Fixed-jacket offshore platforms are susceptible to damage below the water line which may be difficult to observe except by underwater inspections that can be up to several years apart. An instrumentation system installed at deck-level can be used to detect the severance of a jacket member by continuous monitoring of the structural response due to ambient wave loading. Data is presented during a brace failure event that occurred on a North-Sea platform and also for subsequent repair work. The observed changes in structural response are compared to those predicted by finite-element modelling. The ability of this method to detect jacket member failure within hours of severance is an important factor in assessing the risks to personnel as well as maintaining structural integrity. In the case of this jacket member failure, the provisions made by the platform operator meant that the incident was anticipated, planned for and ultimately managed in a way that enabled production at the platform to continue without interruption.

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