Chapter 3: Causes of Bridge Failures

This chapter identifies eight basic causes of bridge failure or collapse. These are errors made during the bridge’s design, construction, maintenance or operation plus those which are due to factors which were unknown at the time of the initial design and construction. These include occasions when engineering understanding was being stretched beyond the current envelope, or when a material does not perform as expected. There are also external factors: environmental (more recently exacerbated by climate change) and force majeure. Each are covered in detail, but an over-arching cause is also identified: failure that is attributable to human error or negligence. The chapter points out that there is seldom a single cause but more likely several. These are related to the Swiss cheese model of risk. Interspersed in the sections on the eight causes are mini-case studies, not only with regard to bridges but also other engineering sectors.