Shell Foundations  Geometry, Analysis, Design and Construction

Shell Foundations  Geometry, Analysis, Design and Construction

The present book under the title "Shell Foundations", covering various aspects pertaining to the subject such as geometry, geotechnical design, soil-structure interaction, analysis by the membrane, bending and ultimate theories, design, construction and research,as a separate volume, is the offshoot of Part I of the author's earlier book: Modem Foundations~lntroduction to Advanced Techniques.

Much water has flowed under the proverbial bridge (even in the dry city of Madras!) since 1982, which has made the revision of the book eminently due; In revising the book from the earlier source, chapters 2 and 3 have been compressed into one chapter (Chapter 2: Geotechnical Design of Shell Foundations and Soil-Structure Interaction) by presenting only the material as it applies to shell foundations. This has been possible by shifting the material from the earlier book to the author's second book 'Design of Foundation Systems: Principles and Practices'-third revised and enlarged edition $-in which geotechnical design forms the mainstay-of Part I-for introducing soil-structure interaction in chapter lOon the flexible design of shallow foundations.

On the geotechnical performance of shell foundations, only experimental evidence was available at the time of writing the previous book, researchers having shied away from developing closed-form solutions, the same being extremely complex and formidable. The advent of the finite element technique changed the scenario, this problem having the attributes of an ideal field for the application of the same. The author's student Mr. Y.M. Jayakrishna Devaki attempted this with remarkable success and his results are presented in chapter 2. The author is immensely thankful to him for this contribution which is seminal to the understanding of soil response under shell foundations.

On the shell side, even though several shell forms offer scope for use in foundations (chapter 1), three simple shells with the highest potential have been identified as the cone, the inverted spherical shell segment (and their combinations) and the hyperbolic paraboloid, in that order, following the logic of starting from the
simplest. Hence attention is focused on these shells for detailed treatment in chapters 3 to 7. The highlight of chapter 4, which gives several finite element solutions in the bending analysis of shell foundations, is the highly sophisticated experimental investigations carried out by the author on conical, spherical and double cone folded shell models at the Technical University of Berlin, Germany, during 1978-79 and 1984-85, which was enthusiastically supported by o.Prof. Dr. -Ing. habil. Klaus Dierks at the Institut fUr Trangkonstrucktionen und wirtschaftliche Fertigung. As far as the author's knowledge goes-from his familiarity with literature on the subject-this work, which carries the stamp of German precision and perfection, remains unsurpassed in technical sophistication to this day.

Professor Dierks is one who combines a high level of competence on the technical front with great warmth, friendliness and sincerity of purpose at the personal level. The author deems it a privilege to have worked with him, in Hanover and Berlin. It is indeed gratifying to this author
that Professor Dierks has graced this book with an authentic Foreword.

By far the chapter which has undergone vast changes is chapter 5 on ultimate strength analysis, complemented by microconcrete model testing. These changes ate mainly in the form of additional material-mostly the contributions by the author and his coworkers. In chapter 6 presenting typical design plates, the designs which were by the working stress method in the earlier book have been reworked to the limit state method. Reference has also been made to the Indian code in chapter 7, which h~ been an early milestone
in the field of shell foundations giving it the stamp of official acceptance in modern construction. Since the present revised edition is more in the nature of a monograph than a textbook, the short review questions given in the earlier book do not find a place in the present work.


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