented in the Update to NCHRP Report No. 350

DEVELOPMENT AND EVALUATION OF A TIE-DOWN SYSTEM FOR THE REDESIGNED F-SHAPE CONCRETE TEMPORARY BARRIER

Often, temporary barriers are used in applications where it is desired that their deflection during vehicular impact be limited. One such application is in the installation of temporary barriers placed adjacent to the edge of a concrete bridge deck in order to maximize lane width. Acceptable tie-down systems for temporary barriers have previously been developed, but there are concerns when the barriers and tie-down systems are used on bridges that are reconstructed in stages and where very little tolerance in barrier deflection is allowable. Therefore, a rigid tie-down system was developed that minimizes barrier deflections. For this system, the original Kansas temporary barrier was redesigned in order to strengthen the barrier around the tie-down holes and to standardize the barriers for use in adjacent states and in various temporary and tied-down configurations. The tie-down anchor system fastened the traffic-side of the barriers to the concrete bridge deck with three 29-mm (1.125-in.) diameter ASTM A307 anchor bolts with heavy hex nuts and 76-mm (3-in.) x 76-mm (3-in.) x 13-mm (0.5-in.) thick washers. The research study included one full-scale vehicle crash test, using a 3⁄4-ton pickup truck. The full-scale test, with an impact speed of 99.8 km/hr (62.0 mph) and an impact angle of 25.3 degrees, was conducted and reported in accordance with the requirements specified in the National Cooperative Highway Research Program (NCHRP) Report No. 350, Recommended Procedures for the Safety Performance Evaluation of Highway Features. The safety performance of the tie-down anchor system for use with concrete bridge decks and the redesigned F-shape temporary concrete barrier was determined to be acceptable according to the Test Level 3 (TL-3) evaluation criteria specified in NCHRP Report No. 350

PERFORMANCE EVALUATION OF THE PERMANENT NEW JERSEY SAFETY SHAPE BARRIER – UPDATE TO NCHRP 350 TEST NO. 4-12 (2214NJ-2)

Based on the proposed changes to the National Cooperative Highway Research Program (NCHRP) Report No. 350 guidelines, NCHRP Project 22-14(2) researchers deemed it appropriate to evaluate permanent safety shape barrier systems prior to finalizing the new crash testing procedures and guidelines. For this effort, the permanent New Jersey Safety Shape barrier was selected for evaluation. One full-scale vehicle crash test was performed on the longitudinal barrier system in accordance with the Test Level 4 (TL-4) requirements presented in the Update to NCHRP Report No. 350. For the permanent barrier testing program, a 10000S single unit truck was used. The permanent safety shape barrier provided an unacceptable safety performance when impacted by the single unit truck, thus failing to meet the proposed TL-4 requirements presented in the Update to NCHRP Report No. 350

Midwest Guardrail System for Standard and Special Applications

Development, testing, and evaluation of the Midwest Guardrail System were continued from the original research started in 2000. This new strong-post W-beam guardrail system provides increased safety for impacts with higher-center-of-mass vehicles. Additional design variations of the new system included stiffened versions using reduced (half and quarter) post spacings as well as a standard guardrail design configured with a concrete curb 152 mm (6 in.) high. All full-scale vehicle crash tests were successfully performed in accordance with the Test Level 3 requirements specified in NCHRP Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features. The research study also included dynamic bogie testing on steel posts placed at various embedment depths and computer simulation modeling with BARRIER VII to analyze and predict dynamic guardrail performance. Recommendations for the placement of the original Midwest Guardrail System as well as its stiffened variations were also made