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Stress-level buffeting analysis is necessary for evaluating stress-related performance and safety of long-span bridges. A stress-level buffeting analysis requires knowledge of characteristics of distributed aerodynamic pressures on a bridge deck. This paper, therefore, presents a framework for modelling distributed aerodynamic pressures on the surfaces of a bridge deck in terms of the proper orthogonal decomposition (POD) method. The characteristics of aerodynamic pressure modes, such as covariance modes, principal coordinates, pressure modal coefficients, and pressure modal admittance functions are introduced in the formulation. Wind tunnel pressure tests of a sectional motionless deck model were conducted to identify the characteristics of distributed aerodynamic pressures on a twin-box bridge deck as a case study. The pressure modal admittance functions were identified by using a colligated least-square method. The results show that the higher-order POD pressure modes provide a very limited contribution to the aerodynamic pressures and can be truncated without notable loss of accuracy. The aerodynamic pressures distributed over the bridge deck surface can be well represented by a superposition of a limited number of POD pressure modes that include the first two pressure modes. The use of pressure modal admittance functions greatly simplifies the identification of many individual aerodynamic pressure admittance functions. [ABSTRACT FROM AUTHOR]

Abstract: To assess the safety of road vehicles running over a long span bridge in high wind, the knowledge of aerodynamic forces and moments on the vehicles is required. This could be obtained through wind tunnel investigations and expressed in terms of aerodynamic coefficients. However, very few investigations have been carried out to find aerodynamic coefficients of road vehicles on a bridge deck, compared with the aerodynamic coefficients of road vehicles on the ground. This paper therefore presents the results of wind tunnel tests carried out to determine aerodynamic coefficients of four types of road vehicles over a typical bridge deck. The aerodynamic coefficients of the same road vehicles on the ground are also presented to explore the effects of the bridge deck on aerodynamic coefficients. Different wind directions are taken into consideration to observe variations of aerodynamic coefficients with wind direction. Furthermore, the effects of vehicle position in different road lanes of the bridge deck are investigated. The test results show that the existence of bridge deck reduces side forces for all four types of vehicles remarkably but increases rolling moments to some extent. Such effects also vary with types of vehicles and lanes of the bridge deck where vehicles run. [Copyright &y& Elsevier]

To extend the knowledge of aerodynamic and aeroelastic behaviour of long-span bridges and to acquire an accurate wind-induced stress distribution of the bridge deck for fatigue analysis, the modelling of distributed aerodynamic and aeroelastic pressures on the bridge deck is imperative. A modelling method based on proper orthogonal decomposition (POD) is therefore proposed in this paper. The characteristic parameters of POD pressure modes, such as covariance modes, principal coordinates, pressure modal coefficients, pressure modal admittance functions and pressure modal derivatives are introduced. Indicial function-based parameter identification method is developed to identify pressure modal derivatives and admittances. Wind tunnel pressure tests were conducted on a spring-suspended sectional twin-box deck model of the Stonecutters cable-stayed bridge. With the pressure modal coefficients, covariance modes, and principal coordinates calculated from the measured distributed pressures, the pressure modal derivatives were identified. Thereupon, the aerodynamic and aeroelastic components of the pressure modes were separated, and the pressure modal admittance functions were then identified with the isolated aerodynamic components. The results show that the aerodynamic and aeroelastic components of wind-induced pressures can be separated successfully and the distributed pressures on the deck can be well reconstructed with a limited number of POD pressure modes. [ABSTRACT FROM AUTHOR]