A Stochastic Formulation to Evaluate the Sustainability of Structural Systems

During their life cycle, engineering systems typically suffer from deterioration due to aging and exposure to extreme events and harsh environmental conditions. As a result, regular or exceptional recovery strategies can be required to restore the system to a target structural performance level. This paper proposes a novel stochastic formulation for evaluating the sustainability of engineering systems as a function of their structural performance over a fixed time horizon. The life-cycle sustainability of the system is evaluated in terms of its cost and environmental impact, which includes the impact of the construction and possible recovery strategies. The formulation integrates state-dependent stochastic models that sequentially capture the effects of gradual and shock deterioration processes and the subsequent recovery processes on the system's sustainability. Moreover, the formulation accounts for the relevant uncertainties, such as those in the external conditions (e.g., environmental exposure and potential hazards) and those in the environmental emissions associated with the materials and energy used throughout the system life cycle. The formulation uses the Renewal Theory-based Life-Cycle Analysis (RTLCA) formulation for a more computationally efficient evaluation of sustainability measures. As an illustration, the proposed analysis was used to evaluate the life-cycle sustainability of a typical reinforced concrete (RC) bridge.