Applied Methods Of Structural Reliability

A quarter of the century has elapsed since I gave my first course in structural reliability to graduate students at the University of Waterloo in Canada. Since that time on I have given many courses and seminars to students, researchers, designers, and site engineers interested in reliability. I also participated in and was responsible for numerous projects where reliability solutions were required. During that period, the scope of structural reliability gradually enlarged to become a substantial part of the general reliability theory. First, it is apparent that bearing structures should not be isolated objectives of interest, and, consequently, that constntCted facilities should be studied. Second, a new engineering branch has emerged -reliability engineering. These two facts have highlighted new aspects and asked for new approaches to the theory and applications. I always state in my lectures that the reliability theory is nothing more than mathematized engineering judgment. In fact, thanks mainly to probability and statistics, and also to computers, the empirical knowledge gained by Humankind's construction experience could have been transposed into a pattern of logic thinking, able to produce conclusions and to forecast the behavior of engineering entities. This manner of thinking has developed into an intricate network linked by certain rules, which, in a way, can be considered a type of reliability grammar. We can discern many grammatical concepts in the general structure of the reliability theory.

A quarter of the century has elapsed since I gave my first course in structural reliability to graduate students at the University of Waterloo in Canada. Since that time on I have given many courses and seminars to students, researchers, designers, and site engineers interested in reliability. I also participated in and was responsible for numerous projects where reliability solutions were required. During that period, the scope of structural reliability gradually enlarged to become a substantial part of the general reliability theory. First, it is apparent that bearing structures should not be isolated objectives of interest, and, consequently, that constntCted facilities should be studied. Second, a new engineering branch has emerged -reliability engineering. These two facts have highlighted new aspects and asked for new approaches to the theory and applications. I always state in my lectures that the reliability theory is nothing more than mathematized engineering judgment. In fact, thanks mainly to probability and statistics, and also to computers, the empirical knowledge gained by Humankind's construction experience could have been transposed into a pattern of logic thinking, able to produce conclusions and to forecast the behavior of engineering entities. This manner of thinking has developed into an intricate network linked by certain rules, which, in a way, can be considered a type of reliability grammar. We can discern many grammatical concepts in the general structure of the reliability theory.

Structural Reliability Analysis and Prediction, Third Edition is a textbook which addresses the important issue of predicting the safety of structures at the design stage and also the safety of existing, perhaps deteriorating structures. Attention is focused on the development and definition of limit states such as serviceability and ultimate strength, the definition of failure and the various models which might be used to describe strength and loading. This book emphasises concepts and applications, built up from basic principles and avoids undue mathematical rigour. It presents an accessible and unified account of the theory and techniques for the analysis of the reliability of engineering structures using probability theory. This new edition has been updated to cover new developments and applications and a new chapter is included which covers structural optimization in the context of reliability analysis. New examples and end of chapter problems are also now included.

Structural reliability theory is concerned with the rational treatment of uncertainties in struc tural engineering and with the methods for assessing the safety and serviceability of civil en gineering and other structures. It is a subject which has grown rapidly during the last decade and has evolved from being a topic for academic research to a set of well-developed or develop ing methodologies with a wide range of practical applications. Uncertainties exist in most areas of civil and structural engineeri'1.g and rational design decisions cannot be made without modelling them and taking them into account. Many structural en gineers are shielded from having to think about such problems, at least when designing simple structures, because of the prescriptive and essentially deterministic nature of most codes of practice. This is an undesirable situation. Most loads and other structural design parameters are rarely known with certainty and should be regarded as random variables or stochastic processes, even if in design calculations they are eventually treated as deterministic. Some problems such as the analysis of load combinations cannot even be formulated without recourse to probabilistic reasoning.

This book addresses probabilistic methods for the evaluation of structural reliability, including the theoretical basis of these methods. Partial safety factor codes under current practice are briefly introduced and discussed. A probabilistic code format for obtaining a formal reliability evaluation system that catches the most essential features of the nature of the uncertainties and their interplay is then gradually developed. The concepts presented are illustrated by numerous examples throughout the text. The modular approach of the book allows the reader to navigate through the different stages of the methods.

Publisher Description

The last decades have witnessed the development of methods for solving struc tural reliability problems, which emerged from the efforts of numerous re searchers all over the world. For the specific and most common problem of determining the probability of failure of a structural system in which the limit state function g( x) = 0 is only implicitly known, the proposed methods can be grouped into two main categories: • Methods based on the Taylor expansion of the performance function g(x) about the most likely failure point (the design point), which is determined in the solution process. These methods are known as FORM and SORM (First- and Second Order Reliability Methods, respectively). • Monte Carlo methods, which require repeated calls of the numerical (nor mally finite element) solver of the structural model using a random real ization of the basic variable set x each time. In the first category of methods only SORM can be considered of a wide applicability. However, it requires the knowledge of the first and second deriva tives of the performance function, whose calculation in several dimensions either implies a high computational effort when faced with finite difference techniques or special programs when using perturbation techniques, which nevertheless require the use of large matrices in their computations. In or der to simplify this task, use has been proposed of techniques that can be regarded as variants of the Response Surface Method.