Large moored offshore floating structures (OFSs), such as multi-purpose platforms, renewable energy and aquaculture technologies, artificial islands and floating breakwaters, are mainly exposed to large environmental loads which induce hydroelastic response and structural deformations. Therefore, accurate numerical modelling is essential to assess their serviceability and survivability; this can be only achieved by resolving significant non-linearities in the fluid medium, and the hydroelastic response in solid medium. To address knowledge gaps related to high fidelity simulations, a numerical platform will be here developed based on smoothed particle hydrodynamic (SPH) methods. This SPH platform will be coupled with a finite element analysis (FEA) structural solver and a mooring line solver. The coupling will benefit from: (i) the capacity of SPH mesh-less in handling complex geometries and non-linearities, (ii) the accuracy of the FEA mesh-based method in capturing the hydroelastic response and the OFSs' deformations, and (iii) the ability of the mooring line solver to predict loads accurately. The developed numerical platform will be validated using available 3-D experiments and will be demonstrated to deal with challenges of new emerging technologies such as offshore floating photovoltaics. This interdisciplinary research will create high impact results with applications in multiple fields, i.e. offshore, coastal and maritime engineering, and offshore renewable energy.