Effect of scale factor on the dynamic response of frame foundations

Abstract

In geotechnical engineering, a scale factor “n” is a numerical ratio that relates the physical properties of a physical model to those of a prototype. The effect of scale factor on the dynamic response of a frame foundation used for high-speed turbo machines is examined through numerical analyses to clarify the influence of scaling dimensions, frequency, static and dynamic loads, and scaled models’ material on the dynamic responses of the frame foundation. The static and dynamic analyses were conducted using Ansys Workbench software. The total number of analyses used to investigate the scale factor effect was 28. Both modal and harmonic analyses were performed to calculate the natural frequencies and displacement responses of the scaled and prototype models under the scaled dynamic loading. Five scale factors were used in this study for concrete models (1, 20, 25, 32, and 40), and two additional analyses on steel models of scale (1 and 20) were used to study the material scaling. The prototype results were first verified, and then the models were investigated after scaling the dynamic loads and dimensions. The results of this study revealed the importance of scaling the frequency when studying the high-speed turbo machine foundation models to reflect the correct responses of the prototype foundation.

Keywords

• scale factor
• modal analysis
• harmonic analysis
• frame foundation
• ansys workbench