Fragility analysis of cross-sea highway cable-stayed bridges under seismic-wind combined loading

Abstract

Cable-stayed bridges in seismic zones are inevitably exposed to strong winds and earthquakes throughout their service life. This study examines the fragility of cable-stayed bridges under the combined influence of earthquakes and wind, using the Hong Kong-Zhuhai-Macao Bridge as a case study. Utilizing the PEER database, 150 seismic motion records with Peak Ground Acceleration (PGA) ranging from 0.01 g to 1.0 g were generated, accounting for non-uniform seismic excitation. Pulsating wind speeds are simulated using the harmonic synthesis method.Design reference periods of 500 years and return periods of 10, 50, and 120 years for basic wind speeds are selected separately. Wind load time history curves are established and combined randomly with seismic motions to generate seismic-wind speed samples. Fragility curves for bridge components and systems are established through incremental dynamic analysis.The research findings indicate that in the presence of both earthquakes and wind, bridge towers and piers are primarily affected by seismic loads.The effect of wind on the amplification of cable fragility increases significantly with wind speed. However, an increase in seismic intensity reduces the impact of wind loads on cable fragility.Seismic action is the primary cause of damage to the cable-stayed bridge system in cases of low wind speeds.However, as wind speeds increase, slight and moderate damage states are primarily caused by seismic action, while extensive damage and complete destruction states are significantly influenced by both seismic and wind factors.