POD-based spanwise correlation analysis of aerodynamic and aeroelastic pressures on twin-box bridge decks

The conventional spanwise correlation analysis based on buffeting-induced forces is not quite suitable for stress and fatigue analysis of a long-span cable-supported bridge, especially with a twin-box deck made of orthotropic steel plates. This study thus investigates the spanwise correlation of wind-induced pressures over the surface of a twin-box bridge deck in terms of the pressure modes calculated by using the proper orthogonal decomposition (POD) method. Each POD pressure mode obtained is likely to be associated with a particular excitation mechanism, aeroelastic (self-excited) pressure component due to motion or aerodynamic (buffeting) pressure component due to both incident and signature turbulence. Since the spanwise correlation of each pressure component can be quite different from others, the indicial functions are introduced to separate the aeroelastic component from the aerodynamic component. The empirical mode decomposition (EMD) method is applied to the aerodynamic component to further separate the incident turbulence-induced component from the signature turbulence-induced counterpart. The spanwise correlation coefficient and root coherence of each pressure component are investigated by using the pressure data measured from wind tunnel tests on a spring-suspended sectional twin-box deck model. The results show that the spanwise correlation coefficients of the aeroelastic pressures are close to 1. The root coherences of the signature turbulence-induced pressures show completely different characteristics from the incident turbulence-induced pressures. Therefore, a new coherence fitting scheme for signature turbulence-induced pressures is proposed based on the empirical functions for incident turbulence component. With this framework for the POD-based spanwise correlation analysis, the root coherence of each component pressures can be obtained, and the root coherence of the pressures at any two points on the surface of the twin-box deck can be reconstructed.