Dynamic analyses of a curved cable-stayed footbridge under human induced vibrations: numerical models and experimental tests

摘要

Nowadays, pedestrian bridges are increasingly lively and slender structures due to the devel-opment of improved structural materials and aesthetic requirements. As a result of this trend, contemporary footbridges are more and more prone to human-induced vertical and lateral vibrations that can compromise the comfort serviceability conditions. The goal of this paper is to characterize the dynamic behaviour of a curved cable-stayed footbridge subjected to pedestrian loads starting from experimental tests and numerical dynamic analyses. The dynamic behaviour of the footbridge is investigated thanks to an experimental campaign per-formed by means of an advanced MEMS-based SHM system. Accelerations due to ambient vibrations are recorded and the modal parameters of the structure are identified by means of a classic identification method. Then, to investigate the dynamic response of the footbridge subjected to pedestrian actions, a wide number of experimental tests were performed with dif-ferent-sized groups of pedestrians crossing the footbridge, running, free or synchronized walking with different pacing frequencies. Then, a finite element model of the footbridge is developed and calibrated so that the numerical dynamic predictions agree with the experi-mental modal properties. Then, to simulate dynamic loading conditions due to a single pedes-trian or a crowd of people crossing the footbridge, two mathematical models are examined. In the first approach both the non-calibrated and the updated FE model are adopted to evaluate the vertical dynamic response of the footbridge when subjected to pedestrian loads. Dynamic analyses are performed by simulating the pedestrian walking through a periodic load model representing the human-induced force as a deterministic force. The second approach is based on the solution of the equation of motion via modal decomposition, considering multi-harmonic forces and experimental mode shapes and frequencies. Finally, the accelerations obtained through the mathematical approaches are compared with the experimental results.