Case Studies with Innovative Technology

   doi:10.3850/978-981-07-0188-8_P037

ABSTRACT

Embedment of machine foundations has considerable influence on the dynamic response of the foundation system due to increase of overall damping. This paper investigates the effect of embedment for a Gas Turbine Generator (GTG) foundation for power project in Saudi Arabia. The paper discusses the development of design criterions, selection of soil parameters for design purpose as per the geotechnical investigation report and study of machine foundation design parameters provided by the machine manufacturer.

This type of foundation system had been generally analyzed worldwide by the procedure initially presented by Dr. D. D. Barkan and subsequently advocated by Dr. A. Major. But this procedure yields sufficiently good results for small to medium sized machines where permissible amplitude of vibration is relatively high, say, of the order of 30 to 40 micron. With the advancement of superior analytical procedures using high speed computers, large sized centrifugal machines with stringent design criteria and extremely low permissible amplitude of the order of 3 to 6 micron, adoption of finite element analysis and design technique with soil foundation interaction have become imperative to meet manufacturer’s and codal stipulations.

Analysis of the soil-foundation system has been carried out by three
-dimensional finite element method. Finite element software package STAAD Pro.V8i has been extensively used for modeling and analysis purpose. Eight noded brick elements have been adopted for modeling of the reinforced concrete block type foundation system and the soil has been modeled by spring elements. Equivalent spring stiffness constants have been evaluated for rigid embedded concrete block foundation based on approach established by F. E. Richart & R. V. Whitman’s design procedures.

Foundation performance under dynamic loading has been investigated for different embedment conditions. The design of foundation considering worst load combinations has also been discussed. The paper also discusses the usefulness of such rigorous analysis and various shortcomings which still persist to represent machine foundation-soil system.

© 2012 by Geotechnical Society of Singapore (GeoSS)