It has been widely accepted that a stationary human body, such as a person when sitting or standing, acts as a single degree of freedom (SDOF) system in structural vibration. However, it is not clear what form the SDOF model should take and what are the appropriate parameters for the model. The significance of considering human body models in structural vibration comes from the fact that human involvement affects the dynamic behaviour of the structure when a crowd is present and that human body response is different from structural vibration. This forms the basis of this study.
This thesis presents both experimental and theoretical studies to develop human body models. It examines the characteristics of two interaction human body models, determines the parameters of the two body models in structural vibration and explores their applications.
A continuous model of a standing human body in vertical vibrations is first developed using an anthropomorphic model and two available natural frequencies obtained from shaking table tests. A standing human body is represented as a bar with seven mass segments using the anthropomorphic model and two stiffnesses of the model are identified using the two natural frequencies. The relationships between the continuous model and discrete body models are provided.
The masses, damping ratios and stiffnesses of two interaction body models are identified by curve fitting of the measured apparent mass curves from shaking table tests in published biomechanics studies. In this identification process it was identified that one or two conditions have to be applied which can be derived from the outcome of the continuous body model.
The characteristics of human-structure interaction models are investigated using both theoretical and experimental Fourier Response Functions. The comparative studies based on 10 tests help to show that the interaction body model is more appropriate than the conventional body model used in structural vibration, and identify the appropriate parameters for the interaction model. The theoretical study shows that the response of stationary people is always larger than structural vibration when human loads are applied, such as walking, jumping and bouncing. The conditions for observing two resonance frequencies are provided graphically for a human-structure system where the interaction body model is used.
A method is proposed to identify the parameters of the interaction model through 45 free vibration tests of a standing person on a test rig. The identified values of the natural frequency and damping ratio of a standing body are not close to those from the biomechanics tests. Sensitivity studies show that the two parameters are sensitive to the input data, the damped natural frequency and damping ratio of the human-structure system, which are obtained from free vibration tests.
As an extension of the application of FRF and the human-structure model, the optimum parameters of a tuned-mass-damper are obtained based on the concept of equivalent damping ratio of a SDOF structure system. The results are tabulated for practical use. An example of floor vibration induced by rhythmic crowd loads is provided to demonstrate the use of the optimum TMDs and shows the effect of vibration reduction.