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The paper presents a GIS plugin, named Bridge Assessment System via MTInSAR (BAS-MTInSAR), aimed at assessing deformations in existing simply supported concrete girder bridges through Multi-Temporal Interferometry Synthetic Aperture Radar (MTInSAR). Existing bridges require continuous maintenance to ensure functionality toward external effects undermining the safety of these structures, such as aging, material degradation, and environmental factors. Although effective and standardized methodologies exist (e.g., structural monitoring, periodic onsite inspections), new emerging technologies could be employed to provide time- and cost-effective information on the current state of structures and to drive prompt interventions to mitigate risk. One example is represented by MTInSAR data, which can provide near-continuous information about structural displacements over time. To easily manage these data, the paper presents BAS-MTInSAR. The tool allows users to insert information of the focused bridge (displacement time series, structural information, temperature data) and, through a user-friendly GUI, observe the occurrence of abnormal deformations. In addition, the tool implements a procedure of multisource data management and defines proper thresholds to assess bridge behavior against current code prescriptions. BAS-MTInSAR is fully described throughout the text and was tested on a real case study, showing the main potentialities of the tool in managing bridge portfolios. [ABSTRACT FROM AUTHOR]

Several recent studies have investigated the opportunities of differential interferometry synthetic aperture radar (DInSAR) using satellite data for structural health monitoring (SHM) of civil structures. However, its use in structural engineering is still debated because of the lack of a general understanding of the potential and limitations of the technology for bridge SHM. To overcome this issue, specific methods of data processing and displacement assessment with error quantification need to be developed. The present paper aims at giving an insight into the use of small baseline subset-differential synthetic aperture radar interferometry (SBAS-DInSAR) as a remote-sensing technology for civil infrastructure monitoring combining information at a large scale with those associated with a single bridge. In particular, an operational framework for the selection and processing of a measurement time series representative of the structural behavior of the bridge of interest is designed in a way that fully remote characterization and assessment can be carried out by exploiting web-mapping platforms according to the crowd-sensing paradigm. The workflow, designed consistently with a structural engineering perspective, has been tested with reference to a number of bridges crossing the Tiber river in Rome (Italy), showing that the proposed fully remote monitoring procedure can effectively support satellite data processing and interpretation. Moreover, some issues in view of the general use of satellite data for bridge monitoring emerged from the study. Gaps in the measurement point distribution over the bridge decks are frequently observed over all the monitored area, therefore simplified methodologies aimed at estimating expected displacement ranges of different bridge typologies under serviceability loads have been defined enabling a rational interpretation of the data in the light of the selected radar sensor band of operation. Simplified formulations and charts for service and environmental loads are then presented with a twofold objective: (1) supporting the satellite data elaboration and interpretation by means of easy to manage open-source tools; and (2) providing estimates of the expected operational displacements of healthy structures to guide data interpretation and even algorithms for radar signals processing able to incorporate the response of structures to temperature variations. [ABSTRACT FROM AUTHOR]

Evaluation and strengthening of existing bridges – historical outlines and findings regarding the Hessian road bridge inventory Two short histographical sketches introduce the concepts of refurbishment, condition and load‐bearing capacity assessment between 1700 and 2010 and take a look at the development of the recalculation of existing bridges. Based on project sketches, the hidden safety features of existing road bridges are worked out and procedures for achieving efficient structural bridge strengthening are presented. The focus is on the determination of real object‐specific traffic load models, calibrated structural analyses and additive and non‐destructive strengthening methods. Some critical comments on planning acceleration and the current approval system, together with the demand that bridge construction should be reflected in the common objective of "traffic", broaden the definition of strengthening holistically. This offers the opportunity to stimulate a discussion about the sensible handling of existing bridges as part of our road infrastructure. [ABSTRACT FROM AUTHOR]

The management of existing civil infrastructure is becoming more crucial as a large share of bridges is approaching their theoretical end of service duration. Structural performance monitoring aims to verify bridge safety at a given time, and it should be differentiated from structural health monitoring, which aims at detecting structural damage. Possible monitoring techniques include bridge load testing, non-destructive testing, and continuous monitoring of structural behaviour, environmental conditions, and load levels. Nonetheless, selecting the optimal combination of monitoring techniques is challenging as each method provides unique but also redundant information. This study proposes a framework to assess the value of information from multiple bridge monitoring techniques. This framework enables defining the appropriate set of monitoring techniques to ensure that the collected information will potentially correct engineering decisions regarding structural safety. A full-scale bridge in Switzerland is used for validating the framework predictions. Combining four monitoring techniques, the expected average increase of degrees of compliance of structural verification is estimated to 19%, which is consistent with the 36% obtained after performing these monitoring techniques. The methodology supports decision-makers in selecting an optimal combination of monitoring techniques for structural performance monitoring by maximizing the value of information. [ABSTRACT FROM AUTHOR]

This paper addresses the need for accurate and objective safety assessments of bridges in Brazil taking into account the increase in traffic load and limited funding for infrastructure. In Brazil, the usual method of ensuring bridge safety involves strengthening based on design codes using deterministic analysis and partial safety factors. This method leads to an increase in the maintenance cost of the bridges. Structural reliability assessment, a higher-tier assessment method, is recommended globally for assessing the safety of existing bridges beyond current deterministic methods. This paper presents a study that evaluates the structural safety of existing road bridges in Brazil using the semi-probabilistic method defined in Brazilian standards and the full probabilistic method. The study selected six case studies of existing reinforced and prestressed concrete bridges to evaluate their structural safety concerning current normative loads. The results suggest that the partial safety factors defined in the Brazilian standards are consistent with international standards. The reliability analysis can guarantee the bridges' safety, even with increased traffic loads, without additional costs for structural strengthening. Therefore, the paper highlights the importance of promoting reliability analysis in Brazil to ensure the safety of existing bridges and promote cost-effective and objective safety assessments. [ABSTRACT FROM AUTHOR]

A case study was conducted to explore a more rational and robust process for determining the characteristic in-situ compressive strength of concrete structures from core samples. Slabs and girders were obtained from a total of seven bridges, earmarked for demolition due to social and performance considerations. Approximately 600 concrete core samples were extracted from various locations on these bridges. Statistical simulations were carried out using both conventional protocols and a newly proposed method to ascertain the characteristic strength from the cores. This led to a comprehensive discussion on the appropriate sample size, as well as the probabilistic robustness and reliability of the protocols. The proposed method demonstrated the ability to minimize over- or under-estimation of the characteristic strength, providing stable values less affected by fluctuations in core strengths.

The paper presents a GIS plugin, named Bridge Assessment System via MTInSAR (BAS-MTInSAR), aimed at assessing deformations in existing simply supported concrete girder bridges through Multi-Temporal Interferometry Synthetic Aperture Radar (MTInSAR). Existing bridges require continuous maintenance to ensure functionality toward external effects undermining the safety of these structures, such as aging, material degradation, and environmental factors. Although effective and standardized methodologies exist (e.g., structural monitoring, periodic onsite inspections), new emerging technologies could be employed to provide time- and cost-effective information on the current state of structures and to drive prompt interventions to mitigate risk. One example is represented by MTInSAR data, which can provide near-continuous information about structural displacements over time. To easily manage these data, the paper presents BAS-MTInSAR. The tool allows users to insert information of the focused bridge (displacement time series, structural information, temperature data) and, through a user-friendly GUI, observe the occurrence of abnormal deformations. In addition, the tool implements a procedure of multisource data management and defines proper thresholds to assess bridge behavior against current code prescriptions. BAS-MTInSAR is fully described throughout the text and was tested on a real case study, showing the main potentialities of the tool in managing bridge portfolios.

A methodology is introduced that allows to determine the reliability of railway bridges subject to freight trains and which comply with code based assessment according to the Swiss structural code SIA 269. The methodology uses probabilistic models for section forces from freight trains. These models are based on a large database of wheel load measurements. A case study demonstrates how the methodology is applied to determine the reliability of generic bridges and subsequently allows the assessment of the reliability for a portfolio of railway bridges. The results show that the target reliability is achieved according to SIA 269 considering the code format and current set of partial safety factors. The study identifies potential load bearing reserves for bridges with longer spans. [ABSTRACT FROM AUTHOR]

There is great interest in developing an adequate partial factor format for the assessment of existing structures, and in particular bridges, that should be able to take various aspects into account linked to the fact that the structure already exists. As the structure is existing, additional information related to material parameters, loading conditions, local structural defects, etc. can be accounted for. In addition, the degree of conservatism needs to be well balanced to avoid unnecessary investment of resources in replacement or retrofitting. This contribution considers the experience gained in recent years in parallel with some ongoing standardisation work in relation to Eurocodes and the next edition of the fib Model Code for new and existing concrete structures. The current state of the art of partial factors for the assessment of existing structures is explored and the differences are assessed based on a comparison between (i) the use of recommended fixed partial factors as provided in many national and international codes, (ii) adjusted (flexible) partial factors derived for the individual case under consideration, and (ii) reliability-based verification. In order to assess the adequacy of proposals and identify some differences, the available partial factor formats are applied to two case studies of reinforced concrete bridges and they are critically assessed. [ABSTRACT FROM AUTHOR]

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The paper presents a systematic review about the use of artificial intelligence (AI) in the field of structural health management of existing bridges. Using the PRISMA protocol, 81 journal articles were analysed. Three areas of investigation were addressed: (1) use of computer vision (CV) to automatize visual inspection of existing bridges; (b) use of AI with data provided by sensors employed in structural health monitoring (SHM); (c) use of AI for enhancing prediction of existing bridges deterioration, to improve risk estimation. The findings indicated that while the first two areas are covered by the scientific literature, the most intriguing challenges regard the use of AI in the field of bridge performance and risk assessment, in which new technologies could be exploited for predicting structural decay over time and residual life. This synthesis could significantly contribute to facilitate the indispensable fusion between the traditional civil-structural engineering and the contemporary technological progresses. [Display omitted] • AI methods for structural health management of existing bridges are reviewed. • CV techniques to improve current practices of visual defect detection were discussed. • AI methods for improving input and output from SHM of existing bridges were defined. • Improvements given by AI in assessing bridge performance and risks were shown. • Open challenges and future research directions were highlighted. [ABSTRACT FROM AUTHOR]

In recent years, several catastrophic collapses of existing bridges have highlighted the need for rapid risk analysis methods aimed at supporting infrastructure managers in the prioritisation of detailed assessments and, if any, risk mitigation actions. A large percentage of existing road bridges were built between the 1960s and 1980s, having thus already reached or even exceeded their design lifetime. Several studies have also shown that bridges often collapse due to either natural or human-related events, such as floods, collisions or overloading that, in addition to earthquakes, should be duly considered in risk assessment. This calls for multi-hazard approaches that provide an integrated perspective of the risk of bridge portfolios, to identify critical structures to support decision-makers. This study proposes a multi-hazard risk-based prioritisation methodology for application to a large number of bridges under limited level of knowledge. Specifically, the risk level is quantified through indices, accounting for uncertainties, that are used for comparative purposes among bridges. The methodology is applied to a highway bridge portfolio located in northern Italy, producing a risk-based ranking that is critically discussed. Analysis results are then compared with the outcome of the current Italian guidelines for safety assessment and maintenance of existing bridges. • Multi-hazard risk assessment of existing road bridges for prioritisation. • Proposal and investigation of alternative formulations of a multi-hazard risk index. • Application to bridge portfolio under traffic, earthquake, fire and impact hazards. • Bridge ranking and classification based on statistical thresholds. • Incorporation of visual inspection data. [ABSTRACT FROM AUTHOR]

In this study, the overall carbonation depth of existing bridges was investigated to establish practical guidelines for diagnosing structural carbonation. Carbonation depth was measured by obtaining cross-sections and core samples of girder-slabs from six existing concrete bridges scheduled for dismantling. The variation in carbonation depth based on the structures' location was analyzed. Moreover, various protocols were proposed for deriving the characteristic values of in-situ carbonation depth for concrete structures and each protocol was verified through probabilistic simulations. Carbonation depth exhibited inconsistency across the cross-section, varying significantly depending on the location, but a deeper carbonation was especially noticeable in locations subjected to bending or tensile stress by design. The method to select the largest value from the core data obtained are considered suitable to prevent both underestimation and overestimation. • Carbonation depth varies widely (0–100 mm) across bridge sections. • Normal distribution of carbonation depth observed in experiments. • Upper girder sections showed relatively consistent carbonation. • Lower flange portions exhibited deeper carbonation due to stress. • Method selecting the largest core value suitable to prevent bias. [ABSTRACT FROM AUTHOR]