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Mis-fabricated Stirrup for Barrier Rail, RFI 90, Project IM-NHS-074-1(199)5--03-82, 2274' Welded Girder Bridge-WBL

Question
State IA
Description Text
 We have an issue on one of our projects where the reinforcing supplier misfabricated one of the reinforcing bars. A tail was missed on bar 5c1, see the plan sheet excerpt last page. The picture on the last page of the first attachment shows what was actually fabricated.

The contractor has requested to use these bars for every other instance of 5c1 in the barrier rail. The spacing for this bar is every 6 inches in the rail. The bars that go into the deck are every 12 inches. We were thinking they could use the misfabricted bars between the bar that go into the deck.

A consultant designed this project and used rail designs from other states so we are not very familiar with the design. It is intended to be a TL5 system. Do you see a concern with using the misfabricated bars as we described? As always the contractor is anxiously awaiting our decision. I know this question is out of left field with a short fuse so if you think it is too much for our question and answer let me know.

Brian

______________________________________________________________________________

Brian,
This is to follow up on our conversation this morning by you, Stuart Nielsen, and myself regarding whether mis-fabricated barrier stirrups can be used as proposed by the contractor in a request for information (CnRFI 90.pdf). A pdf of CnRFI 90 is attached which describes the issue.

Also attached for reference are plan sheet excerpts from the project plans. See attachment “Plan_Sheet_Excerpts.pdf.” Note that Section A-A on Design Sheet 199 of 258 shows a section thru the barrier rail, and reinforcement bar details are on Design Sheet 207 of 258.)

I will also mention for your information that the subject barrier rail is a combination of a Pennsylvania and a Texas rail and it was reviewed by the by the Midwest Roadside Safety Facility in 2010. Attached is a pdf of project Task_209 which has some background information regarding the 2010 review of the rail design.

Please let me know if you have any questions or would like to discuss this.
Thank you.



Bridge Rails


Date October 3, 2018
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Attachment CnRFI_90.pdf Attachment Plan_Sheet_Excerpts (003).pdf Attachment Task_209.pdf
Response
Response
(active)

I reviewed the information you sent.

 

While typical stirrup design would have hooked ends like those shown in your detail, the as-fabricated stirrup may function appropriately. Based on the function and loading of that stirrup in the bridge rail, the development of the vertical arms of the stirrup is most critical. This can be developed through a simple 90 degree bend. According to code, that would require a length of 12*db or 7.5” in this case. It appears that the as-fabricated stirrup has this length in the bend adjacent to the vertical arms.

 

The other load directions on the stirrup are less critical here during impact loading, and the additional stirrups that tie into the deck at 12” spacing will help reduce the potential for overloading of the 5c1 stirrup.

 

As such we don’t see a major issue with using the as-fabricated stirrup as proposed below.

 

Thanks

Date October 3, 2018
Previous Views (150) Favorites (0)