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Development of the Manitoba Constrained-Width, Tall Wall Barrier

REPORT NUMBER

TRP-03-356-16

AUTHORS

Scott Rosenbaugh, Jennifer Rasmussen (Schmidt), Elizabeth Regier, Ronald Faller

PUBLICATION DATE

2016-09-26

ABSTRACT

Manitoba Infrastructure (MI) desired a new, tall concrete median barrier capable of satisfying the Test Level 5 (TL- 5) safety requirements of the Manual for Assessing Safety Hardware (MASH). The barrier was designed with a 1,250-mm (49¼-in.) height, a maximum width of 600 mm (23¾ in.), and to resist a 845-kN (190-kip) load applied at the top of the barrier. The Manitoba Constrained-Width, Tall Wall was optimized to withstand the design load while minimizing the amount of steel reinforcement. Variations of the barrier were developed, including a bridge rail, and roadside barrier. The bridge rail was considered to be the critical design due to its narrow width and anchorage to a thin, cantilevered bridge deck. Thus, one full-scale vehicle crash test was conducted on the bridge rail system to verify the entire family of barriers. The 45.7-m (150-ft) long single-slope bridge rail had a height of 1,250 mm (49¼ in.) and widths of 450 mm (17¾ in.) and 250 mm (10 in.) at the base and top, respectively. The upstream 22.86 m (75 ft) of the barrier was installed on a 280-mm (11-in.) thick simulated bridge deck. A 168-mm (6⅝-in.) gap in the bridge rail and a 20-mm (¾-in.) gap in the bridge deck were placed at the deck mid-span to simulate an expansion joint. A steel cover plate was placed over the barrier joint to prevent vehicle snag. During the test, the tractor trailer impacted just upstream from the joint and was safely redirected. The barrier sustained minor damage in the form of cracks and spalling. Data from on board accelerometers located near the front tandem axles was analyzed to estimate the impact load, which ranged between 1,027 kN and 1,183 kN (231 kips and 266 kips). However, the actual maximum loading applied by the rear tandem axles was thought to be significantly higher. Anchorage options were developed for use with the TL-5 barrier system, including a foundation slab, an independent footing, and an asphalt keyway. Additionally, transitions systems were detailed for the connection of the TL-5 median barrier to various other new and existing barrier shapes. Finally, implementation guidance was provided.