2015 CSCE Annual Conference Regina - Building on our Growth Opportunities Conference
Mr. Sébastien Langlois, Université de Sherbrooke (Presenter)
Mr. Frederic Legeron
This paper presents an innovative method for the optimum design of seismically isolated bridges incorporating energy dissipating devices. For an isolated bridge subjected to an earthquake, the deformation is concentrated in the isolators. This greatly reduces the seismic forces transmitted from the superstructure to the substructures. However, some factors such as space limitations, stability requirement, etc. limit the allowable deformation taking place across an isolator. To control the deformation of the isolators, supplemental energy dissipating devices can be introduced into the isolation system. This may in return increase the total structure force and the merit of adding dampers has to be evaluated properly. In this study, a simplified damper design method has been used to optimize the performance of an isolated structure. This method is based on a simplification of the system and by setting objectives for displacement reduction as well as acceptable force increase. Based on this approach, damper stiffness and damping ratio is determined as a function of pier and isolator stiffness. The method provides a range of added stiffness and damping that will be needed to reduce the total displacement of the structure while controlling the increased structural force. Response spectrum analysis method has been performed to validate the method for a typical isolated bridge structure. The numerical simulation showed a close relation with the proposed simplified method. It is concluded that the proposed simplified approach has the potential to optimize the performance of isolated bridges incorporating energy dissipating devices.