Browsing by Subject "Deterioration"

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    A maintanence policy for a system with multi-state components: an approximate solution
    (Elsevier, 2002) Gürler, Ü.; Kaya, A.
    For maintenance and quality assessment purposes, various performance levels for both systems and components are identified, usually as a function of the deterioration. In this study, we consider a multicomponent system where the lifetime of each component is described by several stages, (0,…,S), which are further classified as good, doubtful, preventive maintenance due (PM due) and down. A control policy is suggested where the system is replaced when a component enters a PM due or a down state and the number of components in the doubtful states (K,…,S−2) is at least N. All maintenance activities are assumed to take negligible time. The exact description of the underlying stochastic model under the policy is very complicated. We therefore propose some approximations, which allow an explicit expression for the long run average cost function, which is minimized w.r.t. (K,N) by numerical methods. Sensitivity of the model to system parameters and the performance of the approximation are investigated through several examples.
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    A multiscale method to analyze the deterioration due to alkali silica reaction considering the effects of temperature and relative humidity
    (International Center for Numerical Methods in Engineering, 2013) Wu, T.; Temizer I.; Wriggers P.
    This work presents a three-dimensional multiscale framework to investigate the deterioration resulting from alkali silica reaction (ASR) in the concrete. In this contribution, 3D micro-CT scan of hardened cement paste (HCP) and aggregates with a random distribution embedded in a homogenized cement paste matrix represent the microscale and mesoscale of the concrete respectively. A 3D hydro-chemo-thermo-mechanical model based on staggered method is developed at the mesoscale of the concrete, yet taking into account the deterioration at the microscale due to ASR.