The start of a new year — and a new decade — is a good time to take inventory of the way you currently do things and reassess past priorities and practices.
If you’re a highway bridge owner, engineer, or designer and cost efficiency is what drives your materials decisions, it’s time to take a new look at using steel for bridge structures with lengths of up to 140 feet. A common misconception is that steel is more costly than other materials for short span bridges—but that’s typically not true.
A case in point is the Scott County Bridge in southeast Missouri. The bridge, MoDOT Bridge No. A8682, is located on Route W over Drainage Ditch #289 between the towns of Sikeston and Cape Girardeau. The replacement bridge was designed as a single 45’-0” span x 26’-8” width structure; wider than the original structure to accommodate two 12-foot lanes; and longer for improved hydraulics.
Bids were accepted for both a prestressed concrete I-beam and rolled steel beam alternate, both four-beam lines. The concrete I-girders were 2’-8” deep, while the galvanized steel rolled beams were 2’-6″, saving 2 inches in bridge depth.
The project was bid by eight general contractors. Half of them bid steel, and the other half bid concrete. For both the bridge and the overall project, which included all of the roadway items, steel came in low. For bridge items only, the galvanized rolled steel beam was still the lower-cost option, beating out concrete by 2.5 percent.*
The contract was let on December 14, 2018 and awarded in early January 2019 to Delong’s, Inc. Steel was delivered during the week of April 1, 2019. The structure was completed and opened to traffic during the week of May 19, 2019.
Short span steel bridges deliver significant cost savings because of steel’s light weight, the allowance of smaller abutments, rapid installation, and the use of lighter equipment and local crews. Steel also delivers durability with an expected service life of more than 100 years for many bridges, considerable life cycle advantages, and minimal maintenance requirements over the service life of the structure.
You can design a structure like the Scott County Bridge for free using web-based design tool eSPAN140. The tool offers customized steel solutions for bridges up to 140 feet in length, with results delivered in less than five minutes. eSPAN140 can be accessed at https://www.espan140.com/.
If you have never installed a short span steel bridge or have minimal experience, challenge yourself this year to learn more by visiting www.shortspansteelbridges.org or contacting Dan Snyder at email@example.com.
*Bid Tab Results: Missouri Department of Transportation Bid Tabulations.
For more information:
- Case Study: “Short Span Shake-Up: Missouri Short Span Bridge Study Finds Steel Saved 25 Percent Over Concrete” — In a side-by-side comparison of construction square footage costs for nearly identical steel and concrete bridges in Audrain County, Missouri, the steel short span superstructure provided a 25.8 percent cost savings with an overall 19.3 percent savings in the total cost of the structure.
- Fact Sheet: “Steel Offers High Value for Bridge Life Service and Life Cycle Costs” —This fact sheet presents the results of research conducted to explore the initial costs, life cycle costs, future costs and bridge life of 1,186 typical steel and concrete state bridges in Pennsylvania built between 1960 and 2010.