Wind Characteristics and Deck Vibration of Xihoumen Bridge during Strong Typhoon Muifa

Field measurements are usually recognized as the most reliable method for investigating wind effects on structures. A limited study has been conducted on the behavior of long-span suspension bridges during the direct attack of strong typhoons based on the in-situ measurements. Recently, a strong typhoon (2212 Muifa) made landfall in the site of Xihoumen long-span suspension bridge, which was the first time that the bridge was directly attacked by a strong typhoon after its completion in 2009. The wind and bridge deck vibrations are captured by the structural health monitoring system (SHMS) installed at the bridge. The wind characteristics in terms of mean wind speed, angle of attack (AOA), gust factor, turbulence intensity, turbulence length scale, and power spectrum were first analyzed utilizing 33 h of data. Modal characteristics are extracted from vibration signals recorded during the typhoon, and two regression analyses are conducted to explore the structural damping ratio. Theoretical buffeting responses are calculated and compared with the measured vibrations. The findings reveal significant variability in the typhoon wind parameters, with an AOA larger than that in normal wind. The gust factor and turbulence intensity initially decrease at low wind speeds (approximately 15 m/s) and remain relatively stable at higher wind speeds. Notably, no amplitude dependence of vertical natural frequencies is observed during the typhoon, while the modal damping ratio increases with mean wind speed. Although the theoretical models generally align with the measured values in trend, they underestimate torsional response and fail to account for the scatter, highlighting the limitations of these approaches.