Method newStep

SRC/analysis/integrator/Collocation.cpp:135–190

int Collocation::newStep(double _deltaT)
{
    if (theta <= 0.0 )  {
        opserr << "Collocation::newStep() - error in variable\n";
        opserr << "theta: " << theta << " <= 0.0\n";
        return -1;
    }
    
    deltaT = _deltaT;
    if (deltaT <= 0.0)  {
        opserr << "Collocation::newStep() - error in variable\n";
        opserr << "dT = " << deltaT << endln;
        return -2;
    }
    
    // get a pointer to the AnalysisModel
    AnalysisModel *theModel = this->getAnalysisModel();
    
    // set the constants
    c1 = 1.0;
    c2 = gamma/(beta*theta*deltaT);
    c3 = 1.0/(beta*theta*theta*deltaT*deltaT);
    
    if (U == 0)  {
        opserr << "Collocation::newStep() - domainChange() failed or hasn't been called\n"; 
        return -3;
    }
    
    // set response at t to be that at t+deltaT of previous step
    (*Ut) = *U;
    (*Utdot) = *Udot;
    (*Utdotdot) = *Udotdot;
    
    // determine new velocities and accelerations at t+theta*deltaT
    double a1 = (1.0 - gamma/beta); 
    double a2 = theta*deltaT*(1.0 - 0.5*gamma/beta);
    Udot->addVector(a1, *Utdotdot, a2);
    
    double a3 = -1.0/(beta*theta*deltaT);
    double a4 = 1.0 - 0.5/beta;
    Udotdot->addVector(a4, *Utdot, a3);
    
    // set the trial response quantities
    theModel->setVel(*Udot);
    theModel->setAccel(*Udotdot);
    
    // increment the time to t+theta*deltaT and apply the load
    double time = theModel->getCurrentDomainTime();
    time += theta*deltaT;
    if (theModel->updateDomain(time, deltaT) < 0)  {
        opserr << "Collocation::newStep() - failed to update the domain\n";
        return -4;
    }
    
    return 0;
}