## 4 Discussion  
This article presents the determination of the load of an open car with elastic, viscous components in the bearing structure during ro-ro transportation. The improvement was made via the application of elastic, viscous honeycomb panels between the vertical sheets of the intermediate, end, and bolster beams; the intermediate beams of an open car frame were made of a boxed section. This engineering solution can decrease the load of the bearing structure of an open car during interactions with multiple-use lashing devices. The manufacturability of this solution can be explained by the fact that the typical open car design contains reinforcing diaphragms in the bolster beam, with two on each side. The authors proposed the use of honeycomb elements instead of these diaphragms. They can be installed in the bolster beam at the stage of car production. It is possible to use heat-resistant honeycomb elements. Such a solution can ensure the safety of cars during their repair, e.g., during welding.  
A mathematical model was used for determining the dynamic load of an open car during the rolling motion of a train ferry. However, the model did not include the impact force of a sea wave on the train ferry. This can be explained by the fact that the centre of gravity of the open car body is 3 m from the bulwark. In accordance with the normative document [38], the impact force of the wave in this case can be neglected.  
It was also found that the application of honeycomb panels could decrease the dynamic load of a rail car by about 25% more in comparison to that of a standard structure (Figure 6). It should be noted that, by taking into account the introduction of more advanced energy-absorbing materials in the car structure, the magnitude of the dynamic load can be reduced further.  
The loads obtained were included in the strength calculation for the bearing structure of an open car with honeycomb panels in the body bolster. It was found that the maximum equivalent stresses in the bearing structure of an open car did not exceed the allowable values and were 30% lower than the stresses in the standard bolster beam (Figure 13).  
The scientific novelty of this study is that the authors built a mathematical model for calculating the dynamic load acting on rail cars transported via sea. It should be noted that this mathematical model was verified through a physical experiment presented in earlier publications by the authors [10,24].  
In addition, this study presents a scientific approach for assessing the strength of the bearing structure of an open car, taking into account the improvement for sea transportation.  
However, only one type of rail car was studied regarding sea transportation. Therefore, future studies should include other types of rail cars. Moreover, the study conducted did not include the welding seams between the structural components. Thus, future studies will include an evaluation of the strength of these welds [39,40].  
The advantage of this study compared to those analysed in the first section of the article is that, in order to ensure the strength of the open car, the authors proposed a reduction in the dynamic loads rather than strengthening the structure. This can be achieved by applying energy-absorbing materials to the frame.  
The next stage of this study will include an experimental determination of the strength of an open car body with honeycomb elements using a similar method. This experiment can be carried out under laboratory conditions.  
The research conducted can be used by engineers who are concerned about safe and environmentally friendly transportation via train ferries and more efficient ro-ro transportation.