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|Description Text||We need to get an anchored temporary barrier wall 350 approved for INDOT. Because time is of the essence, our concept is to take a 350 approved anchored system such as the Drop Pin or Kansas anchored system and modify the design to fit within the 350 approved Indiana "â€¹Ã…â€œF' shape. That is we would use the reinforcing and anchoring system from the approved wall and modify it to fit within the INDOT barrier wall.
I have attached the approval letter and INDOT standard for your review. I will also try to retrieve the report completed for the INDOT wall.
In the meantime, please review and provide any comments you have concerning our approach.
|Date||October 20, 2010|
|Attachment||b84 INDOT Barrier Wall.pdf|
We have reviewed your TCB details. I have attached details for the F-shape barrier used by Kansas developed at MwRSF.
We would recommend the following with respect to modifying your barrier section.
|Date||October 29, 2010|
Attached preliminary drawings show modified INDOT F-shape TCB with Kansas F-shape TCB reinforcing bars and anchor bolt details.
Please review these modifications to the Indiana F-shape anchored barrier and provide your feedback and let us know if this anchored barrier can be qualified and approved to NCHRP 350, TL3 without test. We are planning to prepare final drawings of the Indiana modified barrier after we hear from you. We will send you the final drawings again for your review.
|Date||December 20, 2010|
I have reviewed the details you sent and have the following comments.
1. You list loop bars as ¾" diameter smooth bars with Fy = 60 ksi. This is not the correct spec. The proper spec for the loop bar steel is, "The loop bars (6d1, 6d2, and 6d3) shall be A706 Grade 60 or A709 Grade 70 0.75"  smooth or deformed steel bars. Alternative steel chemistry may be used as long as the alternative material provides a minimum yield of 60 ksi [420 MPa], a tensile strength of not less than 1.25 times the yield strength but a minimum of 78 ksi [550 MPa], a minimum 14% elongation in 8" , and passing a 180 degree bend test using a 3.5D pin bend diameter. The loops shall be installed within 0.12"  of the plan dimensions."
2. We are concerned that the height of the barrier is only 31". All previous testing of the MwRSF F-shape barrier was conducted with a 32" high barrier. In F-shape barrier impacts we have observed a tendency for the vehicle to climb the barrier face. Thus, the height of the barrier is critical in achieving proper redirection. As such, we would recommend that the barrier be 32" high.
3. With the shorter toe on your proposed barrier, there is slightly less cover for the loops used to retain the anchor bolts. This may adversely affect the longevity of the barrier segment and potentially it capacity.
4. On one of your details, you show the three loop connection attached to your current F-shape barrier with two loops. While we believe that this type of connection can work, we would only recommend mixing barrier segments in free-standing barrier installations. Also, when connecting barriers with dissimilar loop connections, we would recommend that a ½" dia. x 10" Grade 5 Hex bolt and 2.5"x4"x1/2" keeper plate be used at the bottom of the connection pin to insure the pin does not pull out of the loops under load. This bolt and keeper plate were part of the original barrier connection, but were eliminated after switching to the 3 loop connection. However, if you connect the three loop connection to your current F-shape barrier with two loops, we would recommend that the bolt and keeper plate be used.
Other than the four issues above, we see no other problems with the barrier as shown. I should also note that we cannot determine if this barrier can be qualified and approved to NCHRP 350, TL3 without test. The acceptance of the design must be done by FHWA through their approval process. We can help you get in contact with Nick Artimovich if need be. I am not certain at this time that the barrier could be approved to NCHRP 350 as the deadline for all NCHRP 350 approvals was 12/31/10. As such, you may need to seek approval under MASH. This may be possible as the MwRSF F-shape has undergone several full-scale tests using the MASH criteria.
|Date||December 21, 2010|
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