Ivar Björnsson

A bridge failure can result in significant social, economic, and environmental problems; therefore, its reliability and risk management are essential. Bridges’ system reliability and risks are governed mainly by their redundancy and robustness, which currently are not adequately included in most design code specifications. Thus, in this study, a comprehensive comparison between relevant importance, redundancy, and robustness indicators found in the literature with different levels of complexity is carried out. The indicators under analysis have been used separately in different studies but have never been addressed together. Therefore, this study presents a joint evaluation of deterministic, reliability- and risk-based indicators to evaluate the differences in interpretation and information provided by the indicators. The approach is exemplified by analyzing a prestressed concrete bridge subjected to continuous degradation due to chloride ingress. A procedure is implemented to couple a metamodel-based reliability approach with a Nonlinear Finite Element Analysis (NLFEA). Based on the analysis performed, the comparison between indicators showed how different interpretations can be obtained depending on the implemented approach. Thus, creating more uniform formulations and agreeing on target values is necessary to help with redundancy and robustness interpretation.

The potential risks of climate change on the built environment involve large uncertainties. This poses an intricate problem to designers and challenges a long-standing tradition of built infrastructure design. More specifically, designers are faced with this challenging question: how to rationally account for climate change risks when designing a new asset? A framework that holistically addresses this difficult question is missing from the current literature. This study contributes to this gap by (1) proposing a conceptual framework for rationally considering the effects of climate change in the design of these assets and (2) identifying the challenges that need to be overcome to facilitate the transition, and further development, of the proposed framework into practice. First, a detailed overview of important infrastructure performance requirements that are relevant to the proposed framework is presented. The different stages of the proposed conceptual framework are then outlined. The proposed framework progresses in the following order: ranking the importance of the asset, identifying the potential climate change risks, analyzing these risks, selecting a design strategy, and finally evaluating the final design. Lastly, several challenges that impede the application of the proposed framework in practical settings are identified. The proposed conceptual framework and the identified challenges comprise a necessary steppingstone towards addressing this pressing issue and developing a more practically applicable framework for considering the risks of climate change in the design of built infrastructure assets.

For practical decisions on common recurring maintenance actions, the information from routine inspections form a decision basis for the bridge manager. It is often difficult to assess whether this information is sufficient for deciding on a repair action, or if more information is needed. For many bridges the information for supporting decisions may be limited, although those bridges cause large yearly maintenance costs for the society. The purpose of the study presented in this paper is to show how two different models for decision making based on Bayesian decision theory, a point-in-time decision model and a sequential updating decision model, can be used to improve the decision-making process for common maintenance decisions. The models use information from routine inspections and incorporates time dependent aspects such as material degradation and time value of money to improve the decision-making process. The focus is on presenting the methodology with a case study of a concrete bridge in Sweden where the edge beams may have to be replaced. Three assessment approaches are considered: (i) no assessment, (ii) desktop evaluation and (iii) measurements. The main finding is that sequential updating decision making will provide a higher benefit than a point-in-time decision, and thus give higher Value of Information. This value becomes even higher when the measurements are selected for the assessment. The results also show that the edge beams should be replaced. The general approach presented can be applicable to many decision scenarios related to maintenance of deteriorating structures.

The condition assessment of bridges considers a combination of information from different sources rendering multiple levels of assessment possible. This paper illustrates how successive condition assessment strategies increase the expected utility compared to single choice decisions through Bayesian inference. Multiple levels of assessment allow for additional possibilities for obtaining structural health information and updating one’s beliefs about structural condition. Thus, more informed decision-making is possible with respect to the gain in accuracy versus the costs of the assessment options. The paper aims to introduce how the successive approach can be implemented and in which scenarios it provides an increase in expected utility in comparison to one instant decision. To highlight this, a few pedagogical numerical examples are provided.

Climate change may have multifaceted impacts on the safety and performance of infrastructure. Accounting for the different ways in which potential climate change scenarios can affect our infrastructure is paramount in determining appropriate adaptation and risk management strategies. Despite gaining some attention among researchers in recent years, this research area is still largely uninvestigated. Several studies have indicated bridges to be especially susceptible to the effects of climate change. This article presents the potential impacts of climate change on bridges and combines the findings of close to 70 research articles to construct a broad list of their possible adaptation techniques. Although this study focuses on bridges, many of the presented climate change impacts and their adaptations are of relevance also to other types of infrastructure.

In this contribution a practical and rational decision-making approach is presented to be applied for common bridges typically managed by public authorities. The authors have developed a model with the intention to be applicable for practical cases for common bridges in the daily work of bride operators responsible for a large number of assets, yet still maintain the principles of more generic frameworks based on probabilistic decision-theory.Three main attributes of the verification of sufficiency of structural performance are considered, namely: 1) the level of sophistication of modelling performance, 2) the degree of verification and acceptance criteria in terms of dealing with uncertainties and consequences, 3) the extent of information is obtained and incorporated in the verification.The simplicity of the approach is demonstrated through an illustrative case study inspired by practical condition assessment decision problems. It is argued that in practical cases it may be desirable to utilize less advanced methods owing to constraints in resources or lack of reliable data (e.g. based on structural health monitoring or other on-site measurement techniques).

Climate change and its impacts on infrastructures may seriously affect the functionality of societies. Despite the alarming potential consequences climate change pose, not enough effort has been directed towards averting these impacts or managing them in some other way (e.g. mitigation, reduction, etc.). Well-functioning infrastructure networks play a key role in societies’ resilience and their ability to cope with climate-induced hazards. Therefore, ensuring the efficient performance of infrastructure networks, even during climate related emergencies, is central to the resilience of societies in the face of climate change. At the heart of a resilient transportation infrastructure network lays robust bridge structures. This paper builds on previous work where the potential risks from climate change on bridges were surveyed. Here, a qualitative risk prioritization scheme for bridges to rank these risks is presented. The aim of this work is hence to provide a tool for determining which of these risks are more worthy of closer investigation. The suggested framework is based on the basic elements of risk; i.e. hazard, exposure, vulnerability, and consequences. Several indices reflecting these four components and their different characteristics are introduced. Subsequently, a method for ranking the different risks based on these indices is presented. This framework can be used to optimize investments in adapting bridges to climate change.