So many human damages have been reported during past earthquake. Some of them got injured due to falling and crashing to furniture. Critical structures such as chemical plants and nuclear power plants, it is required to take countermeasures after accidents to prevent harmful substance leakage in the event of a severe accident caused by an earthquake. However, if the workers are injured during earthquake, the retrieval activities might become difficult for the workers. In addition, in order to predict the indoor human damage due to huge earthquake such as the Nankai Trough earthquake, it is important to grasp the behavior of human during an earthquake. To predict injuries resulting from human falling and crashing to furniture due to earthquake shaking, it is necessary to evaluate the seismic response of the human body.
From the view point of the above background, in order to construct a seismic response analytical model of a human body, we conducted shaking table tests with human subject. The seismic response characteristics of the human body during shaking were investigated. The behavior of human subject during excitation was observed by 3-D motion capture system. The center of pressure (CoP) on the floor of the human subject was measured by a force plate during the excitation. Then, the mechanisms of postural control of the human subject were investigated. The human subject controlled his posture by moving the CoP to place the center of gravity (CoG) within the base of support (BoS). When CoG deviates from BoS, the human subject controlled his posture by widening BoS through the stepping strategy.
Next, the seismic response analytical model in the forward-backward direction (sagittal plane direction) of a human was constructed based on the cart-type single-link inverted pendulum model with state feedback controller. The displacement of CoP, CoG, velocity of CoG and head could be evaluated by the model. The frequency response function of human subject during excitation in the experiment and that of the analytical model were compared in order to set the appropriate feedback gain of the controller. The displacement of CoP, CoG, velocity of CoG and head evaluated by the analytical model showed good agreement with those of the experimental results.
Finally, the validity of the model was verified by the simulation analysis with other input motion. The maximum displacement of CoP and CoG could be well reproduced. On the other hand, the velocity of CoG was slightly overestimated compared to the experimental result, and the velocity of the head was slightly underestimated compared with the experimental result. Improvement of accuracy of the seismic response model (e.g. modeling with double inverted pendulum or using other control methods, etc.) is a future task.
