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New Jersey Shape PCB Anchorage

Question
State OH
Description Text

Here are the drawings for New Jersey shaped PCB that is anchored on our structures.  These standards are followed on structures or if there is limited deflection.  

 

The run of New Jersey shaped PCB before anchored pieces do not have to be anchored and have a deflection of 5.5'.  Here is the drawing for that.  

 

I will not be in the office very much this week, no hurry on this.  Thanks for your time.  Let me know if you need any additional information.

Keywords
  • Temporary Barriers
Other Keywords none
Date July 13, 2009
Attachment rm42_oct07.pdf
Attachment pcbdd.pdf
Attachment pcb91.pdf


Response
Response

We developed just such an approach transition for the Kansas F-shape PCB.  MwRSF Report no. TRP-03-180-06 details the transition.

 

While the transition we designed worked successfully with the Kansas F-shape barrier, we have concerns with regards to how it will function with your PCB design. I will try to lay out these concerns below.

  1. First, we do not believe that the anchorage system on your PCB is equivalent to the anchorage used in the transition we developed. Your barrier uses 1" dia. high-strength steel rods embedded 6.5" into the concrete with a grout mixture. Our experience with this type of anchorage is that it is not sufficient to develop much of the strength of a 1" dia. high-strength steel rod. We believe that these anchors will pull out of the concrete surface much more easily than the anchors we tested with. This will change the stiffness and deflection of the anchored barriers as compared to the ones use in the transition we tested.
  2. We did recognize that you have more anchors than use used in our anchored barriers, but that is another cause for concern. We do not recommend placing anchors on the backside of barriers. There are concerns that placing anchorage on back side of the barrier can induce increased vertical rotation of the barrier segments which could increase the potential for vehicles to climb the sloped barrier face and become unstable. Thus, we would recommend no anchorage on the backside of your barrier.
  3. Barrier reinforcement in your barrier is not sufficient to derive the full strength of the 1" dia. high-strength steel rod used. In our anchored barriers, the anchor pockets have reinforcement loops that go around the packet to contain the anchors. Without this type of reinforcement, we do believe your anchors will fracture through the anchor pocket and become ineffective.
  4. I also noted that you allow the use of JJ-Hooks barrier segment connections with your PCB. We would not recommend this connection for use in an anchored barrier system. The JJ-Hooks connection is fine for free-standing systems. However, to be safely used in an anchored barrier or approach transition, the barrier joints must have comparable or greater torsional rigidity about the longitudinal barrier axis when compared to that of the as-tested configuration. JJ Hooks connection is not similar in torsion to the Kansas barrier joint, and the JJ Hooks connection is also non-symmetric in that it has different capacities depending on the direction it is loaded.

 

At this time, if you need to have anchored barrier sections and an approach transition from free-standing barrier, we would suggest using the Kansas F-shape design and the transition and tie-down systems we have tested with it.

 

In order to adapt your barrier to safely use the approach transition, we would recommend that you change your current barrier and anchorage system to:

  1. Remove backside anchors.
  2. Increase anchorage of front anchors to develop the full strength of the threaded rods.
  3. Reinforce the anchor pockets.
  4. Disallow the use of JJ-hooks in the anchored configuration
Date July 16, 2009
Attachment B-180 - Asphalt Tiedown & Transition for TCB acceptance letter.pdf


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