bridge rivetsbolts for historic structure

huangyhg

bridge rivets/bolts for historic structure
i have a historic bridge where rivets that are to be replaced.  new bolt heads are required to have the appearance of the existing rivets(on both ends of the bolt). historic commission has input. i've been looking for tc bolts that would look like this. anyone have any experience with this kind of bolt?  does it exist? i called lejeune - no luck!
thanks.

i don't think you can get a bolt that looks like that on both ends.  well, you certainly can't get a *bolt* that looks like that on both ends, since the nature of a bolt is to have a shaft that goes through the hole and it can't do that with a thingy on both ends, to state the obvious.  the best you can hope for is some kind of cap nut (probably not the right term but you know what i mean), and they don't make those for structural applications.
i don't see how it could exist.  if your bolt head is just a button, then in order to tension the bolt you would need to twist it from the end of the bolt shaft, and that means a hex nut and a grippable spline on the end of the bolt shaft, going all the way through the nut.  the closest you could come to capping the ends of the bolt would be making sure the shaft extends several threads beyond the nut, and then putting on some kind of cosmetic cap but (a) i don't know that you could get those on tight enough to be sure they wouldn't fall off, possibly creating a hazard to those below, not to mention a maintenance issue because you'd (presumably) leave unpainted steel where they came off (b) it still wouldn't look like a rivet, just a rounded cap on top of a hex nut.  unless someone sells some kind of cosmetic cap big enough to go all the way over the hex nut, but that would be really big and still not look like a rivet, and i'd still have my doubts about permanent attachment.
the historical society is going to have to compromise, or else find a modern-day riveting crew.  (i hear mass highway uses them sometimes.)  but good luck finding the aashto specs on design of riveted connections.
hg
i guess you could make a bolt with a conventional external thread and add a stem onto a nut with an internal thread and have allen key sockets in both of them, with a plastic cover to add on after installation.
you could use a conventional (hex) bolt head and nut with a plastic hemi-spherical cover.
this has been asked before ...
try a square head bolt, square head nut first: they will look "antique" and almost hand-made - even if not exactly a true replicant of the rivets.  stronger, available, able to be reliably torques and so make a more reliable joint.
alternate: "i guess you could make a bolt with a conventional external thread and add a stem onto a nut with an internal thread and have allen key sockets in both of them, with a plastic cover to add on after installation."
try that, but make the "bolt" round-headed.  only two sides of the "round" bolt head are ground parallel across their midpoints.  thus a wrench can grip the two "almost flat" parallel sides, but the majority of the head looks round: the top is rounded and the other two ends of the bolt are round.
for the nut:  it will need a two-sided "round" head like the bolt, and an internally threaded shaft that goes into the old rivet hole.  thus, you can tighten the bolt into the internally threaded part of the shaft, but have no exposed thread poking out of the end of the "round-headed nut".

thanks for the input so far...
i'm thinking the nut would look like the button end of a rivet, except it would have a hole in it for the bolt to thread - these would be tc twist-off type bolts, so the bolt end would shear off with the use of a shear wrench, perhaps leaving a flat face aligning with button bolt end/hole.  
round head huck-bolts might look okay:
1.  we've been through this before:  
i did see that post. looks like the thread is closed - is there a way to contact the original poster? i would be interested to ask tobyt how he resolved his issue.
op of this thread:
"i have a historic bridge where rivets that are to be replaced.  new bolt heads are required to have the appearance of the existing rivets(on both ends of the bolt). historic commission has input. i've been looking for tc bolts that would look like this. anyone have any experience with this kind of bolt?  does it exist?"
2006 thread:
"i have an historic bridge where select rivets are to be replaced with high strength bolts.  new bolt heads are required to have the appearance of the existing rivets (on both ends of the bolt).  anyone have any experience with this kind of bolt?  does it exist?"
eerie.
hg
  
looks like you and tobyt are working to the same spec, and i think someone needs to have a bit of a word with the specifier to bring them in line with reality so that one doesn't have to go through this over and over again.
tobyt's profile shows that they haven't posted anything in a few years but still log in.  maybe they're reading this?
hg
huckbolts are not threaded.  the grooves are annular, and the 'nut' is swaged onto them while the 'pintail' is being pulled.  the 'nut', called a 'collar', is cylindrical, with a shoulder.  when the collar is fully swaged, pulling continues until the pintail fractures.   
you might be able to talk huck into making a barrel of custom collars and a custom swaging die to form them into a more nearly rivet-like shape.
i agree, though, that you can't responsibly use a fully 'faux' solution; it still needs to be engineered to be as strong as a rivet, and to provide equivalent clamp load.  i assume there's nothing in the budget for actually engineering the faux rivets, which leaves just the one choice; actual rivets.
mike halloran
pembroke pines, fl, usa