an oversized hole in bearing connection.

[malikasal]

hey guys,

assume that in a shear connection designed as bearing type, an over sized holes were used for the holes instead of standard(24mm hole was used for m20 bolt).
the structure is already painted so no slip critical connection could be assumed, and the bolts are already bought so they cannot replace it with m22 bolts.

can you suggest a solution for this problem? .



ôIf you don't build your dream someone will hire you to help build theirs.ö

Tony A. Gaskins Jr.

 

[XR250]

How many bolts are you talking about?

 

[malikasal]

about 4000 bolts !



ôIf you don't build your dream someone will hire you to help build theirs.ö

Tony A. Gaskins Jr.

 

[TehMightyEngineer]

Welded plate washers with normal hole sizes? Use oversized bolts? Are both sets of holes oversized or is it only in one part?

4,000 bolts... And I thought my day was going bad.

Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries

http://www.americanconcrete.com

 

[malikasal]

both parts have over sized holes, a welded plate washer was my first suggestion, but the contractor refused it.





ôIf you don't build your dream someone will hire you to help build theirs.ö

Tony A. Gaskins Jr.

 

[CANPRO]

Who drilled the holes too big? How do they propose to fix the problem? For connections with just gravity loads and no load-reversal, can you justify leaving it as is?

The quick and easy answers are mentioned above - replace the bolts or add welded washers. Replacing the bolts likely being the easiest/cheapest. If the contractor didn't like those options I would tell him to propose his own solution.

 

[structSU10]

All you can do is present reasonable solutions that still meet the code requirements. Truly, If the contractor rejects your repair solutions they always have the option of buying all new steel and starting from scratch. Either way this is going to hurt.

They might be able to prep the faying surface for the bolts to make it slip critical, but they also might need more bolts to get the connection to work due to the reduced capacity. They could also drill new standard holes in the beam at an acceptable offset, and have an extended connection be designed.

 

[XR250]

I wonder why the bolts cannot be returned unless they are something special? Buying new ones is likely the cheapest solution.

 

[malikasal]

it was the fabricator mistake, and the issue that it is already erected and the bolts are tightened thats why they cannot replace the bolts.



ôIf you don't build your dream someone will hire you to help build theirs.ö

Tony A. Gaskins Jr.

 

[CANPRO]

well, they can replace the bolts, they just really don't want to. Lesson learned for them, don't drill 4000 holes the wrong size. I'd be curious to see what was on the shop drawings. How do you repeat the same mistake 4000 times, was there no QC in their shop?

 

[malikasal]

they are telling me about their CNC plasma machine limitation when cutting high thicknesses, i am not an expert in fabrication but it seems that the more the thickness of the plate the harder it is to cut a straight cut so they increased the radius to achieve the minimum of 22mm (Smart decision !!).



ôIf you don't build your dream someone will hire you to help build theirs.ö

Tony A. Gaskins Jr.

 

[bootlegend]

malikasal,

They are likely telling you the truth about the small radius in the thick plate, but they should have made you aware of the issue and not simply increase the hole size. Sounds to me like they need to pay someone to switch out the bolts.

 

[bigmig]

Pull the bolts off sequentially (don't remove them all at the same time), prep the surface, come back in and do a slip critical bolt with special inspection.

 

[Lomarandil]

Maybe I'm missing something, but how can the faying surfaces be prepped without totally disassembling each connection?

Sounds like sequentially replacing bolts (provide some number that can be removed from each connection at a time) is the way to go here.

Unless you can justify somehow that the slop is acceptable (no pin bearing issues, no load reversal, some allowance that not all bolts may bear at the same time)

 

[hokie66]

If the coating is inorganic zinc, slip critical conditions may be met. If not, replacing the bolts one by one is required. Depending on the required capacities, it may be possible to replace only most of the bolts, but that would create an inspection nightmare.

 

[Sawbux]

Would it be possible to weld the connections and touch up paint?

 

[nutte]

I'm not sure what the governing specification is. The AISC specification does not allow bolts in the bearing condition in holes that are more than 1/16" larger than the bolt. If the holes are bigger than this, the connection has to be slip critical.

So replace them with bigger bolts, after checking the rest of the connection to see if it still works. (Shear rupture through the connection material is lessened with larger holes, for example.) Or weld the connection material to the beams (with the usual caveats about ensuring that connection works).

 

[KootK]

In my area, the cost of the extra inspection on the bolts as slip critical would far outway the cost of just swapping them out.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.