If the position of the center of gravity and the orientation of a structure at a time is known, the nodal location in the fixed reference axes (FRA) can be determined from Equation 1–7 and Equation 1–8, i.e.

(13–70)

where is the position of the center of gravity of the structure in the fixed reference axes and is the location of the node in the local structure axes.

Employing the notations in Equation 13–15 and Equation 13–18, the nodal velocity response in the fixed reference axes is

(13–71)

and the acceleration is

(13–72)