Stainless steel is a revolutionary material that has produced countless advances in all manner of industries. But perhaps no arena has been more transformed by the many benefits of stainless steel than architecture and engineering. Because of its tremendous strength, corrosion resistance properties, and aesthetic appeal, stainless steel can be found in modern bridges around the world.
Stainless steel is an ideal material for use in bridges. It is equally useful for both large and small bridges, thanks to its durability and cost effectiveness. All kinds of bridges in the United States feature stainless steel of some kind, such as large span bridges, railroad bridges, highway bridges, and pedestrian bridges. Especially considering the current decline in much of America’s highway infrastructure, including many bridges that are in a critical state of decay, the potential to extend the lifetime of these structures by using stainless steel is very appealing.
The History Of Stainless Steel In Engineering And Architecture
The earliest bridges were made of wood. Ancient engineers then began using stone and concrete. Iron was not used as the primary bridge support until 1741 in England. Steel eventually became common in bridges in the late 1800’s. But regular steel can be susceptible to corrosion, especially in extreme environments, such as when exposed to saltwater. So it wasn’t until the use of stainless steel became common that bridges were able to enjoy all of the benefits that this material has to offer.
Just after the turn of the century, in the early 1900s, several scientists working separately made advances that paved the way for stainless steel. Finally, in 1912, Harry Brearly was looking for a corrosion-resistant solution for gun barrels and was able to industrialize a martensitic stainless steel alloy. Brearly later teamed with Elwood Haynes to form the American Stainless Steel Corporation.
It didn’t take long for stainless steel’s potential to be recognized by engineers. In 1925, stainless steel figured prominently in the refurbishing of St. Paul’s Cathedral in London. Here in the United States, the iconic spire of the Chrysler Building was made with stainless steel in 1928.
While bridges have relied on general carbon steel for close to 150 years, stainless steel, because of its relative expensiveness, was generally used only for support materials. In particular, it was valued for its anti-corrosion properties and used in safety features such as guardrails and handrails. As more alloys were developed and the costs came down, it began to be used in more structural components, such as beams, welded plate sections, tie-rods, suspension systems, cables, and pylons.
It is only in this century that stainless steel has become a primary bridge material.
The Current Trend Of Stainless Steel In Bridges
The Cala Galdana Bridge is the first duplex stainless steel arch bridge for motor vehicles. It was built over Algendar Creek on the island of Menorca, Spain in 2003. It was constructed to replace the previous reinforced concrete bridge, which had become corroded due to the marine environment. The bridge’s total length is 55 meters (180 feet), with a main span of 45 meters. The grade of stainless steel was 1.4462 and was selected because it has a high resistance to corrosion by chlorides.
In the last 20 years, more and more stainless steel bridges are being built, both for pedestrians and vehicles. With the most recent advancements, the cost of such bridges has gone down, and combined with their greater durability, the investment now makes sense. Stainless steel is also prized for its aesthetic appeal, an important consideration in modern architecture.
Various grades of duplex stainless steel are especially popular. For example, in 2011 San Diego built the Harbor Drive Pedestrian Bridge. Again, the marine environment was a critical factor in material selection, and duplex stainless steel 2205 was the main metal used. This was the second pedestrian bridge in the U.S. made of stainless steel. The finish of this bridge was important because pedestrians would be using the bridge. They also wanted at least a 100-year service life.
Duplex stainless steel is the most recent family of stainless steel alloys. Another name for this class of steel is austenitic-ferritic because its metallurgical structure consists of austenite and ferrite stainless steels in roughly equal proportions. When duplex stainless steel is melted, the metal reverts to a completely ferritic structure. As the metal is then cooled, roughly half of the ferritic grains become transformed into austenitic grains.
Duplex stainless steels are becoming increasingly popular in bridges and other engineering applications because of their superior properties. This includes the fact that these steels are typically twice as strong as austenitic or ferritic alloys. Because of their increased strength, less material is needed, saving both money and weight.
These alloys show greater toughness and ductility than comparable ferritic grades as well, though they lag behind some of the best austenitic grades in this regard. As for corrosion resistance, duplex stainless steels have proven to have a performance comparable to 304 or 316 stainless steels, and with particular grades, they have the corrosion resistance required of marine environments, an important consideration for coastal bridges.
Another factor in bridge design is a material’s stress corrosion cracking (SCC) resistance. In this regard, duplex stainless steels have the preferred properties of ferritic alloys, and do not suffer the same vulnerabilities that can be found in 304 and 316 alloys, which can suffer corrosion cracking in conditions such as high humidity and heat.
Because duplex stainless steels have lower nickel and molybdenum content, they tend to be cheaper than comparable austenitic steels. This, combined with the weight savings mentioned previously, means that duplex stainless steels are extremely competitive on price.
Clinton Aluminum and Steel, with our deep experience working with engineers in all kinds of fields, understands what our customers most need when it comes to a materials provider. We take pride in on our ability to provide the exact product at the exact specifications, quickly and without any hassle. Moreover, we’ll work with you at every step of your production process to make sure that you have all the information you need to make an informed decision.
Our staff of experienced technical professionals has an average of nearly 13 years working for Clinton. It’s due to their practical expertise that Clinton is recognized as the Midwest’s leading supplier of aluminum and stainless steel products. Contact us today to learn more about how we can help you get the maximum value out of your purchasing decisions.