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PCB Tie-Down Applications

Question
State WI
Description Text

I have a few questions about temporary concrete barrier.

  1. When installing a crash cushion, should the temporary barriers after the crash cushion be pinned into position?
  2. If the crash cushion needs to be pinned, what method should be used if
    1. Traffic is on one side (e.g. a lane shift)
    2. Traffic is on both sides (e.g. in a gore area)
  3. In MwRSF, crash testing of a thrie beam transition from temporary barrier to permanent barrier, MwRSF used 4 barrier staked into asphalt.  MwRSF also crash tested a temporary barrier run that was attached to a bridge deck using a tie-down strap.  Is there a way of using the tie-down strap system to build a transition from temporary barrier to permanent barrier?
  4. I believe that at one time I asked this question, the LON point of free standing temporary barrier is 8 pieces.  Is this correct?
Keywords
  • Temporary Barriers
Other Keywords none
Date September 18, 2009


Response
Response

Replies to your questions are below in red.

 

  1. When installing a crash cushion, should the temporary barriers after the crash cushion be pinned into position?

Typically, we recommend that unprotected ends of TCB systems be extended out of the clear zone in order to reduce impacts with these ends. We also tend to recommend that sufficient barriers be placed outside of the clear zone to provide anchorage for the length of need. However, there are instances when this cannot be done and the end of the barrier system must be protected by some form of crash cushion. In the case of a proprietary crash cushion, we would recommend that you follow their guidelines for connecting the crash cushion to the system. If you are using sand barrels, MwRSF recently completely development of an upstream anchorage for the F-shape TCB used by most of the Pooled Fund states that can be used with sand barrels. We recently sent the draft report of that research out for review and I will have the final draft out by the end of the month. Thus, we are not recommending pinning the barriers at this time.

  1. If the crash cushion needs to be pinned, what method should be used if

a.       Traffic is on one side (e.g. a lane shift)

b.      Traffic is on both sides (e.g. in a gore area)

As mentioned above, we are not recommending that the barrier be pinned at this time.

  1. In MwRSF, crash testing of a thrie beam transition from temporary barrier to permanent barrier, MwRSF used 4 barrier staked into asphalt.  MwRSF also crash tested a temporary barrier run that was attached to a bridge deck using a tie-down strap.  Is there a way of using the tie-down strap system to build a transition from temporary barrier to permanent barrier?

We considered the use of the strap tie-down when we designed the temporary barrier transition especially the median transition because it performs similarly when impacted on either side of the barrier. We abandoned its use in the transition design because it was not possible to make the transition sufficiently stiff as you approach the rigid hazard with the strap tie-down. Recall that the strap tie-down allowed approximately 33 inches of dynamic deflection of the system. This amount of deflection of the system could not be allowed adjacent to the end of the barrier. Thus, no transition design exists using the strap tie-down. I suppose that it could be revisited though.

  1. I believe that at one time I asked this question, the LON point of free standing temporary barrier is 8 pieces.  Is this correct?

That is correct. Without anchoring the barrier as I mentioned previously, we recommend 8 barriers adjacent to the length of need for anchorage.

 

Date September 21, 2009


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