Cross-section definition

Cross-section properties

The cross-section definition available in MatrixFrame® consists of:

1. Geometrical properties:

User-defined – basic cross-section properties such as section area (A), elasticity (E), and moment of inertia (I) are calculated and entered manually.
Parametric – cross-section properties with the option to enter custom section parameters.
Database – cross-section properties defined using the manufacturer’s structural shapes database.

2. Material properties – cross-section material type, available only for parametric and database sections.

All geometrical properties are defined and calculated in meters. The input is validated to prevent incorrect values. Once a cross-section is assigned to a structural member, its geometrical and physical properties are displayed in the grid.

Note: the reverse assignment (modifying the cross-section after assignment) is not possible.

Cross-section names

Cross-section names are generated in different ways depending on the type of section:

User-defined – names must be entered manually.
Parametric – names are generated automatically using the short name of the section shape and its dimensions in millimeters.
Database – names are generated automatically from the original manufacturer names.

In all cases, it is possible to modify the section names in the grid.

Parameters of database cross-sections are defined by the manufacturer and cannot be modified directly. However, if a section or material name is changed at your discretion, the section becomes editable, and any modifications to its parameters are saved in the database as a new section or material.

Advanced cross section properties

Several advanced cross section properties are available:

Property	Definition	Comments
Tapered	A tapered cross-section has different height values at the start and end of the member. Only parametric rectangular cross-sections can be tapered in both height and width simultaneously.
BiMaterial	Only parametric rectangular cross-sections can be defined as BiMaterial, consisting of two different materials.
Tension	A structural member defined as tension-only carries load only in tension, e.g., a bracing. If a tension-only member is subjected to compression, it is excluded from the calculations.	By default, both Tension and Compression options are active. If both options are disabled simultaneously, the member is temporarily removed from the calculations.
Compression	A structural member defined as compression-only carries load only in compression. If a compression-only member is subjected to tension, it is excluded from the calculations.
Cable	A structural member defined as a cable (only applicable to circular parametric cross-sections) carries load primarily in tension. It can optionally be influenced by pre-stressing, a method used to overcome the natural weakness of the member in tension.
Castellated	Only I- and H-shaped cross-sections can be defined as castellated. Restriction: the height of a castellated cross-section must be less than twice the height of the original cross-section from which it is produced.	The main geometric characteristic values of a castellated cross-section with hexagonal openings depend on the height of the original cross-section $h$ $h$ , the height of the castellated cross-section $h_t$ $h$ $t$ $$ , and the geometry and positioning of the hexagonal openings. For the Castellated profile branch in the sections database, the geometric relationships are defined as follows: The DB section properties are recalculated using the characteristic geometric values described above, which can be entered freely in the DB. Modifying these values triggers a recalculation of the section properties and can serve as a solid basis for creating new cross-section families.
Density, [kN/m³]	Mass per unit volume, used for the calculation of self-weight.
Torsional/Polar moment of inertia (I_t), [m⁴]	Moment of inertia used for torsion calculations.
Second moment of area (Mom. Inn.), [m⁴]	The second moment of area (also known as the area moment of inertia, planar moment of inertia, or second moment of inertia) is a property of a cross-section used to predict the resistance of beams to bending and deflection around an axis lying in the cross-sectional plane.	2D-Frame: The moments of inertia depend on the cross-section rotation angle (for 2D-Frame, angles in multiples of 90°), as well as the cross-section shape and dimensions. The rotation angle is formal: the local axes and related properties (moments of inertia, loads, etc.) are not physically rotated. Instead, the moments of inertia switch the values of $I_y$ $I$ $y$ $$ and $I_z$ $I$ $z$ $$ according to the cross-section rotation angle: 3D-Frame: The moments of inertia do not change with the cross-section rotation angle about the X′ axis. In 3D-Frame, the local coordinate system is used: when the rotation angle is changed, the cross-section and all related properties (moments of inertia, loads, etc.) rotate together with the Y′ and Z′ axes:
Moment of inertia (I_uv), [m⁴]	Used for stability analysis (for example, tension-only elements) as the minimum of $I_y$ $I$ $y$ $$ , $I_z$ $I$ $z$ $$ , $I_u$ $I$ $u$ $$ , and $I_v$ $I$ $v$ $$ : I_uv=min(I_y,I_z,I_u,I_v) where: $I$ $u$ $$ $,$ $I$ $v$ $$ – moments of inertia related to the principal axes $u′$ $u$ $'$ and $v′$ $v$ $'$ , rotated by angle $\alpha$ $α$ counterclockwise (CCW) from the vertical.
Poisson's ratio (ν)	The ratio of transverse strain (perpendicular to the applied load) to axial strain (in the direction of the applied load) when a material is stretched (under tensile loading).	Poisson’s ratio is used, for example, in the calculation of torsional rigidity GJ under applied torque and in shear force correction of nodal rotations during structural analysis. The shear modulus (also called the modulus of rigidity, G) is calculated as: where: E - Young's modulus, [kN/m²] ν – Poisson’s ratio
Shear area (A_vy, A_vz), [m²]	Used in the calculation of the form factor for performing shear force correction on nodal rotations during structural analysis (only if shear force correction is enabled in the analysis options).	The form factor v of the cross section is related to the shear area as follows: where: A_v - shear area of the cross section A - total area of the cross section For a rectangular cross section, the form factor can be calculated as:
Prestressing, [kN]	Prestressing is applicable only to cable elements. Prestressing defined as a predefined action on a member affects all load cases and load combinations. Initial prestressing applied to an element indirectly affects the members connected to it; therefore, this action is similar to a temperature-induced elongation.	Prestressing applied to prefabricated concrete elements represents a different concept, where the prestressing action is confined to the element itself and is not distributed to the connected members.

The definition of cross-sections may be restricted in Technical modules No. 60-70 and 72. In such cases, the corresponding branches in the "Sections" tree will be disabled.

Cross-section distribution

The cross-section definition allows sections to be assigned based on member characteristics. There is a difference in functionality between 2D/3D-Frame projects and 2D-Grillage / 1D-Beam projects in MatrixFrame®:

2D- and 3D-Frame – a single cross-section can be assigned to a member. If a new section is assigned, it updates the existing one.
2D-Grillage and 1D-Beam – multiple user-defined cross-sections can be assigned to a single member.