Logged in as: Public User |
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 |
|
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 |
Contact Us: 130 Whittier Research Center 2200 Vine Street Lincoln, NE 68583-0853 (402) 472-0965 Email: mwrsf@unl.edu |
Disclaimer: The information contained on the Midwest Roadside Safety Facility (MwRSF) website is subject to change without prior notice. The University of Nebraska and the MwRSF is not responsible or liable, directly or indirectly, for any damage or loss caused or alleged to be caused by or in connection with the use or misuse of or reliance upon any such content, goods, or services available on this site. |