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Reference Guide
This manual provides a detailed list of all the input keywords and options available in Radioss.
Engine Input
This manual provides a list of all the solution definition keywords and options available in Radioss.
Kinematics and Loading
Engine Keyword In this group, keywords are used to define the kinematic condition (constrain/release rotation or translation DOF) and initial condition (rotational/translational velocity).
Kinematic Conditions
/BCS/LAG
Engine Keyword Given node numbers will be Lagrangian in specified directions X, Y or Z: V = W.

Welcome
What's New
View new features for Radioss 2025.1.
Overview
Radioss^® is a leading explicit finite element solver for crash and impact simulation.
Tutorials
Discover Radioss functionality with interactive tutorials.
User Guide
This manual provides details on the features, functionality, and simulation methods available in Altair Radioss.
Reference Guide
This manual provides a detailed list of all the input keywords and options available in Radioss.
- File Extensions and Formats
  Current Radioss format uses the 12x extension format.
- Single File Input
  This format allows running either Starter or Engine with the same file.
- New Keywords in 2025
  New and modified features in Radioss.
- Starter Input
  This manual provides a list of all the model definition keywords and options available in Radioss.
- Engine Input
  This manual provides a list of all the solution definition keywords and options available in Radioss.
  - Engine Keywords Syntax
  - General Controls
    Engine Keyword In this group keywords are used to generally define the output style, control of computation, damping and ALE setup during the computation.
  - Deletion/Input Modifications
    Engine Keyword In this group, keywords are used for modification (deletion or add options) in Engine.
  - Animation and Post-processing Output Files
    Generates animation files containing results according to the keywords specified. The keywords are specified in the topics within Animation and Post-processing Output Files.
  - Implicit Solution
    Engine Keyword In this group keywords are used for implicit solution. Different implicit solver methods (linear, nonlinear, buckling or quasi-static), different options to control the implicit computation, different implicit time step method and implicit output messages are introduced.
  - Kinematics and Loading
    Engine Keyword In this group, keywords are used to define the kinematic condition (constrain/release rotation or translation DOF) and initial condition (rotational/translational velocity).
    - Kinematic Conditions
      - /BCS/ALE
        Engine Keyword Given node numbers will be constrained in specified directions X, Y or Z for grid DOF: Ω = 0.
      - /BCS/LAG
        Engine Keyword Given node numbers will be Lagrangian in specified directions X, Y or Z: V = W.
      - /BCS/ROT
        Engine Keyword Given node numbers will be constrained in specified directions X, Y or Z for rotational DOF: Ω = 0.
      - /BCS/TRA
        Engine Keyword Given node numbers will be constrained in specified directions X, Y or Z for material translational DOF: V = 0.
      - /BCSR/ALE
        Engine Keyword Given node numbers will be released in specified directions X, Y or Z for grid DOF.
      - /BCSR/LAG
        Engine Keyword Given node numbers will no longer be lagrangian in specified directions X, Y or Z.
      - /BCSR/ROT
        Engine Keyword Given node numbers will be released in specified directions X, Y or Z for rotational DOF.
      - /BCSR/TRA
        Engine Keyword Given node numbers will be released in specified directions X, Y or Z for material translational DOF.
      - /VEL/ROT
        Engine Keyword Given node numbers have the same rotational velocity in a specified direction X, Y or Z.
      - /VEL/TRA
        Engine Keyword Given node numbers have the same velocity in a specified direction X, Y or Z for material translational DOF.
    - Initial Conditions
      Engine Keyword
  - Time Step
    Engine Keyword In this group, keywords are used to define different time step control (STOP, KILL, CST or DEL, and so on) for different entities (shell, brick, beam, airbag, interface, and so on) during the computation.
  - Initial State
    Engine Keyword In this group, keywords are used to output different info (like stress, strain, orthotropy direction, temperature, and so on) in a state file (STA-File).
- LS-DYNA Input
  This manual provides a list of LS-DYNA input files available in Radioss.
- Multi-Domain
  This manual contains the description of the keywords for the Radioss Multi-Domain.
- Obsolete Keywords
  Keywords that are still supported, but no longer maintained (*) are considered obsolete.
- Other Files
- Definition
Example Guide
This manual presents examples solved using Radioss with regard to common problem types.
Verification Problems
This manual presents solved verification models.
Frequently Asked Questions
This section provides quick responses to typical and frequently asked questions regarding Radioss.
Theory Manual
This manual provides detailed information about the theory used in the Altair Radioss Solver.
User Subroutines
This manual describes the interface between Altair Radioss and user subroutines.

/BCS/LAG

Engine Keyword Given node numbers will be Lagrangian in specified directions X, Y or Z: V = W.

Format

/BCS/LAG/Keyword3/skew_ID

N₁, N₂, . . ., N_N

Definition


Field	Contents	SI Unit Example
`Keyword3`	Any combination of `X`, `Y`, and `Z`: `X`, `Y`, `Z`, `XY`, `XZ`, `YZ`, `YX`, `ZX`, `ZY`, `XYZ`, `YXZ`, ...
`skew_ID`	Skew identifier (optional). If omitted, the boundary conditions are applied in the global skew system; otherwise they are applied in the given `skew_ID`.
`N`₁, `N`₂ ... `N`_N	List of nodes numbers to which the boundary conditions will be applied.