  Nowadays, the shipbuilding industry is facing a radical change towards
solutions with a smaller environmental impact. This can be achieved with low
emissions engines, optimized shape designs with lower wave resistance and noise
generation, and by reducing the metal raw materials used during the
manufacturing. This work focuses on the last aspect by presenting a complete
structural optimization pipeline for modern passenger ship hulls which exploits
advanced model order reduction techniques to reduce the dimensionality of both
input parameters and outputs of interest. We introduce a novel approach which
incorporates parameter space reduction through active subspaces into the proper
orthogonal decomposition with interpolation method. This is done in a
multi-fidelity setting. We test the whole framework on a simplified model of a
midship section and on the full model of a passenger ship, controlled by 20 and
16 parameters, respectively. We present a comprehensive error analysis and show
the capabilities and usefulness of the methods especially during the
preliminary design phase, finding new unconsidered designs while handling high
dimensional parameterizations.
