author: David Stritzl
title: Statistical Analysis of Continuous Degradation Processes in Fault Trees
topics: Dependability, security and performance
committee: Enno Ruijters
started: January 2016
end: January 2016


Fault Tree Analysis (FTA) is an important method for analyzing the reliability of critital systems, such as power plants and airplanes. A Fault Tree is a graphical model to describe how failures of components interact to cause system failure.

Traditional FTA assumes that component failure times follow exponential distributions. More recent types of Fault Trees also allow Erlang Distributions,but still do not allow the description of physical systems, where failures are often caused by degradation following a continuous function. For example, the treads on a car's tires degrade over time, and the tire fails when the treads become too shallow.

This project will introduce a descriptions of such continuous degradation processes into FTA, and extend the analysis techniques to analyze such FTs.


  • W.E. Vesely, F.F. Goldberg, N.H. Roberts, D.F. Haasl, Fault Tree Handbook, Office of Nuclear Regulatory Research, US Nuclear Regulatory Commision, 1981 (
  • E. Ruijters, D. Guck, P. Drolenga, M. Stoelinga, Fault maintenance trees: reliability centered maintenance via statistical model checking. Accepted for publication in the Proceedings of RAMS 2016, text available on request.

Additional Resources

  1. The paper