EPISTEMIC UNCERTAINTY IN THE SEISMIC ASSESSMENT OF EXISTING REINFORCED CONCRETE BUILDINGS: FORMAT AND VALUES OF THE CONFIDENCE FACTOR

EC8-3, devoted to assessment/retrofitting of existing buildings, accounts for epistemic uncertainty with an adjustment factor, called “confidence factor (CF)”, whose value depends on the knowledge of properties such as geometry, reinforcement layout and detailing, and materials. This solution, plausible from a logical point of view, cannot yet profit from the experience of use in practice, hence it needs to be substantiated by a higher level probabilistic analysis accounting for and propagating epistemic uncertainty (i.e., incomplete knowledge of a structure) throughout the seismic assessment procedure. The paper investigates the soundness of the proposed format and pinpoints some problematic aspects that would require refinement. The approach taken rests on the simulation of the entire assessment procedure and the evaluation the distribution of the assessment results conditional on the acquired knowledge. Based on this distribution a criterion is proposed to calibrate the CF values. The obtained values are then critically examined and compared with code-specified ones.