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

Abstract Developed within the Consiglio Superiore dei Lavori Pubblici (Italian High Council of Public Works)–Rete dei Laboratori Universitari di Ingegneria Sismica e Strutturale (Network of University Laboratories of Earthquake and Structural Engineering) research program supporting the ongoing revision of the Italian Guidelines for existing bridges, this study investigates partial safety factors for material properties of existing reinforced concrete (RC) and prestressed concrete (PC) bridges through a reliability‐based framework. The assessment accounts for residual service life, level of knowledge, and reduced target reliability levels consistent with economic and life‐safety criteria, incorporating recent diagnostic data from Italian bridges. Experimental results from eight beam‐type RC and PC bridges representative of roadway bridges constructed in Italy between 1960 and 1980 are analyzed. Partial safety factors are evaluated at multiple spatial scales—that is, entire structural system, sub‐systems (superstructure and substructure), individual components (slabs, girders, cross girders, pier caps, piers, and abutments)—for both concrete and reinforcing steel. The sensitivity of the resulting design values to data aggregation and disaggregation is systematically evaluated. The results are finally compared with current Italian guidelines for safety assessment and maintenance of existing bridges, highlighting the differences between actual code provisions and reliability‐based values proposed herein. An illustrative application to a single existing highway bridge demonstrates how the proposed partial safety factors can be implemented in engineering practice and further highlights the need for their reliability‐based calibration.