Bridges over water bodies are exposed to corrosive environments that lead to structural damage. Statistics show that over 36% of bridges in the US need replacement, accounting for around 220,000 structures. Therefore, it’s a must to use durable materials to build bridges so they last longer. That’s where stainless steel comes in! If you wonder which stainless steel for bridges is best and why to choose it, keep on reading!
What Stainless Steel is Used in Bridges?
The common stainless steel options to use in bridges include duplex, austenitic, and ASTM A709 Grade 50 CR stainless steel. They offer exceptional corrosion resistance and durability. Let’s discuss these types in detail:
Duplex Stainless Steel
Duplex stainless steel has the properties of both austenitic and ferritic stainless steel. Typically, the name “Duplex” comes from the dual-phase microstructure of these materials. They have superior mechanical properties compared to both austenitic and ferritic steels alone.
For instance, they can easily withstand wear and tear without getting damaged. On top of this, they have high corrosion resistance in challenging environments. This is primarily because of their higher chromium, molybdenum, and nitrogen content.
The best part is that duplex stainless steel enables the creation of lightweight designs without compromising on strength. When we look at history, this steel was first used in bridge construction around 1999. A prominent example is the Suransuns pedestrian bridge in Switzerland.
However, it was London’s Millennium Bridge (2001) that shed light on the usage of duplex stainless steel for bridges. Foster and Partners, Anthony Caro, and Ove Arup and Partners built it with Duplex 2205. After some time, duplex stainless steel bridges were everywhere, including in Spain and Sweden. Here’s an overview of the composition of duplex steel 2205:
Elements | Percentage |
Chromium | 21-23% |
Carbon | 0-0.03% |
Manganese | 2.0% |
Phosphorus | 0-0.03% |
Sulfur | 0-0.02% |
Nickel | 4.5-6.5% |
Nitrogen | 0.08-0.2% |
Silicone | 1% |
Molybdenum | 2.5-3.5% |
Austenitic Stainless Steel
Another stainless steel option is the austenitic stainless steel. The term austenite refers to a face-centered cubic iron or metal alloy. It’s named after Sir William Chandler Roberts-Austen, who was an Englishman and known for discovering the physical properties of metals.
Austenitic stainless steel is quite tough and has incredible ductility. You can bend it in any shape or design without worrying about fractures or damage. Nonetheless, what truly stands out is the exceptional heat and corrosion resistance of this steel. It contains 10.5% chromium, which is quite high.
That’s why it’s used to make pedestrian and vehicular bridges. It also finds applications in the automotive and aerospace industries. The aesthetic of this stainless steel is also good, as it makes the bridge look visually appealing.
Currently, the austenitic steel market size is booming and is expected to hit USD 88.81 Bn by 2030. Prominent examples of austenitic stainless steel for bridge usage include the Waldeck-Rousseau road bridge at Saint-Brieuc, France, in 1998. These are a series of bridges made via austenitic grades like 316L and 314. The following table gives you an overview of the composition of austenitic stainless steel:
Elements | Percentage |
Chromium | 18-20% |
Nickel | 8-10.5% |
Manganese | 2% |
Carbon | 0.08% |
Phosphorus | 0.045% |
Silicone | 1.0% |
Sulfur | 0.030% |
ASTM A709 Grade 50CR Stainless Steel
ASTM A709 Grade 50CR stainless steel is also known to be used for bridge construction. It’s a utility-grade stainless steel with incredible strength and mechanical properties. It has 10.5% to 12.5% chromium that greatly enhances its corrosion resistance.
Structural detail reveals that the ASTM A709 Grade 50cr has a nominal yield strength of 50 ksi and a nominal ultimate strength of 70 ksi. But it doesn’t stop here! It has 4 to 10 times the corrosion resistance of uncoated weathering steel, performing well in corrosive environments.
Particularly, it’s suitable for bridges where wetness and chloride exposure are high. For instance, in 2004, the Grade 50CR was used in welded plate girders on the Fairview Road Bridge in California. Then, one after the other, such bridges were being built. It includes one at ArcelorMittal and two in Canada.
Why Choose Stainless Steel for Bridges?
Now that you are aware of the different types of stainless steel, let’s look at the reasons to choose these materials:
High Durability
One of the popular reasons to choose stainless steel is its high durability. It lasts way longer than traditional steel or other materials. You’ll be surprised to know that the duplex stainless steel lasts for as long as a hundred years.
This material can easily withstand all environmental rigors without much damage. It also provides high corrosion resistance in salt and water, stemming from its self-healing layer. So, what happens is that the chromium content in its structure reacts with atmospheric oxygen.
There’s a chromium oxide layer that acts as a protective barrier for the stainless steel bridge. All corrosion agents, including oxygen and water, are blocked, offering amazing protection. The best part is that stainless steel requires very little maintenance. Just a bit of cleaning and it’ll be as good as new!
More Sustainable
The world is fighting against global warming and climate change, all due to unsustainable practices. However, one of the perks of using stainless steel is sustainability. It’s 100% recyclable, which means you can recycle it repeatedly without any quality loss.
Almost 99% of stainless steel that’s demolished or retired makes it back to the steel-making process. In addition, it requires very little chemical treatment during manufacturing. So, there are few to no harmful chemical agents that impact the environment.
Quick Bridge Construction
Stainless steel is very lightweight despite its abundant strength. Businesses and construction firms can build components off-site.
They can then ship these parts to the bridge construction site for assembly. Hence, bridge construction becomes faster, taking merely weeks, and in some cases, days.
It also leads to significant cost savings as you can save on parts needed to support heavy bridge construction materials. The cherry on the cake? It also lowers the cost of handling and transferring materials.
Conclusion
Stainless steel is the ideal option due to its versatility and durability. Wondering where you can get steel products? Jianglin is the one-stop shop! Contact us today to explore our certified and high-quality range of steel to serve your needs.
