Aerodynamic admittance of truss girder in homogenous turbulence

Abstract

An approach to directly identify truss girder's aerodynamic lift admittance by buffeting force measurement is put forward. Based on an assumption that a truss girder is equivalent to a continuous cross-section girder, three forms of aerodynamic lift admittance are deduced: complete 2-dimensional, 3-dimensional and 2-wavenumber. Span-wise lift coherence and correlation functions of the equivalent truss cross-section are derived as well. A large-span truss girder bridge is adopted as prototype to validate the approach. Numerical solutions of above-mentioned items are obtained through wind tunnel tests. The configuration of truss girder lift admittance is proved different from traditional known admittance feature. Energy transferring tendency is revealed by 2-wavenumber admittance. Complete 2-dimensional lift admittance is found possible to overestimate truss girder's buffeting response at the most concerned wavenumber range. Span-wise lift correlation and coherence of the equivalent cross-section are proved slightly lower than that of truss segment. In addition, a brief study on influence of slight varied incident angle is carried out, in which aerodynamic lift span-wise coherence is proved obviously affected at low wavenumber range.