github_edit: False

SeismicForce Syntax

The input file syntax for SeismicForce with the the [BCs] block provides syntax for creating the correct SeismicForce boundary conditions for each direction components specified.

In some cases, the ground excitation is measured at a rock outcrop (where rock is found at surface level and there is no soil above it). To apply this to a location where rock is say $var element = document.getElementById("moose-equation-deadc067-6780-4d70-b6b6-c34ae45881d6");katex.render("10", element, {displayMode:false,throwOnError:false});$ m deep and there is soil above it, a sideset is created at $var element = document.getElementById("moose-equation-c448df7c-17de-419e-acd8-c12a15184e4d");katex.render("10", element, {displayMode:false,throwOnError:false});$ m depth and the ground excitation (converted into a stress) is applied at this depth. To apply ground excitation as a stress, the input function should be given as ground velocity. More details about the conversion of ground velocity to stress can be found in SeismicForce.

Example Usage

[BCs<<<{"href": "../index.html"}>>>]
  [./SeismicForce<<<{"href": "index.html"}>>>]
    [./front]
      displacements<<<{"description": "The displacement variables for the problem."}>>> = 'disp_x disp_y disp_z'
      input_components<<<{"description": "The directions in which the input ground motions are applied."}>>> = '0 1'
      boundary<<<{"description": "The list of boundary IDs from the mesh where this boundary condition will be applied."}>>> = 'front'
      velocity_functions<<<{"description": "The vector of function names that describes the input ground motions. Must be same size as input_component."}>>> = 'x_vel y_vel' # input velocity functions
      shear_wave_speed<<<{"description": "shear wave speed of the underlying bedrock."}>>> = 1.0
      p_wave_speed<<<{"description": "P-wave speed of the underlying bedrock."}>>> = 3.5
      density<<<{"description": "Density of the underlying bedrock."}>>> = 1.0
    [../]
  [../]
  [./back_x]
    type = DirichletBC<<<{"description": "Imposes the essential boundary condition $u=g$, where $g$ is a constant, controllable value.", "href": "../../../source/bcs/DirichletBC.html"}>>>
    variable<<<{"description": "The name of the variable that this residual object operates on"}>>> = disp_x
    value<<<{"description": "Value of the BC"}>>> = 0.0
    boundary<<<{"description": "The list of boundary IDs from the mesh where this object applies"}>>> = back
  [../]
  [./back_y]
    type = DirichletBC<<<{"description": "Imposes the essential boundary condition $u=g$, where $g$ is a constant, controllable value.", "href": "../../../source/bcs/DirichletBC.html"}>>>
    variable<<<{"description": "The name of the variable that this residual object operates on"}>>> = disp_y
    value<<<{"description": "Value of the BC"}>>> = 0.0
    boundary<<<{"description": "The list of boundary IDs from the mesh where this object applies"}>>> = back
  [../]
  [./back_z]
    type = DirichletBC<<<{"description": "Imposes the essential boundary condition $u=g$, where $g$ is a constant, controllable value.", "href": "../../../source/bcs/DirichletBC.html"}>>>
    variable<<<{"description": "The name of the variable that this residual object operates on"}>>> = disp_z
    value<<<{"description": "Value of the BC"}>>> = 0.0
    boundary<<<{"description": "The list of boundary IDs from the mesh where this object applies"}>>> = back
  [../]
  [./Periodic<<<{"href": "../Periodic/index.html"}>>>]
    [./left_right]
      variable<<<{"description": "Variable for the periodic boundary condition"}>>> = 'disp_x disp_y disp_z'
      primary<<<{"description": "Boundary ID associated with the primary boundary."}>>> = 'left'
      secondary<<<{"description": "Boundary ID associated with the secondary boundary."}>>> = 'right'
      translation<<<{"description": "Vector that translates coordinates on the primary boundary to coordinates on the secondary boundary."}>>> = '1 0 0'
    [../]
    [./top_bottom]
      variable<<<{"description": "Variable for the periodic boundary condition"}>>> = 'disp_x disp_y disp_z'
      primary<<<{"description": "Boundary ID associated with the primary boundary."}>>> = 'bottom'
      secondary<<<{"description": "Boundary ID associated with the secondary boundary."}>>> = 'top'
      translation<<<{"description": "Vector that translates coordinates on the primary boundary to coordinates on the secondary boundary."}>>> = '0 1 0'
    [../]
  [../]
[]

Input Parameters

boundaryThe list of boundary IDs from the mesh where this boundary condition will be applied.
C++ Type:std::vector<BoundaryName>
Controllable:No
Description:The list of boundary IDs from the mesh where this boundary condition will be applied.
densityDensity of the underlying bedrock.
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:Density of the underlying bedrock.
displacementsThe displacement variables for the problem.
C++ Type:std::vector<VariableName>
Unit:(no unit assumed)
Controllable:No
Description:The displacement variables for the problem.
input_componentsThe directions in which the input ground motions are applied.
C++ Type:std::vector<unsigned int>
Controllable:No
Description:The directions in which the input ground motions are applied.
p_wave_speedP-wave speed of the underlying bedrock.
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:P-wave speed of the underlying bedrock.
shear_wave_speedshear wave speed of the underlying bedrock.
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:shear wave speed of the underlying bedrock.

Required Parameters

active__all__ If specified only the blocks named will be visited and made active
Default:__all__
C++ Type:std::vector<std::string>
Controllable:No
Description:If specified only the blocks named will be visited and made active
alpha0The alpha parameter required for HHT time integration scheme.
Default:0
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:The alpha parameter required for HHT time integration scheme.
inactiveIf specified blocks matching these identifiers will be skipped.
C++ Type:std::vector<std::string>
Controllable:No
Description:If specified blocks matching these identifiers will be skipped.
velocitiesThe vector of velocity variables names. The input velocities can be obtained from this variable. The size of this vector must be same size as input_component.
C++ Type:std::vector<VariableName>
Unit:(no unit assumed)
Controllable:No
Description:The vector of velocity variables names. The input velocities can be obtained from this variable. The size of this vector must be same size as input_component.
velocity_functionsThe vector of function names that describes the input ground motions. Must be same size as input_component.
C++ Type:std::vector<FunctionName>
Unit:(no unit assumed)
Controllable:No
Description:The vector of function names that describes the input ground motions. Must be same size as input_component.

Optional Parameters

control_tagsAdds user-defined labels for accessing object parameters via control logic.
C++ Type:std::vector<std::string>
Controllable:No
Description:Adds user-defined labels for accessing object parameters via control logic.

Advanced Parameters

(test/tests/bcs/seismic_force/seismic_force_test_x_y.i)

#@requirement F6.4

# Test for application of seismic force which converts ground velocity in x and y directions into shear stress.

# This test consists of 20 brick elements stacked in the z direction.

# Back surface (z=0) is fixed in all three coordinate directions.

# Seismic stress proportional to a 2D input velocity is applied to the front surface (z=1).

# The nodes on the sides are constrained to move together to using periodic boundary.

# The shear wave speed in the soil is 1 m/s. So it will take 1 second for a shear wave from the front surface to reach the back surface and 2 seconds for the wave reflected off the back surface to reach the front surface.

# Result: The velocity at the front surface should almost be same as input velocity in the x and y directions before 2 seconds (i.e., before the reflected shear wave reaches the front surface).

[Mesh]
  type = GeneratedMesh
  dim = 3
  nx = 1
  ny = 1
  nz = 25
  xmin = 0.0
  ymin = 0.0
  zmin = 0.0
  xmax = 1.0
  ymax = 1.0
  zmax = 1.0
[]


[Variables]
  [./disp_x]
  [../]
  [./disp_y]
  [../]
  [./disp_z]
  [../]
[]

[AuxVariables]
  [./vel_x]
  [../]
  [./accel_x]
  [../]
  [./vel_y]
  [../]
  [./accel_y]
  [../]
  [./vel_z]
  [../]
  [./accel_z]
  [../]
  [./layer]
    order = CONSTANT
    family = MONOMIAL
  [../]
[]

[ICs]
  [./layer_ic]
    type = FunctionIC
    variable = layer
    function = layers
  [../]
[]

[Kernels]
  [./DynamicTensorMechanics]
    displacements = 'disp_x disp_y disp_z'
  [../]
  [./inertia_x]
    type = InertialForce
    variable = disp_x
    velocity = vel_x
    acceleration = accel_x
    beta = 0.25
    gamma = 0.5
  [../]
  [./inertia_y]
    type = InertialForce
    variable = disp_y
    velocity = vel_y
    acceleration = accel_y
    beta = 0.25
    gamma = 0.5
  [../]
  [./inertia_z]
    type = InertialForce
    variable = disp_z
    velocity = vel_z
    acceleration = accel_z
    beta = 0.25
    gamma = 0.5
  [../]
[]

[AuxKernels]
  [./accel_x]
    type = NewmarkAccelAux
    variable = accel_x
    displacement = disp_x
    velocity = vel_x
    beta = 0.25
    execute_on = timestep_end
  [../]
  [./vel_x]
    type = NewmarkVelAux
    variable = vel_x
    acceleration = accel_x
    gamma = 0.5
    execute_on = timestep_end
  [../]
  [./accel_y]
    type = NewmarkAccelAux
    variable = accel_y
    displacement = disp_y
    velocity = vel_y
    beta = 0.25
    execute_on = timestep_end
  [../]
  [./vel_y]
    type = NewmarkVelAux
    variable = vel_y
    acceleration = accel_y
    gamma = 0.5
    execute_on = timestep_end
  [../]
  [./accel_z]
    type = NewmarkAccelAux
    variable = accel_z
    displacement = disp_z
    velocity = vel_z
    beta = 0.25
    execute_on = timestep_end
  [../]
  [./vel_z]
    type = NewmarkVelAux
    variable = vel_z
    acceleration = accel_z
    gamma = 0.5
    execute_on = timestep_end
  [../]
[]


[BCs]
  [./SeismicForce]
    [./front]
      displacements = 'disp_x disp_y disp_z'
      input_components = '0 1'
      boundary = 'front'
      velocity_functions = 'x_vel y_vel' # input velocity functions
      shear_wave_speed = 1.0
      p_wave_speed = 3.5
      density = 1.0
    [../]
  [../]
  [./back_x]
    type = DirichletBC
    variable = disp_x
    value = 0.0
    boundary = back
  [../]
  [./back_y]
    type = DirichletBC
    variable = disp_y
    value = 0.0
    boundary = back
  [../]
  [./back_z]
    type = DirichletBC
    variable = disp_z
    value = 0.0
    boundary = back
  [../]
  [./Periodic]
    [./left_right]
      variable = 'disp_x disp_y disp_z'
      primary = 'left'
      secondary = 'right'
      translation = '1 0 0'
    [../]
    [./top_bottom]
      variable = 'disp_x disp_y disp_z'
      primary = 'bottom'
      secondary = 'top'
      translation = '0 1 0'
    [../]
  [../]
[]

[Materials]
  [./Elasticity_tensor_1]
    type = ComputeIsotropicElasticityTensorSoil
    block = 0
    layer_variable = layer
    layer_ids = '10'
    shear_modulus = '1.0'
    poissons_ratio = '0.3'
    density = '1.0'
  [../]

  [./strain_1]
    type = ComputeSmallStrain
    block = 0
    displacements = 'disp_x disp_y disp_z'
  [../]

  [./stress_1]
    type = ComputeLinearElasticStress
    block = 0
  [../]

[]

[Executioner]
  type = Transient
  solve_type = 'PJFNK'
  start_time = 0
  end_time = 2.0
  l_tol = 1e-10
  nl_rel_tol = 1e-10
  nl_abs_tol = 1e-12
  dt = 0.02
  timestep_tolerance = 1e-12
[]

[Functions]
  [./y_vel]
    type = PiecewiseLinear
    x = '0.0 0.25 0.5 0.75 1.0 1.25 1.5 2.0 3.0'
    y = '0.0 0.0  0.5 0.0 -0.5 0.0  0.0 0.0 0.0'
  [../]
  [./x_vel]
    type = ParsedFunction
    value = 'if (t<=1.0, sin(pi*t), 0.0)'
  [../]
  [./layers]
    type = ConstantFunction
    value = 10
  [../]
[]

[Postprocessors]
  [./_dt]
    type = TimestepSize
  [../]
  [./disp_1]
    type = NodalVariableValue
    nodeid = 103
    variable = vel_x
  [../]
  [./disp_2]
    type = NodalVariableValue
    nodeid = 103
    variable = vel_y
  [../]
[]

[Outputs]
  exodus = true
  csv = true
  print_linear_residuals = true
  perf_graph = true
[]

Example Usage
Input Parameters

Usage

Development

Demonstration