Identification of a load model for crowd-rhythmic activities based on acceleration measurements of a building floor

The floors of modern buildings are prone to excessive vibrations induced by human actions, especially when a group of people perform rhythmic activities in a coordinated manner. A reliable model for this load case, taking into account the experimentally observed group effect, is thus essential for the serviceability assessment of such structures. In this paper, a frequency-domain load model for either a single person or multiple individuals was established for two rhythmic activities. The model parameters were determined by an indirect identification method from acceleration responses. An extensive experimental test campaign was conducted on a steel–concrete composite floor in order to provide input data for identification, including experimental modal analysis and human-induced vibration tests for up to 32 individuals. The load parameters were first determined for the single-person load model. Root Mean Square (RMS) forces were then calculated from the identified load models, and corresponding coordination factors as a function of crowd size are suggested. A decreasing exponential was obtained for up to 8 persons for skipping and 12 persons for jumping, followed by a constant plateau for larger groups. The proposed models involve a global coordination factor to be used in conjunction with the identified model corresponding to skipping and jumping activities. A comparison of the proposed model and three existing coordination factor models against experimentally identified forces was performed. The comparison revealed the accuracy of the suggested models with respect to experimentally identified forces, whereas differences to existing factors were found especially for jumping.