The Panama Metro Line 3 is a 25.5 kilometer long monorail line with 14 stations under construction as part of the Panama Metro project. It will be the largest project in Panama since the expansion of the Panama Canal. The line will connect Panama City with the western province of Arraijan. The line crosses an active earthquake fault (the Pedro Miguel Fault), requiring seismic design for a magnitude 9.0 earthquake. BANDI was involved in the design of the 5.4-kilometer-long monorail bridge.

The superstructure of the bridge is made of prestressed concrete beams (also known as track beams) that serve as girders and tracks. Concrete drilled shafts with a diameter of 2.5 meters were used. Because the project site is located in a seismic hazard area near an active fault, the Employer required a performance-based seismic design to ensure the bridge's seismic performance. 

A state-of-the-art displacement-based seismic design methodology complying with the AASHTO LRFD seismic bridge design specifications was adopted. All structural components of the bridge were designed to ensure seismic performance levels for both expected and maximum considered earthquakes (EE and MCE). In addition, nonlinear soil-structure interactions were considered in the global finite element analysis considering the p-y curve of the soil, and the displacement capacity of the bridge was precisely evaluated through moment curvature and pushover analysis to optimize the substructure dimensions to the satisfaction of the client.

Monorail-type track beams require lateral restraints on the axis of the piers. The tender design proposal proposed a monolithic connection where track beams and pier columns are rigidly integrated. However, during the detailed design phase, it was realized that the connection required a significant amount of reinforcement when the pier columns reached their maximum capacity and formed a plastic hinge. To optimize the local reinforcement, specific steel bearings were selected that allowed longitudinal movement while restraining lateral rotation.

The composite section using precast shells was adopted in the piercap design of portal piers which have been applied for the section crossing the existing roads. The precast shell is used to act as formwork during construction, and detailed reviews including construction stage analysis were conducted to ensure the structural integrity during construction and in service.