Dynamic analysis of the Bercy-Tolbiac footbridge

This paper deals with SETEC TPI's dynamic analysis of the Bercy-Tolbiac footbridge, currently under construction in Paris. The first twelve significant modes of the bridge are located in a 0-2.1 Hz range, with the 4 main vertical modes between 1.6 and 2.1 Hz. These frequencies mean the bridge is highly susceptible to pedestrian loading, and it follows that external damping is needed. Two main types of dampers were used to bring the dynamic response of the bridge to an acceptable level: viscous dampers and tuned mass dampers (TMD).

After a brief introduction to the dynamic context of the Bercy-Tolbiac footbridge, we will go into a more detailed examination of the methods used to calculate the specifications the damping systems. To avoid resorting to lengthy timestep calculations, we implemented powerful numeric tools. Complex modal analysis was used for the viscous damper to access modal damping of all modes in a very convenient way. For the tuned mass dampers, harmonic analysis was used to compute the response of the system.

This paper quickly introduces the theoretical basis of each method, illustrates their uses in the design of the Bercy- Tolbiac footbridge, and attracts the reader's attention as to a few pitfalls to avoid when using them.