$\newcommand{\Dev}{\operatorname{Dev}}$ $\newcommand{\dev}{\operatorname{dev}}$ $\newcommand{\grad}{\operatorname{grad}}$ $\newcommand{\Grad}{\operatorname{Grad}}$ $\newcommand{\divg}{\operatorname{div}}$ $\newcommand{\Ei}{\operatorname{Ei}}$ $\newcommand{\tr}{\operatorname{tr}}$ $\newcommand{\Divg}{\operatorname{Div}}$ $\newcommand{\cay}{\operatorname{cay}}$ $\newcommand{\rot}{\operatorname{rot}}$

When a shell is coincident with the face of a solid element, we assume that the face of the solid element coincides with the back face ($\xi_{3}=-1$ ) of the shell element. This means that the solid element nodal displacements $\mathbf{u}_{b}$ on that face coincide with the shell nodal displacements $\mathbf{w}_{b}$ . Therefore, when we use UnpackLM for those solid elements, we should reassign the DOF ID's of the $\mathbf{u}_{b}$ displacements to those of the $\mathbf{w}_{b}$ displacements stored in that same node.