Keywords: dynamics, bridge, human gait, multibody system, vibration, interaction, moving load.

Modern pedestrian bridges tend to become more and more light-weight and flexible structures, very often of unusual structural systems, e.g. of stressed ribbon, suspended or cable-stayed types. In such cases first natural frequencies of vibration may fall close to dominant frequencies of the dynamic excitation due to walking or running, leading to a resonant response characterized by high levels of vibration [1]. Such bridges are susceptible to vertical as well as to horizontal vibrations and a dynamic design is necessary.

Although such vibrations do not usually cause structural problems, they can induce some uncomfortable sensation, and so some codes or standards establish maximum acceptable values of acceleration, normally expressed as function of the fundamental frequency of the bridge. The improved design of elastic bridges must take into account the phenomena of the man-bridge interaction and its vibration perception by human beings.

The paper deals with the investigation of the interaction between human gait and elastic bridges for the prediction of human body vibration and bridge response. First the difference between the response of the bridge loaded by the contact force, representing the walking person, which was fixed in position and by the force moving in time has been demonstrated. The developed time and position dependent model for walking persons gives realistic results for different simulations.

The ultimate goal of this investigation is the influence of bridge design on the human perception. The suitable model of interaction between human gait and elastic bridge has been developed [2]. It consists of the multibody model of a walking human being and of the finite element model of an elastic bridge. The interaction between both structures is modelled by contact force influence. The model is capable to simulate both the stable and unstable human gait effects on the bridge stiffness. Several real elastic bridges are investigated. The mutual influence seems to be a complex phenomenon. The proposed co-simulation model of a pedestrian footbridge system can be used in the practical design of bridges in all situations when the dynamic response from moving people can be significant. The dynamic loading is defined more precisely in comparison with traditional methods (i.e. pedestrian load-time function analysis)

1

H. Bachman, W. Ammann, "Vibrations in Structures Induced by Man and Machines", IABSE Structural Engineering Document 3e, 1987.

2

M. Valášek, M. Víšek, T. Vampola, "Simulation of Human Gait over the Elastic Bridge", Engineering Mechanics 2007, Prague, 299-300, 2007.

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