Calibration of partial safety factors for structural assessment of existing Italian bridges based on experimental data

The main goal of this study is to investigate partial safety factors for material properties of existing reinforced concrete (RC) and prestressed concrete (PC) bridges, making use of several reliability methods and current provisions. The investigation considers the residual service life, level of knowledge, reduced target reliability according to economic and human safety criteria, and recent data from diagnostic tests on real Italian bridges. Specifically, experimental data from eight existing beam-type RC and PC bridges, representative of roadway bridges built in Italy between 1970 and 1980, are considered. Calibration of partial safety factors is provided at multiple spatial scales, including the entire structural systems, sub-systems (i.e., superstructure and substructure) and components (e.g., slabs, girders, piers), assessing the effects of aggregation and disaggregation of information on design values of material properties. Analysis results are then compared with the current Italian guidelines for safety assessment and maintenance of existing bridges, highlighting the main differences between current partial safety factors and those proposed in this study.