## 1 Introduction
The same authors [15], in another publication, proposed an experimental study to measure the dynamic response of a scaled lashing bridge and container stack based on the similarity theory. As it was shown, unlike standardized cargo, where intelligent cargo stowage plans and securing arrangements were proposed and used, the stowage plan and securing design of non-standardized cargo is far more complex. Maybe for this reason, studies referring to non-standardized cargo items have not gained much attention from scholars, and the number of works in the literature is limited [16]. It is worth highlighting the paper of [PERSON] et al. [2], where a revised evidential reasoning approach was introduced to cope with the complex problem associated with the cargo stowage plans of multipurpose vessels. Despite the research gap in this topic, the cargo shifting on board due to large rolling motion and high accelerations is often the cause of several problems or the origin of serious stability accidents, together with the negative influences of waves and wind [17]. In this sense, the inertia and external forces (wind pressure and sea sloshing) must be considered in the calculation. The effect of green sea load on general cargo ships was studied due to the serious damage that the waves cause in bow decks and structures, including the cargo items stowed in these sections. Other researchers, such as [PERSON] et al. [18], proposed an estimation method of ship motion and green sea loads using a model of a general cargo ship. Therefore, the stowage planning and the securing arrangement are critical tasks for guaranteeing the safety of sea transport from port to port, preventing damages to the cargo items, the ship, the crew members, and the environment. Then, to fulfill this mission, the forces acting on the cargo items have to be calculated, although this calculation is highly dependent on the classification society in charge of the ship's certification. However, the formulation is different for each different case [13], except for when the ship's CargoSecuring Manual refers to the Code of Safe Practice for Cargo Stowage and Securing (named CSS Code), as occurs in many cases. Cargo shifting can be identified as an important factor of cargo claims worldwide, jeopardizing the safety of sea passage. To avoid this problem, more attention should be focused on the stowage planning and the securing systems employed to avoid cargo shifting to guarantee cargo safety. However, the optimization of the stowage position and the securing arrangements is a highly complex process, which offers enormous possibilities for improving overall safety and reducing economic costs at the same time. This is performed by ensuring that cargo items are loaded in the best stowage position to suffer the lowest accelerations and employing the lowest number of hashing devices, but fixed in the optimum position. Regarding the economic costs, they can be analyzed from two points of view. The first one is the costs derived from the designed hashing arrangement due to the quantity and hashing material used and the time spent in port during the securing works, and the second one is the economic loss derived from the accidents as a consequence of a failure in the securing system, putting at risk the ship, the crew members, the cargo, and the environment. Therefore, the securing arrangement should be as economical as possible while safe standards are maintained [6]. Cargo losses occur because of large accelerations (determined by the stowage position), the improper stowage position, the influence of waves, and the pressure of wind on the cargo items stowed on deck, so all these factors are considered in the present research. However, more emphasis was put on the transverse direction because from the six degrees of freedom, the rolling motion (transverse force) is the most important factor and generates the most inertia forces to be counteracted by the lashing system [19], being the condition where the ship can sail in a situation close to synchronism [20].