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TCB to Bridge Rail Connection

State IA
Description Text

As we spoke on the phone, I have a question regarding the roadside TCB to bridge connection utilizing thrie-beam panels.  Do you have any rules of thumb regarding how the length of thrie-beam sections should be distributed onto the bridge and the first TCB section?  For example, I would like to connect the thrie-beam end shoe to the bridge through existing bolt holes.  This would place a significant majority of the thrie-beam length onto the first TCB section (see attached file).   Do you see any issues with this approach?

  • Bridge Rails
  • Temporary Barriers
Other Keywords none
Date September 2, 2009
Attachment Faller.pdf


The thrie beam connection shown in your schematic should be acceptable and I don't see any problems with the attachment as you have it shown.


The schematic you sent me is acceptable even with a gap as large as 12" between the final PCB and the bridge transition piece as long as the there is only one way traffic on the roadway. We would recommend gaps smaller than 12" if at all possible. If traffic is moving from the PCB's towards the bridge in your schematic, then the chance for snagging on the end of the bride is minimal, and the thrie beam sections should possess sufficient capacity to hold the joint between the bridge transition and the PCB together even with the larger gap.


If the traffic is moving the other direction, we would recommend filling the overlap area with concrete to reduce the snag potential. This is necessary and quite critical. It may be your best option to fill that area for now, but you may want to think about a redesigned transition section in the future to reduce the snag potential. In general, we would recommend not running two way traffic in this type of installation unless the snag issues can be sufficiently eliminated.

Date September 28, 2009


Upon further inspection, I realized that my scaling was off on the thrie-beam section I showed in my drawing. Having corrected that, and using the dimensions to the existing bolt holes in the bridge rail and a 12-inch gap between the bridge and the first PCB, I am now showing that the thrie-beam piece will extend entirely beyond the first PCB section. I assume this is an issue (maybe not?).

Minimizing the gap between the bridge and the first PCB would allow bolting the rail into both the first and second PCBs. Would this be acceptable? Are there any other spacings or modifications you might recommend, such as using a shorter thrie-beam section?

Date September 29, 2009
Attachment 12-inch gap.pdf
Attachment 3.625-inch gap.pdf


I don't like the idea of extending the thrie beam past the end barrier in either of those schematics. If we do so, the thrie beam is no longer tied to the end barrier. In addition, the 12" gap detail would create a snag hazard on the thrie beam end shoe.

I have attached details of the connection that Florida uses. They have many different variations of the thrie beam connection to permanent railing that they worked out with us when the transition was first developed. Will these details work for you?

Date October 1, 2009
Attachment 00414.pdf


I've been using Florida's details as a guide. Unfortunately, they don't have anything that would solve this particular issue. Since my main goal is to try and utilize the existing bolt holes in the bridge end post, the only other option to make it work would be to use a thrie-beam section SHORTER than 12'-6". What are your thoughts on that?

Date October 1, 2009


We do not have a problem with using shorter thrie beam sections, such as 6'-3" sections, rather than the 12.5' sections we tested with. We went with the longer section because it was more common.

Date October 2, 2009

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