An animated display of a vibrating structure along with its associated modes and phases. Dr. Shakes is a simple program designed to help illustrate many of the basic concepts underlying modal analysis for structural systems. It is intended to be used for instruction both in demonstration and hands-on contexts.

What does Dr. Shakes do?
Dr. Shakes presents an animated display of a vibrating structure along with its associated modes and phases. By adjusting the sliders, one can alter the contribution of each mode to the overall motion, set the phase lag for each mode (e.g., to match initial conditions), and adjust the associated story mass and stiffnesses. One can also change the number of stories (degrees of freedom), adjust the animation speed, and set the displacement scale.

Similarly, for the case of forced harmonic motion as shown in the screen shot below, Dr. Shakes presents an animated display of the structure as it responds to ground motion. By moving the appropriate sliders, one can adjust the damping in each mode and adjust the associated story mass and stiffnesses. The amplitude and frequency of the ground motion can be set, as well. The forced vibration starts with at-rest initial conditions, so one view both transient and steady-state response.

The animation is started via the Go/Stop button, and time can be set back to zero using the Reset button. Single time steps can be viewed by typing the 'g' (for 'go') key on your keyboard.

The license of this software is Freeware, you can free download and free use this cad software.