We would like to request a review of our Concrete Barrier Standard Drawings to see what needs to be improved upon. I have attached a pdf copy of our standard drawings and calculations used at the time when they were created.
Along with the entire set, I do have a couple specific concerns as follows:
TL-3 CIP Barrier Design:
TL-5 CIP Barrier Design:
Thank you for your time,
Scott and I have reviewed you details. Comments and responses to your questions are located below.
For you PCB standards.
i. The connection loops are denoted as ¾” dia. bar and use a 1” radius loop bend for the connection pin. In previous development of the F-shape barrier, MwRSF found that the bend radius and the grade of the loop steel were critical to developing proper load in the connection loops. That research used a 2 ¾” dia. bend radius and specified an ASTM A709 Gr. 70 or A706 Gr. 60 rebar for the loops in order to prevent fracture of the loops under impact loads.
ii. MwRSF’s F-shape PCB also uses double shear loops for the connection loops. This lowers the load in each loop and reduces pin bending. Previous designs of the F-shape PCB found it necessary to use a constraint bolt at the base of the PCB connection pin to prevent the connection pin from bending and pulling through the loops under load. This may be an option to consider for your system as well. You appear to use the double shear loops in the 42” tall single-slope design.
Similar concerns would apply to the slope end treatment shown on sheet BA 3H.
Safe termination of PCB’s is a significant safety issue that has not been dealt with over time, and few options are available other than sand barrels and crash cushions. We have done preliminary work on the length of need, but the issue of safe termination of PCBs likely need more research.
Scott looked at your CIP barrier questions and standards. In response to your questions:
BA 2D: This is a short stand alone barrier section. My concern is that it does not have a foundation. Currently this design in most cases is installed on PCCP of 9 inch thickness.
Let me know if you have any comments or questions.
Has there been any testing of cast-in-place barrier anchorage itself? For example, has a physical test or computer analysis been run to see what would happen if a vehicle impacts the last 10 feet of the barrier run to ensure the barrier will not push back or rotate exposing a concrete bridge rail end? That being the pickup for TL-3 and Semi for TL-5.
If not, would Midwest Roadside Safety Facility be willing to run computer analysis on our current design attached?
Another thought if other agencies have similar question, this issue could also be incorporated within the RPFP-19-CONC-1 Evaluation of Permanent Concrete Barriers to MASH 2016?
We have conducted TL-3 crash testing on an end section buttress supported by and anchored to reinforced concrete foundations. This crash testing was performed under NCHRP Report No. 350 impact conditions. Lateral impact loading from pickup trucks on buttresses under MASH 2009/2016 would be slightly higher than previously observed under NCHRP 350. I am providing weblinks to reports that utilized a foundation system for the transition system as well as another to anchor a TL-5 barrier. Note that the TL-5 barrier was not impacted at the end but rather designed to anchor the end of the barrier.
https://mwrsf.unl.edu/reportresult.php?reportId=84&search-textbox=transition
https://mwrsf.unl.edu/reportresult.php?reportId=106&search-textbox=tl-5
Further, there exists a TRB journal paper from the late 1980s that provide suggested sizes for anchorage foundations at barrier ends or buttresses where AGTs are often connected.
https://unl.box.com/s/psiose59ebda2mfds3l4zakofyljnufi
Finally, Scott has already conducted structural analysis and design guidance for this configuration to the Wisconsin DOT. This include included shape and height transitions, interior and end designs, etc. I can ask that Scott either send you his details or details which details now exist in the Wisconsin DOT’s plans.
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