SAP2000 - Solid Shell Interaction

👉 For full details, downloadable SAP2000 models, and additional resources, check out the complete article on Structural Academy: https://structuralacademy.com/article/en/solid-shell-interaction Combining Shell and Solid (3D) elements in finite element models allows you to represent, within the same model, slabs, walls, and plates connected to regions with greater thickness/volume, such as foundation blocks and other massive elements. However, these two element types have different formulations and degrees of freedom: Solids have only 3 translational DOFs per node, while Shells include 3 translations and 3 rotational DOFs per node, which are necessary to properly represent flexural behavior. If the Shell–Solid interface is modeled only by matching nodes, without any additional care, kinematic incompatibilities often arise. These manifest as numerical instabilities, non-physical deformed shapes, spurious rotations, and unrealistic internal force distributions. The solution is to introduce appropriate kinematic constraints that allow consistent transfer of forces and moments between the shell and solid elements.