Wrought Iron Material Properties 2

Cast iron really had no clearly defined yield point. Link

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.

Have you tried SlideRuleEra's site? He has a Phoenix Handbook from 1888, which contains information on wrought iron design.


Do you have a photo of the truss that you can post? I saw one around Danbury CT about 25 years ago. There was also a bridge here in NYC crossing the Harlem River that used Phoenix columns on the approach spans. Alas, it was demolished and replaced a few years ago.

Thanks for the article KootK. I am pretty much finding the same thing. Even the AASHTO Manual for Condition Evaluation of Bridges gives only the allowable stress for tension and bending of wrought iron.

For this rehab, I am using high strength bolts at some of the connections and I want to check the bolt bearing on the existing wrought iron members. I was just going to use the allowable stress given for wrought iron, but doing so gives me an unreasonable amount of bolts. I'm just wondering now, if I would be able to back into something reasonable?

I can see your dilemma. I imagine that bolt bearing strength would more closely resemble the 80 ksi. But, then, it's scary to make assumptions in a brittle material governed by fracture mechanics. I found this for rivets: Link. It's encouraging with respect to potential capacity but it would be nice if we could dig up something more official and, perhaps, local. And bolt specific.

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.

Thanks for the Link Bridgebuster! I didn't think to look at SlideRule's site. This actually helps me out a lot. This one in Pennsylvania and is approximately 131' long c/c brgs.

Here is a few pictures:

Pitt- nice photos; thanks. I assume from your handle you're on the western side of the state. I'm in the Poconos. This weekend I'll scan the photos I took years ago.

Look online at the New York City Building Code 1901 edition. It has ultimate tensile strength values for wrought iron and steel that apply to buildings of that era.

@ KootK:

KootK said:

it's scary to make assumptions in a brittle material governed by fracture mechanics

Click to expand...

I could not agree more, especially when coupling that with a non-redundant structure.

KootK said:

I imagine that bolt bearing strength would more closely resemble the 80 ksi.

Click to expand...

How did you arrive at this value? The reason ask, is because I was thinking more like in the 20 ksi range. Unless you mean the shear strength of the bolt itself?

KootK said:

It's encouraging with respect to potential capacity but it would be nice if we could dig up something more official and, perhaps, local. And bolt specific.

Click to expand...

I actually did find some equations for rivet bearing on wrought iron in the Phoenix Handbook from SlideRule's site, which I am going to use. Whether its a bolt or rivet, should not matter. The equations call for 12 to 15 ksi for allowable bearing. They are a bit lower than what I had hoped, but at least I now have some valid/official equations and allowables I can lean on.

@ Bridgebuster: I am from the Harrisburg Area, I went to Pitt for school. This bridge is actually the only access point for a development on the one side of the creek (there is one other access point at the other end of the development) and the creek wraps around about 3/4 of the community. So it kind of creates a private little peninsula for them...its pretty neat.

Thanks for your help guys!

PittEng88 said:

Whether its a bolt or rivet, should not matter.

Click to expand...

Make sure you double check that assumption. I do remember from my undergrad steel course that forming the head of the rivet expands the shank to completely fill the rivet hole. I know that the stress distribution from the bolt will be different from the rivet; I just don't know if that will be trivial.

try
Variability of the Mechanical Properties of Wrought Iron from Historic American Truss Bridges
or
or
Structure Magazine had a antique structural series ~2009

Here's some historical info from J.A.L. Waddell from his book Bridge Engineering (Volume 1, 1916). I came across it while I was looking for information on how our ancestors designed reinforced concrete bridge piers.

@RobertHale: I understand what you are saying and I appreciate the heads ups. It makes sense when you think about it, a rivet would have a little bit better stress distribution into the member as opposed to a bolt placed loosely in the hole. However, according to my steel book, the analysis of rivets verses bolts is essentially the same, only the material properties would be different. For both rivets and bolts, the bearing stress is computed as an average over the contact area with the contact area being the fastener diameter times the thickness of the member. So I would assume that this variation in stress distribution can be considered trivial.

@boo1: Thanks for the articles, they were all very interesting reads.

@Bridgebuster: The allowables in this blurb actually match up very nicely with what I was seeing in the Phoenix Handbook, but it gives a better description as to how one would arrive at this numbers. So, thank you.