Failures of major engineering systems always raise public concern on the safety and reliability of engineering infrastructure. Decades ago quantitative evaluations of the reliability of complex infrastructure systems were not practical, if not impossible. Engineers had to resort to the use of a safety factor mainly determined through experience and judgment. The contribution of human factors to structural safety still remains elusive for analytical treatment. The main areas of concern and application in this book are hydrosystems and related environmental engineering.
Without exception, failures of hydrosystem infrastructure (e. g., dams, levees, and storm sewers) could potentially pose significant threats to public safety and inflict enormous damage on properties and the environment. The traditional approach of considering occurrence frequency of heavy rainfalls or floods, along with an arbitrarily chosen safety factor, has been found inadequate for assessing the reliability of hydrosystem infrastructure and for risk-based cost analysis and decision making. In the past two decades or so, there has been a steady growth in the development and application of reliability analysis in hydrosystems engineering and other disciplines. The main objective ofthe book is to bring together some of these developments and applications in one volume and to present them in a systematic and understandable manner to the water resource related engineering profession. Through this book it is hoped to demonstrate how to integrate involved physical processes, along with some knowledge in mathematics, probability, and statistics, to perform reliability assessment and risk analysis of hydrosystem engineering problems. An accompanying book, Hydrosystems Engineering Uncertainty Analysis, provides treatments and quantifications of various types of uncertainty, which serve as essential information needed for the reliability assessment and risk analysis of hydrosystems.
Hydrosystems is the term used to describe collectively the technical areas of hydrology, hydraulics, and water resources. The term has now been widely used to encompass various water resource systems including surface water storage, groundwater, water distribution, flood control, drainage, and others. In many hydrosystem infrastructural engineering and management problems, both quantity as well as quality aspects of water and other environmental issues have to be addressed simultaneously. Due to the presence of numerous uncertainties, the ability of the system to achieve the goals of design and management decisions cannot be assessed definitely. It is almost mandatory for an engineer involved in major hydrosystem infrastructural design or hazardous waste management to quantify the potential risk of failure and the associated consequences.
Application of reliability analysis to hydrosystems engineering covers a wide scope of subfields, ranging from data collection and gauging network design to turbulence loading on structures; and from inland surface water to groundwater to coastal water. In terms of the system scale, it could involve entire river basins containing many components, or a large dam and reservoir, or a single culvert or pipe. Depending on the objective, the application could be for designing the geometry and dimension of hydraulic facilities, for planning of a hydraulic project, for determining operation procedure or management strategy, for risk-cost analysis, or for risk-based decision making.
The book is not intended to be a review of literature, but is an introduction for upper level undergraduate and graduate students to methods applicable for reliability analysis of hydrosystem infrastructure. Most of the principles and methodologies presented in the book can equally be applied to other civil engineering disciplines. The book presents relevant theories of reliability analysis in a systematic fashion and illustrates applications to various hydrosystem engineering problems. Although more advanced statistical and mathematical skills are occasionally required, the great majority of the problems can be solved with basic knowledge of probability and statistics. Illustrations in the book bring together the use of probability and statistics, along with knowledge of hydrology, hydraulics, water resources, and operations research for the reliability analysis and optimal reliability-based design of various hydrosystem engineering problems. The book provides added dimensions to water resource engineers beyond conventional frequency analysis.
The book consists of eight chapters. In each chapter of the book, ample examples are given to illustrate the methodology for enhancing the understanding of the materials. The book can serve as an excellent reference book not only for engineers, planners, system analysts, and managers in area of hydrosystems, but also other civil engineering disciplines. In addition, end-of-chapter problems are provided for practice and homework assignments for classroom teaching.
The book focuses on integration of reliability analysis with knowledge in hydrosystems engineering with applications made to hydraulics, hydrology, water resources, and occasionally, to environmental and water quality management related problems. Since many good books on basic probability, statistics, and hydrologic frequency analysis have been written, background in probability, statistics, and frequency analysis that are relevant to reliability analysis are summarized in Chapters 2 and 3, respectively. The book, instead of dwelling on the subject of data analysis, focuses on how to perform reliability analysis of hydrosystem engineering problems once relevant statistical data analysis has been conducted. As real-life hydrosystems generally involve various uncertainties other than just inherent natural randomness of hydrologic events, the book goes beyond conventional frequency analysis by considering reliability issues in a more general context of hydrosystems engineering and management. Chapter 4 elaborates the reliability analysis methods considering load-resistance interaction under the static and time-dependent conditions. First-order and second-order reliability methods, with the emphasis given to the former, are derived. For many hydrosystem infrastructures, it is sometimes practical to treat the system as a whole and analyze its performance over time without considering detailed load-resistance interaction. Chapter 5 is devoted to time-to-failure analysis that is particularly useful for dealing with systems that are repairable. Chapter 6 provides a detailed treatment of using Monte Carlo simulation and its variations applicable to reliability analysis. The subject, in most books, is covered in the context of univariate problems in which stochastic variables are treated as independent and uncorrelated. In reality, the great majority of the hydrosystem infrastructural engineering problems involve multiple stochastic variables, which are correlated. Treatment of such problems is emphasized. Chapter 7 focuses on the evaluation of system reliability by integrating load-resistance reliability analysis methods or time-to-failure analysis, along with system configuration, for assessing system reliability. Different methods for system reliability analysis are presented and demonstrated through examples. Chapter 8 presents the framework that integrates uncertainties, risk, reliability, and economics for an optimal design of hydrosystem infrastructure. A brief description of system optimization is also given.
The intended uses and audiences for the book are: (1) as a textbook for an intermediate course at the undergraduate senior level or graduate level in water resources engineering on the risk and reliability related subjects; (2) as a textbook for an advanced course in risk and reliability analysis of hydrosystem engineering; and (3) as a reference book for researchers and practicing engineers dealing risk and reliability issues in hydrosystems engineering, planning, management, and decision making.
The expected background for the readers of this book is a minimum of 12 credits of mathematics including calculus, matrix algebra, probability, and statistics; a one-semester course in elementary fluid mechanics; and a one- semester course in elementary water resources covering basic principles in hydrology and hydraulics. Additional knowledge on engineering economics, water-quality models, and optimization would be desirable.
Two possible one-semester courses could be taught from this book depending on the background of the students and the type of course designed by the instructor. Instructors can also refer to the accompanying book Hydrosystems Engineering Uncertainty Analysis for other relevant materials to compliment this book. The possible course outlines are presented below.
Outline 1. (For students who have taken a one-semester probability and statistics course). The objective of this outline aims at achieving higher level of capability to perform reliability analysis. The optimal risk-based design concept can be introduced without having to formally cover subjects on optimization techniques. The subject materials could include Chapter 1, Chapter 2 (2.7), Chapter 3, Chapter 4 (4.1—4.4), Chapter 5 (5.1-5.3), Chapter 6 (6.1-6.4, 6.6), Chapter 7 (7.1-7.3), and Chapter 8 (8.1-8.4).
Outline 2. (For water resource engineers or students who have a good understanding in basic statistics, probability, and operations research.) The aim of this outline is for readers to achieve higher level and deeper appreciation of the applications of reliability assessment techniques in hydrosystems engineering. The topics might include Chapters 1, 4, 5, 6, 7, and 8.
The uncertainty and reliability issues in hydrosystem engineering problems have been attracting a lot of attention of engineers and researchers. A tremendous amount of progress has been made in the area. This book, and the accompanying book Hydrosystems Engineering Uncertainty Analysis, merely represent our humble offer to the hydrosystem engineering community. We hope that readers will find this book useful and enjoyable. Due to our limited knowledge and exposure in the exciting area of stochastic hydraulics, we are unable to incorporate many brilliant works in this book. It is our sincere wish that this effort will bring out much greater works from others to improve and enhance our contribution to society and mankind.
