Evaluation of building performance using fuzzy FTA

Estimating exact probabilities of occurrence of fault events for use in the conventional fault tree analysis (FTA) is difficult when failure data are insufficient or fault events are imprecise such as human error. A hybrid approach employing fuzzy sets and possibility theory is proposed to overcome this problem. In this approach, failure possibilities of vague events are characterised by fuzzy sets to translate expert subjective judgements while fuzzy fault rates are derived from fuzzy possibility scores based on a transformed Onisawa's possibility function. An example of beam failure illustrates the use of the approach and demonstrates the capability of the model that can assist safety engineers to effectively assess fault possibilities and better evaluate building performance.