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Serviceability failures of concrete structures involving excessive cracking or deflection are relatively common, even in structures that comply with code requirements. This is often as a result of a failure to adequately account for the time-dependent deformations of concrete in the design of the structure. The serviceability provisions embodied in
Serviceability failures of concrete structures involving excessive cracking or deflection are relatively common, even in structures that comply with code requirements. This is often as a result of a failure to adequately account for the time-dependent deformations of concrete in the design of the structure. The serviceability provisions embodied in codes of practice are relatively crude and, in some situations, unreliable and do not adequately model the in-service behaviour of structures. In particular, they fail to adequately account for the effects of creep and shrinkage of the concrete. Design for serviceability is complicated by the non-linear and inelastic behaviour of concrete at service loads. Providing detailed information, this book helps engineers to rationally predict the time-varying deformation of concrete structures under typical in-service conditions. It gives analytical methods to help anticipate time-dependent cracking, the gradual change in tension stiffening with time, creep induced deformations and the load independent strains caused by shrinkage and temperature changes. The calculation procedures are illustrated with many worked examples. A vital guide for practising engineers and advanced students of structural engineering on the design of concrete structures for serviceability and provides a penetrating insight into the time-dependent behaviour of reinforced and prestressed concrete structures.
This comprehensive treatise covers in detail practical methods of analysis as well as advanced mathematical models for structures highly sensitive to creep and shrinkage. Effective computational algorithms for century-long creep effects in structures, moisture diffusion and high temperature effects are presented. The main design codes and recommendations (including RILEM B3 and B4) are critically compared. Statistical uncertainty of century-long predictions is analyzed and its reduction by extrapolation is discussed, with emphasis on updating based on short-time tests and on long-term measurements on existing structures. Testing methods and the statistics of large randomly collected databases are critically appraised and improvements of predictions of multi-decade relaxation of prestressing steel, cyclic creep in bridges, cracking damage, etc., are demonstrated. Important research directions, such as nanomechanical and probabilistic modeling, are identified, and the need for separating the long-lasting autogenous shrinkage of modern concretes from the creep and drying shrinkage data and introducing it into practical prediction models is emphasized. All the results are derived mathematically and justified as much as possible by extensive test data. The theoretical background in linear viscoelasticity with aging is covered in detail. The didactic style makes the book suitable as a textbook. Everything is properly explained, step by step, with a wealth of application examples as well as simple illustrations of the basic phenomena which could alternate as homeworks or exams. The book is of interest to practicing engineers, researchers, educators and graduate students.
This book is based on Reinforced Concrete-Prestressed Concrete, Volume 2, Accounting for the Effects of Creep and Shrinkage on the Behavior of Structural Systems by Hubert Rusch and Dieter Jungwirth, which appeared in German in 1976. Even then, it was Hubert Rusch's fervent wish to have his thoughts on the deformations of concrete translated into English in order to reach a wider audience. His earlier efforts to contribute a study to the Series of Monographs of the Ameri can Institute had unfortunately not succeeded. Despite a serious illness, Hubert Rusch undertook, with his characteristic prudence and thoroughness, the preparatory work for the translation and related revision of his book. Unfortunately fate did not grant him the satisfaction of seeing his work completed. Hubert Rusch died on October 17, 1979. In writing this book, Hubert Rusch drew on his many years of devoted study of the creep problem. These investigations go back to 1934. His awareness of the plastic deformation of concrete under sustained load, which had been reported to him on the occasion of an American sojourn, led him to discover the causes of a major building collapse. At his urging, Professor A. Hummel published, in 1935, a critical survey of the test results then available on concrete creep.
Today research on creep and shrinkage of concrete is diversified to such a degree that specialists working in different areas sometimes find it difficult to understand one-another. Materials scientists are mainly interested in processes on a microstructural level but they do not necessarily understand the relevance of time dependent deformation in structural design. On the other hand engineers who apply simplified model laws in non-elastic structural analysis are not always in the position to judge the limitations implied in their approach. It is generally realized that further development can be stimulated by a more effective exchange of results and ideas among the different groups involved. In an attempt to bridge this obvious gap in September 1980 there was a Conference organized at Swiss Federal Institute of Technology in Lausanne. The papers presented at this meeting covered the wide range starting with microstructural aspects and mechanisms and including constitutive modelling and structural creep analysis. These contributions together with summaries of two panel discussions are being published in this volume. All serious of the meeting have been introduced by invited lectures. These papers will be published in a special volume "Creep and Moisture Effects in Concrete". This special volume is rather to be a general survey of the different areas covered while the present conference proceedings provide a unique selection of research papers. Nowadays time-dependent deformation of concrete can be taken into consideration realistically by computerized structural analysis.
This book presents a selection of the author‘s firsthand experience with incidents related to reinforced and prestressed concrete structures, helping readers gain an understanding of errors that can occur in order to avoid making them. He includes mistakes discovered at the design stage, ones that led to failures, and some that involved partial structure collapse all of which required remedial action to ensure safety. The book focuses on specific incidents that occurred at various points in the construction process, including mistakes related to structural misunderstanding, extrapolation of codes of practice, and poor construction.