Link to Report: Coming Soon
Background :
The Simple for Dead Load and Continuous for Live Load (SDCL) steel bridge system has been successfully implemented across the United States, primarily using steel I-girders. These bridges have demonstrated excellent performance, cost-effectiveness, and constructability, with more than 60 SDCL bridges built in Missouri alone. Building on this proven concept, the proposed research aims to extend the SDCL system to shallow steel box sections specifically optimized for short-span, multi-span bridges and for Accelerated Bridge Construction (ABC) applications.
The project develops a new box configuration formed by bending a flat steel plate into a U-shape and welding tension flanges to complete the section. This fabrication approach reduces depth, simplifies detailing, and allows integration with reinforced concrete decks while preserving SDCL behavior. To enhance local buckling resistance of the thin bottom flange near supports, a thin concrete layer will be added externally. Additionally, Ultra-High-Performance Concrete (UHPC) diaphragms will be explored to improve force transfer, simplify connection details, and increase durability in pier regions.
The research includes (1) development of detailed nonlinear finite element models to evaluate structural behavior and conduct parametric studies; (2) laboratory testing of prototype shallow SDCL box sections to validate the analytical findings; (3) development of practical design recommendations, tables, and provisions tailored for spans up to 80 ft; and (4) preparation of sample design plans to facilitate immediate adoption by state DOTs and consulting engineers.
The anticipated outcome is a next-generation SDCL box system that maintains the simplicity and efficiency of the original SDCL concept while meeting the geometric, fabrication, and durability requirements of modern ABC practices. The research will produce directly implementable guidance and design tools that can significantly improve constructability, reduce dead load, and extend service life of short-span bridge infrastructure across the nation.
Objectives :
The objectives of this project are to:
- Extend the SDCL concept from traditional I-girders to shallow steel box sections optimized for short-span, multi-span bridges.
- Develop and validate nonlinear FE models to characterize behavior, assess key parameters, and guide specimen design.
- Conduct experimental studies to verify the structural performance and feasibility of the proposed shallow SDCL box system.
- Develop practical design recommendations, design tables, and preliminary provisions for spans up to 80 ft.
- Prepare sample design plans to facilitate rapid adoption by state DOTs and consulting engineers.
- Investigate the use of UHPC diaphragms to simplify details, enhance force transfer, and improve durability for ABC applications.
Scope :
Task 1 – Development of Nonlinear Finite Element Model and Parametric Studies
A detailed nonlinear finite element (FE) model of the proposed shallow SDCL box section will be developed using advanced material and geometric nonlinearities. The model will capture local flange buckling, composite action with the concrete deck, and UHPC diaphragm behavior. Parametric studies will evaluate the influence of span length, box depth, flange thickness, bottom-flange concrete overlays, and diaphragm configurations. The results will guide the design of experimental specimens and identify efficient section geometries for spans up to 80 ft.
Task 2 – Design and Fabrication of Experimental Specimens
Based on Task 1 findings, prototype shallow SDCL box specimens will be designed with welded tension flanges and thin concrete layers at the bottom flange near supports. UHPC-enhanced diaphragm regions will also be incorporated. Final detailing will reflect realistic fabrication practices suitable for ABC applications. Specimens will be fabricated in-house or through industry partners following approved design drawings.
Task 3 – Experimental Testing and Validation
Laboratory testing will be conducted to evaluate global behavior, load-deformation response, buckling resistance of thin flanges, and diaphragm effectiveness. The tests will validate FE model predictions, confirm the feasibility of the shallow SDCL box system, and quantify performance improvements due to UHPC diaphragms. Test results will be used to refine analytical models and support development of practical design limits.
Task 4 – Development of Design Recommendations, Design Tables, and Preliminary Provisions
Analytical and experimental findings will be synthesized into practical design recommendations for short-span SDCL box bridges. Design tables covering a range of geometries and span lengths will be developed, along with preliminary design provisions aligned with ABC construction needs. Guidance will focus on shallow depths, reduced welding, buckling control, and improved durability.
Task 5 – Preparation of Sample Design Plans and Final Report
Prototype design plan sheets for multi-span shallow SDCL box bridges will be prepared in a format consistent with DOT standards. These plans will illustrate diaphragm details, box geometry, and construction features suitable for ABC. A comprehensive final report will document all methodology, results, design tools, and recommendations, enabling immediate use by DOTs and consultants.
Research Team :
Principal Investigator: Atorod Azizinamini, Ph.D., P.E.
Co-Principal Investigator: Mahyar Ramezani, Ph.D., and Arslan Khan, Ph.D.