Schemes for Improving Flutter Performance of Suspension Bridges during Deck Erection under Normal and Skew Winds

Abstract

To ensure the flutter stability of long-span suspension bridges during deck erection under normal and skew winds, by taking the Runyang suspension bridge as example, the evolution of flutter stability of the bridge under normal and skew winds during the symmetric deck erection from the midspan to towers is investigated numerically by the computational procedure of three-dimensional refined flutter analysis of long-span bridges under skew wind, and the erection stages with weak flutter stability are pointed out. To improve the flutter stability of suspension bridges during deck erection under normal and skew winds, two schemes of symmetric towers-to-midspan erection and nonsymmetric erection scheme from middle part to the towers are investigated numerically, and the favorable deck erection schemes of suspension bridges are obtained. The results show that the flutter stability of suspension bridges during erection is significantly reduced by the skew wind effect; when the deck is erected as the symmetric midspan-to-towers scheme, both the early period (the erection ratio is below 20%) and the middle-later period (the erection ratio is between 40% and 80%) have weak flutter stability; following the symmetric towers-to-midspan erection scheme, the flutter stability at the early stages is significantly improved, and basically the whole erection period has good flutter stability, and the flutter critical wind speed has an overall average increase of 34.2% as compared with the symmetric midspan-to-towers erection scheme; in the case of nonsymmetric erection from middle part to towers, the flutter critical wind speed does not increase monotonically with the eccentricity, showing a trend of increasing first and then decreasing, and reaches the peak at the eccentricity of 8.6%. Under the optimal eccentricity, the flutter stability throughout the erection process is significantly improved compared with the symmetric erection scheme, and the overall average increase is 14.5%; from the viewpoint of flutter stability, the symmetric towers-to-midspan erection scheme is the best, followed by the nonsymmetric erection scheme from middle part to towers, and the traditional symmetric midspan-to-towers erection scheme is the worst.