A new joint modeling method for a beam-based analysis of a car body applied during the concept design phase is presented. The body-in-white (BIW) of a car mainly consists of thin-walled beams with closed cross-sections, the joints of which show a significant flexibility owing to higher-order deformation modes. The joint flexibility effect cannot be evaluated using conventional beam theories. Although a hybrid modeling method using shell elements for a joint region, condensed in the form of a superelement, can be employed, its increase in accuracy for the joint flexibility is marginal. This is because the interface of the shell-modeled joint and that of conventional beam elements is rigidly connected, and thus the flexibility of the shell elements of the joint disappears at the interface. In this investigation, a thin elastic layer is introduced to account for a flexible connection between the interfaces of the shell-modeled joint and those of the beam elements. By employing an absorption parameter, the stiffness of the thin layer is set such that the thin layer can represent not only the accurate flexibility of the shell-modeled joint, but also higher-order deformations such as distortion and warping of thin-walled beams that are connected to the joint. To determine the absorption parameter of a thin layer, a surrogate model is built with respect to the geometric parameters of the cross-section of a connected beam, joint angle, and wall thickness. The effectiveness of the proposed beam-joint modeling method is shown by solving two-beam joint problems with various cross-sections and the BIW of a passenger car. (c) 2021 Elsevier Ltd. All rights reserved.
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