History of Structural Steel

The application of structural steel in construction works began only in late 1800s. According to Murphy (1957), around 4000 B.C., iron was primarily used material to produce small tools. During an Iron age, wrought iron was the most used form of material. Wrought iron is produced from an iron ore using a process called Smelting. During this process, the iron ore or iron-stone is heated in a charcoal fire. The molten metal from the process contains waste materials, such as charcoal mix and some unwanted material from iron ore (Slag). Slags are then removed adding the flux, a material such as limestones, silica, rosins, etc., to the molten mass. The purified molten iron is then hammered into desired shapes and tools, thus producing wrought iron (with carbon content of less than 0.08 %wt.). Wrought iron were historically used in making railings, gates, canopies and in some structures as a tension member (I, H and other beams).

 

Cast iron is another alloy of iron which is said to be discovered in China during 5th century. When the iron ore is melted at very high temperature, it absorbs carbon, thus, lowering the melting point of the iron. The hardened produce in a mould is called cast iron and is high in carbon content (usually 2 to 4 %). Sometimes, the molten iron is laid out in sand troughs from blast furnace. The moulds looked similar to a sucking pigs. Thus the cast iron molded in this way were called pig irons. The pig irons are also remelted to produce various cast iron tools.

 

Due to the lower percentage carbon content in wrought iron, its malleability is high, meaning it can be reheated and hammered into different shapes. On the other hand, the higher carbon content in cast iron makes it more brittle and less malleable compared to wrought iron. Thus, the tensile strength of cast iron is low.

 

These irons were used in construction for structural purpose only after late 1770s. They were mainly used in various types of bridges. Some of the examples of cast iron bridges are the Iron Bridge by Abraham Darby III, Water Street Bridge at Manchester terminal of Liverpool and Manchester Railway. However, several structural failures occurred due to poor design, excessive loading and lower tensile strength of cast irons. In 1879, after Tay Rail Bridge disaster use of cast iron as structural material was in doubt. The replacements were sought with different material and Steel was deemed necessary.

 

Steel is also an alloy of iron and carbon, but it has a carbon content of 0.2 to 1.5% which makes it harder than wrought iron but not as brittle as cast iron. The steel was malleable, less brittle, and higher in tensile strength lying just between the physical properties of wrought and cast iron. Thus, it was found to be a better structural material. However, the manufacturing of steel was only possible in small scale, not enough for structural purposes until 1850s. Sir Henry Bessemir, also known as the father of steel industry, invented Bessemer Converter in 1855. The Bessemer process was able to reduce carbon content in molten pig iron and remove impurities. In 1879, a method to remove phosphorous from the steel was also invented by Sidney Thomas which increased the quality of the material. After these inventions, it was possible to produce steel in a cheaper cost and higher quantities. The steel then began to displace the use of wrought iron and cast iron for construction purposes. Steels were primarily used in railroad structures in the beginning.

 

In 1875, the first structural steel bridge for railroad, the Eads Bridge located in St. Louis, Missouri, was constructed. Also, the first steel framed building, Home Insurance Building, was constructed and completed in Chicago in 1884. This building is also termed as the father of the skyscraper and it was demolished in 1931. Another all-steel framed skyscraper, The Rand McNally Building, was also built in Chicago in 1890 and demolished in 1911. Steel production in the United States grew tremendously from 380,000 tons to 60 million tons annually from 1875 to 1920. In 1913, a 60-story tower, Woolworth Building, was built in New York. By 1940s, the use of steel in building construction was high and is still regularly used in many construction projects.

Tokyo Skytree: The tallest freestanding steel tower in the world (2,080 ft)

Image Source: https://en.wikipedia.org/wiki/Tokyo_Skytree#/media/File:Tokyo_Skytree_2014_%E2%85%A2.jpg

References:

Dillmann, P. Watkinson, D. Angelini, E. Adriaens, A.. (2013). Corrosion and Conservation of Cultural Heritage Metallic Artefacts - 15.1 Introduction. (pp. 311). Elsevier. Retrieved from https://app.knovel.com/hotlink/pdf/id:kt011NUEG1/corrosion-conservation/corrosion--introduction-3

MacRae, M. (2012). “Henry Bessemer.” The American Society of Mechanical Engineers, <https://www.asme.org/topics-resources/content/henry-bessemer> (Jun. 10, 2021).

Steel LLC (2018). “A Brief History of Steel Construction.” Steel LLC, <https://www.steelincga.com/a-brief-history-of-steel-construction/> (Jun. 10, 2021).