December 3, 2024
Horner & Shifrin Selected by MoDOT for Innovative Bridge Design Guidance
Pioneering SDCL Steel Girder Bridges for Enhanced Infrastructure
Horner & Shifrin (H&S) has been chosen by the Missouri Department of Transportation (MoDOT) to develop Engineering Policy Guidance for the design and construction of Simple for Dead, Continuous for Live Load (SDCL) steel girder bridges. This innovative approach addresses the challenges of traditional steel girder construction, which often involves costly field splices or simple span girders with expansion joints at each pier, leading to long-term maintenance issues.
The SDCL Advantage
SDCL construction places steel girders in each span and makes them continuous with a concrete diaphragm, similar to prestressed concrete bridges. This method combines the simplicity of individual girders with the continuity needed for improved longevity. Steel thrust blocks transfer compressive forces at the bottom flange, while slab steel is designed to carry tensile forces across the bent.
Fabrication Benefits
Compared to traditional continuous steel girder bridges, SDCL construction offers several fabrication advantages:
- No costly splices: Reduces overall construction costs.
- No bearing stiffeners: Simplifies the design.
- Shorter spans: Typically used for spans that do not require cambering of the girders.
- Lower certification requirements: Allows more fabricators to bid on projects, increasing competition and lowering bids.
Proven Technique
SDCL methods have been successfully used in other states for several years and were introduced to MoDOT through their FARM Design-Build project. H&S is currently designing numerous SDCL structures for MoDOT, including:
- The Northwest Bridge Bundle Design Build Project
- Two SDCL bridges in MoDOT’s Southeast District
- An SDCL superstructure replacement in MoDOT’s Northwest District
- Two bridge rehabilitations with SDCL details in MoDOT’s Central District
Developing Best Practices
Despite the advantages, there is no consensus on best practice details for SDCL structures. To address this, H&S is partnering with the University of Missouri-Columbia’s School of Engineering to develop standard details and design guidance for MoDOT. The project includes:
- A literature review of other states’ practices
- Development of a finite element model calibrated to construction and in-service data from a representative bridge
- Creation of standard details and guidance on when to use SDCL bridges
Capital Paving and Construction will support the project by providing access to one of the Northwest Bridge Bundle bridges for instrumentation.
Horner & Shifrin’s collaboration with MoDOT and the University of Missouri-Columbia aims to standardize SDCL bridge construction, enhancing the efficiency and longevity of Missouri’s infrastructure.
