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Abstract
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Asymmetric thin-walled box girders (e.g. asymmetric prestressed ducts or webs) caused by inevitable construction errors are applied in bridge engineering. Triply coupled torsional-flexural forced vibrations of thin-walled beams can be induced by moving loads, which further endangers structural or driving safety. However, no such work on analytical methods for triply coupled torsional-flexural dynamic responses of asymmetric beams is reported. Thus, this study develops analytical solutions for triply coupled torsional-flexural vibration response of an asymmetric thin-walled beam under concentrated moving loads. Considering the effects of rotary inertia and warping resistance, the triply coupled dynamic governing equations of an asymmetric thin-walled beam under concentrated moving loads are firstly derived. The equations are then decoupled and resolved using mode superposition method and Laplace integral transformation. The analytical vibration response expressions in vertical, lateral and torsional directions are obtained from this approach, and the resonance conditions are further explored. The results conclude that the vertical, lateral and torsional responses will be simultaneously set in resonance if the parameter related to velocity Ωcn approaches the natural frequency ωni. Subsequently, a novel numerical approach which combines the Galerkin approach and precise integration method is employed to verify the validity of the above analytical solutions. An extensive parametric study is performed. As per the results, the maximum midspan lateral displacements at the load velocity of 120 m/s and 90 m/s are about 25.0% and 43.2% higher than those at the load velocity of 30 m/s or 60 m/s, respectively.
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