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Computational methods for offshore structures
BOOK REVIEWS Soil dynamics Shamsher Prakash
McGraw-Hill, New York, xiv +426, 1981. US $25. In a field of engineering in which there has been in recent years very m u c h activity it is surprising that this is the first major t e x t - b o o k to appear for about a decade. The reason for this is partly the lack of courses at undergraduate or even graduate level, but it probably also has much to do with the heterogeneous nature of the subject matter. On the one hand, the classical mathematically-developed t h e o r y of vibrations of single- and multi-degree of f r e e d o m systems finds application in some problems in soil dynamics, e.g. machine foundations, while, on the other hand, the d y n a m i c material behaviour of soils, e.g. soil liquefaction, is a branch of material t e c h n o l o g y where a satisfactory understanding of the mechanical behaviour is only slowly emerging. Thus it is difficult to address the various topics included in soil dynamics in a uniform manner and with equal authority. The author must be given credit for a t t e m p t i n g this. In c o m m o n with previous text books the t h e o r y of the vibrations of simple systems and wave propagation in an elastic m e d i u m is dealt with in i n t r o d u c t o r y chapters. With regard to wave propagation in the ground there are two problems which have considerable importance, namely vertical wave propagation through soil layers and the emission of waves from a structure resting on or e m b e d d e d in an elastic half space. The first of these topics receives very scant coverage in the text, while the latter is briefly dealt with in the final chapter on machine foundations. The a u t h o r presents a short summary of the dynamic stress-deformation and strength characteristics of soils including a description of some testing techniques especially those relevant to Indian Standards. Unfortunately, he gives only half a page to the resonant column test, which is assuming an ever increasing role in the investigation of soil properties at very small strains. The evaluation of the test would require a more detailed knowledge of vibrational behaviour of a colunm than that presented in the chapter on wave propagation, i.e. influence of end masses. Fairly comprehensive coverage is given of the behaviour of retaining wails and foundations under earth-
132
Eng. Struct., 1982, Vol. 4, April
quakes, where emphasis is placed on limit equilibrium analytical solutions. This reflects the author's own research interests in these fields and the corresponding chapters are replete with test data and theoretical curves resulting from his investigations. However, he reminds the reader of the many gaps that still exist in our knowledge of these topics. For those concerned with pile foundations there is a useful summary of m e t h o d s applied in current practice, i.e. with the restriction of modelling the soil using Winkler springs. Much space is devoted to the statical behaviour (22 out of about 50 pages), whereas only brief mention is made of more exact solutions allowing for radiation damping in the layered halfspace and resonance effects. Regarding the question of soil liquefaction there has been a proliferation of technical and research publications in the last one and a half decades. Here the author gives a t h o r o u g h treatment and, for the student, a useful review of the subject. With reference to the text as a whole, in the reviewer's opinion it would be more useful to include greater detail here and there, and not simply a brief reference to related publications, than to present a resum~ of the statical behaviour of materials and structures as is done in chapters 4, 5, 6 and 7. Some c o m m e n t s regarding wave propagation problems have already been made. Another neglected area is the numerical t r e a t m e n t of the vibration of multi-degree of freedom systems using for example finite element techniques. In practice the seismic analysis of earth structures (e.g. dams) and soil-structure interaction systems relies heavily on these methods. For the book to represent a state-of-the-art as claimed in the Preface an a t t e m p t should be made, even in an introductory text, to describe in a simplified manner the structural methods of analysis, including the substructure method. Notwithstanding, the author has done well to provide a basic, more or less self-contained text intended to meet the needs of those c o m m e n c i n g studies in this field. The book is easy to follow partly due to the arrangement of topics and balance of subject matter and partly due to the relatively simple language style. The p r o d n c t i o n of the book is of a good standard and being relatively inexpensive it can be r e c o m m e n d e d to students of various backgrounds, to
soils engineers not familiar with the dynamical behaviour of soils, while the book should also appeal to practicing structural engineers who want to further their knowledge on the soils side of soil dynamics.
E. G. Prater
Computational methods for offshore structu res Eds H. Armen and S. Stiansen Americal Society of Mechanical Engineers, 1980, US $24.00 The book contains the proceedings of the Winter Annual Meeting of the A m e r i c a n Society of Mechanical Engineers held in Chicago during the 16-21 N o v e m b e r 1980, and is published in the Applied Mechanics Symposia Series of the society as AMD Vol. 37. In this volume 14 research papers on c o m p u t a t i o n a l m e t h o d s applied to offshore structures are presented. The papers deal primarily with analysis of h y d r o d y n a m i c loads and load effects, including structure-fluid interactions, by means of sink-source methods, boundary integral techniques and finite element methods. These techniques are applied in the analysis of fixed oftshore platforms, submerged shells, semi-submersibles, m o o r e d surface vessels, tension leg platforms, marine risers, offshore pipelines, barge m o u n t e d cranes among others, emphasizing static and dynamic response effects as well as buckling and fatigue. The volume has been reproduced from the original typescripts of the authors which has resulted in some n o n u n i f o r m i t y of the printed text. However, the results are clear and legible in most cases. It is the impression of the reviewer that this publication contains nmch useful information and enlightens some of the current research activities concerning c o m p u t a t i o n a l methods for offshore structures. Even though some of the material presented has appeared elsewhere such presentations can be regarded as an update of previous work, and therefore useful. Hence, this v o l u m e can be r e c o m m e n d e d to engineers doing research work on or applying c o m p u t a t i o n a l methods for offshore structures.
Ragnar SigbjSrnsson
McGraw-Hill, New York, xiv +426, 1981. US $25. In a field of engineering in which there has been in recent years very m u c h activity it is surprising that this is the first major t e x t - b o o k to appear for about a decade. The reason for this is partly the lack of courses at undergraduate or even graduate level, but it probably also has much to do with the heterogeneous nature of the subject matter. On the one hand, the classical mathematically-developed t h e o r y of vibrations of single- and multi-degree of f r e e d o m systems finds application in some problems in soil dynamics, e.g. machine foundations, while, on the other hand, the d y n a m i c material behaviour of soils, e.g. soil liquefaction, is a branch of material t e c h n o l o g y where a satisfactory understanding of the mechanical behaviour is only slowly emerging. Thus it is difficult to address the various topics included in soil dynamics in a uniform manner and with equal authority. The author must be given credit for a t t e m p t i n g this. In c o m m o n with previous text books the t h e o r y of the vibrations of simple systems and wave propagation in an elastic m e d i u m is dealt with in i n t r o d u c t o r y chapters. With regard to wave propagation in the ground there are two problems which have considerable importance, namely vertical wave propagation through soil layers and the emission of waves from a structure resting on or e m b e d d e d in an elastic half space. The first of these topics receives very scant coverage in the text, while the latter is briefly dealt with in the final chapter on machine foundations. The a u t h o r presents a short summary of the dynamic stress-deformation and strength characteristics of soils including a description of some testing techniques especially those relevant to Indian Standards. Unfortunately, he gives only half a page to the resonant column test, which is assuming an ever increasing role in the investigation of soil properties at very small strains. The evaluation of the test would require a more detailed knowledge of vibrational behaviour of a colunm than that presented in the chapter on wave propagation, i.e. influence of end masses. Fairly comprehensive coverage is given of the behaviour of retaining wails and foundations under earth-
132
Eng. Struct., 1982, Vol. 4, April
quakes, where emphasis is placed on limit equilibrium analytical solutions. This reflects the author's own research interests in these fields and the corresponding chapters are replete with test data and theoretical curves resulting from his investigations. However, he reminds the reader of the many gaps that still exist in our knowledge of these topics. For those concerned with pile foundations there is a useful summary of m e t h o d s applied in current practice, i.e. with the restriction of modelling the soil using Winkler springs. Much space is devoted to the statical behaviour (22 out of about 50 pages), whereas only brief mention is made of more exact solutions allowing for radiation damping in the layered halfspace and resonance effects. Regarding the question of soil liquefaction there has been a proliferation of technical and research publications in the last one and a half decades. Here the author gives a t h o r o u g h treatment and, for the student, a useful review of the subject. With reference to the text as a whole, in the reviewer's opinion it would be more useful to include greater detail here and there, and not simply a brief reference to related publications, than to present a resum~ of the statical behaviour of materials and structures as is done in chapters 4, 5, 6 and 7. Some c o m m e n t s regarding wave propagation problems have already been made. Another neglected area is the numerical t r e a t m e n t of the vibration of multi-degree of freedom systems using for example finite element techniques. In practice the seismic analysis of earth structures (e.g. dams) and soil-structure interaction systems relies heavily on these methods. For the book to represent a state-of-the-art as claimed in the Preface an a t t e m p t should be made, even in an introductory text, to describe in a simplified manner the structural methods of analysis, including the substructure method. Notwithstanding, the author has done well to provide a basic, more or less self-contained text intended to meet the needs of those c o m m e n c i n g studies in this field. The book is easy to follow partly due to the arrangement of topics and balance of subject matter and partly due to the relatively simple language style. The p r o d n c t i o n of the book is of a good standard and being relatively inexpensive it can be r e c o m m e n d e d to students of various backgrounds, to
soils engineers not familiar with the dynamical behaviour of soils, while the book should also appeal to practicing structural engineers who want to further their knowledge on the soils side of soil dynamics.
E. G. Prater
Computational methods for offshore structu res Eds H. Armen and S. Stiansen Americal Society of Mechanical Engineers, 1980, US $24.00 The book contains the proceedings of the Winter Annual Meeting of the A m e r i c a n Society of Mechanical Engineers held in Chicago during the 16-21 N o v e m b e r 1980, and is published in the Applied Mechanics Symposia Series of the society as AMD Vol. 37. In this volume 14 research papers on c o m p u t a t i o n a l m e t h o d s applied to offshore structures are presented. The papers deal primarily with analysis of h y d r o d y n a m i c loads and load effects, including structure-fluid interactions, by means of sink-source methods, boundary integral techniques and finite element methods. These techniques are applied in the analysis of fixed oftshore platforms, submerged shells, semi-submersibles, m o o r e d surface vessels, tension leg platforms, marine risers, offshore pipelines, barge m o u n t e d cranes among others, emphasizing static and dynamic response effects as well as buckling and fatigue. The volume has been reproduced from the original typescripts of the authors which has resulted in some n o n u n i f o r m i t y of the printed text. However, the results are clear and legible in most cases. It is the impression of the reviewer that this publication contains nmch useful information and enlightens some of the current research activities concerning c o m p u t a t i o n a l methods for offshore structures. Even though some of the material presented has appeared elsewhere such presentations can be regarded as an update of previous work, and therefore useful. Hence, this v o l u m e can be r e c o m m e n d e d to engineers doing research work on or applying c o m p u t a t i o n a l methods for offshore structures.
Ragnar SigbjSrnsson