Abstract: The arm structures of certain radial gates in operation have experienced dynamic instabilities (parametric resonances) under flow-induced periodic loads, leading to considerable structural damage. At present, the mechanism of parametric resonance in radial gates is not fully understood yet, and few practical methods of structural dynamics analysis are applicable to real engineering projects. Many of the previous studies on the dynamic stability simplified the arm structure as a single-span beam, neglecting the dynamic behavior of the whole structure. The computational models often deviated from actual conditions significantly. This paper presents a finite element model of the entire radial gate structure and an in-plane parametric vibration equation. Then, we evaluate the dynamic stability of structural parametric resonance by integrating the Newmark method with the energy growth exponent. Numerical examples demonstrate that in the case of its excitation parameters falling within the instability region, the structure undergoes parametric resonance characterized by an exponential growth in structural amplitude. Hydrostatic loads reduce its overall stiffness, leading to a shift of the instability boundary toward lower frequencies. And, an increase in structural damping results in a smaller instability region. We have conducted an experiment to test a radial gate model and observed its parametric resonance. The measured instability boundary shows good agreement with the numerical prediction, confirming the accuracy and applicability of our method. This study achieves a practical novel method for numerical simulations of radial gates and their dynamic stability assessment.

Key words: radial gate, arm structure, flow-induced periodic load, parametric resonance, stability analysis, experimental study