A unified state-space model of aerodynamic forces on bridge decks

In bridge aerodynamics, motion-induced and buffeting forces are traditionally modeled in the frequency domain, which inherently fails to capture non-stationary effects such as downbursts or localized storms. This thesis presents a comprehensive State-Space Model (SSM) that generalizes time-domain aeroelastic formulations. Motion-induced forces are described by a system of differential equations based on the Wagner function, where deviations from steady-state values are modeled as time-evolving state variables, allowing for direct calibration via flutter derivatives. A significant contribution of this work is the extension of this framework to buffeting forces by integrating the Küssner and Sears functions. We propose a unified approach through the concept of an effective velocity, generated by passing the incident wind input through an additional state-space module. The framework is validated across various geometries and wind conditions, showing good performance in reproducing both steady and unsteady aerodynamic responses. Furthermore, an investigation into non-linear behavior under large-amplitude harmonic motions reveals the accuracy limits of the linear framework compared to high-fidelity CFD simulations. Despite these limitations, the proposed model provides a big computational advantage, operating in a short time, thereby offering an efficient, physically-based tool for the preliminary design and aeroelastic analysis of bridge decks under extreme wind conditions.