Modal Identification of Sutong Cable-Stayed Bridge during Typhoon Haikui Using Wavelet Transform Method

Abstract

In order to provide a realistic basis for structural damage identification and safety evaluation of long-span bridges, the modal parameters of a kilometer-scale cable-stayed bridge are identified using the wavelet transform (WT) method. Sutong cable-stayed bridge (SCB), which was excited by typhoon Haikui, was taken as the research object. Based on the structural vibration responses recorded by structural health monitoring system (SHMS) of SCB, modal parameters including the frequency and the damping ratio of the bridge were identified using the WT method. Four vertical, two torsional, and one lateral modes were selected for analysis. After comparing the analysis results with those from the related references, the whole-process variation of modal parameters of the SCB during typhoon Haikui was investigated. Furthermore, the relationship between modal parameters and wind speed was analyzed. Results show that the modal parameter identification based on the WT method is stable and reliable. The influence of wind speed on modal frequencies is small. However, its influence on modal damping ratios is remarkable and shows some of regularity. With the increase of wind speed, the first four vertical and first torsional modal damping ratios increase while the first lateral and second torsional modal damping ratios decrease.