Experimental and Numerical Studies of the People Effects on a Structure Modal Parameters Topics on the Dynamics of Civil Structures, Volume 1

In this paper the problem of human structure interaction is faced considering the case of a lightly damped steel staircase. People are a source of excitation forces and an added mass for structures but not only. It is well known human presence affects damping properties too. The aspect authors are interested in is the dependency of structure modal parameters on people presence, just due to the abovementioned aspect. Experimental measurements on a steel stair walkway, which is a lowly damped civil structure, have shown that heavy damping ratio value changes are experienced due to the presence of people. Particularly, the higher people number is, the higher the damping ratio associated to the very first modes increases. This aspect has been then studied by developing a numerical model, partly based on modal approach, able to describe people effect on this structure. Such a model is intended to show how the structure first eigenfrequencies and non-dimensional damping ratios are changed by people presence. The model describes people as mass-damper-spring systems. A model validation is provided by comparing its results to the experimental data collected thanks to the stair tests. Then such a model is exploited to fully investigate people influence on lowly damped structures