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Steps

Steps

The Steps Icon toggle section defines the stages of a simulation and controls the analysis process, including time integration, solution settings, boundary conditions, and output configurations. Each step represents a phase in the simulation where specific loads, boundary conditions, and analysis settings are applied.

Step Configuration

  • Active: Icon toggle Indicates if the step is active for the simulation. By default, the first step is set to Yes.

Analysis Type: Icon toggle Select the type of analysis:

  • Static: Time-independent simulations.
  • Geostatic: Establishes initial stress due to self-weight.
  • Transient: Time-dependent simulations.
  • Dynamic: Simulates inertia and damping effects.
  • Reduction: Gradually reduces material strength to failure.

Updated Lagrangian:

Set to Yes if large deformation is expected. Default is No for small deformation.

Solution Settings Icon toggle

Controls numerical solver parameters (e.g., tolerance values, iteration limits) to ensure accuracy and convergence during analysis.

Linear Solver

  • Specifies the solver used to solve the system of equations.
  • Default: Pardiso (recommended for large and complex models).

Extrapolation

  • Controls the extrapolation of the solution between increments.
  • Default: Extrapolation: Default (can be adjusted based on the problem type).

Maximum Number of Increments

  • Sets the maximum number of increments allowed for the solution to progress.
  • Default: 1e4 (10,000 increments).

Maximum and Minimum Number of Iterations

  • Maximum Number of Iterations: Limits the number of iterations for each increment to ensure convergence.
  • Default: 32 iterations.
  • Minimum Number of Iterations: Ensures the solver performs at least a set number of iterations before convergence is checked.
  • Default: 1 iteration.

Controls Controls allow users to monitor and adjust specific parameters during the solution process.

  • Displacement:
  • Monitors the displacement convergence during the simulation.

  • Status: Set to Default but can be customized based on convergence criteria.

  • Pore Water Pressure:

  • Monitors the convergence of pore water pressure in simulations involving fluid phases.
  • Status: Set to Default but can be adjusted for specific hydraulic problems.

Line Search The Line Search method is used to improve convergence in non-linear problems.

  • Method: Can be set to Active or Deactive.
  • Deactive: The default setting.
  • Active: Useful for problems with high non-linearity to stabilize convergence.

Time Integration Icon toggle

  • Relevant for transient and dynamic simulations to control time progression.
  • Initial Time Step Specifies the time increment for the initial step.
  • Default: 0.01 s. Step Time (Total) Sets the total duration of the simulation step.
  • Default: 1 s. Minimum Time Step Defines the smallest allowable time step to ensure stability.
  • Default: 0.001 s. Maximum Time Step Defines the largest allowable time step to maintain efficiency.
  • Default: 0.1 s.

Proper time integration ensures that the simulation progresses smoothly without instability or excessive computational time.

Factor of Safety

  • Used to calculate the stability of the structure or material under various loads.
  • Essential for geotechnical problems like slope stability analysis.

Reset Icon toggle

The Reset option allows users to reset the step to its initial state.

Options Available for Reset:

  • Reset: Set to Yes to enable the reset feature.
  • Displacement: Resets displacement values to their initial state. Default is No.
  • Strain: Resets strain values. Default is No.
  • Stress: Resets stress values. Default is No.
  • Void Ratio: Resets the void ratio values. Default is No.

The reset option is useful for restarting simulations from a clean initial state or applying different load conditions in subsequent steps.

Reaction Forces (RF) Icon toggle

The Reaction Forces option calculates and outputs reaction forces at specified points to verify boundary condition accuracy and ensure equilibrium.

Options for Reaction Forces:

  • Save Reaction Forces: Saves the calculated reaction forces for use in subsequent steps.
  • Use Saved Reaction Forces: Utilizes previously saved reaction forces in the current step.

Dirichlet Boundary Conditions Icon toggle

The Dirichlet Boundary Conditions control fixed variables at the boundaries of the model.

Types of Dirichlet Boundary Conditions:

  • Solid Displacement: Fixes displacement values at the boundary.
  • Pore Water Pressure: Fixes pore water pressure values.
  • Pore Air Pressure: Fixes air pressure values in unsaturated soils.
  • Water Displacement: Controls the movement of water at the boundary.
  • User Boundary: Allows users to define custom boundary conditions as needed.

Proper boundary condition setup is crucial to ensure the simulation behaves as expected under applied loads and constraints.

Constraints Icon toggle

The Constraints section defines relationships between different degrees of freedom in the model.

Equal Degree of Freedom

  • Enforces equal displacements or rotations between different nodes.
  • Used to apply symmetry or coupling conditions in the model.

Neumann Boundary Conditions Icon toggle

The Neumann Boundary Conditions section specifies loads or fluxes applied to the model boundaries.

Types of Neumann Boundary Conditions:

  • Gravity: Applies gravitational acceleration to the entire model.
  • Point Load: Applies a concentrated load at a specific point.
  • Distributed Load: Applies a load distributed over a surface or edge.
  • Pressure: Applies pressure on surfaces.
  • Water Pressure: Defines fluid pressure in geotechnical models.
  • Drainage: Sets boundary conditions for fluid drainage.
  • Compliant Base: Used to simulate flexible or elastic boundary supports.

Outputs Icon toggle

The Outputs section specifies what results will be saved or displayed at the end of each simulation step.

Field Output Specifies field variables (e.g., displacements, stresses) to be saved during the simulation.

  • Frequency: Determines how often the output is saved. Default is 1.
  • Format: Specifies the file format for the output. Common format is VTK.
  • Node Output: Saves field variables at nodes.
  • Element Output: Saves field variables at elements.

Print Output Specifies what variables will be printed in the output files.

  • Frequency: Determines how often the output is printed. Default is 1.
  • Print Node Output: Prints node-specific results (e.g., displacements, forces).
  • Element Output: Prints element-specific results (e.g., stresses, strains).
  • Integration Points: Prints values at the integration points within each element.