DYNAMIC ANALYSIS OF THE FOOTBRIDGE EXPOSED TO PEDESTRIAN LOADING

Abstract

The submitted paper is dealing with the phenomenon of the human induced vibration caused by walking pedestrians. Pedestrians naturally work as a source of a periodic load, which is typically in the resonance range with some of the natural frequencies of the crossed footbridge. Typical pacing frequency of the normal walk is close to 2 Hz. Unfortunately, the most of footbridges have some of the natural frequencies in the range 1.5 – 3 Hz. These values can be easily reached by pedestrians, which could lead to the uncomfortable level of the structural vibration as could be seen at the Millennium bridge in London. In the submitted paper, we are going to subject the footbridge, acting as the simply supported beam, to the theoretical dynamic analysis. The dynamic analysis will be divided into the modal analysis and the force vibration analysis, which is accomplished by the modal decomposition method. This approach allows us to execute direct integration of the independent equations of motion. Total number of these modal equations is significantly less than number of equations directly assembled by the Finite element method. The pedestrians will be mathematically described by the periodic shifting force with constant velocity of motion.