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Wisconsin was interested in installing a TL-2, low profile bridge rail that will be backfilled with soil and were looking for guidance pertaining to the foundation/anchorage requirements. The barrier in question was the TL-2 concrete barrier designed by MwRSF in report TRP-03-109. It was planned for use in both median or roadside applications. The backfill was expected to be 21 feet in median applications, and the roadside application may place a 6:1 on the backside. The roadway in question was being reconstructed. In the median, the expected barrier placement was at least 2' from edge of lane, and on the roadside the region is pushing for 10' shoulder on the outside, but may not get it.
|Date||July 9, 2009|
To adapt the low profile, TL-2, concrete bridge rail to roadside applications, I see three options. These options are shown in the PDF file in the folder noted below. Also, 2 digital videos of the full-scale crash test are in the folder.
(1) Place the barrier on top of the shoulder and tie the vertical steel directly into the shoulder slab. This, to me, seems like the easiest and most efficient method. Even if the shoulder slab is only 6" thick (shorter than the development length of the rebar, and shorter than the 8" embedment depth used during the crash test), the combination of overturning resistance provided by the rebar and the resistance provided by the soil backfill should create adequate strength to redirect a vehicle. Also, the rebar ties should prevent the barrier from lateral and rotational movement due to lateral soil pressure. Again, I would recommend this method.
(2) Place the barrier adjacent to the shoulder slab, extend the barrier downward, and tie in the internal steel to the slab through the end. This should also provide adequate strength to resist impacts and lateral movement due to soil pressure. However, the internal steel reinforcement must be designed correctly to carry the load and it will be more difficult to cast with the bends.
(3) The barrier is not in contact with the shoulder in any way. For this method, the barrier must be attached to a footer, as shown. The footer would need to be at least 12" in depth and run the length of the barrier. Calculations for the necessary internal steel can be done using the design method described in the MwRSF report " "Development of a Stand-Alone Concrete Pier Protection System" Report No. TRP-03-190-09. This will proof to be the most costly design.
|Date||July 14, 2009|
130 Whittier Research Center
2200 Vine Street
Lincoln, NE 68583-0853
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