Crowd size effect on floor vibration response due to random and rhythmic excitations

In order to investigate crowd size effect on building floors response, human-induced vibra-tions have been measured on a flexible composite floor exposed to various activities. Exper-imental Modal Analysis has revealed the existence of 20 mode shapes below 10Hz, with a fundamental frequency of 3.56Hz. The floor has then been exposed to various human-induced activities, covering both sedentary rhythmic activities (skipping and jumping) and ac-tivities where the individuals were moving randomly across the floor (walking and running). Accelerations have been registered at 10 different locations. By repeating these activities with a number of 1, 2, 4, 8, 16 and 32 participants, the group size effect has been evaluated through the measured accelerations. The observed trends not only differ for each activity but also slightly depart from well-accepted laws proposed by current design guidelines. A com-prehensive data analysis and discussion is provided in order to support the proposal of size-effect laws for these types of activities that will allow a more realistic vibration serviceability assessment of building floors with multiple usages.