Study On Aerostatic Stability Of Long-span Suspension Bridges

With the span of the bridge is become longer and longer,the static and dynamic problems of the bridge structure induced by wind are more and more serious. According to the results of the wind tunnel model tests domestic and abroad, the critical wind speed of the aerostatic stability of long-span bridges may be less than that of the aerodynamic stability. In addition, the effects of geometric nonlinearity and the aerostatic load nonlinearity of long-span bridges under strong wind load shouldn't be neglected. The problems of the aerostatic stability of long-span and super long-span suspension bridges are also crux. The research on the aerostatic stability of the long-span suspension bridges is developed in this dissertation based on Sidu River Suspension Bridge in the west of national highway from Shanghai to Chengdu. The main contents and achievements are as following:1 .The linear method used to calculate the critical wind speed of aerostatic stability by national guideline is expatiated and the formula used to calculate the critical wind speed of torsional divergence is briefly deduced. The methds used to analyze the dynamic performances are described and the dynamic performances of Sidu River Suspension Bridge are analyzed with the finite-element method. Finally, the critical wind speed of aerostatic stability of Sidu River Suspension Bridge is calcaulated with the linear method;2.The first and the second question of the structural spacial stability theory are simply introduced,and then the nonlinear aerostatic stability theory and its realizing methods are illustrated.Finally,the analysis methods of aerostatic stability based on the MIDAS FEM software is expatiated;3.The critical wind speed of torsional divergence is calculated and linea and nonline methds is compared. The linea methd may be overvalued the aerostatic stability of suspension bridge. Elastic buckling analysis results,which is the maximum can be treat as the limits of the nonlinear buckling analysis results;4.The whole procession of aerostatic instability of suspension bridge is analyzed and thus the critical wind speed of the aerostatic stability is obtained. The effects of the wind load of main cable or the tower on the aerostatic stability is studied and found that the influences of the wind load of main cable or the tower on the aerostatic stability of long-span suspension bridge is not allowed to ignore;5.The aerostatic stability of Sidu River Suspension of different initial attack angles is anylized with the linea and the nonline methd;6.The effects of the wind spatial non-uniformity on the aerostatic stability of long-span suspension bridge is researched. The wind spatial distribution width and the asymmetric parameter has a very big effection on the aerostatic stability.