Sustainable Marine Structures

This study presents a fuzzy finite difference framework for the wave-induced lateral vibration of a fixed offshore platform idealized as an equivalent cantilever. The motivation is that key inputs in offshore response analysis, including hydrodynamic coefficients, structural stiffness, wave height, and damping, are often bounded but not known precisely enough to support a fully probabilistic description. The governing Euler-Bernoulli vibration model is driven by a linearized Morison-type load, and the uncertain quantities , and are represented by triangular fuzzy numbers. Alpha-cut decomposition reduces the fuzzy problem to one with an equivalent family of deterministic corner problems, and an implicit finite difference scheme is used to solve each corner problem. The mesh-converged deterministic first-mode frequency of the representative benchmark is 0.134 Hz, and its time-asymptotic top-displacement amplitude is 37.22 mm. As α decreases from 1 to 0, the fuzzy peak response widens from a precise value at  to an interval [28.06, 47.87] mm at α = 0, of width 19.81 mm. The results provide insight that inertia coefficient , followed by wave height H and elastic modulus E are the most influential variables upon response width. The parametric framework produces various nested fuzzy response sets while ensuring stable mesh-converged solutions, as well as an interpretable uncertainty band, enabling a preliminary serviceability assessment process. The study serves as a simplified benchmark model, and the assumptions, such as equivalent-cantilever idealization and linearisation of drag, are explicitly stated.