Hydroelastic Analysis and Response of Damaged Beam-Type VLFS

Very large floating structures (VLFS) are considered to be an appealing economic and sustainable solution to create additional lands in the sea, which has been realized in a wide range of engineering applications, including floating breakwaters, floating barges, floating piers, floating bridges, etc. As for the in-service VLFS, damage may occur due to the long-term wave action and seawater erosion, leading to performance degradation and potential safety risks. This paper is concerned with the hydroelastic response of VLFS in various damage conditions for the life-cycle consideration. The linear potential wave theory and the Euler–Bernoulli beam theory are used to model the fluid and the floating structure, while the rotational spring method is adopted to simulate the damage. The hybrid finite element method (FEM)-boundary element method (BEM) code is developed to analyze the hydroelastic response of damaged VLFS, and the applicability is verified by comparing with results in the existing literature. Parametric studies on a significant number of numerical cases are further presented to systematically evaluate the effects of structure parameters, fluid parameters and damage parameters on the wave-induced dynamic responses of damaged beam-type VLFS. The numerical results indicate that a remarkable increase occurs in the hydroelastic displacement response of the floating beam as the damage index ranges from 0.5 to 1 and the displacement increment is over 30% at the damage location. When the flexure stiffness increases from 0.5[Formula: see text] to [Formula: see text], the maximum hydroelastic displacement magnitude can be reduced by 50% for fully damaged free-free floating beam, in particular. When the wavelength-to-beam-length ratio is over 0.6, the maximum displacement magnitudes at the damage location of the fully damaged free-free floating beam are 30% higher than values in other wavelength cases, while the maximum moment responses can be 50% lower. A trade-off needs to be considered between structural motions and internal loads in the conceptual design of a beam-type VLFS. The damage number and the distribution of damages significantly affect the hydroelastic response curve shape and also the peak value magnitude. The maximum normalized displacement response at the damage location of [Formula: see text] may reach 1.4 in the fully damaged pin-free floating beam, which is much larger than the value in the base case of damage located at the middle point. The existence of damage is prone to mitigating hydroelastic displacements of other locations of interest inside the floating beam, but will increase the bending moment taken by undamaged beam segments, which should be handled with caution in the design procedure. The findings presented in this study provide useful references for the life-cycle operation and maintenance of in-service VLFS.