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Infrastructure asset management systems require a flexible deterioration model that can handle various degradation patterns in a unified way. Due to their appealing monotonic sample paths, independent increments, and mathematical tractability, gamma processes have been widely employed as a model for infrastructure performance deterioration. This model was recently enhanced by introducing an upper bound to satisfy a practical modelling need that physical or managerial limits constrain many deterioration processes. Several bounded transformed gamma process (BTGP) alternatives had been proposed; however, they lacked sufficient flexibility to characterise different deterioration patterns. This paper proposed a new BTGP model that is deeply rooted in the traditional regression modelling widely used in most infrastructure asset management systems. Qualitative and quantitative comparisons were carried out between the proposed BTGP and a bounded nonstationary gamma process (BNGP) model from both deterioration modelling and asset management decision-making perspectives. An empirical study using real-world historical bridge condition data was conducted to examine the flexibility of the BTGP compared to the BNGP and six other BTGP alternatives. The results confirmed the flexibility and significance of the proposed BTGP model for infrastructure systems.
Chen et al. (Tue,) studied this question.