PSI - Issue 64

Francesco Pentassuglia et al. / Procedia Structural Integrity 64 (2024) 254–261 F. Pentassuglia et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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1. Introduction Concrete bridges worldwide are experiencing increasing rates of failure (Zhang et al., 2022) due to the various deterioration mechanisms − primarily attributed to the long-term effects − e.g., tendon corrosion, creep, shrinkage, and cracking (Domaneschi et al., 2023). Traditional methods for assessing the structural health of bridges, such as visual inspection, may not effectively capture subtle issues, like early fatigue cracks, corrosion of embedded reinforcement, or localised damage. Moreover, these methods heavily rely on human judgment and can be time-consuming (An et al., 2019). To monitor the structural health of bridges more effectively, advanced technologies such as in-situ sensors, point clouds, drones, and satellite imagery are recently being utilised for detecting early signs of deterioration that could compromise the structural integrity of such assets. These signs often manifest on the bridge as deck deflections. However, interpreting these deflections accurately to assess the bridge's condition is a non-trivial task that however is crucial for effective asset management and decision-making regarding end-of-life strategies. Nowadays, artificial intelligence-based methods offer advanced computational techniques to handle complex and uncertain scenarios. As a result, they could provide more efficient and accurate ways to assess the health state of a bridge by leveraging machine learning (ML) algorithms and sensor data analysis to automate the detection of subtle issues, leading to improvements in the maintenance planning and the overall safety of bridge infrastructure (Salehi and Burgueño, 2018). 1.1 Causes of bridge deck deflections Creep and shrinkage are significant factors influencing the long-term behaviour of concrete structures, including the prestressed concrete bridges. Creep refers to the gradual deformation that occurs in a concrete structure when subjected to sustained loads over time. On the other hand, shrinkage is the reduction in volume of concrete due to environmental conditions leading to moisture loss. Both creep and shrinkage are influenced by factors such as the water-cement content, the relative humidity, the temperature, the aggregate content, and the size of the member (Dey et al., 2021). The collapse of the Koror-Babeldaob Bridge in Palau in 1996, was linked to inadequate predictions of creep and shrinkage models that lead to excessive deflections at the mid-span of the box-girder balanced cantilever bridge (Bažant et al., 2010). Corrosion of steel reinforcement in concrete structures, including bridges, is a critical issue that can lead to significant structural deterioration and compromise the safety and longevity of the infrastructure. The presence of environmental factors such as moisture, oxygen, and chloride-based compounds accelerates the corrosion process, ultimately weakening the material and reducing its load-bearing capacity (Messina and Proverbio, 2022). Corrosion can manifest as pitting or general, with pitting corrosion causing localised section loss that may be challenging to detect without exposing the reinforcement bars for inspection (Dimitri and Chernin, 2009). Instances of prestressing loss due to corrosion have led to structural failures in bridges, such as the collapse of the Ynys-y-Gwas bridge in the UK in 1985 and the Morandi Bridge in Italy in 2018, emphasising the importance of addressing corrosion effects in bridge design and maintenance (Calvi et al., 2018; Domaneschi et al., 2020). Concrete cracking in prestressed concrete bridges is a common issue that can significantly impact the structural behaviour and performance of the bridge. Cracks in concrete structures, especially in post-tensioned concrete box girder bridges, can result from various factors such as thermal movements, tensioning of tendons, shrinkage, and construction errors (Podolny, 1985; Jun et al., 2007). The impact of heavy traffic loads on long-span bridges, especially from extra heavy trucks, can also pose significant threats to their structural integrity and safety (Han et al., 2015). The repeated loading conditions imposed by traffic can result in long-term deflection in the bridge structure, which, if excessive, can compromise its integrity and lead to deformation, cracking, or even collapse in the most severe cases (Jun et al., 2007). The growth in traffic volume, coupled with the presence of overloaded trucks, can increase the probability of deflection limit exceedance, further stressing the bridge (Lu et al., 2017).