Early-Stage BIW Design Evaluation Using Higher-Order Beam–Shell Hybrid Models

Achieving favorable NVH and durability performance in the vehicle requires sufficient static and dynamic stiffness of the Body-in-White (BIW). Virtual development of BIW performance targets in the early stages is essential to minimizing costly modifications in later phases. In the automotive industry, full-scale finite element models are widely used for this purpose, offering high fidelity and enabling virtual performance evaluation. However, their complexity and the significant computational resources they demand limit their practicality for early-stage sensitivity and optimization studies. Beam-based models offer a faster alternative, but conventional formulations based on Euler or Timoshenko theory often fail to capture the complex deformation behaviors of thin-walled structures typical of BIW designs. This limitation generally leads to poor correlation with detailed models unless artificial joint flexibility is introduced. To address these challenges, we propose a hybrid modeling approach that combines Higher-Order Beam (HOB) elements with shell elements. HOB elements account for sectional deformation modes—such as warping and distortion—beyond standard translational and rotational degrees of freedom, allowing for a more accurate representation of thin-walled member behavior. This study extends prior work by applying HOB theory to BIW modeling, including panel components such as the floor and roof. Comparative analyses with fully detailed models show strong agreement, validating the accuracy and efficiency of the proposed method. The results demonstrate the potential of HOB-based hybrid models as a reliable and efficient tool for early BIW design evaluation and layout optimization.