Dr. Shakes Home
What is Dr. Shakes?
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?
As indicated in the screen shot below, for the case of free vibration, 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.
What platforms does Dr. Shakes run on?
Dr. Shakes started its life as a Mac-only program, was ported to Java around 2001, and now (2005) has been re-implemented on top of a simple cross-platform interface framework that allows it to run natively on MacOS X, Windows, and Linux. The program uses OpenGL for its graphics, so performance can sometimes be slow on older machines with poor OpenGL support.
Who developed this program?
Dr. Shakes was originally developed by Stephen Cooper and Greg Miller in 1994 at the University of Washington. The current port ws done by Greg Miller in 2005. This program might get fancier over time, so check back periodically if the program is useful to you.
Download for free:
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Implementation Notes
Dr. Shakes intentionally hides most the complexity of its inner workings, and in its current configuration it is set up for qualitative rather than quantitative observations. For interested parties, though, the following value ranges can be used to relate Dr. Shakes observations to other calculations (using any consistent units system desired):
| Slider | Value Range |
|---|---|
| Mass | 1.0-10.0 |
| Stiffness | 1.0-20.0 |
| Damping | 0.0-0.5 |
| Frequency | 0.025-3.0 |
| Amplitude | 0.0-5.0 |
Feedback
Gripes, suggestions, and bugs can be sent to Greg Miller.
last update: March 30, 2005