As the Samples Professor of Civil and Environmental Engineering at West Virginia University, Dr. Karl Barth knows a thing or two about giving and receiving grades. So when he sees a C+ assigned to the condition of bridges in the United States by The American Society of Civil Engineers (ASCE) in its 2013 Report Card for America’s Infrastructure, he’s motivated to bump the grade up. And as technical director for the Short Span Steel Bridge Alliance’s (SSSBA) Bridge Technology Center, he has some ideas on how to do it.
Approximately one-half of the bridges cited in the ASCE report are short span bridges (those under 140 feet), and most are owned and maintained by local governments. Two of the biggest challenges standing in the way of repairing or replacing these bridges are time and cost restraints. Barth says that steel has solutions for both.
Design Phase – Steel Saves Time. In 2012, a free online tool that provides standardized short span steel bridge designs was introduced to the marketplace. The new tool, eSPAN140, also connects bridge owners with SSSBA member companies that can take the project from design to completion. By using standardized designs and making available specific contact information for companies that can complete the project, eSPAN140 speeds up the time it takes to construct the bridge and cuts down on design and construction costs. Dr. Barth and a team of 30 experts from the steel and bridge construction industries reviewed more than 3,000 designs over several years during the development of eSPAN140.
“What eSPAN140 does is allow county engineers to go online and input some very simple geometric property information and from the standard designs we’ve developed, receive a set of preliminary bridge plans,” explained Barth. “Now they have a way for getting a steel solution on the table in less than five minutes, where before it would have taken several days and additional personnel.
“When looking at short span bridges, most situations do not require complex designs,” said Barth. ”Therefore, the standardized plans provided by eSPAN140 can greatly reduce the amount of time required to design a short span bridge.”
The Jesup South Bridge in Buchanan County, Iowa was designed with eSPAN140 and went into service in November 2013. The story behind the bridge is included in an April 14, 2014 article in Roads and Bridges.
Construction Phase – Steel Saves Money. According to Barth, steel can be more cost-effective, sustainable, lighter and more aesthetically pleasing than alternative materials for short span bridge construction. Steel can be less expensive because: 1) fewer girders may be required for the project, 2) most city and county governments can use smaller cranes to install the lighter steel beams, and 3) in many cases, local work crews can be utilized to construct the bridge.
The Next Phase – New Technology. Dr. Barth and his team at West Virginia University have developed and are testing a steel option for new and replacement bridges that could speed up the construction process and reduce the cost of the superstructure. This innovative accelerated bridge construction (ABC) technique involves a shallow steel press-brake tub girder technology that consists of modular shallow trapezoidal boxes (either galvanized or made from weathering steel) and is fabricated from cold-bent structural steel plate. The deck can be precast on the girder, and the modular units can be hauled by trucks to the bridge site.
The first demonstration bridge using this new technology will begin construction in 2015 in Buchanan County, Iowa. The Amish Sawmill Bridge will be constructed with funding from the Federal Highway Administration’s Innovative Bridge Research and Deployment (IBRD) program. When completed, Dr. Barth will conduct field testing on the bent plate system to validate design assumptions and evaluate performance over the long term. This new system could significantly impact future best design practices, and other states have already expressed interest in initiating projects of their own.
For more information on the benefits of steel for short span bridge design and construction, contact Dan Snyder at email@example.com.