Types of Steel Bridges
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 throughout the United 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 Bridges
Bridge engineers choose weathering steel for its performance, economic 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 140’ 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. An interactive, web-based design tool called eSPAN140 was developed to assist bridge professionals with their individual projects, with customized results delivered in minutes.
Through its involvement with the Short Span Steel Bridge Alliance, AISI 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.