A novel experimental setup for the identification of human actions on laterally oscillating structures

Pedestrian lateral excitation of bridges has received considerable attention since the large vibrations of the Solférino Footbridge and the London Millennium Footbridge. Many loading models have been proposed, generally assuming frequency synchronisation of pedestrians to the bridge motion. However, some measurements from bridges and tests of pedestrians on oscillating surfaces seem to be inconsistent with this assumption. Rather they indicate self - excited forces at the bridge frequency, which is generally different from the walking frequency. A simple model of human gait has been proposed, drawing on findings in the biomechanics field, which is consistent with the above observations. It predicts that pedestrians walking more slowly, such as in a denser crow d, generate larger self - excited forces. There is, however, a need to verify this predicted feature and validate or refine other details of the model. To this end, this paper presents a new experimental campaign of the human - structure interaction. A custom - built instrumented treadmill with a generous walking area, equipped with a mechanism allowing for automatic adjustment of speed of the belt to that of the pedestrian, is placed on a hydraulic shaking table. A virtual reality representation of a vibrating b ridge gives a realistic visual environment. Preliminary findings of the pedestrian response and the resulting dynamic forces on the structure are presented and related to the proposed pedestrian model and the response of bridges to crowd loading.