Statistical characteristics of modal damping of long-span suspension bridge at different wind speeds

Abstract

The present paper combined the natural environment excitation technology (NExT) with the eigen system realization algorithm (ERA) to identify the modal parameters of a suspension bridge. Firstly, the critical parameters in NExt–ERA, such as record length, window length, and ranks of the Hankel matrix, and their influence on identification accuracy have been discussed. Subsequently, based on the acceleration series obtained from the Xihoumen Bridge Health Monitoring System, 3015 sets of modal frequencies and modal damping ratios of the Xihoumen Bridge were identified under 7 sets of wind speeds by the NExt–ERA. Finally, the probability distribution and confidence interval of the structural modal damping ratios were analyzed. Besides, the dependence of identified frequencies damping ratios on wind speed was also discussed. The results show that at the same wind speed, the mean value, and variance of the torsional and lateral mode damping ratios are larger than those of the vertical mode, but this difference gradually decreases with the increment of wind speed. The modal damping ratios along three directions under different wind speeds all follow the generalized extreme value distribution, but wind speed affects the tailing properties of probability distribution of the vertical and torsional mode damping ratios. The estimated damping ratios could provide references for structural design and vibration control of similar long-span bridges.

In Situ Testing and FEM Analysis of Dynamic Characteristics of a Masonry Pagoda under Natural Excitation

“…Abdelbarr, MH et al [14] utilized the NExT-ERA method to identify modal characteristics of ultra-high-rise office buildings, verified the accuracy of the sub-structure method proposed in the nonparametric identification method outlined in their paper, and facilitated the practical application of the method to structural health inspections of ultra-high-rise office buildings. Guo Zengwei et al [15] extracted modal characteristics of suspension bridges using the NExT-ERA method, examined key parameters in NExT-ERA, and explored the relationship between the identification frequency damping ratio and wind speed based on data from the health inspection system. However, most existing research focuses on identifying parameters of dynamic characteristics in large-scale geotechnical buildings, with less attention given to the dynamic characteristics of ancient buildings.…”