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Concrete Pier Protection AGT attachment

Question
State NE
Description Text This installation problem has control bolts that will miss the bottom of a concrete rail along our piers.

Proposed solution; Can the control bolts be eliminated if we run the thrie-beam continuously along the face of the concrete rail 40’ to 45’?
I would connect the trie-beam to the bridge approach section on each end of the concrete rail.
Reason this would give us tension in the rail, and only be connected to the wall at the 6’-3” post spacing’s(one button head bolt … or not).
This would allow for easy resetting of guardrail when it will be overlaid 20 years from now.

What else is possible other than rebuilding the concrete?
Keywords
  • Approach Guardrail Transitions
Other Keywords none
Date October 22, 2015
Attachment IMG_20151019_180412251.jpg
Attachment IMG_20151020_093611477.jpg
Attachment Guardrail 68589 Big Springs - Brule.pdf


Response
Response

If the five anchorage/control bolts are eliminated, then there may be excessive slack available from the downstream guardrail, splices and soil anchorage system that may possibly increase pocketing/snag on the upstream side of the buttress. It may not be an issue, but I am uncertain at this time. Is it possible to construct a taller parapet in the future that allows for two sets of threaded inserts for bolt placement?

 

Date October 22, 2015


Response
Response

taller parapet?

It is already tooo tall.

 

Shouldn’t the tension from the upstream & downstream anchors & the bridge approach section posts - keep the vehicle from pocketing/ snagging?

Date October 23, 2015


Response
Response

Approach guardrail transitions are rigidly anchored to the buttress end. There is only one guardrail joint at this location between the thrie beam end shoe and the nested thrie beam rails. The only joint slip downstream of this location occurs at the one splice location on the face of the buttress.

 

For a long run of guardrail downstream of this location, there would be multiple joints plus another anchorage. Additional slip could occur that could potentially allow for more rail deflection upstream of rigid buttress. I do not know how significant that this may be but only pointing out that we would not have exactly the same scenario as most testing programs. More rail rotation may occur when the rail is not clamped down to buttress face as well. That could potentially increase pocketing/snag as well; since, one bolt every 6 ft – 3 in. may not replicate the end shoe clamped behavior.

 

When I noted taller parapets, I was referring to future height to allow for an overlay with second set of 5 bolts.

 

Again, the long run of thrie beam may be okay. However, I am not as certain that other issues will not crop up.

 

Date October 24, 2015


Response
Response

Can the five bolt pattern be adjusted to keep them in the concrete.

Can the 5 bolts be in the top ¾ of the end shoe?

Date October 25, 2015


Response
Response

Today, Scott and I were able to further discuss this immediate need involving pier protection adjacent roadway reconstruction. As we understand, the roadway adjacent to numerous bridge piers and concrete/guardrail protection systems was milled/removed and reconstructed. During this process, the new roadway is much lower than originally used relative to the barriers. As such, there are concerns with the replacement of the barriers as well as safety concerns regarding roadway elevation changes.

 

To effectively address these concerns, we believe the best solution involves the downward extension of the RC parapet below the existing parapet. Second and due to such variability between sites, it would be best to just extend the parapet to the current ground elevation. The RC parapet would be supported against the piers in a similar manner to that used for the existing parapet. If desired, one could utilize minimal attachment to the concrete ground surface, although not required. New anchorage hardware would be either cast into the new parapet or placed into old/new concrete with epoxy anchors. The old exposed anchors could be cut off to reduced snag hazards. On the upstream end of the flared buttress, you will likely have the concrete end extend above the thrie beam, which provides some snag hazard for vehicles extending over the thrie beam. If possible, we would prefer to have a top taper on this region to reduce snag risk. However, a taper could provide challenges in the future when the rail needs to be raised. We may want to further discuss options here and note that some risk would exist if you do nothing here.

 

Please let us know if you have further questions regarding the enclosed information or want to discuss other options. Thanks!

 

Date October 26, 2015
Attachment 20151023085924233.pdf


Response
Response I would suggest not changing the 5-bolt pattern away from that used in the standard steel end shoe. Such changes may potentially cause different failure patterns or capacities to occur in the end shoe. The 5 bolts were likely placed to maximize tensile capacity and provide even distribution within the end shoe. 
Date October 26, 2015


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