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Cable corrosion in bridges and other structures
888 is concerned with applications of the theory. Chap. 1 gives an excellent introduction to the concepts of fracture mechanics, and their possible use is championed for overcoming various problems inherent in current design thinking for structural concrete such as, for example, the calculation of deflections and the presence of fibres. The principles of linear elastic fracture mechanics are outlined in Chap. 2 (which also contains useful formulae for several types of commonly occurring stress intensity factors) while those of nonlinear fracture mechanics are explained in Chap. 3. In Chap. 4 the structure and fracture processes of concrete are discussed, as well as the concept of strain localization. Several chapters devoted to the nonlinear fracture mechanics of quasi-brittle materials follow, encompassing basic principles, proposed models and finite element analysis (Chap. 5), test methods for determining mode-I material fracture parameters (Chap. 6), and fracture resistance curves (Chap. 7); fracture-mechanics approaches for a wider range of deformation modes (I, II, III), or for their combination (mixedmode cracks), with proposed failure criteria and various test methods for the evaluation of the appropriate fracture toughnesses, are dealt with in Chap. 8. Applications of fracture-mechanics theory, contained in the last four chapters of the book, open with a substantial section on concrete structures (Chap. 9). Here, a wide range of structural problems is covered, including reinforced-concrete members in tension, bending, shear, torsion and combined loading, as well as specific structural elements such as anchor bolts, pipes and dams. Various fracturemechanics approaches to simulate compressive failure in concrete are presented in Chap. 10, while relationships between fracture mechanics and damage mechanics are explored in Chap. 11. Finally, Chap. 12 considers the application of fracture mechanics to the areas of toughening mechanisms in fibre-reinforced concrete, fatigue fracture of concrete, and the effect of creep on concrete crack growth and fracture. There is little doubt that one of the two main aims of the authors in writing the book, namely to provide an educational text in a rapidly developing area of research, has been successfully accomplished with this important publication. In this respect, only some relatively minor criticisms may be levelled at their presentation. One of these concems the somewhat abrupt introduction of certain concepts which, though well known to specialists working in the field, might cause problems for the general reader; however, such instances are not frequent and, moreover, the concepts in question are usually explained in more detail later on in the book (an example of this is the sudden mention of mode III, without apparent definition, in Chap. 2 - - b u t this
Book reviews phenomenon is discussed at considerable length in later chapters (e.g. Chap. 8)). Another criticism is the slightly aboveaverage number of misprints for a book of this quality. Thus, one encounters several instances of mispellings of words (e.g.p.7) and names (e.g.p. xiii), wrong punctuation (e.g.p. 7), careless referencing (e.g.p. 65), and especially - and perhaps most annoyingly - faulty grammar (e.g. pp. 11, 66, 71, 96). A more serious criticism can be levelled at an apparent lack of care in describing some of the works of other authors: for example in Chap. 10 it is stated that 'many previous constitutive models ]°']~ based on softening types of stress-strain relationships may not be appropriate for concrete' (p.433), although Reference 10 (published in 1980) has been superseded by several publications widely known in the literature (for instance, the 1983 paper quoted by the authors themselves as Reference 8 in the same chapter). Nevertheless, despite these drawbacks which, in a book of this size and in which the production responsibility was shared by three authors, are not entirely surprising, this text is likely to become a standard reference not only for research but also and, as intended by the authors - for the teaching of fracture-mechanics concepts and their possible application to quasibrittle materials. On the whole, the book also succeeds in its other intended aim, that of providing useful and comprehensive reference data for the practising engineer. Whether it will also advance the cause of fracture mechanics in actual structural concrete design practice is, however, less certain as some basic - but, nonetheless formidable practical difficulties remain. Firstly, one can argue that actual material-data measurement has not kept up with recent advances in structural analysis and hence theoretical computations are now more likely to be limited by the lack of availability, as input, of meaningful material properties. In this respect, as regards fracture-mechanics theories, one does not really know what happens at the tip of a crack and, in the case of structural concrete, its heterogeneous composition raises questions which look more relevant to material scientists than of use to design engineers. Secondly, there seem to be far too many theories, models, constants and tests (often quite complex) to determine these constants (see especially Chaps 5 l l). This goes against the simplicity required in everyday practice and, in particular, the need to rely on a few, or even a single, test(s) (often simple cubes or cylinders in compression). Thirdly, the measurement of constants often appears to stem from what amounts to a structural test, and this goes against an engineer's intuition that one should seek material constants in order to predict the behaviour of a structure and not the other way around. Fourthly, material constants often depend
on the size of the specimen tested and, even if this problem is resolved, one often finds in the literature that, while a set of constants may work well in predicting the response of a particular structure, such constants need to be readjusted if similarly successful predictions of other structures are to be achieved. The latter point leads one to question the validity of the theory itself, especially in view of the trend to adopt a theory a priori and then to try to adjust various material parameters so as to fit it. At the same time, there is a tendency to eventually extrapolate such theories to a wider range of materials which, while often exhibiting undoubted similarities, might need to be treated in different ways. (There is an echo of this in the relation of the main title of the book (Fracture mechanics of concrete) to its subtitle
(Applications of fracture mechanics to concrete, rock and other quasi-brittle materials).) A final point revolves around the use and meaning of the term 'quasi-brittle' as the book is clearly concerned primarily with this type of material. For concrete, at least, such terminology may be interpreted in various ways by different schools of thought and, while the authors' usage of it implies that strain-softening properties are inherent to concrete, others will argue for more brittle behaviour at the material level while, at the same time, attaining through other mechanisms the sort of strains associated with descending branches. The key feature for concrete, however, can be summarized in the statement, quoted by the authors, that 'no material fails for lack of compressive strength' (p.31). This is a view to which both good designers and experienced researchers should adhere and such a quotation in this important book is an encouraging sign that a more general consensus on the causes of failure of concrete at both material and structural levels may eventually be reached.
M. N. Pavlovic Cable corrosion in bridges and other structures F. L. Stahl and C. P. Gagnon, ASCE, New York, 1995, $40.00 This publication provides a practical and very useful review of cable corrosion. Half of the text is devoted to the background adopted in the choice of cable systems and their corrosion protection and half to case histories. Up to this time the subject matter has been largely ignored, and consequently this publication serves as an extremely useful and possibly unique reference guide. As such it is directed primarily at the practising engineer rather than the researcher. A brief history of the development and application of cables is followed by a general guide on cable types and their manufacture. Construction of major cable sup-
889
Book reviews ported bridges is outlined before the authors describe both cable-corrosion mechanisms and how they are likely to develop. Here the authors deal exclusively with suspension and cable stayed bridge main cables and hangers. Methods of protection are outlined including the use of proprietory products. Maintenance regimes including testing methods conclude the general text. The case histories, understandably, concentrate on the suspension bridges of North America but the information provided, whilst specific to each structure, contains invaluable guidance for designers and manufacturers. Of p;u'ticular interest are the description of the rehabilitation of the Brooklyn and Williamsburg bridges, constructed in 1883 and 1903, respectively, and of the extensive studies and testing undertaken on the cables of Golden Gate bridge. The consequences of corrosion are shown all toc, vividly in the main illustrations. A summary of the case histories, highlighting the relative sensitivity of the parameters, possibly using figures or graphs would have been useful. The text suffers to a certain extent from repetition and lacks in-depth information on the chemical aspects of corrosion. It would also have been valuable to have had some information on future trends and the use of modern materials. The inclusion of just a short paragraph on cable roofs and one case history of a hangar (as opposed to 18 case histories of bridges) hardly justifies the general title of the publication. More information on cable roofs, on guyed masts and on cable nets, would have been valuable and shown that each form of structure has particular corrosion aspects which need to be addressed. Notwithstanding these comments, the book would form a very useful guide and reference document for all those involved in cable design, construction and maintenance.
B. W. Smith
Scale issues in hydrological modelling Editors J. D. Kalma and M. Sivapalan, Wiley and Sons, Chichester, UK, 1995, £50 paperback, 489 pp., ISBN 0-47195847-6 The papers in this volume were originally published in H y d r o l o g i c a l P r o c e s s e s - A n I nternational J o u r n a l (1995, 9 (3-4, 237482) and (5-6, 483-728), being the subject of the proceedings of a special three-day workshop on scale issues in hydrological/environmental modelling held at Ranelagh House, Robertson, NSW, Australia, November-December 1993. The volume contains 27 papers on scale problems in hydrological modelling, by contributors from Australia, Belgium, Germany, Japan, New Zealand, UK and USA.
The contents of the book can be divided into three thematic groups: (i) basic definitions and a review of the origins of the different types of scale problems in catchment modelling (on regional and catchment scales) and methods of their solution; (ii) scale problems originating on the land surface - meteorological boundary-layer model interface; and (iii) case studies relating to both the above mentioned problems. The book is a collection of papers and lacks a coherent structure. Papers with definitions and strictly hdyrological catchment modelling problems mostly (but with exceptions) are placed in the first part of the book, whilst the last part deals with boundary layer problems. In between, there is a mixture of more detailed and specific case studies. In the first paper, Sivapalan and Kalma summarize the contributions of the Robertson workshop and recent progress in environmental and hydrological modelling. A very good and comprehensive review of scale issues is given in the second paper by Bloschl and Sivapalan. Some basic definitions are given, along with descriptions of the ranges of time and space scales corresponding to hydrological processes. Linkage across scales from the modelling point of view and a more holistic perspective dealing with dimensional analysis and similarity concepts are discussed. The 15th paper (by Beven) also gives a summary of the basic objectives of developing a scaledependent subgrid parameterization together with a list of principles which can be useful in model development. The third, and the following three, papers analyse the validity and applicability of the representative elementary area (REA) concept in rainfall-runoff modelling, problems of aggregation of hydrological responses and the critical drainage area hypothesis. The next two papers discuss scale problems in geomorphological modelling. The possibilities and requirements of use of geographical information systems (GIS) in scaling hydrological models over heterogeneous land surfaces are discussed in the paper by Band and Moore. The scaling is understood to be the estimation of spatial variation of hydrological parameters over the catchment and larger watershed regions, expressed in the form of distribution functions from point measurements and sampling. Scale and resolution effects on surface attributes are discussed. The use of GIS analysis of physiographic basin properties in the classification of modified hydrological response units (HRUs) is presented by Flugel. The developed hydrological system for the river Brrl basin contains 23 delineated HRUs and allows analysis of the regional water flow processes with spatial up- and down-scaling. The following two papers give an analysis of moisture and water fluxes distribution in time and space. The applicability of the kinematic wave approximation for the modelling of hill-slope flow is analysed
and discussion of the construction of the metachannel hydraulic geometry and its application for a natural catchment model are presented in the following two papers. The vegetation model (tree water use) parameterization is described by Hatton and Wu. The following three papers present the development of the distributed catchment scale model of subsurface runoff generation, based on the synthesis of small-scale hydrological processes. The next (20th) paper by Raupach and Finnigan is the first of a series of papers on scale issues in boundary-layer modelling for global circulation models. It deals with the problem of surface energy balances in heterogeneous terrain. After a review of scale issues in hydrology and meteorology the up-scaling problem in boundary layer meteorology is outlined. The hypothesis of insensitivity of regionally averaged energy balances to the scale of heterogeneity is also tested. The next paper by Silberstein and Sivapalan continues discussion of the problem of the effects of land surface heterogeneity on the estimation of terrestrial water and energy balances on the catchment scale. Xinmei and co-anthors describe the estimation of plant-energy parameters from high resolution radiometer satellite data and surface observations. The estimated parameters are subsequently used to model energy exchange between the surface and lower atmospheric layers. The influence of heterogeneity of the ground surface at different scales on energy and mass fluxes in the atmosphere and its dynamic responses within hypothetical GCM grid square are analysed by Avissar and subsequently by Sivapalan and Woods. At the end Pitman gives an analysis of the influence of different aggregation methods of vegetation data for the GCMs on the resulting simulations. In summary, the papers represent the most recent developments on scale problems in hydrological modelling in the seven contributing countries. The reader is provided with a good and comprehensive review of the basic issues and methods for linking model parameterization across a range of spatial and temporal scales. However, the book would gain much in terms of clarity if the editors had put the papers in some more logical, structured order, even as basic as that presented by the reviewer.
Renata Romanowicz
Acceptable risks for major infrastructure P. Heinrichs and R. Fell A. A. Balkema, Rotterdam, The Netherlands, 1995, 203 pages, £45, ISBN 9054105925 This is a book of papers which were originally presented at a symposium organized jointly by the Australian National Commit-
Book reviews phenomenon is discussed at considerable length in later chapters (e.g. Chap. 8)). Another criticism is the slightly aboveaverage number of misprints for a book of this quality. Thus, one encounters several instances of mispellings of words (e.g.p.7) and names (e.g.p. xiii), wrong punctuation (e.g.p. 7), careless referencing (e.g.p. 65), and especially - and perhaps most annoyingly - faulty grammar (e.g. pp. 11, 66, 71, 96). A more serious criticism can be levelled at an apparent lack of care in describing some of the works of other authors: for example in Chap. 10 it is stated that 'many previous constitutive models ]°']~ based on softening types of stress-strain relationships may not be appropriate for concrete' (p.433), although Reference 10 (published in 1980) has been superseded by several publications widely known in the literature (for instance, the 1983 paper quoted by the authors themselves as Reference 8 in the same chapter). Nevertheless, despite these drawbacks which, in a book of this size and in which the production responsibility was shared by three authors, are not entirely surprising, this text is likely to become a standard reference not only for research but also and, as intended by the authors - for the teaching of fracture-mechanics concepts and their possible application to quasibrittle materials. On the whole, the book also succeeds in its other intended aim, that of providing useful and comprehensive reference data for the practising engineer. Whether it will also advance the cause of fracture mechanics in actual structural concrete design practice is, however, less certain as some basic - but, nonetheless formidable practical difficulties remain. Firstly, one can argue that actual material-data measurement has not kept up with recent advances in structural analysis and hence theoretical computations are now more likely to be limited by the lack of availability, as input, of meaningful material properties. In this respect, as regards fracture-mechanics theories, one does not really know what happens at the tip of a crack and, in the case of structural concrete, its heterogeneous composition raises questions which look more relevant to material scientists than of use to design engineers. Secondly, there seem to be far too many theories, models, constants and tests (often quite complex) to determine these constants (see especially Chaps 5 l l). This goes against the simplicity required in everyday practice and, in particular, the need to rely on a few, or even a single, test(s) (often simple cubes or cylinders in compression). Thirdly, the measurement of constants often appears to stem from what amounts to a structural test, and this goes against an engineer's intuition that one should seek material constants in order to predict the behaviour of a structure and not the other way around. Fourthly, material constants often depend
on the size of the specimen tested and, even if this problem is resolved, one often finds in the literature that, while a set of constants may work well in predicting the response of a particular structure, such constants need to be readjusted if similarly successful predictions of other structures are to be achieved. The latter point leads one to question the validity of the theory itself, especially in view of the trend to adopt a theory a priori and then to try to adjust various material parameters so as to fit it. At the same time, there is a tendency to eventually extrapolate such theories to a wider range of materials which, while often exhibiting undoubted similarities, might need to be treated in different ways. (There is an echo of this in the relation of the main title of the book (Fracture mechanics of concrete) to its subtitle
(Applications of fracture mechanics to concrete, rock and other quasi-brittle materials).) A final point revolves around the use and meaning of the term 'quasi-brittle' as the book is clearly concerned primarily with this type of material. For concrete, at least, such terminology may be interpreted in various ways by different schools of thought and, while the authors' usage of it implies that strain-softening properties are inherent to concrete, others will argue for more brittle behaviour at the material level while, at the same time, attaining through other mechanisms the sort of strains associated with descending branches. The key feature for concrete, however, can be summarized in the statement, quoted by the authors, that 'no material fails for lack of compressive strength' (p.31). This is a view to which both good designers and experienced researchers should adhere and such a quotation in this important book is an encouraging sign that a more general consensus on the causes of failure of concrete at both material and structural levels may eventually be reached.
M. N. Pavlovic Cable corrosion in bridges and other structures F. L. Stahl and C. P. Gagnon, ASCE, New York, 1995, $40.00 This publication provides a practical and very useful review of cable corrosion. Half of the text is devoted to the background adopted in the choice of cable systems and their corrosion protection and half to case histories. Up to this time the subject matter has been largely ignored, and consequently this publication serves as an extremely useful and possibly unique reference guide. As such it is directed primarily at the practising engineer rather than the researcher. A brief history of the development and application of cables is followed by a general guide on cable types and their manufacture. Construction of major cable sup-
889
Book reviews ported bridges is outlined before the authors describe both cable-corrosion mechanisms and how they are likely to develop. Here the authors deal exclusively with suspension and cable stayed bridge main cables and hangers. Methods of protection are outlined including the use of proprietory products. Maintenance regimes including testing methods conclude the general text. The case histories, understandably, concentrate on the suspension bridges of North America but the information provided, whilst specific to each structure, contains invaluable guidance for designers and manufacturers. Of p;u'ticular interest are the description of the rehabilitation of the Brooklyn and Williamsburg bridges, constructed in 1883 and 1903, respectively, and of the extensive studies and testing undertaken on the cables of Golden Gate bridge. The consequences of corrosion are shown all toc, vividly in the main illustrations. A summary of the case histories, highlighting the relative sensitivity of the parameters, possibly using figures or graphs would have been useful. The text suffers to a certain extent from repetition and lacks in-depth information on the chemical aspects of corrosion. It would also have been valuable to have had some information on future trends and the use of modern materials. The inclusion of just a short paragraph on cable roofs and one case history of a hangar (as opposed to 18 case histories of bridges) hardly justifies the general title of the publication. More information on cable roofs, on guyed masts and on cable nets, would have been valuable and shown that each form of structure has particular corrosion aspects which need to be addressed. Notwithstanding these comments, the book would form a very useful guide and reference document for all those involved in cable design, construction and maintenance.
B. W. Smith
Scale issues in hydrological modelling Editors J. D. Kalma and M. Sivapalan, Wiley and Sons, Chichester, UK, 1995, £50 paperback, 489 pp., ISBN 0-47195847-6 The papers in this volume were originally published in H y d r o l o g i c a l P r o c e s s e s - A n I nternational J o u r n a l (1995, 9 (3-4, 237482) and (5-6, 483-728), being the subject of the proceedings of a special three-day workshop on scale issues in hydrological/environmental modelling held at Ranelagh House, Robertson, NSW, Australia, November-December 1993. The volume contains 27 papers on scale problems in hydrological modelling, by contributors from Australia, Belgium, Germany, Japan, New Zealand, UK and USA.
The contents of the book can be divided into three thematic groups: (i) basic definitions and a review of the origins of the different types of scale problems in catchment modelling (on regional and catchment scales) and methods of their solution; (ii) scale problems originating on the land surface - meteorological boundary-layer model interface; and (iii) case studies relating to both the above mentioned problems. The book is a collection of papers and lacks a coherent structure. Papers with definitions and strictly hdyrological catchment modelling problems mostly (but with exceptions) are placed in the first part of the book, whilst the last part deals with boundary layer problems. In between, there is a mixture of more detailed and specific case studies. In the first paper, Sivapalan and Kalma summarize the contributions of the Robertson workshop and recent progress in environmental and hydrological modelling. A very good and comprehensive review of scale issues is given in the second paper by Bloschl and Sivapalan. Some basic definitions are given, along with descriptions of the ranges of time and space scales corresponding to hydrological processes. Linkage across scales from the modelling point of view and a more holistic perspective dealing with dimensional analysis and similarity concepts are discussed. The 15th paper (by Beven) also gives a summary of the basic objectives of developing a scaledependent subgrid parameterization together with a list of principles which can be useful in model development. The third, and the following three, papers analyse the validity and applicability of the representative elementary area (REA) concept in rainfall-runoff modelling, problems of aggregation of hydrological responses and the critical drainage area hypothesis. The next two papers discuss scale problems in geomorphological modelling. The possibilities and requirements of use of geographical information systems (GIS) in scaling hydrological models over heterogeneous land surfaces are discussed in the paper by Band and Moore. The scaling is understood to be the estimation of spatial variation of hydrological parameters over the catchment and larger watershed regions, expressed in the form of distribution functions from point measurements and sampling. Scale and resolution effects on surface attributes are discussed. The use of GIS analysis of physiographic basin properties in the classification of modified hydrological response units (HRUs) is presented by Flugel. The developed hydrological system for the river Brrl basin contains 23 delineated HRUs and allows analysis of the regional water flow processes with spatial up- and down-scaling. The following two papers give an analysis of moisture and water fluxes distribution in time and space. The applicability of the kinematic wave approximation for the modelling of hill-slope flow is analysed
and discussion of the construction of the metachannel hydraulic geometry and its application for a natural catchment model are presented in the following two papers. The vegetation model (tree water use) parameterization is described by Hatton and Wu. The following three papers present the development of the distributed catchment scale model of subsurface runoff generation, based on the synthesis of small-scale hydrological processes. The next (20th) paper by Raupach and Finnigan is the first of a series of papers on scale issues in boundary-layer modelling for global circulation models. It deals with the problem of surface energy balances in heterogeneous terrain. After a review of scale issues in hydrology and meteorology the up-scaling problem in boundary layer meteorology is outlined. The hypothesis of insensitivity of regionally averaged energy balances to the scale of heterogeneity is also tested. The next paper by Silberstein and Sivapalan continues discussion of the problem of the effects of land surface heterogeneity on the estimation of terrestrial water and energy balances on the catchment scale. Xinmei and co-anthors describe the estimation of plant-energy parameters from high resolution radiometer satellite data and surface observations. The estimated parameters are subsequently used to model energy exchange between the surface and lower atmospheric layers. The influence of heterogeneity of the ground surface at different scales on energy and mass fluxes in the atmosphere and its dynamic responses within hypothetical GCM grid square are analysed by Avissar and subsequently by Sivapalan and Woods. At the end Pitman gives an analysis of the influence of different aggregation methods of vegetation data for the GCMs on the resulting simulations. In summary, the papers represent the most recent developments on scale problems in hydrological modelling in the seven contributing countries. The reader is provided with a good and comprehensive review of the basic issues and methods for linking model parameterization across a range of spatial and temporal scales. However, the book would gain much in terms of clarity if the editors had put the papers in some more logical, structured order, even as basic as that presented by the reviewer.
Renata Romanowicz
Acceptable risks for major infrastructure P. Heinrichs and R. Fell A. A. Balkema, Rotterdam, The Netherlands, 1995, 203 pages, £45, ISBN 9054105925 This is a book of papers which were originally presented at a symposium organized jointly by the Australian National Commit-