Method newStep

SRC/analysis/integrator/ExplicitDifferenceStatic.cpp:99–141

Advance to a new time step This method implements the leap-frog scheme: - Velocity is stored at half time steps: v_{t+0.5*dt} - Displacement is at full time steps: u_t, u_{t+dt} - Acceleration is at full time steps: a_t, a_{t+dt}

// - Displacement is at full time steps: u_t, u_{t+dt}
// - Acceleration is at full time steps: a_t, a_{t+dt}
int ExplicitDifferenceStatic::newStep(double _deltaT)
{
    updateCount = 0;
    deltaT = _deltaT;

    if (deltaT <= 0.0)  {
        opserr << "ExplicitDifferenceStatic::newStep() - error in variable\n";
        opserr << "dT = " << deltaT << endln;
        return -1;
    }

    AnalysisModel *theModel = this->getAnalysisModel();

    // Leap-frog update: advance velocity to t+0.5*dt and displacement to t+dt
    Utdot->addVector(1.0, *Utdotdot, deltaT);           // v_{t+0.5*dt} += a_t * dt
    Ut->addVector(1.0, *Utdot, deltaT);                 // u_{t+dt} = u_t + v_{t+0.5*dt} * dt

    if (Ut == 0)  {
        opserr << "ExplicitDifferenceStatic::newStep() - domainChange() failed or hasn't been called\n";
        return -2;
    }

    // Zero acceleration for explicit method (Ma = RHS, no Ma on LHS)
    (*Utdotdot) *= 0.0;

    // Set trial response quantities
    theModel->setVel(*Utdot);
    theModel->setAccel(*Utdotdot);
    theModel->setDisp(*Ut);

    // Increment time and apply loads
    double time = theModel->getCurrentDomainTime();
    time += deltaT;
    if (theModel->updateDomain(time, deltaT) < 0)  {
        opserr << "ExplicitDifferenceStatic::newStep() - failed to update the domain\n";
        return -3;
    }

    // Set response at t to be that at t+deltaT of previous step
    (*Utdotdot) = (*Utdotdot1);
    
    return 0;
}

// Form element tangent matrix (mass matrix for explicit scheme)
int ExplicitDifferenceStatic::formEleTangent(FE_Element *theEle)