## 1 Introduction  
Tsunami events such as the one occurred in Japan in 2011 in Tohoku [1] and the ones in Indonesia in 2004 and 2018 [2] resulted in catastrophic consequences on coastal communities and structures causing many casualties. Studies in the literature often focused on the impact of tsunamis on the coastal region [3; 4; 5; 6; 7]. However, recent research investigated the effects that debris transported by such tsunamis can have on existing structures, especially after the damage documented during the 2011 Tohoku tsunami. Using the evidence found after this event a debris hazard classification was developed by [PERSON] et al. [8] by analysing the damages caused by different debris types. Among the types with most energetic estimated impact forces on structures were shipping containers, especially loaded ones. Forces between 1500 and 6400 kN were estimated by [PERSON] et al. [8] on structures by applying the FEMA P646 [9] guidelines for the design of structures. These recommend a formula for the calculation of the maximum force exerted by floating debris based on the Haehnel and Daly [10] relationship. In the wake of the 2011 Tohoku tsunami, further relationships were incorporated in the American Society for Civil Engineers (ASCE) [11] design codes and provide a simplified model for large floating debris impact forces for structural design,accounting also for impact orientation based on the mean impact orientation of Haehnel and Daly [10]. However, important factors such as debris material are not yet taken into account in any design guideline to date. In order to have more detailed models for large floating debris dynamics, a large number of studies focused on investigating their behaviour when entrained in a flow, e.g., trajectories, spreading, orientation etc. [12; 13; 14; 15; 12] or on analysing their impact forces during a collision with a structure [16; 17; 18; 19]. More recently [PERSON] et al. [20] and [PERSON] et al. [21; 22] studied both processes in conjunction by using a single \"smart debris\" [23] shaped as a 1:40 geometrically scaled 20 ft standard container to analyse both the trajectories and the impact forces on a structure with the aim of improving the reliability of design guidelines for structures that may be exposed to such hazards and to serve as benchmark tests for future numerical simulations. The numerical modelling of these processes is rare in the literature [24] with significant limitations in the numerical methods used. Initial studies on solid-fluid interactions for debris were conducted by [PERSON] et al. [25]. They used Navier-Stokes equations coupled with Volume Of Fluid (VOF) to track the free surface, an approach very often used in modelling fluid-structure impacts (see, e.g., [PERSON] et al. [26]), and a large eddy simulation turbulence model. The motion of the floating body was modelled with a Discrete Element Method (DEM) model validating it with laboratory experiments. However, implementations of floating body mechanisms on mesh-based models are usually very challenging, requiring ad hoc formulations for specific cases and long processing times [27]. Due to these difficulties, Lagrangian particle-based methods, such as the Moving Particle Semi-implicit method (MPS) [28] or the Smoothed Particle Hydrodynamics method (SPH) [29] are often used as good alternatives to mesh-based methods [30; 31]. SPH, due to its formulation, is well suited to investigate high energy phenomena since it is capable of modelling violent flows as well as flow particle detachments in the context of tsunamis [32; 33]. However, even if these methods produced accurate results for solid-fluid interactions [34; 31] they do not inherently account for solid body contact laws, i.e., this contact requires a specific sub- or coupled model. [PERSON] et al. [35] and successively [36] expanded an SPH solver via coupling with a DEM model which was validated with PVC cubes subject to a flow, but showed limitations in correctly simulating the friction between moving and boundary elements of the simulations.