Bridges are essential for guaranteeing the functioning of transportation systems since their failure can cause serious threats to the safety, well-being and economy of modern communities, especially in emergency conditions. Following recent bridge failures, among which include the Morandi bridge in 2018, specific guidelines on risk classification and management, safety assessment and monitoring of existing bridges have been issued in Italy by the Minister of Infrastructure as a mandatory code. They pay particular attention to the evaluation of the residual life span of critical transportation infrastructure dating back to the 1950s and 1960s of the last century. Being a newly issued tool, the Guidelines need to be applied and tested in order to find possible drawbacks and to point out the main factors influencing their results. Therefore, in this study, after a short description of the Italian Guidelines, pointing out some differences with other approaches adopted worldwide, some advantages and disadvantages are discussed by an application to a bridge stock located in the Basilicata region (Italy). Data needed to apply the Guidelines are gathered by a purposely set up procedure that exploits existing databases on road infrastructure (OpenStreetMap) complemented by additional data retrieved by means of public image repositories (Google Street View). By accounting for the qualitative nature of the risk classification results obtained by applying the lower analysis levels of the Guidelines, a prioritization method is proposed for ranking bridges for higher assessment levels and possible interventions, as well as consequent funds allocation. The application shows that the Guidelines’ approach tends to provide conservative results. In fact, even in case of bridges with low degradation levels, the final risk classification induces actions undertaken for preliminary or detailed assessment; thus, normal operation (with periodic inspections) would not be possible anymore.

Guaranteeing adequate safety levels in critical infrastructures such as bridges is essential to modern societies and their vital services. Bridges with reinforced concrete structures are subject to deterioration, especially due to corrosion effects. Gerber saddles are among the key components of bridges which are especially exposed to environmental actions due to their position and reduced possibility of inspection. In this paper, a framework for the durability analysis of these components is proposed, considering the simultaneous presence of permanent loads and environmental actions under the form of chloride ions. Nonlinear numerical simulations adopting the finite element code ATENA are performed, accounting for chloride ingress analyses. The presence of cracks (due to applied loads and/or design/construction defects) which may speed-up corrosion propagation, steel reinforcement loss, cracking and spalling, and their effects on the load-bearing capacity is considered. This framework has been applied to the Gerber saddles of a prominent reinforced concrete (RC) bridge, namely the Musmeci bridge in Potenza, Italy. Durability analyses made it possible to evaluate the saddles’ strength capacity (i) at the time of construction, (ii) after forty-five years since the construction, and (iii) at an extended time of fifty years. The results show that corrosion can influence both the ultimate load capacity and the collapse mechanism.

Gerber road bridges provide clear advantages in terms of stress distribution and absorption of small settlements. For this reason, such bridge designs have been frequently used in Italy and abroad. This static arrangement is provided with connections among spans located in the half-joints, which are prone to the accumulation of deteriorating agents and are difficult to inspect. Furthermore, these bridges were designed based on old code provisions referring to loads lower than those prescribed by current codes. Hence, half-joints frequently need to be assessed and possibly strengthened. This paper reviews the available strengthening techniques based on both practice and experimental results, comparing them in terms of structural performance, failure mode and governing limit state. As result, a decision-making approach is proposed in order to guide intervention choices while accounting for design requirements and constraints. In fact, the presence of curbs and transverse beams close to half-joints prevents the utilization of externally bonded composites making steel-based techniques more suitable. Some remarks on intervention costs highlight the great impact of deteriorated half-joints due to the need for bridge lifting and carry out restoration interventions. Therefore, the need for repair should be carefully evaluated as it significantly influences the overall intervention cost.

Dapped‐end beams are frequently used in roofing and flooring systems of precast reinforced concrete buildings as well as in bridge constructions. Due to design flaws, deterioration, and construction mistakes, they may have unsatisfactory structural performance. Past experimental studies investigated the effectiveness of post‐tension strengthening techniques applied to dapped‐end beams, revealing them as effective solutions, even though a limited range of influencing parameters were considered. This paper numerically investigates the performance improvement provided by post‐tension interventions applied to dapped‐end beams. Numerical models were built through a refined FEM software simulating two experimental tests found in the literature. After the models' calibration, a post‐tension intervention was designed and implemented in the models, considering the level of prestressing as the main intervention's parameter. Afterwards, the behavior in the post‐intervention condition was analyzed to find changes in the failure modes and highlight the performance improvement concerning cracking phenomena and ultimate load‐bearing capacity. It is found that the level of tendons' prestress significantly improves the cracking load, which increases almost linearly with respect to it. Conversely, the significant gain in terms of ultimate load‐bearing capacity (up to 53%) shows only slight variations when the prestress level changes. Finally, accounting also for the reduction of deformation capacity for high prestressing levels, practical suggestions are provided regarding the optimal post‐tension choice.

The Italian Ministry of Infrastructure and Transportation adopted the guidelines on risk classification and management, safety assessment and monitoring of existing bridges through the Decree No. 578 dated 17 December 2020. This document must be used by all managing entities to prevent damage due to a lack of maintenance to these crucial components of the infrastructure system. The approach of the guidelines for existing bridges is developed across six levels, ranging from Level 0 to Level 5. The research work presented in this article is focused on Level 3, which pertains to preliminary assessments conducted on existing bridges. Through an automated procedure, the preliminary verification is performed by comparing bending and shear stress generated by traffic load schemes extracted from previous standards with the ones based on the current code. These loads are applied to a series of girder deck models, selected through a statistical study conducted on a database of bridges. Performance indices are derived from the comparison to evaluate the adequacy of previously designed and constructed structures by applying the load models specified in the current regulations for designing new bridges. The analysis results highlight a performance gap, which varies depending on the standard code at hand.