Repairing damaged bridge rail bolts

[ACtrafficengr]

An equipment operator managed to clip bridge rail mounting bolts on a new precast headwall with his bucket. One was sheared off at the base, one has cracks at the base, and another was bent 10 degrees. These are 1" (25 mm) bolts threaded into a plate and cast into the concrete.

The contractor hired an engineer to design a repair. His suggestion is to core around the broken and cracked ones, double nut them, and try to back them out with an impact wrench so they can be replaced. Failing that, use a coupler nut to attach a new section of bolt. Then fill the core hole around the bolts with non-shrink grout.

He recommends heat-straightening ("not beyond cherry-red") the bent one and repairing the galvanizing with ZRC.

Speed limit is 55 mph, and AADT is ~100. The rail is NYSDOT standard 3-rail box beam bridge rail.

Does this sound reasonable?

 

[kingnero]

What material are the bolts/allthreads?
I assume these are not bolts, but threaded rods?

the double-nut + impact wrench will likely not work without some help (LocTite, welding).
heat-straightening = probably OK, depending on the material. But I'd insist on replacing.

 

[ACtrafficengr]

Yes, they are really threaded rod. It's a variation on this detail:

https://www.dot.ny.gov/main/busines...ge-details-sheets-repostitory-usc/BD-RS1E.pdf

I should check the spec to see what heat treatment they specify (if any) for the studs. That could eliminate heating the bent one.

 

[DDBPE]

If I understand correctly the threaded rods sticking up vertically where the base plate attaches were hit.
What if you cut off the threaded rod to 1" below the surface and grout over.
Then fabricate a larger base plate with holes in a new location that will allow drilling and epoxy anchoring in new bolts, if the epoxy anchors will not work, core drill all the way through the slab and bolt all the way through with a plate on the underside.

 

[ACtrafficengr]

It's a 3 feet high headwall, not a slab. Through-bolting is not an option.

My only experience with epoxy anchors for bridge rail bolts was years ago when I got to tour the Texas A&M crash test facility. They were testing a proposed epoxy system, and the epoxy held, but the concrete didn't.

I'm unwilling to use a system that has not been successfully crash-tested by someone who knows more about it than I do. Maybe a better system has been developed since, but I haven't heard of one.

 

[DDBPE]

Sorry, didn't catch the head-wall you noted.
If you decide to heat and bend the one, make sure they use heat sticks to determine the lowest temperature to bend the bolt, they melt at specified degrees (normally they are also different colors) to prevent overheating of the bolt (which will weaken it) and surrounding concrete.
Also, do not let them hit it with a hammer when it is hot, it will likely crack the concrete, they would need to use a pipe over the bolt and bend it when it is at temperature. I have heated bolts before, hit it with a hammer, and then cracked the concrete when they are close to the edge, then we had to repair the concrete.
If none of the ideas are suitable, remove and replace usually works.

 

[bridgebuster]

You gave me a idea: core around the damage bolts, cut off the damage portion, then splice on a piece of bolt using a coupler.

 

[SlideRuleEra]

Having worked long ago as a bridge contractor, bridge railing is considered a "specialty" product. Suggest that you obtain whatever new materials that are need from a prequalified supplier. Here is a link to that type of supplier:

http://dihighway.com/products/bridgerail/

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[SlideRuleEra]

For clarity, not only is bridge railing itself a "specialty" product but this includes ALL associated anchor bolts, washers, plates, clips and other miscellaneous items needed for a complete bridge rail installation.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net