Structural Optimization of Joined-Wing Beam Model with Bend/Twist Coupling Using ESL

This study is based on the merger of two separate theories to further the efficiency with which joined-wing structural models are designed. The first theory is Geometrically Exact Beam Theory (GEBT). GEBT is a small strain beam theory which is capable of accurately capturing the geometric bend-twist coupling in beam elements. This is cruicial to the joined-wing problem as it is geometrically nonlinear. The second theory concerns Equivalent Static Loads (ESL). These ESL consist of a load vector that produces the same nodal displacements and rotations as those computed from a pure nonlinear analysis. The ESL displacements and rotations are then used to calculate ESL stresses. By merging these two theories into a single structural optimization effort, computational cost is reduced by orders of magnitude when compared to purely nonlinear analysis. The final design obtained by the optimization is the same for both types of analysis. The final result is a much simpler model than a detailed finite element model of the joined-wing aircraft that can be optimized without significant loss in fidelity in a fraction of the time required for a single optimization cycle using finite element analysis.