As a bridge engineer, professor in the College of Engineering and Applied Science at the University of Wyoming, and a member of the Short Span Steel Bridge Alliance’s Bridge Technology Center, Michael Barker, Ph.D., P.E., makes frequent presentations on the economics of short span bridge design to county engineers, state Department of Transportation (DOT) engineers and bridge owners. Over the years, he has received numerous questions about Life Service and Life Cycle Costs, especially concerning steel and concrete girder bridges. His answers were always anecdotal, as research didn’t exist―until now.With a keen interest in finding answers to these persistent questions, Dr. Barker took a sabbatical from the university to conduct his own research. He started with a comprehensive inventory of bridges and consideration of initial costs and installation dates, maintenance costs and timing, and end-of-service dates. After considering the availability of historical data, he narrowed the scope of research to include initial costs, future costs, and service lives of 1,186 typical steel and concrete state bridges in Pennsylvania built between 1960 and 2010.

A portion of Dr. Barker’s research focused on short-length bridges of 140 feet or less, which make up approximately half of the U.S. inventory that needs to be repaired or replaced. The research examined costs with respect to variability in bridge type, span length, number of spans, and bridge life. Typical bridges are defined in the study as those with concrete decks supported by steel rolled beams, steel plate girders, precast concrete boxes, or precast concrete beams. Working from Pennsylvania Department of Transportation (PennDOT) historical records, he developed a database to determine and compare the life cycle costs of steel and concrete girder bridges. More detailed information on the parameters of the research and determination of values for life cycle costs are included in the presentation located here.

For the short-length bridges included in the PennDOT database, the research demonstrated:

• The steel I-beam had the longest life.
• The steel I-beam had the lowest cost.
• Steel bridges have lower future costs compared to initial costs.
• None of the bridges clearly beat out the others, meaning any one type of bridge may be the most economical for a given bridge project.

Overall Results
After analyzing the extensive data collected, Dr. Barker concludes:

• Typical steel and concrete bridges are competitive on initial costs, future costs, life cycle costs and bridge life.
• For any given bridge project, steel or concrete bridge types may be the most economical. Therefore,
• Owners should consider both steel and concrete alternatives for individual bridge projects.

The research results do not provide a clear preference for either material. However, the results clearly disprove generally accepted assumptions by bridge engineers that concrete girder bridges are the least-cost solution for every short span project.

It is clear from the research that bridge owners and design professionals who want to find the most economical and long-lasting solutions for repairing and replacing their bridge inventories should conduct a thorough cost analysis that considers the potential benefits of steel and concrete options. Conducting the analysis upfront could save thousands of dollars down the road in maintenance and repair costs.

To download the complete report, “Historical Life Cycle Costs of Steel and Concrete Girder Bridges,” click here.

To download the Fact Sheet, click here.

For more information, contact Dr. Barker at Barker@uwyo.edu.