Errare humanum est. … We structural engineers are human and so have made a number of errors over the years resulting in narrow escapes, badly performing structures, and even fatal collapses. But as Seneca continues … sed perseverare diabolicum, we must not repeat our errors. To avoid this means that we must learn from our past mistakes; we must know what went wrong and why. Some of the lessons from our past errors get embodied in clauses in codes of practice, but many do not, and the collective memory of the profession tends to fade as the generation of engineers who learnt from the mishaps and catastrophes retires.
Past books on the subject of structural failures tended to deal with the general causes of failures and methods of investigation, illustrated with the more spectacular examples. However, details of some failures that have not made the headlines, but nevertheless hold important lessons, are hard to find or may not even be in the public domain. In the past, Robin Whittle and I worked together at Arup R&D on a variety of problems of concrete structures. Some of these arose from failures, and others were encountered when forestalling undesirable outcomes of the enthusiasm untempered by experience of some of our younger colleagues.
Robin was also in close contact with researchers at the now sadly defunct Cement & Concrete Association, the Polytechnic of Central London, and the universities of Leeds, Durham, and Birmingham, and so was privy to much of the background for the initial draft and subsequent revisions of CP110. Nowadays, a preoccupation with the ever-multiplying minutiae of codes, whether Euro Community or National, can blind designers to the imperatives of first principles.
New patterns of procurement and site management also widen the communication gap between design and execution, and exert pressures to adopt shortcuts that sometimes have unforeseen consequences. With his background, Robin is well placed to present a selection of case studies that have lessons for all of us. This is a book that should be read by those structural engineers who wish to broaden their knowledge by learning from some of the experiences of the last 50 years and also for those who would like to refresh their memories.
This book is a personal selection of incidents that have occurred related to reinforced and prestressed concrete structures. Not all have led to failures and some of the mistakes were discovered at the design stage. Each incident required some form of remedial action to ensure safety of the structure. Some of the incidents were caused by mistakes in design or construction or both. Some involved collapse of part of the structure, but in such cases the cause was from more than one unrelated mistake or problem.
A few of the errors and incidents were caused by deliberate intent. Chapters 1 to 11 describe specific incidents such as structural misunderstanding, extrapolation of codes of practice, detailing, poor construction, and other factors. When a particular incident involved more than one of these causes, it is described in the most relevant section.
Chapters 12 and 13 discuss issues related to procurement and research and development. Care has been taken not to name the particular projects in which the incidents occurred, and the intention in providing the information is to ensure that such mistakes can be understood and avoided in the future. Some of the problems were discovered in association with requests for support about a different topic. In trying to discover the details of the problem it became clear that other more serious issues were at stake. This begs the question, how many unresolved problems and mistakes are out there that have not seen the light of day? It is fortunate that most reinforced and prestressed concrete structures are indeterminate and allow alternative load paths to form and prevent failures that were not foreseen in the design