How to impose displacement excitation?

[docmao]

In the ImposedMotionSP class, I find the method of imposing vel and acc excitation. It also point out that the disp excitation is not in the method as follows,but i can't find the responsibility code in any other constraint class. Could anyone help me to find out that?

int
ImposedMotionSP::applyConstraint(double time)
{
....
/* ***********************************************************
* disp response the responsibility of constraint handler

*theNodeResponse = theNode->getTrialDisp();
(*theNodeResponse)(dofNumber) = theGroundMotionResponse(0);
theNode->setTrialDisp(*theNodeResponse);
*************************************************************/
*theNodeResponse = theNode->getTrialVel();
(*theNodeResponse)(dofNumber) = theGroundMotionResponse(1);
theNode->setTrialVel(*theNodeResponse);

*theNodeResponse = theNode->getTrialAccel();
(*theNodeResponse)(dofNumber) = theGroundMotionResponse(2);
theNode->setTrialAccel(*theNodeResponse);

return 0;
}

[fmk]

the displacement constraint is imposed by the constraint handler and the DOF_Group subclass of that constraint handler.