The benefits of learning the lessons from previous failures are well known to the structural engineering profession. Such lessons are important for preventing future failures, but they also provide a critical feedback loop to the structural design process. After all, regardless of the many tools utilised in modern design, such as advanced analysis techniques, design still proceeds with due respect to the process of trial and error: successful designs are replicated and developed further, while the less favourable options are abandoned.
Forensic engineering, of course, plays a key role in this evolutionary process by identifying the causes of failures and by analysing the broader failure literature to identify trends that point to impending collapses or structural non-performance. One only has to keep in mind the speculation that can be proliferated with respect to causation in the direct aftermath of failures to see how the key lessons can become clouded in the rush for answers, particularly when there is a loss of human life. Ensuring that these key lessons are identified, understood and disseminated to the wider engineering profession should be an aspiration of every structural engineer, with forensic engineering principles providing the framework.
There are many approaches that forensics can take to better understand the lessons from failure, as evident in the diverse perspectives presented in this issue of Forensic Engineering.
In the first paper, Barnes (2013) examines the persistent problem of water ingress in concrete basements. The author reminds us that this is a recurring issue, with half of all basements leaking during construction and a significant portion leaking post-construction. The author presents a number of case studies, and, usefully, groups them by theme, such as the role of workmanship, unexpected events and concrete cracking. By selecting such groupings rather than simply presenting a range of failures, he provides further insight into the causes of these issues and stresses the importance of the straightforward, but often neglected, measures that avert failure, such as the role of site supervision.
The approach of examining failure from a broad perspective is continued by Strobel and Liel (2013), who in our second paper examine snow load failures to buildings in the USA from both a physical and economic perspective. Characteristics examined range from the types of buildings affected by snow loading, the types of physical damage and the sequences of events following failures, including downtime and insurance cover. The author explores a performance-based engineering approach, based on a sample of failures between 2008 and 2011. The approach is used to evaluate if specific buildings are particularly vulnerable to snow loadings, to check the applicability of today's design codes and to predict losses associated with severe snow events in a similar manner to that undertaken by the earthquake engineering fraternity.
The concept of a holistic approach to anticipating future failures is also proposed by Thurlby (2013) who explores how to approach maintaining the performance of the UK's national infrastructure. In particular, he examines the asset ‘time bomb’, when many assets, at a similar time, start to deteriorate rapidly, with an increased of risk of failure. Given the nature of the issue, the author proposes a system dynamics approach, and explores if it can be used as a predictive tool to anticipate failures and to understand how maintenance expenditure can be utilised more efficiently and effectively. Ultimately, such an approach can result in a better understanding of the behaviour of a system, particularly the cause and effect relationships of changes within that system.
Finally, Broadbent and Broadbent (2013) examine the roles for professional engineers in disaster management, such as undertaking rapid assessments and repairs to infrastructure. The authors also discuss an interesting aspect in the pre-disaster stage, known as the ‘incubation period’. This period is characterised by information being available to suggest impending failure, but often goes unnoticed at the critical time. The authors conclude that it is in this area that key contributions can be made by engineers to help ensure these opportunities to prevent failures are acted upon.
These papers illustrate the diverse approaches that forensic engineering takes to learning from failures and serve as a reminder that forensics should not be considered a speciality that is separate from the wider profession, but rather an integral part of a critical feedback loop in the evolution of structural engineering design and construction.
