Greetings Vern,

Publication of the Iron & Steel Preservation newsletter was delayed due to the time required for editing a website and getting it online. Editing with WordPress and working with a website host proved to be challenging. WordPress was quite an educational experience, a steep learning curve that eventually tapered off to where the website has become manageable and online. There is still more to learn and features to add to the website. Its content will eventually lead to a book on craftsmen and women and their fabrication work experience.

I encourage ISP readers to visit the website, and I welcome any suggestions or ideas (links to recent articles are at the end of this newsletter). I did remove the comment form after receiving numerous emails from Russians with no obvious interest in Iron & Steel Preservation; one can respond by replying to this newsletter or by using my gmail email.


Vern Mesler 2024

A Shop Day in the 1980s

It’s early morning, I’ve backed my car into a parking space near the shop lunchroom entrance. On a quick walk through the lunchroom I find some workers, early risers, sitting at the end of a table playing cribbage. A battered blue metal door leads to the shop, with its dirt floor. To the left of the door is a large metal electrical panel. Opening the gray panel door reveals four large black switches. When flipped, they make a hard metallic sound, and four huge overhead lights flicker and slowly light the heavy structural shop. Large steel weldments set on steel bunks are motionless, still, and the shop is quiet. Soon the piercing sound of a five-minute warning horn alerts crews to assemble at their assigned departments in the shop. Working steel, I have known that experience as a shop foreman, and in teaching men and women the use of industrial tools for steel fabrication, and in restoring historic bridges.

Shop fabricators rarely find a voice in libraries filled with books on the narrative of famous metal structures, and in particular riveted historic bridges. I have walked across Michigan’s magnificent riveted Mackinac Bridge, San Francisco’s riveted Golden Gate Bridge and many other USA riveted truss bridges. Also many riveted bridges in Europe and the United Kingdom, and they are as impressive as often described in engineering literature. Occasionally, rarely, there is a glimpse into the fabrication shop. In my library of industrial books, I have a well-worn 1933 ASCE book with a detailed description of the George Washington Bridge I purchased years ago, and one passage led me to use this book to write about shop and field riveting on the GWB, a history that can be applied to many of the famous nineteen century bridges.

No difficulty was experienced in the field in erecting and fitting the steelwork because the shop procedure was so carefully planned and executed. [“George Washington Bridge: Construction of the Steel Superstructure.” Transactions of the American Society of Civil Engineers, volume 97, 1933. p. 260]

These engineers recognized the industrial craftsmanship in this testimonial of the shop craftsmen’s abilities to use their industrial skills to fabricate massive, riveted sections with contemporary industrial tools and to anticipate and solve fabrication disruptions when encountered.

Othmar H. Ammann, Bridge Engineer

I learned of the George Washington Bridge through my collection of bridge books and my library of photographs. The Design Engineer for the GWB, which opened in 1933, was Othmar H. Ammann. He went on to design five more of New York City’s famous riveted bridges. Ammann’s last riveted bridge was the Verrazzano Narrows Bridge, which opened in 1964. One might wonder why such a magnificent steel bridge as the Verrazzano Narrows would be designed and fabricated as a riveted structure at a time when welding and bolting in the steel fabrication of buildings and bridges was well-established. A few biographical fragments from some exceptionally well-written books describing Ammann’s bridges may provide a clue.

At university he found he was exceptionally gifted in mathematics and chose to study engineering but pursued no particular specialty. He became confirmed in his career of bridge engineering during a summer spent working in a bridge fabrication plant. [Reier, Sharon. The Bridges of New York. New York: Quadrant Press, 1977. p. 97 in Dover reprint, 2000]

 The Pennsylvania Steel Company quickly took notice of this intense, soft-spoken spoken foreigner who chose to spend his lunch hours walking through the workshops observing the company’s manufacturing and assembly techniques. [Rastorfer, Darl. Six Bridges, The Legacy of Othmar H. Ammann. New Haven: Yale University Press, 2000. p. 4]

Ammann would have observed the operation of large shop pneumatic riveters, the assembly of riveted sections for buildings and bridges, and the value of shop-driven rivets. There seems to be nothing written on what Ammann observed on the fabrication shop floor or what communication he had with the shop fabricators that led him to use riveting in his design of all six bridges, 1933 to 1964. However, it seems likely that Ammann’s interest in shop operations and knowledge of fabrication processes would have influenced his work. 

Distinction between Field and Shop Riveting

(beware: inaccuracies in the written record)

A hot metal rivet is pulled from a bed of burning coals, thrown in a high arc, and caught in a conical metal catcher-can. It rattles against the can, hot mill scale popping off the rivet. Then the rivet is grasped with a set of tongs and inserted into a hole in the connection plates. A bucking bar or pneumatic holder-on slams against the manufactured button head of the rivet, holding it in place as the pneumatic field rivet hammer repeatedly strikes the protruding rivet shank, forming it into a convex shaped head.

I often refer to this description as “Hollywood riveting.” While this is the most popular portrayal of the hot rivet process in the media, it is misleading, leading many to believe that all the millions of rivets required in the fabrication of famous riveted bridges were driven in this way. In fact, the field riveting process used to connect the larger shop-riveted sections together at the erection site represents only a modest percentage of the driven rivets in a riveted bridge.

Even the “official” records contain inaccuracies that contribute to the lack of distinction between field riveting and shop riveting. For example, engineering reports written at the time of construction of the Golden Gate Bridge and the George Washington Bridge correctly state their towers as having 500,000 to 600,000 field-driven rivets. Over the years, the word “field” has been dropped from written documents, and now the historic record (including information on official websites) refers to each tower as having 500,000 to 600,000 rivets, as if this were the total number of rivets. If that were the case, these riveted towers would probably fall down. Most of the rivets in the towers are shop-driven rivets. 

(The Golden Gate Bridge: Report of the Chief Engineer to the Board of Directors of the Golden Gate Bridge and Highway District - California, September 1937. pp. 148-9)

(George Washington Bridge: Construction of Superstructure. Transactions of the American Society of Civil Engineers, volume 97, 1933. p. 260)

Shop Riveting in Bridge Fabrication 

When a rivet is driven with a pneumatic shop-riveter, the shank of the rivet is upset and completely fills the hole. Due to the machine riveter’s high mechanical compression, rivets of large diameter and shank length can be driven at higher pressure (psi) values than with a field rivet hammer.

A machine driven rivet is so upset under the great pressure of the force applied through the riveter that it is squeezed into and thoroughly fills and conforms to all the irregularities of the rivet holes. Home Study (Volume 1, February 1896 - January 1897). Scranton, PA: The Colliery Engineer Company 1897.

In a 1933 ASCE paper, Mr. Herbert J. Baker (Engineer of Inspection, The Port of New York Authority) reports on workmanship and fabrication of the work required in preparation of materials for shop riveting. While Mr. Baker gives a detailed description of the preparation work for shop riveting, it is his reference to driving rivets with a field rivet hammer (“pneumatic percussion hammer”) and its limitations that is best explained:

Rivets were driven by approved pressure tools wherever practicable. The speed and pressure of such tools were regulated to secure the best results in the work. Rivets were driven with pneumatic percussion hammers only when unavoidable and in such cases a pneumatic “bucker-up” was also used wherever possible. [“George Washington Bridge: Materials and Fabrication of Steel Structure.” Transactions of the American Society of Civil Engineers, volume 97, 1933. p. 341]

Knowledge Base Disappears

When the riveting process was replaced with welding and bolting in steel fabrication, the large pneumatic riveting machinery and shop knowledge of the riveting process disappeared. Engineers with experience in designing riveted structures no longer needed that expertise for new construction. Knowledge and experience with the riveting process declined; there was no transmission of their knowledge through education to a younger generation of engineers.

Yet there exists an enormous number of riveted structures still in service in the United States and a vital component of the working infrastructure. The maintenance and preservation of this vast network of riveted structures could be imperiled by the lack of knowledge within the engineering community of the shop and field riveting processes. It is crucial to enhance their knowledge and skills in this area to ensure the continued maintenance and preservation of these vital structures.

HistoricBridgeRestoration Website

Field Rivet Demonstration at Lansing Community College West Campus

Pittsburgh, Pennsylvania

December 23, 2023

Heinz History Center

Moose Brook Bridge Reconstruction

Fabrication and Riveting

Historic Bridge Postcard Collection

Destination Michigan

Click on the image to view a video about the Calhoun County Historic Bridge Park, produced by Central Michigan University for Destination Michigan, a program aired through PBS.

ISP Chronicle Archive

December 2023, ISP Chronicle

May 2023, ISP Chronicle

February 2023, ISP Chronicle

October 2022, ISP Chronicle

Iron & Steel Preservation Program Fund

Lansing Community College Foundation

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Iron and Steel Preservation Program Fund

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