The B pillar structure, which affects automotive roof crashworthiness, must have a perfect surrogate model to satisfy the early design demands. This work aims to explore the proper approach of simplified model construction. To create the simplified B pillar, the collapse theories of thin-walled hexagonal and channel beams under bending collapse are reviewed and applied to simulate the deforming behavior. Meanwhile, the simplified model is constructed from parallel connection of curved hexagonal and channel section beams. After distributing different rotational nonlinear springs, the same crashworthiness analyses are performed on both simplified and initial FE models to verify the simplified effects. The results demonstrate the potential of the approach and process proposed in developing the simplified model for the concept design of autobody.