Vibration-based sensitivity analysis of a flexible steel footbridge using probabilistic walking models

Many civil engineering structures are concerned with the loads induced by human activity. Human live load modeling of walking and running is very relevant to provide comfort and acceptable structural conditions. The dynamic portion of human loads is often inaccurately modeled or neglected, leading to conservative designs or excessive vibrations. The classical model to consider walking load consists of a dynamic Force Model that considers unique walking parameters along the analysis, related to each pedestrian. Biodynamic models are an alternative to consider the Human-Structure Interaction in the analysis, but also do not vary accordingly to the human activities performed during walking. Human pacing varies continuously during walking, governed by intra- and inter-subject variabilities, giving rise to the possibility of probabilistic modeling of human walking parameters, as already proposed in the literature. In this regard, the article proposes an alternative method by using a Random Walk algorithm to incorporate walking intra-subject variability into the Force or Biodynamic models pacing frequencies. The Random Walk approach shows that walking variability can influence the final service assessment of structures and realistically represent human walking scenarios. It is aimed to discuss the RW parameters' role and its implications on human walking modeling and vibration performance analyses to improve standardized vibration classification by simulating the walking randomness. A sensitivity analysis is performed to define proper probabilistic distributions and the range of values to be used in the random walk algorithm. A study is also conducted with a vibration performance assessment in idealized footbridges with probabilistic walking force and biodynamic models.