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dc.contributor.advisor Abdel Mooty, Mohamed Abou Elsaoud, Ahmed Mounir
dc.creator Abou Elsaoud, Ahmed Mounir 2012-01-17T07:07:49Z 2012-01-17T07:07:49Z 2012-01-17T07:07:49Z 2012-01-17T07:07:49Z 2011 Fall 2012-01-17T07:07:49Z
dc.description.abstract The finite element modeling and dynamic analysis of massive and elevated foundation of steam turbine generator is considered in this thesis. The element type, element size and damping ratio are very important parameters in finite element modeling of massive machine foundation in general and the steam turbine generator foundation in particular. Inefficient modeling of the foundation may result in an unnecessary increase in the foundation size to limit the vibration amplitude within the machine manufacturer specified limits. The work in this thesis investigates the effect of damping ratio (2% to 5%), mesh size (500 mm, 800 mm and 1100 mm), and element types (8-nodded element, 10-nodded element and 20-nodded element) on the response of foundation to dynamic machine load as well as seismic loads. First, a free vibration analysis is performed to accurately determine the natural frequencies and to make sure that the effective modes of vibration are outside the critical frequency range set by the manufacturer of the steam turbine generator. This is followed by harmonic analysis to determine the foundation response to the machine load. Finally, the response of the machine foundation to seismic forces is evaluated. Seismic analysis is performed using two approaches: (1) by applying the seismic forces at the machine anchorage locations, (2) by applying the seismic force at the center of gravity of the machine. Furthermore, concrete with different compressive strength is considered to determine its effect on the critical harmonic response of the structure to machine dynamic loads. A detailed finite element model of the steam turbine generation foundation is constructed using three dimensional solid elements model available in ANSYS finite element package. This model is used to perform the free vibration and forced vibration analysis taking into consideration the above mentioned parameters. The influence of changes is those parameters on the foundation response is determined. The results of the numerical dynamic analysis performed on the machine foundation for free vibrations, harmonic forced vibrations, as well as seismic response are reported and analyzed in this thesis. Free vibration analysis showed that the change in the damping ratio has almost no effect on the natural frequencies. Other parameters, however, slightly affect the free vibration characteristics. For mesh sizes (500 mm to 1100 mm) the fundamental frequency values increase by 1% to 2% for the 8 nodded elements and 0.4% to 0.6% for the 10 & 20 nodded elements. Although the changes are not significant, it indicates that inaccuracy due to using large size element can be overcome by using element with larger number of nodes. However, since such changes are really small, element size of the order of 1000 mm for steam turbine generator foundation of the size used in this study can be considered reasonable. Thus, less complex finite element model can be used in such type of analysis without adversely affecting the accuracy of the results. Forced vibration response of the massive machine foundation is considered through evaluating its steady state harmonic response which is found to be more sensitive to changes in the studied parameters than the free vibrations. The transverse and vertical response values of the foundation at the turbine supporting points are affected by the change in damping ratio, mesh size, and element type. For the same mesh size and element type, the increase in the damping ratios from 2% to 5% results in decreasing the horizontal displacement by a range from 10% to 15% while the vertical displacement decreases by a bigger range from 16% to 32%. Also for the damping ratios (2% to 5%) and mesh sizes (500 mm to 1100 mm) the vertical and horizontal displacements have the same values for the 10-nodded and 20-nodded elements which are 2% to 20% higher than the values of the 8-nodded elements. Therefore, the use of 10-noded element is recommended for forced vibration analysis of machine foundation of the size used in this study. It is concluded that the damping ratio has significant effect on the structural response in the harmonic analysis of the foundation. The difference in response due to the changes in the compressive strength is found to be minor and this can be justified by the fact that the foundation overall dimensions and the member sizes are kept unchanged. The displacement resulting from applying seismic force at the machine sole plates is approximately 2% more than the deflection resulting from applying seismic force at the center of gravity of the machine. This is due to the small distance between the foundation tabletop and the machine as the center of gravity of the machine is located 900 mm above the foundation elevation. en
dc.format.medium theses en
dc.language.iso en en
dc.rights Author retains all rights with regard to copyright. en
dc.subject Machine foundations en
dc.subject Turbine generators en
dc.subject Harmonic analysis en
dc.subject Frequency analysis en
dc.subject Mode shapes en
dc.subject.lcsh Thesis (M.S.)--American University in Cairo en
dc.subject.lcsh Turbogenerators -- Foundations -- Design and construction.
dc.subject.lcsh Finite element method.
dc.title Finite element dynamic study on large framed foundation of steam turbine generator en
dc.type Text en
dc.subject.discipline Construction Engineering en
dc.rights.access This item is available en
dc.contributor.department American University in Cairo. Dept. of Construction and Architectural Engineering en

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  • Theses and Dissertations [1863]
    This collection includes theses and dissertations authored by American University in Cairo graduate students.

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