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I have report TRP-03-180-06, "Development of Tie-Down and Transition Systems for Temporary Concrete Barrier on Asphalt Road Surfaces." From this, we do need to make some updates to our TCB design, and also consider new Standard(s) to implement transitions.
However, I have an immediate question from one of our districts regarding a transition to an existing bridge parapet. In this case the parapet end is curved away from traffic, making connection of the TCB problematic. There is no ready way to adapt to a pinned connection, and also spanning the back side of the joint with the thrie beam is not possible without removing part of the parapet end.
There seem to be a couple possibilities " remove and recast the end of the parapet to work with the TCB, or perhaps fabricate a triangular steel shape to bolt to the face of the parapet and provide a connection point and also fill over the curved portion. This latter idea still leaves the question of how to span the back of the joint.
Do you have any comments on either of these ideas, or other likely approaches?
This is the type of bridge parapet/wingwall. The bridge is a
We do have reinforcement around the holes for the anchor pins, but it is not as substantial as what is used in the testing of the transition. Ours is #4 bars, where the testing used #6.
The curved wingwall does extend above grade.
There is no guardrail between the parapet end and the PCB sections. They propose to abut them and bridge the gap with a section of guardrail with end shoes at each end.
Traffic is one-way, from the PCB's toward the bridge parapet.
I'm not certain of the shape of the bridge parapet, but the curved end and wingwall near the connection, appears to be a vertical wall.
This is all for temporary (3 months use). The bridge will receive new parapet and wing with a permanent thrie beam transition to the approach guardrail.
Pouring a block for attachment seems to make this easier. We talked about making the block such that a PCB could be pinned to it, but we note that this would still not allow for the thrie beam panel on the back of the joint.
|Date||February 4, 2008|
Based on the photo and the sketch that you sent earlier, I think we can make this installation work.
I believe that you can use the asphalt pin tie-down transition with this installation as long as you butt the end barrier up against the curved wing wall as shown in the sketch. The installation should consist of the 4 barrier transition detailed in the report (1 pin, 2 pins, 3 pins, and 3 pins) with the final barrier butted up against the wing wall. A 12.5' section of nested 12 gauge or 10 gauge thrie beam should be used to span the traffic side face of the transition between the temporary concrete barrier and the wing wall. By butting the back of the TCB against the wing wall, it should provide the additional constraint to motion of the final barrier that the thrie beam across the back of the joint would have provided in a more standard installation.
Because you don't have two way traffic in this installation, we don't need to be concerned about making a special connection piece to prevent snag for reverse direction impacts.
Just a reminder that the transition was designed for use on asphalt surfaces and thus a pad would need to be poured for the transition to work effectively.
This will be simpler than installation of a thrie beam region between the PCB and the parapet or wing wall.
|Date||February 6, 2008|
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