High tensile bolts circa mid-1950s 2

[abusementpark]

I'm working on a renovation project of a structural steel building constructed in the mid-1950s.

The plans call for 3/4" diameter "high tensile" bolts. Anybody know how I can figure out the capacity? Does this correspond to A325 properties of present?

 

[abusementpark]

Ok, I've figured out that this was an early term for ASTM A325 bolts.

Is there any reason why I can't use the current capacities for these bolts?

 

[hokie66]

No, but you need to verify that A325 bolts were actually used. You should find three radial lines on the bolt head and maybe the manufacturer's mark, and the nuts should have three short arcs of equal radius. The nuts could also have the number "2" and the manufacturer's mark.

 

[abusementpark]

See attached pic.

 

[dhengr]

Those look like carriage bolts with square nuts, assuming both lines/sets of bolts are all the same. A325's would not have had those light square nuts. Alternatively, the clip angle to the coped beam going to the right might be riveted. Some fab shops used rivets for much of their in-shop attachments and connections in that era. Then bolts were used in the field, as your picture shows.

 

[SlideRuleEra]

I agree with dhengr, the photo appears to show a mix of bolts and rivets. In the 1950's, high strength bolts (A325) were allowed, but were assumed to perform like rivets of the same size. By the mid-1950's evidence was growing that the high strength bolts were better, but the "bolt = rivet" assumption remained in force. Here is a 1954 report addressing that issue:

http://preserve.lehigh.edu/cgi/view...xt=engr-civil-environmental-fritz-lab-reports

For your project, I would suggest performing the calcs as if ALL the fasteners were rivets.

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[hokie66]

Every A325 bolt I have seen had a hex head. If I had to guess, I would say those are A307.

 

[paddingtongreen]

Back then, we did use them A325 bolts interchangeably with rivets but they were only used as friction bolts, like the rivets, they didn't slip where the ordinary bolts had the hole clearances to slide in. They were initially used as a replacement for field rivets, as you see in the picture; the clip angle is riveted to the supported beam.

Those nuts do not look light but I don't remember the use of square nuts. There is a possibility that they were made that way to distinguish them. Unfortunately, you cant rely on that. If the bolt heads can be confirmed as A325 from the other side, you might be able to use the modern bearing capacity since they are not partnered with rivets in the same connection, i.e. clip to supporting beam are all bolts, clip to supported beam are all rivets.

The paint job is in remarkable shape. If it hasn't been repainted, it might be red lead.

Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin

 

[abusementpark]

Thanks for the responses guys. I've attached another photo for good measure.

It looks like 15 ksi is the design shear stress I should use for rivets.

Does anyone how know difficult it is to remove rivets? I may need to rehab or replace some connections.

 

[paddingtongreen]

I don't know the details but they had some efficient mechanical equipment for removing them when I did some modernizing of the Frankfurt El in Philly. They were riveted trusses and some had to be reworked because the architect liked them. I think the equipment sheared the heads off without damaging the steel.

Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin

 

[SlideRuleEra]

Mechanical equipment, that Michael suggested, would be best. The rivet heads can be cut off with an acetylene torch and the remaining rivet driven out with a punch, but that has problems:

1. The steel members could be damaged by the torch.
2. The paint is likely lead based, so fumes from cutting are an issue.

Perhaps adding welds would be another way to repair, without removing rivets, but then the fumes issue comes up again.

Looks like access to the beams is going to be a challenge if you have to do anything to them.

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