G. Hofstetter, H.A. Mang:
"Computational Mechanics of Reinforced Concrete Structures";
Vieweg Verlag, Braunschweig/Wiesbaden, 1995, 366 S.
Almost three decades have passed since publication of the pioneering work by Ngo and Scordelis on finite element analyses of reinforced concrete beams. This period of time is characterized by extensive research activities in the fields of constituive modelling of plain and reinforced concrete and of the development of powerful algorithms for nonlinear finite element analyses of reinforced concrete structures. These research endeavors have resulted in an impressive increase of the scientific level of material modelling of plain and reinforced concrete and of the efficiency of software for nonlinear finite element analyses of reinforced concrete structures.
The impact of these research activities on engineering practice, however, is less impressive. This situation was addressd by Scordelis, in 1985, in a state-of-the-art report: "While extensive research on finite element analysis of reinforced concrete structures has been conducted over the past eighteen years, its implementation in the design of actual structuras has been disappointing. Present designs are still generally based on determining internal forces and moments by elastic analyes in which the reinforced concrete or prestressed concrete system is assumed to be uncracked, homogeneous, isotropic and linearly elastic."
In spite of the growing awareness of the inadequacy of these assumptions and the increasing acceptance of nonlinear finite element analysis of reinforced concrete structures during the last decade, the dominance of traditional methods on analysis of such structures has remained. From the standpoint of engineering parctice, this is understandable. The motivation for replacing conventional methods of analysis of reinforced concrete structures by mechanically more sophisiticated and considerably more complicated methods will remain small as long as the expected increase in quality of the design is not commensurate to the increase in mechanical sophistication and computational complexity. Nevertheless, nonlinear finite element analyses of reinforced concrete structures have gained momentum during the last decade. At present, this mode of analysis is mainly used as a tool for the assessment of the structural safety of non-standard reinforced concrete structures.
The importance of the mentioned class of finite element analyses as powerful research tool in the field of computational mechancis of reinforced concrete structures is indisputed. The two constituent parts of this scientific field are constitutive modelling of reinforced concrete and nonlinear structural analysis of reinforced concrete structures. In the opinion of the writers these tow constituent parts are drifting apart. The conclusions of a survey paper on "Nonlinear finite element analysis of reinforced and prestressed concrete structures" contain a remark on this observation.
This paper was presented at the Second International Conference on Computer Aided Analysis and Design of Concrete Structures. One of the main goals of this scientific conference was to bridge the gap between constitutive modelling and structural analysis. Although this goal was not reached, there was a consensus of opinion that computational mechanics of reinforced concrete structures rests on both constitutive modelling and structural analysis. Constitutive modelling without application of the developed material models to structural analysis runs the risk of becoming an end in itself. Structural analysis based on obsolete, mechanically inconsistent material models may yield useless results.
The writers feel committed to the concept of a synthesis of consitutive modelling of reinforced concrete and of structural analysis of reinforced concrete structures. This commitment has led to the title of the book: Computational Mechanics of Reinforced Concrete Structures. It is tacitly understood that the term "computational mechanics" includes constitutive modelling, with special emphasis on algorithmic aspects, and structural analysis.
The book consists of four chapters. Their titles are:
1. Materials, Physical Phenomena, Experiments
2. Mathematical Models
3. The Finite Element Method for Reinforced Concrete and Prestressed Concrete
4. Application to Engineering Problems
The experimants described in chapter 1 provide the basis for the formulation of mathematical models for the simulation of the material behavior. These models are presented in chapter 2. In chapter 4 they are applied to the analysis of reinforced and prestressed concrete structures by means of the finite element methods described in chapter 3. The numerica anlyses reported in chapter 4 have been carried out at the Institute for Strength of Materials of the University of Technology of Vienna during the last fifteen years.
There is a large body of literature relevant to the topic of the book. It is growing at a great pace. Hence, a selection of subtopics to be treated in the book was necesary. This selection was based on two crieria. The first sriterion was teh possibility of a consistent and well-balanced treatment of a subtopic. In this context, the terms "consistent" and "well-balanced" refer to the four chapters of the bool. The prupose of this criterion was to counteract the aformentioned drifting apart of the two consituent parts of continuum mechanics of reinforced concrete. The second criterion was the pertinent research experience of the writers. These two criteriahave resulted in the restriction of static, deterministic mathematical models.
Basic courses on mathematics, mechanics, material sciences, reinforced concrete and finite element methods, representing standard parts of civil engineering curricula at institutions of higher learning, provide the necessary grounding to benefit from the book.
The writers are idebted to the former students H. Floegl and H. Walter and to the former doctoral students and present colleagues J. Eberhardsteiner and G. Meschke for many helpful discussions and for the permit to use material from their dissertations.
Special thanks go to O. Graf for the drawing of the figures and to Ms. E. Koglbauer for the cooperation in producing the LATEX-file for the camera-ready manuscript.
The writers also wish to thank the publishers, Vieweg-Verlag, Braunschweig/Wiesbaden, and the editors of the book series "Fundamentals and Advances in the Engineering Sciences" W.B. Krätzig, O. Mahrenholtz and P. Hagedorn, for the good cooperation and the patience in connection with the delayed completion of the manuscript. Last, but not least, thanks are due to the late Th. Lehmann, formerly co-editor of the book series, for his part in the realization of the book project.
Vienna, February 1995
G. Hofstetter and H.A. Mang