MoDOT Reimagines Rural Steel Bridges through SDCL Design

Photo Credit: Missouri Department of Transportation

At a recent Short Span Steel Bridge Alliance (SSSBA) Semi-Annual Meeting, Missouri Department of Transportation (MoDOT) representatives Bryan Hartnagel, State Bridge Engineer, and Jeff Gander, FARM Bridge Project Director, presented MoDOT’s successful implementation of the Simple for Dead Load and Continuous for Live Load (SDCL) bridge design.

This approach is a key component of MoDOT’s Fixing Access to Rural Missouri (FARM) Bridge Program, which targets critical bridge replacements in rural areas. The following is information about SDLC and MoDOT’s implementation of the bridge technology. 

What is SDCL?

The SDCL bridge design is an engineering method that applies a simple support system to handle the bridge’s dead load (the weight of the structure itself), while using continuous spans to support live loads (traffic and other dynamic forces). This combination offers multiple advantages for rural bridge construction, making it a practical and economical choice for Missouri’s infrastructure needs.

Advantages of the SDCL Design for Rural Bridges

1. Ease of Construction
   • The SDCL design minimizes complex field splices and uses simple span beams made continuous with concrete slabs, allowing for a straightforward construction process. This is particularly advantageous in rural settings, where resources and construction crews are often limited.
2. Material Efficiency
   • By using lighter steel beams, SDCL bridges significantly reduce the weight compared to traditional concrete structures. For instance, a steel W18x158 beam at 60 feet weighs approximately 9,480 pounds, whereas an equivalent concrete beam could weigh over twice as much. This weight reduction simplifies transport, handling and placement in rural locations.
3. Cost-Effective Foundations
   • The SDCL system’s lighter weight permits the use of more economical foundation types, reducing overall project costs. This design also requires a thinner superstructure, which can eliminate the need for grade raises or additional permits, further lowering expenses.
4. Durability and Long-Term Performance
   • With SDCL’s combination of simple and continuous spans, bridges gain durability with reduced maintenance needs. MoDOT has incorporated galvanized steel beams in SDCL designs, offering an extended maintenance-free lifespan in rural environments.
5. Adaptability to Rural Needs
   • The flexibility of SDCL construction aligns with the goals of MoDOT’s FARM program to replace or upgrade bridges that are often critical single-lane structures or weight-restricted. SDCL bridges can be customized to span a variety of rural site conditions and traffic loads, ensuring that each bridge replacement meets local needs effectively.

The FARM Bridge Program and SDCL’s Role

Through the FARM Bridge Program, MoDOT is applying SDCL designs to replace 31 deteriorating bridges in rural Missouri, using innovative approaches to deliver cost-effective, long-lasting structures. Supported by a grant from the Competitive Highway Bridge Program, the FARM project demonstrates how SDCL bridges can enhance access, safety and durability for communities with limited transportation budgets.

Download a presentation from Dr. Michael Baker, University of Wyoming, presented at the World Steel Bridge Engineering Conference. 

Looking Ahead: SDCL as a Model for Rural Bridge Innovation

MoDOT’s implementation of SDCL bridge design within the FARM Bridge Program serves as a model for infrastructure projects nationwide. With its focus on simplicity, efficiency and longevity, the SDCL approach aligns well with the needs of rural communities and promises a sustainable, cost-effective path forward for bridge construction.

For more information, visit MoDOT’s FARM Bridge Program page at www.modot.org/farm-bridge-program.

Download MoDOT SDCL Presentation

Additional Resources

• Extending Application of Simple for Dead and Continuous for Live Load Steel Bridge System to ABC Applications in Seismic Regions
• Simple for Dead Load–Continuous for Live Load Steel Bridge Systems