Investigation On The Buffeting Force And Three-dimensional Aerodynamic Admittance Of A Complex Box Girder

With the development of bridge engineering in China,more and more bridge sections with complex geometric forms are used in the design of long-span bridges,such as complex box girder sections,truss beams and open-ended bridge sections,which further increases the difficulty of research on bridge wind resistance.Taking the box girder with protecting slab as an example,based on the three-dimensional buffeting analysis theory,this paper establishes the force identification method of buffeting force spatial distribution characteristics and three-dimensional aerodynamic admittance of complex bridge section,and studies the influence of key parameters on turbulent threedimensional effect through force measurement wind tunnel experiment,so as to provide technical reference for improving the wind resistance design.The specific research contents of this paper include the following points:Taking the box girder with protecting slab as an example,the three-dimensional aerodynamic admittance force identification theory suitable for complex bridge sections is proposed,and the calculation method of spatial distribution characteristics of equivalent strip buffeting force is derived.The effectiveness of this method is studied through force measurement wind tunnel experiment,and the universality of this method is pointed out.(Chapter Two and Chapter Three).The effects of turbulence integral scale,incoming wind speed,broadening ratio on three-dimensional aerodynamic admittance and buffeting force cross-correlation were studied by wind tunnel test.Based on the experimental results,an empirical coherence function model and two-dimensional aerodynamic admittance of equivalent strips is proposed,which takes into account the three-dimensional effect of turbulence.(Chapter Four).Based on the proposed coherent function model of buffeting force on box girder with protecting slab and three-dimensional aerodynamic admittance of equivalent strip,the calculation error range of buffeting response of bridge wind resistance design code and strip theory is compared by SRSS frequency domain analysis.The influence of key aerodynamic parameterson the calculation accuracy of buffeting displacement response is clarified and discussed.Finally,the application scope of traditional buffeting analysis method is discussed.(Chapter Five).