Hydroelastic slamming of tubular structures: Experimental and theoretical studies

Abstract

Hydroelastic slamming loads are of primary importance for the design of marine and offshore structures involving slender flexible structures. In this study, a combined experimental and theoretical investigation of the water impact of tubular structures is carried out. First, a dedicated experimental campaign is conducted using a laboratory hydraulic shock machine, which provides controlled impact velocities and high repeatability. Aluminium tubular specimens are tested under horizontal and inclined impact configurations. The transient structural response is measured using strain gauges and accelerometers distributed along the tubes, allowing a detailed characterization of the dominant bending mode, maximum response and coupling effects. Based on these observations, a semi-analytical hydroelastic slamming model is then developed to predict the dynamic response of the structures. The structural behaviour is described using an Euler-Bernoulli beam formulation, while the hydrodynamic loading is evaluated through a strip approach based on Wagner-type impact theory and the Fictitious Body Continuation, accounting for flow separation effects. Fluid-structure coupling is introduced explicitly by expressing the hydrodynamic forces as functions of structural displacement, velocity, and acceleration. A modal decomposition reduces the problem to a system of ordinary differential equations, which is solved numerically. The comparison between model predictions and experimental measurements demonstrates that the semi-analytical approach captures the main features of the hydroelastic response, including oscillation period shifts associated with added mass, the existence of distinct impact response regimes, and the velocity-dependent hydrodynamic damping. The proposed framework provides a computationally efficient tool for the analysis and preliminary design of slender tubular structures subjected to hydrodynamic impact.