Identification and Application of the Aerodynamic Admittance Functions of a Double-Deck Truss Girder

Abstract

This paper presents the aerodynamic admittance functions (AAFs) of a double-deck truss girder (DDTG) under turbulent flows. The objective of the investigation is to identify AAFs using a segment model wind tunnel test. All of the wind tunnel tests were based on the force measurement method and conducted in a passive spire-generated turbulent flow. The segment model adopts a typical DDTG section and is tested in the service and construction stages under 0°, 3°, and 5° wind attack angles. Furthermore, a nonlinear expression is put forward to fit the identified AAFs. The buffeting responses of a long-span road-rail cable-stayed bridge are then calculated for both the service and construction stages using an equivalent ‘fish-bone’ finite element model of the DDTG. The unsteady effect of the buffeting force is considered based on quasi-steady buffeting theory using the identified AAFs. The calculated buffeting responses are finally compared with those for two other AAFs (AAF = 1.0 and the Sears function). The results indicate that the traditional AAFs overestimate vibrations in the vertical and torsional directions but underestimate vibrations in the lateral direction. The identified AAFs of the DDTG can be regarded as a reference for wind-resistant designs with similar girder sections.