Oscillation Suppression of Pedestrian Overpasses

Строительные конструкции, здания и сооружения

The objects of research are pedestrian overpasses. The purpose of this work is to analyze the issues of suppression of such overpasses from oscillation caused by movement of trains and crowds. There are many ways to suppress oscillation, including increasing the longitudinal stiffness, introducing an additional connection, and using elastic or viscoelastic dampers. Problems arise when determining the need for measures to suppress oscillation in particular cases. Method.  The need for suppression is determined for a pedestrian overpass with a span of 44.6 m, which is tested to determine the natural vibration frequency and the logarithmic decrement of attenuation. A comparative analysis of different solutions for oscillation suppression is carried out. A computational model of a pedestrian overpass based on the finite element method is developed. The dynamic impact from the crowd is set as a time – force function, based on the condition that 12.5% of pedestrians move synchronously. The possibility of simplifying the design scheme by replacing the base and supports with boundary conditions is determined. The dynamic influence of a train on a pedestrian overpass is studied. The load from the train is set by the time-force function and the displacement equation. Three different cases of loading from the train are studied, varying on weight and the number of wheels. Results. A comparative analysis of oscillation damping measures shows that the most effective solution is to introduce a viscoelastic damper. This way, it is possible to reduce the mean square acceleration of oscillations by 8.4 times to the required values, with the lowest material consumption.