Historical development of Italian codes for the structural capacity assessment of reinforced concrete bridges

The assessment of structural safety for existing bridges is a critical phase in the preservation of infrastructural heritage. In Italy, as well as globally, many in-service bridges were constructed over 50 years ago; thus, a comprehensive examination of the standards and regulations that established their structural capacity is crucial. Over the decades, the evolution of structural codes induced a significant impact on structural design, driven in particular by increasing traffic loads and technological advancements that have enabled the development of increasingly high-performance materials. Consequently, any analysis of existing bridges needs a detailed understanding of the technologies and design methodologies used in the original construction. The extent of this analysis is contingent upon the level of evaluation within a multi-level approach, as delineated in the current Italian Guidelines for existing bridges. In particular, the third level of analysis proposed therein concerns the estimation of the structural resources of the bridges based on the design code under which they were originally conceived. This paper focuses on the assessment of the structural capacity of reinforced concrete bridges through an examination of the evolution of Italian structural codes throughout the last century. A parametric study has been conducted to ascertain the design capacity in relation to the period of construction. Regardless of the current state of preservation, the proposed methodology facilitates the evaluation of inherent structural deficiencies in light of contemporary requirements.