Reduced order models (ROMs) are computationally efficient techniques, which have been used for predicting unsteady aerodynamic response of airfoils and wings. However, they have not been applied extensively to perform unsteady fluid dynamic analysis of flexible civil engineering structures such as super long-span bridges and wind turbines. This dissertation studies the application of reduced order computational fluid dynamics (CFD) model based on the eigensystem realization algorithm (ERA) in the aerodynamic and aeroelastic analysis of several well-studied super long-span bridges. The aerodynamic impulse responses of the GBB, Stonecutters and Messina Strait Bridge are used to construct the aerodynamic ROMs, and then the aerodynamic forces due to arbitrary inputs are evaluated and compared to those of the model coupled with an advanced Discrete Vortex Method based CFD code. To construct aeroelastic ROM, the aerodynamic ROM is coupled with single and two DOF models of bridge, which predicts results of aeroelastic analysis of elastically suspended sections. Moreover, indicial functions and flutter derivatives of the case studies are derived based on time history of aerodynamic coefficients and compared to those predicted by the proposed ROM method. The memory requirement and CPU time for ROMs are significantly lower than the original CFD program. Also, the ROM results demonstrate reasonable prediction power and high computational efficiency of the technique that can serve for preliminary design, optimization and control purposes. The methodology described in this dissertation has wide applications not only in super long-span bridges in civil engineering but also in many engineering problems where flexible structures interact with unsteady fluid mechanical phenomena.
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