Vortex-induced vibration characteristics and mechanisms of portal steel bridge tower

The steel bridge lower is one kind of tall and slender structure which is highly sensitive to wind loads and prone to vortex-induced vibration (VIV). To investigate the VIV characteristics of a 217-meter-high steel bridge tower, 1 : 100 scale free-standing aeroelastic model wind lunnel tests were conducted. The experimental results show that in-phase VIV occur in the low wind speed range, and out-of-phase VIV occur in the high wind speed range at the wind direction range of 0°-30°. The most unfavorable wind directions of in-phase and out-of-phase VIV are 0° and 10°, respectively. In-phase along-wind displacement and out-of-phase torsion angle are 609.5 mm and 4.3°, respectively. Furthermore, the VIV triggering mechanisms were studied by computational fluid dynamics (CFD). The numerical simulation results show that the frequeney of alternating vortex shedding near the two tower columns is close to the fundamental natural frequency, and the periodic pressure difference generated by this phenomenon leads to both in-phase and out-of-phase VIV. The findings and conclusions provide some reference for the wind-resistant design of similar steel bridge towers. © 2024 Chinese Vibration Engineering Society. All rights reserved.