QUANTIFICATION OF THE STRUCTURAL RESPONSE OF A STAIRCASE DAMPED BY THE PRESENCE OF PEOPLE: NUMERICAL MODEL AND EXPERIMENTAL TESTS

People acting on a structure such as a footbridge or a staircase are a source of ex-citation but can also affect the dynamic behavior of the structure they occupy. Particularly, considerable damping ratio value changes are often experienced. If this phenomenon occurs, considering the dynamic properties of the structure when empty for estimating the structural response can lead to significant overestimation of the amplitudes of vibration. In this paper this problem is faced considering the case of a lightly damped steel staircase. The structure was tested with and without the presence of people. A model, able to describe people effect on a structure, is used to predict the changes of the modal properties due to the presence of people. It is finally proposed a comparison between the amplitudes of vibration measured experimentally and those predicted starting from the model of the structure when empty and the model of the structure with people respectively. Results highlight how the cor-rectly estimated damping values leads to a significant increase in the overall in service vibra-tion level prediction accuracy.