Analysis of thin-walled beam-shell structures for concept modeling based on higher-order beam theory

Many engineering structures consist of thin-walled beams and shells. Especially for fast design in an early design stage, a simplified analysis using beams for load-carrying members and shells for panels is very useful, but there appears no accurate beam-shell combined finite element model. The main reason is that the Timoshenko or Euler beam elements are incapable of representing significant sectional deformations near beam joints or near beam-panel interfaces. Although some progress has been made in developing higher-order beam elements that can accurately capture the sectional deformations, there is no investigation to develop higher-order beam and shell combined models useful to analyze various engineering structures. The main contribution of this work is to present the first attempt to model structures made of thin-walled closed beams and shells in terms of higher-order beam elements and shell elements and to establish the matching conditions between the dissimilar field variables of higher-order beam and shell elements along their interfaces. For the finite element analysis of a whole structure, the interface matching conditions are imposed through Lagrange multipliers. High accuracy of the proposed higher-order beam-shell method is demonstrated through static and modal analyses of various structures including a simplified model of a vehicle body-in-white (BIW).