Seismic Retrofit of Monorail Bridges Considering Soil–Pile–Bridge–Train Interaction

Abstract

Monorail bridges play an important role in urban transportation networks, and their proper seismic performance is an issue of great concern in earthquake-prone countries. Seismic isolation is a strategy that protects the bridges from dynamic forces by increasing their natural periods. Despite the widespread use of seismic base isolation in conventional bridges, there are very limited reports on the use of this technique on monorail bridges. The seismic isolation technique can also be useful for the straddle-type monorail transportation systems. This study aims to investigate the nonlinear performance of the Qom Monorail Bridge (QMB), which is seismically isolated by an isolation system that takes the soil–pile–bridge–train interaction under strong earthquakes into consideration using the 3D finite element method. Results showed that the isolation system can eventually reduce the base shear by 60% and controls the distribution of the forces between the soil and piles. The dynamic monorail train system acts as a damper on the nonisolated QMB. However, the presence of the train on the isolated QMB with the pier height of 15 m or more can increase the base shear.