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|Title: ||Modelling the behaviour of soil-cooling tower-interaction|
|Authors: ||Aly, Emad H.|
|Issue Date: ||2007|
|Publisher: ||© Emad Aly|
|Abstract: ||Natural draught cooling towers belong to a category of exceptional civil engineering structures.
These towers are an effective and economic choice among all technical solutions for
the prevention of thermal pollution of natural water resources caused by heated cooling water
in various industrial facilities. They are therefore widely used in most electric power
generation units, chemical and petroleum industries and space conditioning processes. The
cooling tower shell is the most important part of the cooling tower, both in technical and
financial terms and also the most sensitive, since its collapse would put all or part of the
cooling tower out of action for a considerable length of time.
In this thesis, the 2D and 3D behaviour of soil-cooling tower-interaction, via the idealisation
of the structure and soil on the resulting parameters, have been investigated, taking into
consideration the effect of temperature changes in the cooling tower on the simultaneous
interaction of the cooling tower and underlying soil. The temperature effect has been considered
because it plays an important role in the design of the cooling towers.
The capabilities of the two-dimensional Geotechnical Finite Element Analysis Program (GeoFEAP)
have been updated in this project and the new version has been referred to as
GeoFEAP2. New modelling capabilities and the ability to model 3D problems, with accompanying
postprocessing features, were introduced, including 3D first order 8-noded hexahedrons.
In addition, the Drucker-Prager yield criterion was programmed in GeoFEAP2
to model the elasto-plastic behaviour of the soil. A new 4-noded quadrilateral flat shell
element, based on discrete the Kirchhoff's quadrilateral plate bending element, was also
added to the software to model the elastic behaviour of the cooling tower shell. Furthermore,
this element was modified to accommodate a temperature profile. The new software
(GeoFEAP2) was then validated for soil behaviour and using several standard widely-used
benchmark problems and the results compared well with the analytical and/or numerical
results obtained by other researchers. A 3D finite element model was created, comprising
the cooling tower, columns support, foundation, and elasto-plastic soil behaviour.
The analyses of soil-cooling tower-interaction in this thesis have indicated the need to model
the soil and structure as a combined problem, rather than by applying loads onto soil as
geotechnical engineers' model, or by assuming the soil comprises springs and model the
cooling tower, as structural engineers' model. The results have shown how unrealistic the
latter two approaches are. In addition, the analysis necessitates the incorporation of thermal
effects when modelling cooling tower problems. Moreover, from a design point of view, it has
been recommended that circular footing with two cross-columns is better than pad footings
and/or one column. Several other conclusions have been made that would improve the
modelling of soil-cooling tower-interaction. Furthermore, the designer needs to ensure that
enough modelling of soil conditions is done and an extensive site investigation is required
to ensure that the variation in soil properties is represented correctly. Finally, the engineer
needs also to ensure that the site tests performed to measure shear strength with depth via
drilling and other methods needs to go deep enough into the ground to ensure that enough
site information is available when designing the cooling tower.|
|Description: ||A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.|
|Appears in Collections:||PhD Theses (Civil and Building Engineering)|
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