engleski

The analysis of vibrations induced by pedestrian traffic and the application of damping systems on footbridges

With the fast development of modern materials and the intention to create constructions that are more elegant and architecturally different, pedestrian bridges with slender cross sections and wider spans are build, resulting in reduced mass and stiffness in comparison to older bridges. That leads to increased vertical and horizontal vibrations and low natural frequencies under pedestrian loading which correspond with the frequencies of the human walk and create a very unpleasant occurrence known as resonance. Despite this problem being known from the 1980’s, it is a growing concern in pedestrian bridges nowadays. What is more, the current European Norm that determines the traffic load on bridges does not provide any pedestrian load models to check the serviceability limit state. The Eurocode directs engineers to the application of National Annexes from individual countries where the corresponding dynamic models should be defined. In the Croatian National Annex, such dynamic models are still missing. This paper analyses the impact of pedestrian traffic models on the dynamic behaviour of pedestrian bridges, including numerical dynamic analysis confirmed with experimental dynamic tests using the “Time history” method. Increasing the damping by modifying the structure, connections, supports and non-structural elements may be considered, but often considerable practical problems arise. To increase the damping, it is far more effective, and less expensive, to install a damping system. Damping systems increase the amount of energy that is dissipated by the structure. In this paper the performance and optimization of different damping systems will be presented. The analysis will include the application of considered and confirmed pedestrian load models on numerical systems of vibration sensitive footbridges, where the vibrations tend to be decreased using dampers. Moreover, guidelines for the practical treatment of vibration problems in pedestrian bridges using various dampers will be given.

bridge vibrations ; pedestrians ; damping ; dynamic models

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