GEO5 Logiciel

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This section contains the basic parameters that relate to the proposed structure or truss. The content of the window differs for the "Truss 3D" and "Truss 2D" programs.

Type (Truss 2D)

This setting affects the basic character of the structure and the availability of the different parts of the program:


  • the basic type of truss commonly found in a structure

non-structural truss

  • a truss for which no structural analysis is performed. These are substructures that do not have a load-bearing function


  • this is a separate structural element consisting of a single timber member with no splice. This element has simplified manufacturing documentation

non-structural infill

  • this is a separate non-load-bearing element consisting of a single timber member without splices. No structural analysis and design is carried out for this member. It has simplified production documentation

bracing frame

  • a load-bearing truss which acts as a spatial stiffening of the structure. The deflections of this truss are assessed within the ultimate limit state

gable ladder

  • a non-structural element which serves to carry the roof plane over the gable. In this structure, the timber members are oriented in the vertical direction (the depth and width of the cross-section are interchanged) and no nail plates are inserted in the joints. This structure is not analyzed.

Roofing and ceiling (Truss 3D)

In this section the material of the roofing and ceiling can be selected. The selection is made using the "Edit" buttons in the "Roofing and ceiling" window. The selected material affects the values of the permanent load and also the buckling lengths of the corresponding members.


The following settings can be found in this section:

Truss thickness

  • a value that specifies the thickness of the timber that will be used for production of the truss. It is possible to select from the predefined thicknesses in the timber catalogue or to enter an arbitrary other value.


  • selection of the strength class of the timber. A predefined catalogue of strength classes is available. By pressing the "" icon to the right of the "Edit" button, it is possible to select the "Custom" option and enter the strength characteristics of the timber manually

Parameters (Truss 3D)

This section contains the basic parameters affecting the placement and shape of trusses in the structure:

Offset of horizontal top chords

  • the value by how much the horizontal top chords of the trusses are lowered to allow the rafters or extended top chords of the mono-pitched trusses to be placed above them. The value represents the reduction in the direction perpendicular to the roof plane and is therefore equal to the assumed depth of the rafters and extended top chords

Truss spacing

  • the assumed predominant value of the axial distance between the trusses. This value is passed by the program to the properties of the truss groups and as a loading width to the trusses themselves

Truss (Truss 2D)

The data in this section refer to the number of trusses in the structure and their axial distance:

Loading width of the truss

  • a value that represents the axial distance between the trusses. This value is used to multiply the load values in the load cases in which the "Use loading width" switch is enabled (set in the load case edit dialog). This converts the area load to the actual load of one truss location. This is how most load conditions behave (e.g. roofing, ceiling, snow, wind)

Truss count

  • a value that indicates the number of locations (single or multi-ply) of trusses in the structure

Number of plies

  • it indicates the number of truss layers that make up a single truss location in the structure. Multiple trusses are used in positions with increased stresses

Total number of plies

  • this is the total number of plies to be manufactured. The value is calculated as the product of the truss multiplicity and the number of locations. This value is not editable

Properties (Truss 2D)

This part contains additional settings related to the truss function in the structure:

Girder - supports other trusses

  • if a truss serves as a support for other trusses, different design rules apply in some standards

Girder is loaded symmetrically

  • if the girder is loaded on both sides, there is no reduction of the properties with respect to eccentric loading according to the French standard NF DTU 31.3, as per chapter

User-defined transport length of truss

  • If this setting is checked it is possible to specify a custom transport length of the truss. The length enters into the assessment of the nail plates for pull-out due to out-of-plane stresses on the truss in the German national annex. The manually entered length can take into account, for example, divided trusses.

Part "Parameters" in the program "Truss 2D"