DESIGN FOR ROBUSTNESS
Design for Robustness offers a practical review of the elements of robustness in structural engineering design and strategies for achieving it, followed by a collection of design scenarios and case studies. The authors are Dr Franz Knoll, Vice President of Nicolet Chartland Knoll, structural engineers in Montreal, Canada and Thomas Vogel, Professor of Structural Engineering at the Swiss Federal Institute of Technology in Zürich, Switzerland. The book is published by the International Association for Bridge and Structural Engineering in their Structural Engineering Documents (SED) series.
The aim of the SED series is to provide practical information on topics that are highly relevant to current structural engineering practice but where useful information is either not available or scattered. Design for Robustness offers exactly that.
Structural robustness has received much attention recently, following some high-profile and widely published structural failures. Robustness, however, has remained a somewhat vague concept to most practising engineers, with a diverse range of interpretations and very little actual technical guidance. The Eurocodes, for example, require structures to be robust but do not provide much practical advice on how this can be achieved. The stated aim of the authors is to provide some of that help.
Bridge engineers will be a bit disappointed as the book is written mainly in the context of buildings design while some notorious bridge engineering scenarios are not discussed at all. Nevertheless the principles and strategies are the same and most of the ideas can be applied to bridges.
Chapters 1 to 5 define key terms (including robustness itself) and they set out the basic concepts.
Chapter 6 is the heart of the book. Several strategies and considerations toward achieving robustness are discussed. The list includes strength; structural integrity and solidarisation; second line of defence; multiple load path and redundancy; ductility as opposed to brittle failure; zipper stopper as opposed to progressive failure; capacity design and fuse elements; sacrificial and protective elements; knock-out elements; stiffness; strain hardening; post-buckling resistance; warning signs; testing; monitoring; quality control; correction and prevention; and mechanical devices.
Chapter 7 offers some thoughts on maintaining robustness through time and numerous alterations to the original structure. It contests the popular notion that a structure which has stood for a century will continue to do so for another 100 years. The chapter includes a copy of a letter that Sébastien le Prestre de Vauban, general inspector of fortifications, wrote to his superior, the war minister to King Louis XIV of France in 1685. An English translation is provided. The letter is a very interesting read and has not lost its message over the centuries.
Chapter 8 provides a conclusion to the first part of the book before looking at applications and case studies in the subsequent chapters.
Chapter 9 covers a diverse range of general design scenarios and applications from the authors' practice ranging from punching failure in reinforced concrete slabs to terrorist attacks on buildings. These cases illustrate how the various strategies described in Chapter 6 can be applied to particular design situations.
Chapter 10 looks at some specific design examples where robustness was explicitly considered or failure occurred because the designer failed to provide adequate safety measures beyond traditional codified design rules. The examples include historic buildings, a cable-stayed bridge and power line towers in Canada, and a tunnel, an avalanche gallery and a railway station in Switzerland.
Design for Robustness is a useful practical guide to an important design criterion that has very limited literature. It is strongly recommended to all engineers who have responsibility for structural design.
