Study On The Spatial Correlation Of Buffeting Forces And Areodynamic Admittance Function Of Steel Truss Girder

The research progress of wind resistance of long-span bridges were reviewed and the research of buffeting correlation for long-span bridges, especially for those with truss girders, were summarized in this dissertation. Then the spanwise correlation of aerodynamic force and the aerodynamic admittance of the truss girder are indicated as a important research orientation of the truss girder buffeting refinement study. The aerodynamic forces of truss girder sectional models with two scale ratios under two turbulence integral scales were obtained by wind tunnel tests. Based on the aerodynamic forces obtained from sectional model, the spanwise correlation of aerodynamic force and the aerodynamic admittance of the truss girder is investigated indetail. The main contents of this dissertation are as follows:1. The wind resistance research development of long span bridges, especially the current situation and problems of buffeting analysis of the truss girder, is reviewed and the essentiality and research field of the paper are put forwarded in accordance with the peculiarity of the truss girder cross section.2. Two kinds of turbulence field under different turbulence integral scales were simulated and the characteristics of the two turbulence fields were analyzed.3. A measuring system for truss girder buffeting forces has been invented. The spanwise variation of the buffeting forces acting on a truss girder cross section regarding two scale ratios have been studied by adopting two high frequency dynamic balances simultaneously and statistical characteristics of buffeting forces are indentified.4. Spanwise correlation of buffeting forces of the truss girders has been calculated based on the time history of each section girder model. The testing data demonstrate that the correlation of buffeting forces is larger than that of incoming wind fluctuations and therefore expressing buffeting forces correlation in terms of wind fluctuations correlation in conventional buffeting analysis will lead to unsafe results.5. Three-dimensional aerodynamic admittance of the truss girders has been indentified. Based on the spanwise correlation of aerodynamic force of the truss girders, the two wave number aerodynamic admittance of the truss girders has been obtained.6. Aerodynamic admittance functions of the two different truss girder sectional models in two different turbulence fields are identified in combination of the concept of equivalent aerodynamic admittance for truss girder section. The empirical equivalent aerodynamic admittance formulas for truss girders with model feature sizes are summarized and the difference between aerodynamic admittance functions and Sears function is compared.7. The buffeting frequency domain of the truss girder bridge is calculated through the coherence function of the buffeting forces along the truss girder and the aerodynamic admittance functions meanwhile the influence of aerodynamic admittance and correlation functions on the buffeting responses is analyzed.