Degrees of freedom
Releases can be defined for the following degrees of freedom corresponding to the internal member forces:
Project | Degrees of freedom (local) | Fixed | Free | Spring |
| 1D-Beam | Vz*, My* | ☑ | ☑ | ☑ |
| 2D-Frame | N, Vz, My | ☑ | ☑ | ☑ |
| 2D-Truss | N, Vz | ☑ | ☑ | ☑ |
| 2D-Grillage | Vz*, Mx, My | ☑ | ☑ | ☑ |
| 3D-Frame | N, Vy, Vz, Mx, My, Mz | ☑ | ☑ | ☑ |
| 3D-Truss | N, Vy, Vz | ☑ | ☑ | ☑ |
* displacements along the global axes are expressed in the global coordinate system
For members where the local X' axis is parallel to a global axis, the defined releases correspond directly to the global coordinate system.
A released or fixed degree of freedom is defined with respect to the local axis system of a member and applies to both the start and end nodes of the member.
Interpretation of the definition of releases corresponding to internal member forces:
Force | Definition |
| Bending moment Mx, My, Mz | Releases in the rotational (angular) directions corresponding to released (pinned), semi-rigid (spring), or fixed bending moments about the local X′, Y′, and Z′ axes, respectively |
Axial force N Shear force Vy, Vz | Releases in the linear directions corresponding to released (pinned), semi-rigid (spring), or fixed axial or shear forces along the local X′, Y′, and Z′ axes, respectively |
Dimension units
The units for linear spring releases are [kN/m], and for rotational spring releases are [kN·m/rad].
The default release is fixed in all degrees of freedom. For a fixed release, the default stiffness value is 1E111; for a free release, the default value is 0; and for a spring release, the default value is defined within the range (0, 1E111).
If all members connected to a node have free releases, the resulting kinematic instability is automatically resolved by the software by converting one of the releases to a fixed release. If the structure remains kinematically indeterminate, the software may provide an automated solution based on diagnostic suggestions generated during the calculation.
Release name
Releases can be defined manually in the grid. Entering any alphabetic character sets the degree of freedom to fixed. Entering a numeric value assigns a semi-rigid (spring) release with that specific stiffness; entering zero (0) defines the direction as fully released (pinned).
Release identifiers consist of a default prefix 'R' followed by an incremental index. The numbering sequence begins with R1 and advances for each subsequent release. This default prefix is user-configurable within the Options menu.
Release assignment and positioning
The definition of releases determines how they are assigned and positioned based on nodal characteristics. These properties vary depending on the project type, such as 2D/3D Frame, 2D Grillage, or 1D Beam.
In 2D and 3D Frame projects, releases can be assigned to existing member nodes or any intermediate member location. Assigning a release at an intermediate point automatically generates a new node at that position; consequently, any relocation of the release triggers a corresponding relocation of the associated node.
In 2D Grillage and 1D Beam projects, releases may be assigned to member nodes or any intermediate location without generating new nodes. In these project types, the relocation of a release is independent of the model's nodal geometry; therefore, relocating a release does not trigger a corresponding relocation of the existing nodes.
Release definition is disabled in 2D and 3D Truss projects because all truss members are inherently modeled with releases at both ends.
The application of Mx releases (free, spring) at both member ends in 3D structures causes mechanical instability in the local X′r direction. This configuration is not permitted at both ends simultaneously to avoid a kinematic mechanism