Structural failure modes in vertical tanks: reinforcement evaluation and solutions

Vertical storage tanks are essential components in the safety of nuclear plant systems. It has been shown that the traditional method of analysing seismic loads is not conservative, as it does not take account of the interaction between fluid and tank structure. This paper identifies different possible structural failure modes in tanks due to seismic load, and methods devised by various authors to evaluate tank structure capacity under different failure modes. These methods are based on experimental data relating to the structural behaviour of tanks during actual seismic events, tests, and theoretical analyses. The paper describes the problems of these structures under seismic loads in nuclear plants. It proposes solutions to the main structural problem, tank anchorage, for which the re-evaluation of the anchorage capacity is required, using methods (finite element) less conservative than those proposed by other authors. Also proposed is the local reinforcement of anchorages to increase their capacity. (Author) 4 refs