Condition indicators for inspection and maintenance planning

The identification of cost efficient maintenance strategies for concrete structures usually takes basis in condition assessments achieved through inspections, tests and monitoring. It is well recognized that such condition assessments are subject to significant uncertainties and in general at best provide indications rather than observations about the condition of the structure. The present work proposes a probabilistic framework for the quantification of inspection results for concrete structures in regard to their actual condition and the predicted future degradation. Within this context it is shown how condition indicators, based on non-destructive evaluation methods, can be formulated to enable quality control and inspection and maintenance planning. Furthermore it is investigated how the "strength" of the indicators not only depends on the inspection method but moreover may be significantly dependent on the age of the structure at the time of the inspection.