Analysis of Riveted Structure

[BadgerPE]

I have a RFP for a project that involves built-up, riveted structural roof members. The idea (good or bad) is to add rooftop equipment to this portion of the roof. I have no idea where to start with budgeting for this type of analysis. No drawings/specs exist for the existing structure so intense field verification will be required. It is a square, symmetric building so I have that going for me. Can anyone share their thoughts on how to budget my time for a riveted structure like this? I will also take any advice on papers, books, etc. that will help me with the actual analysis of the structure.

 

[Ingenuity]

This Link document entitled "Rivets In Bridge Construction" from SlideRuleEra's website may be of assistance for analysis etc.

Click on the title about 2/3rds down the page that takes you to a ZIP file download.

 

[KootK]

As for the design, this relatively current document actually still covers rivets: Guide to Design Criteria for Bolted and Riveted

The fee question is a little trickier. With saliva covered thumb in the air...

1) 16 hrs extra for two all day site visits.
2) 12 hrs extra for learning about rivets and developing some tools where needed.
3) $3500 for some materials testing by a sub (or acknowledge as an extra to the contract).
4) 20% contingency on everything related to the riveted members to give you some wiggle room.

I like these kinds of projects as T&E not to exceed. That's not always palatable to the client of course.



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.

 

[Ingenuity]

this relatively current document

About 114 years more current that my reference

 

[SlideRuleEra]

Depending on the age of the structure, AISC specified allowable rivet stress for tension, shear, and bearing. This page gives the allowable values from the 1928 through 1989 AISC manuals. Note that AISC Design Guide 15, where these values are summarized, has an error for the shear value during the World War II time frame (1942 - 1946). A proposed correction to that design guide is pending.

Historical Allowable Stresses For Rivets

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[KootK]

For what it's worth, I think that rivets are the cat's meow of structural connections. Were it not for the economic disadvantages, I'd be game for going back. It also seems to me that, if you decide to do welded reinforcement, you shouldn't have to worry about load sharing as you would with bolts.

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.

 

[JAE]

Any idea on how old the structure is?

I did an upgrade to an old industrial building once with crane rails going from 5 ton bridges to 20 ton...some with rivets.

I learned two things:
1. A bad rivet can be "found" by hitting the head of the rivet with a ball peen hammer - if it rings its good - if it thuds, you've got a bad rivet.
2. Watch out for old steel with paint on it if you need to weld. We had a couple of welders get a bit sick from fumes off the lead based paint.



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[JStephen]

Seems like I heard back in college days that the tendency in olden days was to treat trusses as being pinned at every connection, even if the members were actually continuous. So you have the issue of rivet strength, but also perhaps an analysis itself that differed. Assumptions of unbraced length, and allowable stress based on that length, could vary as well.

I recall hearing the advice from a former welding superintendent that riveted materials were not necessarily weldable- some of the stuff would pop and all when you started welding on it, less chemical control than in later years. (He was referring specifically to plate materials.) The Titanic with high-sulfur plate comes to mind.

 

[dik]

Regarding rivets, I did a repair job to a bridge in Winnipeg, and it was possible to jack the entire span by putting a jack under one of the roadway purlins spanning between the main truss girders... Getting into it, I was surprised at how strong rivets really were...

On a recent project that was to repair a bridge crane using rivetted construction, coupons taken of the original material showed a high sulphur content... and the material was 'hot short' and welding was out of the question.

Dik

 

[BadgerPE]

Thanks for all the good advice! The structure is approximately 100 years old, but we have decided to not pursue the project if it includes analyzing the riveted portion of the project. This is only because they want a fixed fee and not T&E, otherwise we would be interested.

 

[Lomarandil]

That's too bad.. I'm with KootK, a big fan of rivets (which is good.. they're everywhere in my world).

I can also vouch for the difficulty of welding material from that era -- all of our retrofits replace rivets with HS bolts. Lead paint is definitely a big hazard, we often have craft in full suits for the actual work, and everyone observing using respirators.

KootK, where welding is possible metalurgically, I'd back the idea of load sharing. If J1.9 allows sharing between rivets and SC bolts, I think rivets and welds would work similarly.

And just to round out being too late to the party -- Jstephen is right, analysis methods of the time don't always line up with our methods and codes today. Usually it's conservative, but especially on the local level there are sometimes conundrums. Sometimes you just have to use the "it's worked for 80 years" argument to pass the AHJ's review.

 

[OldBldgGuy]

Another one too late to the party but I throw my hat in the "rivets are great" ring. Just watch someone burning the heads off a few for demolition & you'll see that the shaft expanded to fill the holes when they were rivetted and the friction of that alone will keep many connections intact and working, to the frustration of the demo guys. It also means that the cross-sectional area could be more than you think it is for shear.

 

[daranguiz]

I had the chance to work in a 1888 steel riveted project in France (I let you guess which one). We took some bars with rivets and we tested them in order to have an idea of the shear resistance (with very different results for each one!)