Shell property definition
 @SHELL_PROPERTY_DEFINITION {
 @SHELL_PROPERTY_NAME {ShlPropName} {
 @YOUNG'S_MODULUS {E}
 @POISSON'S_RATIO {ν}
 @STIFFNESS_MATRIX_A {a_{1}, ...a_{9}}
 @STIFFNESS_MATRIX_D {d_{1}, ...d_{9}}
 @STIFFNESS_MATRIX_S {s_{1}, ...s_{4}}
 @MATERIAL_DENSITY {ρ}
 @MASS_PER_UNIT_AREA {m}
 @CENTRE_OF_MASS_LOCATION {x_{ cm}}
 @RADIUS_OF_GYRATION {ρ_{g}}
 @STIFFNESS_MATRIX_B {b_{1}, ...b_{9}}
 @STIFFNESS_MATRIX_F {f_{1}, ...f_{6}}
 @STIFFNESS_MATRIX_G {g_{1}, ...g_{6}}
 @DAMPING_COEFFICIENT {μ_{s}}
 @COMMENTS {CommentText}
 }
 }
NOTES

The physical mass and stiffness properties of a shell are defined in this section.

The thickness of the shell is allowed to vary over the surface that defined the shell. Hence, the physical properties will be defined in a nondimensional manner with respect to thickness.

There are two ways of defining the stiffness properties of the crosssection according to the keyword appearing next.

If the keyword @YOUNG'S_MODULUS appears first, the shell is assumed to be made of a homogeneous, isotropic, linearly elastic material. Young's modulus, E, and Poisson's ratio, ν, then completely define the material stiffness characteristics.

If the keyword @STIFFNESS_MATRIX_A appears first, three stiffness matrices must be defined. Shells made of advanced composite materials with arbitrary layups can be defined in this manner. The coupling stiffness matrices B, F, and G are assumed to vanish unless defined below.

The mass characteristics of the shell are defined by three coefficients corresponding to integrals of the mass distribution through the thickness of the shell.

There are two ways of defining the mass properties of the crosssection according to the keyword appearing next.

If the keyword @MATERIAL_DENSITY appears first, the shell is assumed to be made of a homogeneous, linearly elastic material. The material density, ρ, then completely define the shell's mass characteristics.

If the keyword @MASS_PER_UNIT_AREA appears first, the shell three mass coefficients are defined explicitly.

When the shell is made of anisotropic material, elastic coupling can occur between the inplane and bending behaviors (stiffness matrix B), inplane and shearing behaviors (stiffness matrix F), or shearing and bending behaviors (stiffness matrix G). Any of these three matrices can be optionally defined.

Damping in the shell can be modeled by viscous forces F_{d}^{*} proportional to the strain rates, F_{d}^{*} = μ_{s} C^{*} de^{*}/dt, where μ_{s} is the damping coefficient.

It is possible to attach comments to the definition of the object; these comments have no effect on its definition.