That picture shows a 100-year-old fabrication error in some steel framing which, thanks to some facade repairs, is seeing the light of day for the first time since it was built. The rivet holes in the column were punched an inch too far down and, somewhat amazingly, not in a straight line. Since all of the rivets in that connection, the connection plate, and the beam are all in acceptable condition, there’s no work scheduled here. That means, among other things, that I’ll never know if the mistake was caught in the shop and the new holes punched right below the incorrect ones or if the holes were somehow altered in the field. The latter is unlikely, since acetylene torches weren’t ordinary field equipment back then.
The edge distance from the old holes to the new – assuming that there is some and the holes don’t actually overlap – is tiny compared to the steel-code requirement. In any real sense, each pair of an old hole and a new one is effectively one big more-or-less oval hole. And that’s where things get really interesting: the rivets are at the wrong end of that oval. The force in the rivets, transmitted from the beam, is downwards, and the rivet is at the top end of the oval.
To any engineer familiar with steel design, that geometry is no big deal. Modern bolts – “high strength” bolts – are meant to be tightened until there is a great deal of tension in the bolt shaft. This provides a clamping force that prevents the bolted pieces of steel from sliding relative to one another. This is necessary in a lot of connections because the tolerances of fabrication mean that bolt holes have to be a bit oversized. If not for the clamping force, connections would have some play to move, which would be bad for the usefulness and stability of steel-frame structures. There are various scenarios in design for using the clamping force; at the higher levels, you can have a bolt at the top end of a vertically-slotted hole and that’s fine.
The last link in the logic chain: rivets were installed red-hot, with one head and a straight shaft. After they were put in place, the shaft was hammered down to create the second head. As the rivet cooled, it shrank, providing a clamping force. That clamping force was fairly consistent because the amount of shrinkage from red-hot to ambient temperature is consistent, and the rivets could not be cooler than red-hot or it would not be possible to create an acceptable head.
In short: as ugly as this looks, it’s actually okay.
