Bridges

According to ASCE's 2017 Infrastructure Report Card, of the more than 600,000 bridges across the United States, one in 11 (9.1%) were designated structurally deficient in 2016, and more than one in eight (13.6%) were designated as functionally obsolete in 2016. Steel bridges offer viable design solutions for bridge owners because they are durable, cost-effective, and offer ease of maintenance and construction.

The structural advantages of using steel include its high strength, durability, and light weight, which mean lighter foundations and lower erection costs. Steel is ideal for short-span bridges because of its durability, ease of maintenance and ease of construction.

Steel’s strength makes it highly resistant to extreme natural disasters, such as earthquakes. The 1994 Northridge, California earthquake destroyed the surrounding transportation infrastructure. However, 96 percent of the existing steel bridges were completely undamaged, even though they were designed using 1940s technology.

Today, designers and engineers are specifying new high-performance steels that were developed through a partnership of AISI, the U.S. Office of Naval Research and the Federal Highway Administration. These new steels have a yield strength of 50 ksi, 70 ksi and 100 ksi, have superior toughness, and can be welded with little or no preheat. Alternative bridge form designs are being developed that promise even greater design flexibility and cost efficiencies.

Weathering steels are cost-effective and durable. These steels contain certain elements that allow them, when properly exposed to the atmosphere, to form a protective oxide patina or coating. Studies show that using weathering steel reduces both initial and life cycle costs.

High-Performance Steel Bridges

In 1992, AISI partnered with the Carderock Division, Naval Surface Warfare Center and the Federal Highway Administration (FHWA) to develop new and improved steel alternatives for bridges. The team brought together a cadre of professionals in steel production, bridge design, bridge fabrication and welding, as well as specialists from the U.S. government and academia. The result was a new type of steel, known as high-performance steel (or HPS), which provided up to 18% cost savings and up to 28% weight savings when compared with traditional steel bridge design materials.

HPS went from concept to application in just five years, and is now being used in more than 400 bridges in 43 states. HPS 100W, HPS 70W and HPS 50W produce bridges that are more cost-effective, higher in strength, lighter in weight, and have greater atmospheric resistance than conventional steels. They also have improved fatigue and corrosion-resistance properties.

The development and implementation of HPS was considered so significant and innovative that the Civil Engineering Research Foundation (CERF) awarded the Charles Pankow Innovative Applications Award in 1997 to the AISI, U.S. Navy and FHWA partnership.

Weathering Steel

Bridge engineers choose weathering steel for its performance, economical and environmental benefits. Weathering steels contain elements that allow them to form a protective coating patina or coating when properly exposed to the atmosphere. The first bridge using this material was built over the New Jersey Turnpike in 1964.

The use of uncoated weathering steel typically provides initial cost savings of 10 percent or more, and life cycle cost savings of at least 30 percent over the life of the structure. Initial cost savings are realized because weathering steels do not need to be painted. Life cycle cost savings are realized by the material’s durability. Inspections of bridges in service between 18 and 30 years show that weathering steel performs well in most environments.

Weathering steels provide environmental benefits as well. They do not require initial painting, thereby reducing emissions of volatile organic compounds (VOC) when oil-based coatings are used. They do not require coating removal or disposal of contaminated blast debris over the life span of the structure, providing another significant environmental benefit.

A comprehensive research report on the performance of weathering steel bridges in West Virginia is available here.

Short Span Steel Bridges

Many of the United States' substandard bridges are short span bridges, falling within the 20’ to 120’ span range. Virtually every one of them could be replaced with durable, sustainable, economical steel. By utilizing new modular systems, a steel bridge can now be installed in less than 48 hours.

Bridge engineers are always concerned with finding the most cost-effective bridge solutions. However, the time and funding available for comparing alternatives are often limited, particularly for short span bridges. A new interactive, web-based design tool called eSPAN140 is now available to assist bridge professionals with their individual projects, with customized results delivered in less than one minute. Click here to try it out. SMDI has also developed short span bridge design aids, guidelines, and educational seminars to help bridge owners, engineers and designers choose the best material for the job.

Get more information on SMDI's short span steel bridge program.

Research Committees

The American Iron and Steel Institute coordinates the formation and activities of various research committees dedicated to developing new technologies and advancing best practices for steel products. The Corrosion Advisory Group is one of those committees. 

The Corrosion Advisory Group (CAG) is a council of technical experts representing steel producers, fabricators, academia, government officials and related organizations that provide specification and code development, research, technical assistance, site investigations and steel construction market development related to corrosion performance and mitigation of structural steel corrosion.

The CAG general objectives are to:

• Assist in the development of guidelines and specifications to mitigate the corrosion of steel structures through the use of steel grades (ASTM A1010, ASTM A588, HPS 50W/70W/100W, etc.), proven coating systems (galvanizing, metalizing, polymer coatings, etc.) and design details. 
  
  
• Identify and develop research efforts for the continued advancement of steel corrosion mitigation technologies and design details.
  
  
• Provide site investigations to bridge owners at locations in which structural steel is a potential option for a newly constructed or replacement bridge.
  
  
• Facilitate technical knowledge transfer of advances in corrosion technology from mills, fabricators, universities and corrosion engineers to designers, owners and government officials.
  
  
• Collaborate with related organizations to assist in implementing new guidelines, methodologies and research findings.

For more information, please contact AISI Director of Business Development Dan Snyder.