infrastructures Article Durability of Gerber Saddles in RC Bridges: Analyses and Applications (Musmeci Bridge, Italy) Giuseppe Santarsiero * , Angelo Masi and Valentina Picciano   Citation: Santarsiero, G.; Masi, A.; Picciano, V. Durability of Gerber Saddles in RC Bridges: Analyses and Applications (Musmeci Bridge, Italy). Infrastructures 2021, 6, 25. https://doi.org/10.3390/ infrastructures6020025 Academic Editor: Daniel N. Farhey Received: 13 January 2021 Accepted: 1 February 2021 Published: 5 February 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). School of Engineering, University of Basilicata, 85100 Potenza, Italy; angelo.masi@unibas.it (A.M.); valepicc95@gmail.com (V.P.) * Correspondence: giuseppe.santarsiero@unibas.it Abstract: 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. Keywords: critical infrastructure; reinforced concrete bridges; durability analysis; corrosion; chloride ingress; crack propagation; nonlinear analysis 1. Introduction The preservation of critical infrastructures such as hospitals, energy facilities and information and transportation infrastructures [1–3] is of paramount importance for the daily life, safety and security of modern communities. It is even more important when they work as part of a network where the loss of a single branch can lead to whole system failure. Regarding transportation infrastructures, the Morandi bridge collapse [4], with its 43 fatalities, brought a renewed awareness about the ageing and degradation of bridges to the Italian public opinion, politics and engineering community. Unfortunately, once again, such awareness sprang up only after a dramatic event. In some ways, the Morandi bridge collapse had a similar effect to the collapse of F. Jovine primary school at San Giuliano di Puglia, Italy, in the 2002 Molise earthquake [5], causing the death of 27 children and a teacher. Then, the tragedy highlighted the large seismic protection deficit of public buildings such as schools [6], as well as how the obsolete seismic rules in force should be upgraded to keep pace with increased knowledge in the field. Consequently, a new seismic code [7] was introduced and recently further updated [8]. Specifically, the provisions regarding existing structures in the current Italian technical code are mainly focused on buildings, while the commentary [9] provides some rules for the safety assessment of existing bridges under seismic actions but without indications on the assessment under service loads. In addition, current Eurocodes provide specific rules for newly designed bridges [10], while EC8-3 [11], specifically devoted to the assessment and retrofitting of Infrastructures 2021, 6, 25. https://doi.org/10.3390/infrastructures6020025 https://www.mdpi.com/journal/infrastructures