1.College of Civil Engineering and Architecture, Hunan Institute of Science and Technology, Yueyang 414006, China; 2.College of Civil Engineering and Architecture, Hainan University, Haikou 570228, China; 3.Highway Transportation Energy Saving and Environmental Protection Technology Transportation Industry R & D Center, Anhui Transport Consulting & Design Institute Co., Ltd., Hefei 230000, China
Abstract：For the sake of investigating accurately the flutter stability performance of suspension bridges, an aerodynamic force model in which mean wind loads and self-excited forces were integrated was adopted. Based on ANSYS finite element software, time-domain flutter analysis for a long-span suspension bridge with a main-span of 1660 m was conducted, the effect of mean wind loads, geometric nonlinearity and the time step taken for the time domain calculation on the flutter and post-flutter performance of bridges were evaluated following. According to the method presented above, time-domain flutter analysis for the sectional and full-bridge model of a long-span suspension bridge were performed respectively to characterize flutter performance. Numerical results show that the mean wind effects have significant influence on flutter performance of long-span suspension bridges. Neglecting the mean lift and lift moment would overestimate greatly the critical wind speed of flutter. The mean wind drag would causes the vibration amplitude increase in the initial period of motion, but eventually attenuates to zero. The time step set in time-domain simulation must be reasonable, larger time step would result in a larger critical wind speed of flutter. Furthermore, geometric nonlinearities have an inappreciable influence on the flutter threshold, but a significant influence on the motion state of post flutter. As we all know, the linear theory of flutter reveals that bridges will experience a terrible divergence when wind speeds exceed the critical value, but a soft flutter with a smaller amplitude is the final motion state when geometric nonlinearities are involved in the flutter analysis.
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