Probabilistic Criteria for Assessment of Aerodynamic Instability of Long-Span Bridges

Based on the authors’ proposed reliability analysis model to bridge flutter under extreme winds, the objective of this paper is to make the probabilistic reassessment and calibration for flutter instability of several long-span bridges in China and to propose probabilistic criteria for assessment of aerodynamic instability of long-span bridges. The annual maximum wind speed at the bridge site is assumed to follow Gumbel distribution, and is directly calculated by the basic wind velocity provided in Chinese design code. The critical wind speed due to bridge flutter is experimentally determined by wind tunnel tests using an aeroelastic full model and is approximately treated as a lognormal distributed variable. The extended design point approach based on the first order reliability method has been used in calculating the failure probability of ten cable-supported bridges. The probabilistic criteria of the investigated bridges due to aerodynamic flutter are quite different among these ten long-span bridges, and can be broadly classified into three grades in accordance with the magnitudes of their failure probabilities, including very safe withPFat the order smaller than 10-6, quite safe withPFat the order from 10-4 to 10-6 and just safe withPFat the order of 10-3.