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This paper contributes to the research of rhythmic behavior of a group of people, which, more or less synchronized, moves or jumps on a thin and elastic plate, thus performing a dynamically variable load. The analysis of the rhythmic behaviour of the crowd carried out on the basis of the experimental testing on the special steel test platform. The experiment consisted of sixteen measurements of live force and acceleration of the test platform. The dynamic loads caused by the mass of the human crowd and individuals had different intensities. The measurements of acceleration of the test platform were performed in order to estimate how the live human force influences on vibrations of machine structures. This research allows us to gain a picture of how serious the threats are from some human actions on the support structure of machines that are handled when performing works in industry, construction or mining. On the basis of these experiments, the mathematical models of the equivalent excitation forces were developed. The measured accelerations of the test platform tread surface and calculated dynamic coefficients of human force indicate that similar actions can seriously endanger balance of the support structure of some machine, and even, for example, can cause the main girder of the bridge crane to fall out. This and similar experiments allow us to formulate appropriate models of excitation loads by human force, which can then be used in simulation analyses in order to develop future systems of electronic protection of machines structures from adverse events.

Grandstands are structures which are regularly subjected to dynamic loads generated by crowd motions. It is a dangerous situation when spectators induce rhythmic jumping, dancing, stamping, etc. If the synchronized movement of spectators excites a natural frequency of the structure, resonant response might occur. To avoid such situations, temporary steel grandstands are commonly strengthened using additional elements that create bracing system which is selected depending on the size of the structure, type of the event, acting load, etc. It was proved that not only the use but also the arrangement of such structural members is crucial for the dynamic structural resistance. The aim of the present study is to determine the most effective arrangement of bracing system for a typical example of the temporary steel grandstand which is exposed to dynamic load induced by spectators. Three different arrangements of bracing systems have been analysed using five criteria recommended in the literature. The results of the study clearly show that the dynamic parameters of the grandstand are substantially different for various types of bracing systems. The largest improvement in the structural behaviour has been obtained for the grandstand equipped with the bracing system satisfying all proposed criteria. The peak accelerations for this case have been found to be nearly twice as low as for structures with other bracing arrangements. The application of such a system for the grandstand which is exposed to human-induced vibrations allows for safe use of the structure as well as improves comfort of spectators.

The study of the probabilistic response of pedestrian-excited structures as well as their reliability analysis need to take into account the influence of a large number of uncertain parameters ascribed to structural characteristics, single pedestrian walking features and pedestrian traffic phenomena. Although pedestrian traffic is characterized by an intrinsic high variability and plays a key role in determining the pedestrian load, its probabilistic description remains scarce in literature. The present work aims at contributing to the probabilistic evaluation of the pedestrian traffic across footbridges. First, a categorized state of the art focused on sources of uncertainty is provided. Second, a new modeling framework for the probabilistic evaluation of pedestrian traffic is introduced in general and conceptual terms. The framework is conceived in analogy to the approach developed in another engineering field, i.e. wind engineering, on the basis of the phenomenological features of the pedestrian traffic. In order to put the framework in practice, each of its main modeling components is specified. We introduce a statistic approach to evaluate the incoming traffic and a microscopic traffic model to simulate the propagation along the footbridge of the uncertain pedestrian entrance. In order to prove its technical feasibility, the proposed framework is finally applied to an ensemble of real world crowd events and to two ideal footbridges with differently shaped walkway. As a final result, the pedestrian density along the footbridge is described as a random field in terms of its joint and unconditioned probability density functions and correlation lengths.