Civil Engineering Systems

making 1.4 Mathematical Decision-making Models 14 Summary CIVIL ENGINEERING SYSTEMS does not defme a unique solution except in the most trivial of examples. Generally there are very many widely different designs that will satisfy the acceptability criteria and a single design will only be obtained by making decisions which eventually eliminate all alternatives but one. Design is, therefore, adecision-making process, unlike analysis which a110ws no scope for choice or decision-making. It is this decision-making aspect of design which makes it so daunting to civil engineering students. How can beginners in the profession make the right decisions? Clearly an injudicious decision at any stage might ultimately lead to a design that is unnecessarily difficult or expensive to build or even to one that fails to meet the acceptability criteria. How can an ability to make good decisions be learned? Until recently many university courses in civil engineering have treated this question with extreme caution and have concentrated on analysis instead of getting to grips with decision-making and design. In support of this policy it can be argued that good decision-making and good design should be learned through experience, and that the best experience is gained in practical design offices not in universities. There is certainly some truth in this but this should not imply that practical experience is the only route to good decision-making. There are many quantitative techniques available that permit good decisions to be made according to logical, planned principles. It is these techniques with which civil engineering systems is concerned. More precisely civil engineering systems is concerned with quantitative decision-making techniques of use in the planning, design, construction and operation of civil engineering projects. It is essentially concerned with the synthesis rather than with the analysis aspects of civil engineering. It relies on the same mathematical modelling approach as analysis. Instead of constructing a mathematical model for analysis and manipulating it to yield behaviour parameters, a different mathematical model is constructed for synthesis purposes so that the manipulation and solution yields design decisions (numbers, sizes, configurations). Civil engineering systems is concerned with mathematical models of this synthesis type. The noun 'system' has several distinct meanings and it is useful to defme it here in the sense in which it is used in the phrase 'civil engineering systems'. The relevant defmition of 'system' in The Concise Ox{ord Dictionary is: 'Method, organization, considered principles of procedure, (principle of) classification'. Closely related to this is the adjective 'systematic' which is defmed as: 'Methodical, according to a plan, not casual or sporadic or unintentional, classificatory'. In the sense of these defmitions civil engineering systems is the study of systematic methods and procedures used in civil engineering with particular emphasis on decision-making. Perhaps a better phrase which focuses the subject more clearly is systematic decision-making in civil engineering. Important features of the dictionary defmitions are the words 'classification' and 'classificatory'. Civil engineering systems is concerned with examining the mathematical structures of decision-making methods for a11 kinds of civil engin- Front Matter....Pages i-x Systematic Decision-Making in Civil Engineering....Pages 1-16 Systematic Mathematical Modelling — Linear Problems....Pages 17-37 Solution Techniques for Linear Problems....Pages 38-81 Project Planning Methods, Networks and Graphs....Pages 82-128 Serial Systems and Dynamic Programming....Pages 129-166 Systematic Design and Non-Linear Problems....Pages 167-185 Non-Linear Unconstrained Optimisation Methods....Pages 186-236 Non-Linear Constrained Optimisation Methods....Pages 237-290 Non-Linear Optimisation in Civil Engineering....Pages 291-309 Probabilistic Decision-Making....Pages 310-359 Back Matter....Pages 360-370