Probabilistic criteria for lateral dynamic stability of bridges under crowd loading

• Inverted pendulum model is studied for pedestrian-induced lateral structural vibrations.
• Real statistical data is used to obtain the model parameters.
• Statistical measures of self-excited forces are found for different crowd velocities.
• Probabilistic stability criteria for lateral dynamic stability are defined.
• Number of pedestrians and their distribution are acknowledged.

Probabilistic conditions for lateral stability of bridges are proposed, based on output from the inverted pendulum pedestrian model from the field of biomechanics. Statistical variations of the parameters defining the model are studied based on real statistical data of the English population. Variability of the self-excited forces is quantified for crowds of different velocities and critical conditions are identified for bridge natural frequencies below 5 Hz. Allowance is made for the influence of the bridge mode shape and number of pedestrians in the crowd and their spatial distribution. This allows realistic worst case conditions among different loading scenarios for a particular structure to be found.