Thursday, July 05, 2007

Backstory on the I-Beam

One of the projects I've been working on is a comparison of an old engineering drawing of a bridge with a modern drawing. Specifically, the old drawing will come from Errard or Besson and the “new” drawing is a modern technical drawing from 1903. Notably, the new drawing is still over a century old.

For those who really want to see the images, the new drawing is available at:

The old drawing is a bit more elusive and doesn't seem to be on line already. It seems that I'm going to have to scan it. Regardless, my intention is to compare the drawings and illustrate all of the various things that had to be stabilized so that the drawings actually could be useful. Some of the institutional factors are straight forward: mechanical drawing, measurement, strength of materials, etc. Some of the issues are considerably less evident, for example, structural steel shapes.

Although I realize on reflection that the “new image” really doesn't include I-beams. Regardless...

The history of the I-beam is relatively short. The Greeks occasionally built with an I shape in building materials—and even experimented with composite materials using iron. The real development didn't happen until after 1800. The interesting thing is that this development was largely practical rather than theoretical. Jewett (1967) notes: “My research indicates that empirical methods developed the shape and that the theory was written independently.” (p. 346)

A number of issues had to be overcome before the I-beam became practical. Jewett provides the basics. Rolling-mills had to develop to the extent that they could support intensive rolling practices and wrought iron had to become available in significant quantities (post 1780). The shape emerged to meet the needs of three different industries: rail, ship building, and construction. The first “I” shaped rail, for example, was patented in 1789 and mills began to mass produce wrought iron rails in the 1820s. The American T-rail emerged in 1830. Light rails were used as fire-proof floor beams beginning in the early 1850s.

Ship building quickly began to incorporate I-shaped steel members. The first all-iron vessel, for example, was built in Scotland in the year 1818. It used simple rolled shapes such as angles. In certain locations, angles were riveted back-to-back to create a “z” shape. The first rolled angles emerged in France in the period from 1800-1819 and the first rolled “T” was created between 1828 and 1830. More advanced rolled shapes emerged to meet demand: first a rolled z-bar, then a channel, and then a bulb angle. The limiting factor for the ongoing development of these structural members was the relative sophistication of the rolling process. It was still more of an art than a trade or a science and advanced practitioners were hard to find.

Theory started to catch up to these shapes with the experiments of William Fairbairn who developed a means of calculating the theoretical strength of advanced shapes. His work continued the earlier (1827) research of Eaton Hodgkinson who had determined the appropriate proportions of cast-iron members Fairbairn tested a variety of wrought shapes including angles and channels. The strongest design appeared to be a shape built from channels riveted back-to-back to form an “I”. His findings were published in 1850 in the Philosophical Transactions of the Royal Society.

The primary applications of the I shape was for the construction of ships and boilers. The first architectural application was in the construction of fire-proof textile mills. This development owed little to theoretical work. Traditionally, a screw-back was added to the bottom of wooden beams to support a brick arch forming the ceiling vault. As architects began to use iron in beam design, they included an analog of the screw-back in the form of a bottom flange. Structural members that included the bottom flange have the shape of an I-beam. It was really in the 1850s that the I shape began to replace tube shapes in the construction of both large structures such as bridges and for applications such as columns.

While Jewett provides the narrative for this story, it is Peterson (1980) who provides the characters. His version begins much earlier when he notes that the first iron beam of any sort is still buried in the ground in front of a brick furnace at Coalbrookdale on the Severn in Shropshire. It bears the date of 1638. It then zooms forward to 1792 when Charles Bage built a fire-proof flax mill with cast iron beams. Peterson then quickly falls into line with Jewett's account. He notes that the immediate American antecedent of the I-beam was the bulb-tee that was first produced in 1848. He traces the first true I-beam to Trenton New Jersey where it was rolled in Trenton New Jersey. I-beams were used a bit earlier in England. Isambard Kingdom Brunel's “Great Britain,” for example, used riveted I-beam composites to support the deck in 1842, a time when there was great debate about the differences between cast and wrought iron and the benefits of each. Many of these issues were addressed with the experiments of Fairbairns and Hodgkinson.

The first great English proponent of the I-beam was Richard Turner. He rolled and fabricated bulb-tees and I-beams for applications in large span structures such railroad sheds and green houses. His greatest commission was probably the Palm House at Kew Garden. His design called for I-beams but the actual execution process is still unclear. As Peterson notes: “Although Burton' beautifully drawn and tinted plans for the structure as first conceived in cast iron have been carefully preserved in the Public Record Office, the drawings as actually built seem to have been lost.” (Peterson, 1980, p.10)

Other factors led to the use of iron for construction on the continent. The Paris carpenter's strike of 1845 created an immediate market for metal joists. Peterson notes that the first metal beams were installed in a house in 1849. The I-beams were designed by Ch. Ferdinand Zores.

The first real American I-beam was created by Cooper and Hewitt at the Trenton Iron Works. They rolled a 7” high I-shaped rail in 1847. It was perhaps the first section that specifically had application to construction. Peterson (1993) notes that Cooper and Hewitt struggled until William Borrow arrived from Ireland in 1851. This master mechanic was able to construct the milling equipment they required. Cooper and Hewitt weren't the only producers of iron building components. They quickly met with competition from John Griffin and and the Phoenix Company.

Earlier shapes used as rails also were used in building. In the 1830s, for example, Robert Stevens invented the iron “pear rail.” This same section was later used in 1855 renovation of Nassau Hall, Princeton College. By 1856, the use of the I-beam had become institutionalized. Drawings of the Custom Houses at Georgetown D.C. And Alexandria VA, for example, show the use of fully formed I-beams.

The story of the I-beam doesn't end in 1856. The era of iron was ending and the reign of steel was about to begin (Misa, 1992). In 1857 Henry Bessemer finally stabilized his process for making steel. Prior to the Bessemer process, the creation of steel was so expensive that it could only be used for very specific applications such as the production of blades. Bessemer's creation promised to revolutionize industry. But first he had a patent issue. In America, another inventor by the name of William Kelly had already patented some of the components of Bessemer's process. Eventually, various operating groups pooled patents so that progress could be made. The Bessemer Association effectively locked up the American steel trade and collaborated with the rail companies to manage production and supply.

Steel did not emerge as the natural victor over iron. It was a contested process that largely hinged on the definitions of iron and steel. Three different tests were adopted by different parties: mechanical, physical, and chemical. Misa notes that “New and larger markets probably required some standard to guarantee at a distance, but the specific form of the standard owned much to the railroads.” (p. 126) This conflict led to a debate about what, exactly, steel is. Should the classification be based on the physical properties of the material (compressive and tensile strength), the carbon content (chemical), or the “fused” nature of the metal? The newly formed American Institute of Mining Engineers emerged as the main venue for the debate. The depression following the panic of 1873 pushed down prices of steel and the differentiation between iron and steel further diminished. Andrew Carnegie acted on this downturn by consolidating the market and breaking the market stranglehold of the Bessemer Association.

An unlikely source finally settled the dispute. In 1878 the machine tool industry advocated for higher tariffs on imported iron created using the Siemens-Martin method. According to existing laws it was considered iron. As steel, it could be more heavily tariffed.

The 1880s saw an economic rebound and cheap steel flooded the market. Part of this flood was steel building components, notably I-beams. This story doesn't even end here. It continues with the founding of the American Institute of Steel Construction. But this is where I have to leave it.


Dorn, H. (1968). A note on the "structural antecedents of the I-beam". Technology and Culture. 9(3): 415-418.

Jewett, R.A. (1967). Structural antecedents of the I-beam, 1800-1850. Technology and Culture, 8(3): 346-362.

Jewett, R.A. (1968). The response. Technology and Culture. 9(3): 419-426.

Jewett, R.A. (1969). Solving the puzzle of the first American structural i-beam. Technology and Culture. 10(3): 371-391,

Misa, T. J. (1992). Controversy and Closure in Technological Change: Constructing "Steel". In W. E. Bijker & J. Law (Eds.), Shaping Technology/Building Society: Studies in Sociotechnical Change (pp. 109–139). Cambridge, Massachusetts: The MIT Press.

Peterson, C.E. (1980). Inventing the i-beam: Richard Turner, Cooper & Hewitt and others. Bulletin for the Association for Preservation Technology. 12(4): 3-28.

Peterson, C.E. (1993). Inventing the I-beam, Part II: William Borrow at Trenton and John Griffen of Phoenixville. APT Bulletin. 25(3/4): 17-25.


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