Concrete and steel rate about the same for bridge construction in terms of initial and future costs, life-cycle costs and bridge life, according to a study by Dr. Michael Barker, a civil and architectural engineer and a professor at the University of Wyoming. Particular projects may favor one choice over another but overall “there is no one type of bridge that clearly beats the others,” Barker says.
A U.S. engineer has conducted a study on which type of bridge is the best, steel or concrete, and his findings may be surprising to some.
“I talk to a lot of counties, a lot of consultants and a lot of state DOTs (departments of transportation). One of the most common questions they have is which are the best bridges for lifecycle costs,” Dr. Michael Barker, a civil and architectural engineer and a professor University of Wyoming, told the audience at the recent webinar entitled Accelerated Bridge Construction, presented by Acrow and hosted by the Ontario Good Roads Association (OGRA).
Barker carried out a large-scale analysis on bridge structures and summarized his findings during the webinar. The study compares precast I-beam, box adjacent, box spread bridges, steel rolled and welded plate girder bridges. The study found all are “similar” with none “way out” of balance, he said.
“Statistically any one type of bridge may be most economical for a given bridge project. There is no one type of bridge that clearly beats the others,” said Barker, who is also director of education for the Short Span Steel Bridge Alliance.
“There is a preconception out there that concrete is less expensive than steel.
“The results of this, and what we’ve known for a long time, is that typical concrete and steel bridges are competitive on initial costs, future costs, lifecycle costs and bridge life and that owners should consider both steel and concrete alternatives for individual bridge projects.”
In conducting the study, he looked at historical lifecycle costs, historical life service, performance and maintenance, and agency lifecycle costs of steel and concrete girder bridges. He needed a comprehensive inventory of bridges to be able to do comparisons including initial costs, date built, maintenance costs, including the date performed and how long the bridge lasts or the end of service date.
“The bridges in the Pennsylvania inventory are still in service so I had to come up with an end-of-life model,” Barker explained. “If I assumed the bridge was a superstructure condition rating — in the U.S. that’s what we use — of a nine when it was first built, which means it was a perfect bridge, then given that I looked at these bridges in 2014 I can calculate a deterioration rate. Then if I assume that bridge is going to be replaced when it reaches a three then I can calculate the remaining life and then the bridge life is just how old is it now plus the remaining life.