Life-cycle assessment for flutter probability of a long-span suspension bridge based on field monitoring data

Abstract

Assessment of structural safety status is of paramount importance for existing bridges, where accurate evaluation of flutter probability is essential for long-span bridges. In current engineering practice, at the design stage, flutter critical wind speed is usually estimated by the wind tunnel test, which is sensitive to modal frequencies and damping ratios. After construction, structural properties of existing structures will change with time due to various factors, such as structural deteriorations and periodic environments. The structural dynamic properties, such as modal frequencies and damping ratios, cannot be considered as the same values as the initial ones, and the deteriorations should be included when estimating the life-cycle flutter probability. This paper proposes an evaluation framework to assess the life-cycle flutter probability of long-span bridges considering the deteriorations of structural properties, based on field monitoring data. The Bayesian approach is employed for modal identification of a suspension bridge with the main span of 1650 m, and the field monitoring data during 2010-2015 is analyzed to determine the deterioration functions of modal frequencies and damping ratios, as well as their inter-seasonal fluctuations.According to the historical trend, the long-term structural properties can be predicted, and the probability distributions of flutter critical wind speed for each year in the long term are calculated. Consequently, the life-cycle flutter probability is estimated, based on the predicted modal frequencies and damping ratios.

Investigating the Effects of Climate Change on Material Properties and Structural Performance

“…According to Selberg (1963), the change of bridge critical flutter wind speed depends on the relative deterioration degree of the first-order vertical and torsional modal frequencies. With the example of long-span suspension bridges with steel twin-box girders, some long-term field monitoring data suggest that the decease of the firstorder vertical modal frequency due to structural deterioration is more obvious compared to that of the firstorder torsional modal frequency (Chu et al 2021). Accordingly, the intensified deterioration due to climate change may potentially enhance the flutter performance of long-span bridges.…”