3.2.6.11. GimmeMCK Command¶

This command is used to construct a GimmeMCK integrator object. The GimmeMCK Integrator alow the user to return the mass, damping, and stiffness matrix. Depending on the user input, it enable the user to retrieve the desired by using the printA command.

integrator GimmeMCK $m $c $k $ki

Argument	Type	Description
$m	float	If the value is not zero, add mass matrix to tangent matrix with factored value as large as the input.
$c	float	If the value is not zero, add damping matrix to tangent matrix with factored value as large as the input.
$ki	float	If the value is not zero, add the tangent stiffness matrix to tangent matrix with factored value as large as the input.
$kt	float	If the value is not zero, add the initial stiffness matrix to tangent matrix with factored value as large as the input.

3.2.6.11.1. Theory¶

Assembles A = m*M + c*C + kt*KT + ki*KI

Note

The system used for the model must be FullGeneral
To get the desired output (Mass, Stiffness or Damping matrix), you need to print the result using printA command.

Example:

Tcl Code

wipeAnalysis
system FullGeneral
integrator GimmeMCK 0. 0. 1.
analysis Transient

analyze 1 1
printA -file "K.txt"

wipeAnalysis
system FullGeneral
integrator GimmeMCK 1. 0. 0.
analysis Transient

analyze 1 1
printA -file "M.txt"


wipeAnalysis
system FullGeneral
integrator GimmeMCK 0. 1. 0.
analysis Transient

analyze 1 1
printA -file "C.txt"

Python Code

ops.system('FullGeneral')
ops.analysis('Transient')

# Mass
ops.integrator('GimmeMCK',1.0,0.0,0.0)
ops.analyze(1,0.0)

# Number of equations in the model
N = ops.systemSize() # Has to be done after analyze

M = ops.printA('-ret') # Or use ops.printA('-file','M.out')
M = np.array(M) # Convert the list to an array
M.shape = (N,N) # Make the array an NxN matrix

# Stiffness
ops.integrator('GimmeMCK',0.0,0.0,1.0)
ops.analyze(1,0.0)
K = ops.printA('-ret')
K = np.array(K)
K.shape = (N,N)

# Damping
ops.integrator('GimmeMCK',0.0,1.0,0.0)
ops.analyze(1,0.0)
C = ops.printA('-ret')
C = np.array(C)
C.shape = (N,N)

Code Developed by: Michael H. Scott

MHS2020: Scott, M. H., Gimme All Your Damping, All Your Mass and Stiffness Too (https://portwooddigital.com/2020/05/17/gimme-all-your-damping-all-your-mass-and-stiffness-too/)