We will work with structural design and fatigue for ships and marine renewables and operational aspects for ships in ice. Focus will be on two aspects related to the transition to fossil-free power generation and transportation: ship design for vessels with Small Modular Reactors (SMRs); and fatigue assessment of floating offshore wind turbines. Ships in ice is an important aspect of ship safety and efficient design in the baltic and in arctic areas. In Ship design, SMRs can help reduce CO2 emissions and allow longer operations but also brings safety challenges, especially regarding collisions or grounding. Accurately modeling these situations requires detailed simulations that utilize large computing power. This research focuses on the structural solution of SMR-powered ships to improve safety in the event of large-scale accidents. Designs will be tested using extremely heavy and high-fidelity simulations. Abaqus/Explicit will be used, with nonlinear geometry activated and nonlinear material characteristics such as plasticity, strain-rate sensitivity, fracture initiation, and propagation; contact nonlinearity increases the complexity, especially when solid elements are introduced. All these settings are needed to capture realistic structural behavior under nonlinear conditions that represent the complexity of real-life collision scenarios. Perturbation analysis will be performed, which will explore a wide range of collision and grounding scenarios. Heavy simulations are necessary since detailed models can predict how ships will respond to various factors that guarantee the designs remain safe and reliable even under real-life extreme conditions. In the long term, design modifications will be applied to the real ship, potentially requiring larger models than before with different nonlinearities. In Marine renewables, advanced simulation methodologies are needed to advance understanding of fatigue loads. Complete turbines will be studied, where the system perspective—combined with high spatial and temporal fidelity—is essential to capture the load paths that govern fatigue. The first concerns global-to-local stress transfer under non-stationary combined wind–wave loading. Abaqus/Standard implicit dynamic analyses will be performed to obtain interface forces and nominal stresses in shell/beam global models; these histories will then drive resolved solid submodels at welded toes, flanges, and penetrations, with contact and elastoplasticity treated in Abaqus/Explicit. The second concerns long-term damage modelling and its numerical robustness. Canonical “building-block” sea states will be studied using statistically consistent rainflow counting and code-conformant S–N aggregation over multiple seeds. Als the effect of low-frequency platform motions, surge, pitch, and mooring dynamics, and array-scale inflow turbulence on long-term fatigue. The third aspect on ships in ice will use STAR-CCM+ to model how how ships and propellers perform in brash ice channels. The outcomes directly support more energy-efficient winter navigation and provide valuable input for ship design standards and international regulations, reducing risks and operating costs in ice-covered seas.