Use of computer animation for displaying the mode shapes of a three-dimensional framework

This paper presents a method to integrate the free vibration theory and the computer graphical technique for displaying the mode shapes of a three-dimensional framework, so that one may see the real-time animation of the structural mode shapes on the computer screen. Because the graphical parameters, such as view angle, position of the projection plane, ..., etc., cannot be changed arbitrarily (at any time) in the existing post-processing procedures when the animation of the structural mode shapes is in progressing, it is difficult for one to observe the detail of the three-dimensional mode shapes from the computer screen. To solve this problem, some computer subroutines and a graphical user interface are developed for providing an interactive way between the users and the computer. Using the last technique, one may see the real-time animation of structural mode shapes with arbitrary graphical parameters at any time. Furthermore, because the vibration amplitudes and frequencies for the mode shapes are adjustable (enlarged or reduced) in the developed computer programs, one may also see the detail of any part of any mode shape of the structure from the computer screen no matter whether the vibration amplitudes and frequencies are very small or very large.