This chapter presents the procedural, enabling and triggering causes of temporary structures collapses, with an emphasis on falsework and scaffolding. The review into collapses described in Chapter 2 is extended by investigating in detail the causes of collapse in temporary structures and providing comprehensive lists of faults which can occur during design, erection, use and disassembly of these structures. As bridge falsework collapses are more commonly reported, with usually greater financial implications and greater risks to life, a survey, conducted by André, is summarised showing that these collapses occur regularly throughout the world. The chapter concludes with the presentation of two examples of forensic analyses, namely of a scaffold collapse and of a bridge falsework collapse.
Top7.1 Introduction
With the industrial revolution came novel challenges for civil engineers. New infrastructures (such as bridges, commercial, residential and industrial buildings), in larger scales, carrying more and heavier loads, had to be built at a fast pace. Temporary structures also experienced this novel complexity. However, little attention was drawn to this subject and as a result a series of collapses of major significance involving temporary structures occurred in the industrialised countries throughout the 20th century.
In 1970, as a response to the public outcry following a collapse with severe consequences, the UK construction industry established a committee under the chairmanship of S.L. Bragg to investigate the use of falsework. The result was the Bragg report (Bragg, 1975), a pioneer document which established the basis for the subsequent publication of the first UK standards concerning falsework (BSI, 1982).
Since the Bragg report, there have been a number of fundamental changes to the construction industry (HSE, 2003):
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Clients and designers give insufficient consideration to health and safety, despite their obligations under the CDM regulations.
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Price competition among contractors gives advantage to companies less diligent with health and safety.
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Key documentation, such as the health and safety plan, method statements and risk assessments are treated as a paper exercise, having little practical benefit.
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Lengthy sub-contractor chains result in elements of the construction team being distanced from responsibility, inadequately supervised, and with low commitment to projects.
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Frequent revision of work schedules leads to problems with project management and undesirable time pressure.
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A long hours culture in the industry results in fatigue, compromised decision-making, productivity and safety.
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Bonus payments act as a strong incentive, but encourage productivity over safety.
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A skills shortage in the industry is leading to increased reliance on inexperience workers, coupled with difficulties verifying competency.
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Problems exist with the availability, performance and comfort of personal protective equipment(PPE).
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Training is seen as a solution to all problems, but with content often superficial.
The above changes had a profound effect upon the manner temporary structures, in particular falsework, is dealt with by all relevant stakeholders (SCOSS, 2002):
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Falsework design is no longer a task of the main contractor but the responsibility is passed to a sub contractor or a specialized supplier;
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The structural concept of the falsework is no longer arbitrary; proprietary systems and more often modular ones are widely used nowadays in order to optimise costs and operational efficiency. Additionally the number of usage cycles of falsework components has increased dramatically;
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The paradigm of the construction industry has changed: intense competition in a profit orientated environment has produced a reduction of technical competence and responsibility at the design, construction and quality assurance stages of a construction project.
As detailed in Chapter 1, the design and use of temporary structures places very complex and different challenges from the ones associated with permanent structures, such as: