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One of our contractors is in the process of relocating a run of the MwRSF TCB that was pinned through the asphalt with the 38mm dia x 978mm long A36 steel pins. They are having a very difficult time pulling the pins out, most likely due to the extreme cold temperatures we are having. For future installations we would like to consider specifying slightly larger diameter holes, say up to 45mm (1-3/4") diameter holes, to ensure pins could be pulled easier in future. We would also like to consider a threaded top on the pin in order to use double nuts and square plate washer as an alternative to the welded steel top plate. This would allow other devices to be attached to the pin during removal.
Please advise if you and/or contractors using the MwRSF TCB have experienced similar problems during pin removal, and their solution.
Please also advise if it would be advisable to allow larger diameter holes in the asphalt, and/or allow a threaded top on pin for a double nut and washer as an alternative to the welded top plate.
On another matter, have you run a TL-2 crash test or simulation test on the MwRSF TCB? We would be interested to know the approximate deflection distance for a TL-2 freestanding installation for designer information.
|Date||January 23, 2009|
|Response||I don't see any issues with threading the top of the pin and using double nuts if that helps you with extraction. I would recommend that the washer plate have the same thickness and dimensions as the plate used on the tested pin.
We can't allow larger holes in the pavement because it could potentially allow larger deflections and more vertical pullout of the pins. Both of these behaviors would be detrimental to the performance of the system.
As far as deflection limits, of the MwRSF TCB under TL-2 impact conditions, we have not explicitly determined those limits. We have however provided some guidance for barrier deflections based on accident data in TRP-03-113-03. The report basically gives guidance for lower barrier deflection expectations based on accident data. Let me know if I can give you any more assistance.
|Date||January 26, 2009|
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2200 Vine Street
Lincoln, NE 68583-0853
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