Sustainable decisions for life-cycle based design and maintenance

General aspects of sustainable decision making are investigated and a possible formulation of socioeconomic sustainable decision making is illustrated on the problem of life-cycle based design and maintenance of civil engineering facilities. First, an overview is given on the present understanding of sustainability indicators, and on available theoretical and methodical frameworks for including such indicators in sustainable decision making. Thereafter, basic principles of sustainable decision making are suggested by defining the "rules" for optimising decisions that are made at present, but may have consequences in the future. A decision-theoretical framework is then formulated, which allows for modelling the interaction between intra-generational decision making and inter-generational decision making, utilising the recently developed concept of agentbased systems representation. The suggested framework is general, but is illustrated here on the specific and simple decision problems related to life-cycle based design and maintenance of civil engineering facilities. For this problem, sustainable decisions are identified through minimisation of the joint economic consequences for the present and future generations related to design and maintenance over the life cycle of such facilities. The suggested approach is demonstrated on a specific example considering the optimisation of a concrete structure subject to chloride induced corrosion of the reinforcement.