Truss/beam material manager
Truss and beam elements are one-dimensional structural members, and their material definition consists of a stiffness together with section properties rather than a constitutive model. They therefore have their own manager, separate from the material manager.
Open it from the numgeo tools toolbar or from numgeo → Manager → Truss/Beam material.
The window works exactly like the continuum material manager — the same list on the left, the same buttons, the same database pattern. Anything learnt about one applies to the other.
How definitions are stored
Definitions are held in numgeo_truss_beam_materials.tcldata next to the GiD
project, and only the material name is passed to the data tree for assignment
to lines. At calculation time the definitions are written into
material-definitions.inp, together with the continuum materials.
As with continuum materials, this database must be copied along with the project if it is moved by hand.
Element type
Each material is either a Truss or a Beam. The choice determines which section properties are asked for, and the property table is rebuilt immediately when it changes.
Switching type does not discard the parameters of the other type — they are kept in the database, so switching back restores them.
Tabs
Density
A single density value for the member.
Truss/beam properties
The parameters depend on the element type.
Truss
| Parameter | Unit | Meaning |
|---|---|---|
A |
m² | Cross-sectional area |
E |
kN/m² | Young's modulus |
Beam
| Parameter | Unit | Meaning |
|---|---|---|
A |
m² | Cross-sectional area |
E |
kN/m² | Young's modulus |
G |
kN/m² | Shear modulus |
I_yy |
m⁴ | Second moment of area about the local y-axis |
I_zz |
m⁴ | Second moment of area about the local z-axis |
J |
m⁴ | St. Venant torsional constant |
kappa_y |
– | Shear correction factor in the local y-direction |
kappa_z |
– | Shear correction factor in the local z-direction |
A truss carries axial force only, so it needs just an area and a stiffness. A beam additionally resists bending, shear and torsion, which is where the remaining six parameters come in.
Section unit
Section properties can be entered in either m or mm. The setting affects how the values in the table are interpreted and displayed; it is stored with the material, so different materials in the same project may use different units.
Choose the unit before typing the values, or before applying a profile.
Rolled-steel profile catalogue
Instead of typing section properties by hand, they can be filled from a catalogue of IPE profiles:
| IPE 80 | IPE 180 | IPE 300 | IPE 400 |
| IPE 100 | IPE 200 | IPE 330 | IPE 450 |
| IPE 120 | IPE 220 | IPE 360 | |
| IPE 140 | IPE 240 | ||
| IPE 160 | IPE 270 |
Selecting a profile fills A, I_yy, I_zz and J, converted to the section
unit currently selected. The values come from the standard profile tables, where
areas are given in mm² and second moments in 10⁶ mm⁴.
The remaining parameters are not filled by the catalogue: E, G,
kappa_y, kappa_z and the density describe the material rather than the
geometry of the section, and must still be entered. For structural steel, E
and G are the usual constants; the shear correction factors depend on the
section shape.
Applied values are ordinary numbers afterwards and can be edited freely — the material keeps no link to the profile it came from.
Validation
The material is checked when it is saved, and the first problem found is reported:
- The name must not contain commas or line breaks.
- The type must be Truss or Beam.
- The section unit must be m or mm.
- The density must be filled.
- Every parameter of the selected type must be filled.