## Name

property — Property definition block

## Synopsis

property id type t
parameters...
end

## Description

The property command defines element properties identified by the identifier id, a positive integer. Elements for which properties need to be defined include beam elements (section properties), the point-mass elements, the rigid-body element and the distributed coupling element.

## beam_constants property type

beam_constants describes a beam section by all relevant constants. They can be either defined by the cross section constants or by the stiffnesses, which allow for a more general definition, i.e for non-homogeneous materials. The specific stiffness component are selected by the B2000++ solvers as follows: B2000++ first checks if a component x_stiffness is specified. If found, it is selected. If not, the constants forming the specific component are selected.

area a

Cross section area a (F type float).

area_moments Jyy Jzz Jyz

Second area moments Jyy, Jzz, and Jyz (array of 3 F type floats).

bending_stiffness kyy kzz kyz

Bending stiffness coefficients E*Jyy, E*Jzz, E*Jyz (array of 3 F type floats). If bending_stiffness is not specified, area_moments must be specified instead, defining the bending stiffness together with the material identified by mid.

neutral_axis y z

Section y and z coordinates of the neutral axis point. This is the point where, when aligned with the beam axis, an applied axial force does not result in a bending deformation. For cross sections that are made of a homogeneous material, the neutral axis point is identical to the centroid. The y and z coordinates are given with respect to the beam axis. Array of 2 F type floats. Default is 0.0 for all values.

mass m

Mass per unit length of beam (F type float). If mass is not specified, area has to be specified instead, defining the mass per unit length together with the material identified by mid.

mass_center y z

Section y and z coordinates of mass center with respect to the beam axis. Array of 2 F type floats. Default is 0.0 for all values.

mass_inertia_moments Iyy Izz Iyz

Mass inertia moments Iyy, Izz, and Iyz (array of 3 F type floats).

mid id

Element material identifier, a positive integer. Required.

non_structural_mass m

Non-structural mass per unit beam length (float). Default is 0.0.

non_structural_mass_center y z

Section y and z coordinates of non-structural mass center with respect to the neutral axis point (floats). Default is 0.0 for all values.

shear_correction_factors Kyy Kzz Kyz

Shear force correction factors Kyy, Kzz, and Kyz (floats).

shear_stiffness syy szz syz

Shear stiffness A*G*Kyy, A*G*Kzz, and A*G*Kyz (floats). If shear_stiffness is not specified, area and shear_correction_factors have to be specified instead, defining the shear stiffness together with the material identified by mid.

torsional_constant Jt

Torsional constant Jt (float).

torsional_stiffness s

Torsional stiffness Jt*G (float). If torsional_stiffness is not defined,torsional_constant has to be specified instead, defining the mass per unit length together with the density of element material identified by mid.

traction_stiffness s

Axial beam stiffness E*A (F type float). If traction_stiffness is not specified, area has to be specified instead, defining the traction stiffness together with the element material identified by mid.

## beam_section property type

beam_section allows for generating beam element type section properties for some simple beam section shapes. The shape parameter defines the beam section shape and the dimensions dx the actual dimensions.

Required parameters

shape s

Beam section shape (character string, required). In the present version, B2000++ knows the following shapes s:

• box (symmetric 'thin'-walled box): Requires d1 (width), d2 (height), d3 (thickness of walls along y), and d4 thickness of walls along z) to be defined.

• C (C profile): Requires d1 (profile flange width), d2 (profile web height), d3 (web thickness), and d4 (thickness of lower and upper flange) to be defined.

• circular_tube: Requires d1 (outer radius) and d2 (inner radius if tube is not solid) to be defined.

• I (I profile): Requires d1 (profile height), d2 (lower flange width), d3 (upper flange width), d4 (web thickness), d4 (lower flange thickness), and d6 (upper flange thickness) to be defined.

• L (L profile): Requires d1 (width), d2 (height), d3 (thickness of width part), and d4 (thickness of height part) to be defined.

• rectangle (solid rectangle): Requires d1 (width) and d2 (height)to be defined.

"box" cross section dimensions (MDL keywords) Dx and stress evaluation points A-D.

"C" cross section dimensions (MDL keywords) Dx and stress evaluation points A-D.

"circular_tube" cross section dimensions (MDL keywords) Dx and stress evaluation points A-D.

"I" cross section dimensions (MDL keywords) Dx and stress evaluation points A-D.

"L" cross section dimensions (MDL keywords) Dx and stress evaluation points A-D.

"rectangle" cross section dimensions (MDL keywords) Dx and stress evaluation points A-D.

## beam_section_matrix property type

beam_section_matrix describes the beam section by the Timoshenko beam constitutive 6x6 matrix, as obtained by using external cross-sectional analysis tools. Refer to the beam_section_submodel property for direct integration with the B2000++ cross-section solver.

constitutive_matrix list

A list of 36 F type floats, specifying the symmetric beam constitutive (6x6) matrix in row-major order, calculated at the neutral_axis. The first row/column defines extension, the second and third shear, the fourth torsion, and the fifth and sixth bending.

neutral_axis y z

Section y and z coordinates of the neutral axis with respect to the beam axis. Array of 2 F type floats. Default is 0.0 for all values.

mass m

The mass of the beam cross section per length unit. Default is 0.

mass_center y z

Section y and z coordinates of mass center with respect to the beam axis. Array of 2 F type floats. Default is 0.0 for all values.

mass_inertia_moments Iyy Izz Iyz

Mass inertia moments Iyy, Izz, and Iyz (array of 3 F type floats).

## beam_section_submodel property type (B2000++ Pro)

beam_section_submodel is available in B2000++ Pro; it describes the beam section by a dedicated, separate B2000++ FE submodel. The B2000++ processor will then extract from the submodel database the Timoshenko beam constitutive matrix and the other required constants.

name name

Name of the B2000++ MDL file containing the cross-section, or name of the B2000++ database containing the FE cross-section mesh and the results. If name ends with ".mdl", an MDL file is specified, and the B2000++ cross-section solver will be automatically executed on that file, and the cross-sectional data will be extracted from the corresponding database (same name, but ending with ".b2m").

case case

Load case identifier for which to extract the cross-sectional data from the database. Default is 1.

Example with two properties 1 and 2 specifying cross-section submodels for a frame-stringer fuselage. The corresponding database "frame.b2m" and the MDL file "stringer.mdl" must exist. In the case of the latter, the B2000++ cross-section solver will be executed at the beginning of the analysis.

property 1 type beam_section_submodel
name frame
case 1
end
property 2 type beam_section_submodel
name stringer.mdl
case 1
end