33. SMD Model Parameters of Pedestrians for Vertical Human-Structure Interaction

Predictions of footbridge or long-span floor vibrations induced by pedestrian crowds can often prove inaccurate. One of the main deficiencies of the methods used for predicting these vibrations is the lack of consideration or erroneous representation of human-structure interaction (HSI). In this paper, the results from a series of footbridge tests designed to observe and then model HSI are presented. A laboratory footbridge was excited to three predetermined vibration amplitudes by an actuator, with and without the presence of pedestrians. In the tests with pedestrians, 4, 7 and 10 pedestrians were asked to walk repeatedly across the footbridge. Frequency response functions (FRF) of the footbridge with and without pedestrians were extracted from test data. To account for the HSI, pedestrians on the bridge were modeled as a spring-mass-damper (SMD) system attached to the footbridge. The mass, damping and stiffness of a single pedestrian were calculated by fitting the FRF obtained from the tests. It was found that the SMD models of pedestrians could adequately model HSI between a structure and its walking occupants. Furthermore, the stiffness and damping of the SMD model of a single pedestrian were found to be close to half of a standing person with two bent legs.