Swedged Anchor Help

[TS59401]

Does AASHTO or ACI cover the design of Swedged Anchors in Tension? Can swedged Anchors even resist tension? If someone could please point me to some reference material regarding their design I would appreciate it.

Thanks,
Tom

 

[bridgebuster]

In the current LRFD Specs, 7th Edition, Section 14.8.3.1 - Anchorage & Anchor Bolts permits the use of swedged bolts. The commentary says "...uplift should be prevented...". In terms of design, the commentary refers the reader to ACI 318-05 Appendix D.

In the early 80's I worked on some bridges for Mass DPW. They used swedged bolts even in the Boston area, which was considered a high seismic zone. I recall we would upsize the diameter to take into account the reduced section due to the swedging.

Try the link below - they're a bolt manufacturer they might have some insight.

Link

 

[TS59401]

Bridgebuster,

Thanks for the reference, still learning to navigate the LRFD Specs. Good point on the reduced steel area, I will incorporate that into my work.

I am working on a bridge deck demolition plan for a pinned cantilever plate girder system. During the demo sequence, the outside bent will have about 5K uplift when the excavator is on the cantilever section of the bridge.

The (2ea) 1.125" swedged anchors for the rocker connection should handle tension even with the reduced section, but I cannot decide if I trust the pullout strength of the swedged anchor. Would the swedged anchor generate a failure cone like I headed stud, or would it have a pull out type failure mode, or some combination of both?

 

[bridgebuster]

TS59401 - I would err on the side of caution and assume a failure mode similar to an adhesive anchor or post-installed rebar -tensile failure of the bolt or bond failure. I could see the indentations contributing to the formation of a failure cone of sorts. You could argue that the swedge bolt is similar to an undercut or wedge anchor but I couldn't find anything to validate this assumption.

Here's a thought for the uplift in case the numbers don't work out: Could you place a few pieces of temporary concrete barrier as ballast? 10' foot sections are about 400 LB/FT.

 

[TS59401]

Bridgebuster,

Excellent idea on the barriers. My girder spacing is 8.3' so a 10' section would fit nicely. Ran through the bond strength equations and came up OK, but pretty close. I used the cracked lower bound bond stress of 200psi (I believe that to pretty conservative I think). We are going to have the cranes sitting there anyway and I think the barriers are the best option.

Thanks again for taking the time to lend me your advice.

 

[bridgebuster]

You're very welcome. Good luck with the project.