This paper presents the results of 4 full scale impact tests against barriers placed on top of an instrumented MSE wall. The impact was created by a head-on collision of a 2268 kg (5000 lbs) bogie going at about 32.2 km/h(20 mph). The barriers were New Jersey and vertical wall barriers with a 1.37 m (4.5 ft) wide moment slab in 9.14 m (30 ft) long sections. The wallwas 1.52 m (5 ft) high with one panel and two layers of reinforcement. The reinforcement was 2.44 m (8 ft) long strips, 4.88 m (16 ft) long strips and 2.44 m (8 ft) long bar mats. The backfill was crushed rock. The instrumentation consisted of accelerometers, strain gages, contact switch, displacement targets, string lines, and high speed cameras. The test was designed to represent a commonly used installation in current practice includingan impact load on the barrier at least equal to 240 kN (54 kips). Most ofthe barriers sustained significant damage but overall the behavior of thewall was satisfactory since the displacements were minimal and the panel damage was acceptable except possibly in the case of the 4.88 m (16 ft) long strips. The loads measured in the reinforcement indicate that the reinforcement was brought to its ultimate capacity for the duration of the impact but since the impact duration was so short and since the displacements were within tolerable limits, this is considered acceptable. The use of the longer strips (4.88 m (16 ft) long strips) is not necessarily a good thing because, while it did lead to slightly smaller panel displacements, it also leads to higher panel stresses as evidenced by a bending crack in thepanel. The 2.44 m (8 ft) long strips solution is more flexible. The measured maximum dynamic loads in the strips were found to be 3 to 5 times higher than the calculated maximum static loads by AASHTO guidelines.
Samenvatting