Flutter analysis of a long-span triple-tower suspension bridge under typhoon winds with non-uniform spanwise profile

Flutter is a significant concern in the safe design of long-span bridges, and its evaluation traditionally assumes a uniform wind field along the span. However, in the horizontal plane of a typhoon, the tangential wind speed exhibits non-uniformity as one moves further away from the typhoon's eye. Therefore, the assumption of a uniform wind field is not applicable to this specific wind hazard. To gain better insights into the flutter instability of long-span bridges, it is crucial to evaluate the structural flutter performance in a more realistic and non-uniform typhoon field. This paper presents a comprehensive flutter analysis of a long-span triple-tower suspension bridge (TTSB) under typhoon winds. In the parametric analysis, the effect of the radius of the typhoon eye and the relative position between the bridge and the typhoon is considered. Three typical bridge sections are employed for flutter analyses with a comparison to reveal the effect of aerodynamic shapes. The analytical results indicate that the flutter of a TTSB may potentially occur when the wind speed at limited sections of the span in non-uniform typhoon winds exceeds the critical wind speed observed under uniform wind conditions. This phenomenon is particularly significant when the bridge is situated within the typhoon eye and in close proximity to the eyewall. The spanwise variation rates of wind speed for comparable sections are approximately identical, which leads to an expedient determination of the spanwise distribution of non-uniform wind speeds for different sections in the preliminary design of bridge decks once the critical wind speed of the bridge under uniform winds is known. This could facilitate the development of more robust wind-resistant designs for TTSBs in regions prone to typhoons.