Condition based Maintenance of complex systems

Complex industrial assets such as bridges, power transformers etc. are subject to complex deterioration processes. Understanding such complexities, and maintaining such assets is a major challenge.


This research aims to design a novel approaches for optimizing condition-based maintenance policies for assets with complex deterioration processes. These policies aim to optimise the inspection and replacement plans for such assets and their constituent components so as to minimise the costs and risks involved, while maintaining performance.



We have examined a number of complex deterioration processes, e.g., 

  • The state of one component affects the performance of other assets in the system.
  • The state and rate of deterioration of one component affects the rate of deterioration of other components in the asset.
  • Malfunction of one component damages other components in the asset, thereby accelerating the deterioration of the asset (also known as 'fault propagation').
  • Systems subject to aging and cumulative damage

Case studies


Project Partners

  • National Grid
  • State Grid Corporation of China
  • PTT (Funder)
  • ExxonMobil
  • Hertfordshire County Council
  • City University of Hong Kong
  • Rutgers University


  • Mahani, K., Liang, Z., Jafari, M., Parlikad, A.K., "An interactive operation and maintenance strategy for solar-powered Microgrids," Under review.
  • Liang, Z., Liu, B., Xie, M., Parlikad, A.K., “A Hypo-exponential Approximating Approach for the Condition-based Maintenance of Long-Life Assets,” Under review.
  • Liang, Z., Parlikad, A.K., "A Markovian Model for Power Transformer Maintenance," International Journal of Electrical Power and Energy Systems, 2018.
  • Liu, B., Xie, M., Liang, Z., Parlikad, A.K., “Condition-based maintenance for systems with aging and cumulative damage based on proportional hazards model,” Reliability Engineering and System Safety, 2017.
  • Liang, Z., Rasmekomen, N., Srinivasan, R., Parlikad, A.K., “On fault propagation in deterioration of multi-component systems,” Reliability Engineering and System Safety, Volume 162, pp. 72-80, 2017.
  • Rasmekomen, N., Parlikad A.K., "Condition-Based Maintenance of Multi-Component Systems with State-Rate Degradation Interactions" Reliability Engineering and System Safety, Volume 148, pp. 1-10, 2016.
  • Liang, Z., Parlikad, A.K., “A condition-based maintenance model for assets with accelerated deterioration due to fault propagation”, IEEE Transactions on Reliability, Volume 64, Issue 3, pp 972-982, 2015.
  • Liang, Z., Parlikad, A.K., “A tiered modelling approach for condition based maintenance of industrial assets with load sharing interaction and fault propagation,” IMA Journal of Management Mathematics, Volume 26, Issue 2, pp. 125-144, 2015.
  • Rasmekomen, N., Parlikad, A.K., “Maintenance optimization for asset systems with dependent Performance degradation,” IEEE Transactions on Reliability, Volume 62, Issue 2, pp. 362-367, 2013.
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