Condition-based maintenance for systems under dependent competing failures

Failures of complex systems may be various types. Natural failure due to degradation is one main mechanism. Other factors such as traumatic failure caused by random shocks from external environment are also critical to systems' operation. This paper proposes a new model to study complex systems that experience both degradation and shocks which are dependent. System reliability is analyzed and maintenance actions including periodic inspection, preventive maintenance and replacement are adopted to minimize the long-run maintenance cost rate. Sensitivity analysis is also included.