Probabilistic Approach to Assess the Vibration Serviceability of Steel-concrete Composite Footbridges

Nowadays, the structural engineers experience and knowledge allied by the use newly developed materials and technologies have produced pedestrian footbridges with daring architectural concepts, which makes these structures more slender and therefore more susceptible to vibration problems. This fact has changed the serviceability and the ultimate limit states that are associated with the design. Considering all aforementioned aspects, the main objective of this investigation is to present an analysis methodology to modelling the human walking considering the random nature of the dynamic load induced by different pedestrians. This uncertainty is related to the variation of the pedestrian weight, the step frequency, the step length and the dynamic load factors (DLF). The probabilistic approach allows the structural engineers to assess the variation of the human walking force generated by different pedestrians and their impact on the dynamic response of the footbridges. The proposed probabilistic human walking load modelling is applied to calculate the dynamic response of steel-concrete composite footbridges, based on different dynamic load scenarios. Based on an extensive parametric study, the design response spectra of the investigated composite footbridges, which was expressed in terms of the peak accelerations, was drawn and compared to the human comfort criteria that were proposed by several authors and design codes. This probabilistic approach provided a more realistic assessment of the footbridges vibration problems when induced by pedestrian walking.