Comparison of various 1D, 2D and 3D FE models for the analysis of thin-walled box with transverse ribs subjected to load factors

This paper evaluates various Finite Element (FE) models for the static and dynamic analyses of single- and multi-bay metallic box structures. Load factors are considered in the static response, whereas free vibration analyses are addressed to compare the dynamic performances. Different FE models able to include cross-sectional deformations are compared. These comprise solid (3D) and plate/shell (2D) models, which are obtained by using a general-purpose commercial software. Results related to a hierarchical variable kinematic beam (1D) formulation, which opportunely degenerates into classical beam theories with rigid-cross section assumptions (e.g. Euler-Bernoulli and Timoshenko), are also addressed. Displacements as well as axial and shear stress fields are compared for various loading cases. Regarding dynamic analyses, fundamental and higher-order natural frequencies by various models are computed and the Modal Assurance Criterion is used to compare the eigenmodes. It is concluded that refined models are mandatory to accurately describe the static and dynamic characteristics of thin-walled box structures. Classical and lower-order refined beam models show severe limitations in capturing localized stress/strain fields as well as local mode shapes. Nevertheless, the accuracy of lower-order models is improved as a consequence of the adoption for transverse ribs, which lead to more rigid cross-sections.