Fast operational modal analysis of a single-tower cable-stayed bridge by a Bayesian method

Cable-stayed bridges are popular bridge designs and have been widely used all around the world. To investigate the dynamic properties of cable-stayed bridges, many structural health monitoring (SHM) systems have been implemented. The vibration-based operational modal analysis (OMA) has attracted increasing attentions in the past decades by using the ambient data obtained from the SHM system, which plays an important role in extracting the key dynamic parameters of the structure for the purpose of model updating and damage detection. This paper presents the work on operational modal analysis of a single-tower cable-stayed bridge based on the data collected from a SHM system. A fast Bayesian FFT (Fast Fourier Transform) method was used to efficiently carry out the OMA to determine the most probable values of modal parameters and the associated posterior uncertainty. The modal parameters of the bridge deck and cables were identified and investigated. The uncertainty quantification was performed to evaluate the accuracy of the modal parameters. Based on the recorded temperature data, the relationship between the modal parameters and the temperature was studied. Furthermore, a prediction model of the modal parameters was developed incorporating the information of 24-hour data to investigate the probability density function (PDF) of the natural frequency and damping ratio for both the bridge deck and cables.