Method addModalDampingMatrix

SRC/analysis/integrator/IncrementalIntegrator.cpp:562–620

int
IncrementalIntegrator::addModalDampingMatrix(const Vector *modalDampingValues) {
  int res = 0;
  //    return 0;

  if (modalDampingValues == 0)
    return 0;

  double cFactor=this->getCFactor();
  if (cFactor == 0)
    return 0;

  int numModes = modalDampingValues->Size();

  const Vector &eigenvalues = theAnalysisModel->getEigenvalues();
  int numEigen = eigenvalues.Size();

  if (numEigen < numModes) 
    numModes = numEigen;

  int numDOF = theSOE->getNumEqn();

  if (eigenValues == 0 || *eigenValues != eigenvalues) {
    this->setupModal(modalDampingValues);
  }

  for (int dof = 0; dof<numDOF; dof++) {
    dampingForces->Zero();
    bool zeroCol = true;

    for (int i=0; i<numModes; i++) {

      double eigenvalue = (*eigenValues)(i);
      double modalDampingValue = (*modalDampingValues)(i);      
      if (eigenvalue > 0 && modalDampingValue != 0.0) {
	double wn = sqrt(eigenvalue);
	double *eigenVectorI = &eigenVectors[numDOF*i];
	double ei_dof = eigenVectors[numDOF*i+dof];
	
	if (ei_dof != 0.0) {
	  zeroCol = false;
	
	  double beta = 2.0 * modalDampingValue * wn * ei_dof * cFactor;
	  
	  for (int j=0; j<numDOF; j++) {
	    double eij = eigenVectorI[j];
	    if (eij != 0)
	      (*dampingForces)(j) += beta * eij;
	  }
	}
      }
    }
    
    if (zeroCol == false)
      theSOE->addColA(*dampingForces, dof, 1.0);

  }
  return res;