Pedestrian lateral excitation of bridges has received considerable attention since the largevibrations of the Solférino Footbridge and the London Millennium Footbridge. Many loadingmodels have been proposed, generally assuming frequency synchronisation of pedestrians tothe bridge motion. However, some measurements from bridges and tests of pedestrians onoscillating surfaces seem to be inconsistent with this assumption. Rather they indicate selfexcitedforces at the bridge frequency, which is generally different from the walkingfrequency.

A simple model of human gait has been proposed, drawing on findings in thebiomechanics field, which is consistent with the above observations. It predicts thatpedestrians walking more slowly, such as in a denser crowd, generate larger self-excitedforces. There is, however, a need to verify this predicted feature and validate or refine otherdetails of the model.

To this end, this paper presents a new experimental campaign of the human-structureinteraction. A custom-built instrumented treadmill with a generous walking area, equippedwith a mechanism allowing for automatic adjustment of speed of the belt to that of thepedestrian, is placed on a hydraulic shaking table. A virtual reality representation of a vibrating bridge gives a realistic visual environment. Preliminary findings of the pedestrianresponse and the resulting dynamic forces on the structure are presented and related to theproposed pedestrian model and the response of bridges to crowd loading.