The Gridley Road Bridge project focused on developing a replacement design for an existing bridge located in Cerritos, California, that spans Interstate 91. The goal of the project was to evaluate the existing bridge plans and create a simplified structural design that demonstrates the engineering principles used in modern bridge design. The proposed replacement bridge was widened to accommodate increased traffic demands and improved pedestrian accessibility while maintaining structural safety and efficiency. The project addressed the need for aging infrastructure upgrades and provided insight into how bridges are analyzed, designed, and modified to meet changing transportation needs. Communities that rely on this bridge, including motorists, pedestrians, and local agencies responsible for transportation infrastructure, are directly affected by the performance and reliability of structures such as the Gridley Road Bridge. Through this project, our team gained practical experience applying industry design standards and understanding the challenges associated with real-world bridge engineering.
Gridley Road Bridge
Summary
Technical Approach/Methodology
The project was completed using engineering procedures commonly employed in bridge design. Structural loads from vehicle traffic, pedestrians, earth pressure, and the bridge’s own weight were determined using AASHTO LRFD Bridge Design Specifications and Caltrans Bridge Design Standards. Structural analysis was performed using influence lines, hand calculations, spreadsheets, and RISA-3D modeling software to determine the forces acting on critical bridge components. Major bridge elements including the deck, girders, bent cap, abutments, columns, and foundations were then designed using reinforced concrete design procedures based on ACI 318 requirements. AutoCAD was used to develop structural drawings and reinforcement details for the final design. Throughout the project, multiple design iterations were evaluated to balance structural performance, constructability, and efficiency while maintaining compliance with applicable design standards.
Outcomes
The project resulted in a complete conceptual bridge design package for a widened two-span reinforced concrete bridge. Deliverables included structural calculations, load analyses, reinforcement designs, AutoCAD construction drawings, quantity takeoffs, and cost estimates. The final design included a reinforced concrete deck, seven T-shaped girders, a bent cap, columns, abutments, return walls, and supporting footings. Alternative design concepts were also evaluated to compare structural efficiency and constructability. The project culminated in a comprehensive final report documenting the design methodology, assumptions, calculations, drawings, and recommendations for future improvements. Beyond the technical deliverables, the project provided valuable experience applying industry design codes, structural analysis techniques, and engineering judgment to a realistic transportation infrastructure project.