## 1 Introduction
In other literature, the principles of design and methodology for calculating the strength of structural elements of heavy goods vehicles with approvals allowing for road traffic have been described similarly. Figure 1: Platform-container for intermodal transport: (**a**) 10-foot single module with joints in the prototype version where: 1—frame, 2—hook handle, 3—rotating end carriage, 4—lower frame joints with end carriage, 5—mounting screws, 6—rollers, 7—tie rods, 8—stanchions, 9—tie/chain around stanchions, (**b**) 10-foot basic module—initial design concept with visible side joints for connecting into sets. Selected issues related to the development of the FEM calculation model and the analysis of selected strength variants of a semi-trailer equipped with a steered axle system have been presented in [14]. Numerical tests of the special vehicle frame are also described in [15]. Numerical models of boundary conditions adopted to represent the operating conditions of such a structure are characterized. Similarly, load models are presented in detail, and individual calculation variants are adopted in the design analysis. Numerical tests of the strength of the off-road vehicle frame are discussed in [16]. The paper presents the possibility of using typical CAD/CAE systems for modeling and numerical analysis of the frame strength. Static and dynamic variants of the analysis of the vehicle's supporting frame are discussed, and selected results of numerical tests in the form of deformations and stress maps are shown. Such results of tests of the road vehicle frame cannot be used directly for comparative analysis of the stresses and displacements of the considered intermodal platform, for example. No items were found in the domestic and foreign literature referring to intermodal platforms approved for both road and rail traffic. Few works, such as [17], are advertising and marketing websites promoting platforms designed to support transport exclusively in road traffic. The manufacturer's commercial offer includes various platforms approved exclusively for road traffic, including those designed for the transport of long loads, platforms with hook and forklifting, etc. Apart from a few operational parameters discussed in these studies, there is no information on the design process, construction, or strength tests and sample results that could be used in any comparative analysis. The intermodal platforms (Figure 1) considered in this paper are structures that differ fundamentally from the platforms described in [17], approved exclusively for transport operations for use in domestic and foreign countries, with the restriction to road traffic only. The original intermodal platforms are the subject of the research described in our paper. An innovative structure was designed to handle both road and rail transport. Such platforms can also be used after minor modifications in air operations. After using an additional original superstructure, they can be used to transport not only long goods but also sheet metal in coils, bales of paper [7], as well as bulk materials, e.g., crushed agricultural products and grains [18]. The existing body of literature highlights various advancements in intermodal transport technologies. For instance, standardized containerization methods have significantly improved logistics efficiency by reducing handling time and costs. Studies have elaborated on the structural design and stress testing of traditional containers; however, there remains a gap concerning hybrid intermodal platforms designed for multimodal applications. Although prior studies provide detailed analyses of specific transport systems, they fail to address the integration of modular components in platforms used for both road and rail systems. This study aims to bridge this gap by offering a comprehensive design methodology for innovative intermodal platforms with enhanced modularity and mobility.