| 1. |
- Björnsson, Ivar, et al.
(author)
-
Decision support framework for bridge condition assessments
- 2019
-
In: Structural Safety. - : Elsevier BV. - 0167-4730 .- 1879-3355. ; 81
-
Journal article (peer-reviewed)abstract
- An essential aspect in the maintenance of existing bridges is the ability to adequately and accurately assess and evaluate the condition of the structure. Condition assessments, which can be carried out in any number of ways, provide valuable information concerning the actual state of a bridge, including the severity of potential damages, and form the basis for further maintenance decisions. Any decision support concerning the management of existing structures thus requires attention towards the uncertainties associated with the assessment methods when applied in practice as well as the maintenance actions these support. These uncertainties cannot be solely described as model uncertainties but are also a result of the variation in engineering performance observed in practice. In the current paper a rational and systematic framework is presented which provides practical decision support concerning whether condition assessments are necessary, what assessment methods are recommended, if invasive actions are needed, or if some other non-invasive option may be more appropriate. The framework takes into account three main attributes of an enhanced condition assessment, namely, modelling sophistication, considerations of uncertainties and risks, and knowledge/information content. Increasing the level of one or more of these attributes may be advantageous only if the expected benefits or added value of information is considered appropriate in relation to the cost of implementation in practice. A decision making model, based on Bayesian decision theory, is adopted to evaluate this problem. Two case studies, in which the framework is applied, are provided for illustrative purposes; the first is a generic numerical example and the second a decision scenario related to the fatigue assessment of an existing railway bridge.
|
|
| 2. |
- Björnsson, Ivar, et al.
(author)
-
Determining Appropriate Design Impact Loads to Roadside Structures Using Stochastic Modeling
- 2015
-
In: Journal of Bridge Engineering. - 1943-5592. ; , s. 1-05015001
-
Journal article (peer-reviewed)abstract
- The design and verification of built structures requires structural engineers to consider accidental loading situations. The accidental loading situation investigated in this paper is heavy-goods vehicle (HGV) collisions with roadside structures; focus is on the design of bridge-supporting structures. The impact loads were determined from Monte Carlo simulations of a probabilistic model in which highway traffic measurements and accident statistics in Sweden are input. These loads were calculated for structures adjacent to straight roads as well as roads with curvature, and include considerations of the directional load components. Comparisons were made between the simulation results and approaches given in design codes, with focus on the Eurocode. The simplified approaches provided in the code were inadequate in their treatment of these design situations. Alternative equations for calculating impact forces and energies are presented. These equations can be used for determining design values for impact forces or for conducting probability/risk-based assessments of bridge supports subjected to HGV impacts. In this way, a more consistent treatment of HGV impacts in the design of bridge structures is achieved.
|
|
| 3. |
- Björnsson, Ivar
(author)
-
From Code Compliance to Holistic Approaches in Structural Design of Bridges
- 2016
-
In: Journal of Professional Issues in Engineering Education and Practice. - 1052-3928. ; 142:1
-
Journal article (peer-reviewed)abstract
- Forum papers are thought-provoking opinion pieces or essays founded in fact, sometimes containing speculation, on a civil engineering topic of general interest and relevance to the readership of the journal. The views expressed in this Forum article do not necessarily reflect the views of ASCE or the Editorial Board of the journal.
|
|
| 4. |
- Björnsson, Ivar
(author)
-
Holistic approach for treatment of accidental hazards during conceptual design of bridge - A case study in Sweden
- 2016
-
In: Safety Science. - : Elsevier BV. - 0925-7535. ; 91, s. 168-180
-
Journal article (peer-reviewed)abstract
- The control of risks in engineering design is, for most conventional construction projects, achieved through the use of design codes. However, relying on design based on code-compliance can lead to situations where risks are overlooked or inadequately treated; a complementary approach is needed. In this paper, a holistic risk-informed approach for the treatment of accidental hazards during the conceptual design of bridges is considered and a framework for such an approach is provided. The treatment of these design situations is incompatible with current codified approaches. Although risk assessments are commonly used in the design of large scale infrastructure projects, such approaches are rarely used for more common bridge designs. The assessment procedure, applicable for more conventional bridge projects, is described and some background information is provided that is useful for applying the proposed approach in practice. To illustrate the application of the proposed approach in practice, a case study of a bridge construction project in the west of Sweden is considered in which the approach is applied.
|
|
| 5. |
- Björnsson, Ivar
(author)
-
Holistic approach in engineering design - controlling risks from accidental hazards in bridge design
- 2015
-
Doctoral thesis (other academic/artistic)abstract
- Engineering design, in concise terms, is what engineers do using what they know. It is the underlying decision making activity that determines what is to be built and how it should be built. An ever present requirement in engineering design is that the structure should be safe. While historical approaches to safety in design relied on experience and engineering judgment, modern approaches have rationalized uncertainty in an effort to treat risks in a more consistent and objective way. Concurrent to these advancements, design codes have been developed which include safety formats that are calibrated using these rationalized approaches. This thesis investigates the limitations of the design codes in controlling risks in engineering design and proposes that a complementary approach – involving case-specific risk assessments – is necessary for addressing the risks that are not properly treated by the design codes. The main advantage of such an approach is that: • it broadens the scope of assessment to consider structural systems and possibly non-structural constituents; • it is also applicable during the conceptual design phase for the bridge structure; and • it is complementary to current codified approaches While similar approaches are common in large scale construction projects they are rarely applied in the design of more conventional bridge structures. However, in this thesis it is argued that the application of such approaches is also useful in more common bridge projects to better control risks inadequately treated by design based on code compliance. A framework for a holistic risk-informed approach is provided which focuses on the conceptual design of bridge structures and on the control of risks from accidental hazards. Case studies are conducted to highlight the usefulness of the approach and to help develop crucial aspects of the approach while providing useful background information for its possible implementation in future projects. Specific attention is also paid to the modeling of risks from heavy goods vehicle (HGV) impacts to bridge substructures – a design situation which was found to be inadequate treated using current codified approaches.
|
|
| 6. |
- Björnsson, Ivar
(author)
-
Opportunities and challenges of digitalization and automation in bridge design : A pre-study
- 2022
-
Reports (other academic/artistic)abstract
- This report presents the findings from a pre-study concerning the opportunities and challenges of digitalization and automation in bridge design. The project approach is divided into three parts: 1) a short review of the relevant literature, 2) investigations concerning bridge industry perspectives (with focus on bridge consultants), and 3) the identification of future research needs based on parts 1 and 2. The literature review found that digital transformation is often a desirable goal within different industries in Europe and Sweden with the justification that it could improve productivity. Specific digital technologies which have been identified as providing the most potential specifically in the building sector include the automation of knowledge-based work, the utilization of cloud-based services, internet of things (IoT) as well as mobile internet. When it comes to structural engineering, there is a clear indication that the profession is undergoing a paradigm shift towards a greater reliance on digital tools. Professional societies in both the US (ASCE) and the UK (IStructE) highlight the need for the profession to evolve and both have published insights concerning opportunities, challenges, and future needs. Some specific challenges include the need for broadening expertise as well as reforming and improving education for both students and practicing engineers (continuing profession development). The latter was also highlighted in a recent study in Sweden by af Klintberg (2018).Bridge industry perspectives were investigated through a small focus-group and questionnaire study, which involved bridge engineering consultants and experts. The results from both highlighted a high interest in and trends toward increased digital transformation and automation in bridge engineering practice today. Some opportunities which were mentioned include the possibility to reduce conservatism and optimize structures considering a variety of criteria, automation of routine work allowing for more time towards other relevant tasks, as well as the adoption of digital platforms and tools for improved communication, coordination, and management. One interesting ongoing trend within companies is the development of in-house digital tools, often viewed as giving a competitive edge. Challenges of digital transformation and automation which were identified often focussed on risks associated with over-reliance and faith in digital tools coupled with the need for adopting suitable design checking procedures considering potentially complex and comprehensive input/output in calculation (FE) software. Another interesting aspect which was discussed concerned the trend of increased specialization within the sector leading to the question of whether there is a need for ‘general practitioners’ of structural engineering.In synthesizing the results from the first two parts of the project, broad future research needs were identified. These include the necessity to investigate further, and in more detail, both positive and negative impacts of ongoing and future digital transformation and automation. To facilitate a more informed way forward, such impacts should be assessed and evaluated in relation to the structural engineering profession, the bridge and construction sector (including all relevant stakeholders), the individual engineer(s), as well as society at large. Some specific relevant future research topics relate to the investigation of professional variability and its implications, the human-machine interface, the transfer of IT models from design and planning to facility management, as well as effective knowledge and experience transfer in modern design practice. The final sections of the report also elaborate briefly on two common digital technologies used today: digital tools for structural design calculations and Building Information Modelling (BIM).
|
|
| 7. |
- Björnsson, Ivar
(author)
-
Reliability of RC Bridge Supports Designed to Resist Heavy Goods Vehicle Collisions
- 2015
-
In: Structural Engineering International. - 1683-0350. ; 25:4, s. 395-404
-
Journal article (peer-reviewed)abstract
- The reliability of bridge-supporting structures to resist impacts from heavy goods-vehicles (HGV) is investigated. Probabilistic simulations are carried out to calculate the reliability index of a circular reinforced concrete column that has been designed using historical values for equivalent static impact loads provided in the Eurocode. Considerations are made for the uncertainties related to the dynamic response and resistance of reinforced concrete bridge supports subjected to vehicular impact. A general procedure is outlined for determining the dynamic resistance of the structure. As input for the impact force, results from previous probabilistic simulations of HGV impacts to road side structures were used. It is found that the design based on the codified approach does not provide adequate safety levels in the case of the structure studied. An alternative formulation for determining more appropriate values for the impact load is suggested and some discussion was given pertaining to other possible design strategies for the treatment of these types of loading situations.
|
|
| 8. |
- Björnsson, Ivar, et al.
(author)
-
Robustness analysis of bridge when exposed to train collision due to derailment
- 2010
-
In: COST Action C26 Final Conference; Urban habitat constructions under catastrophic events. Proceedings of the final conference (Naples, Italy, 16-18 Sept. 2010). - 9780415606851 ; , s. 603-608
-
Conference paper (peer-reviewed)abstract
- This paper considers evaluation of structural robustness for a multi-span concrete bridge crossing multiple rail tracks, in particular the effect of extraordinary exposures on the bridge system. A case study is performed investigating the bridge system’s response to a train collision caused by derailment in an area near the bridge supports. The probability of such an event occurring is estimated from derailment statistics on the railway net. An examination of subsequent propagating actions is carried out based on mechanical and structural considerations. Conclusions drawn here concern the issues of low probability exposures with high con-sequence and possible strategies for increasing overall robustness of these types of bridges.
|
|
| 9. |
- Björnsson, Ivar, et al.
(author)
-
Simulation of collision loads to bridge supporting structures from heavy goods vehicle traffic on Swedish highways
- 2013
-
In: Safety, Reliability, Risk and Life-Cycle Performace of Structures & Infrastructures. - 9781138000865 ; , s. 2113-2120
-
Conference paper (peer-reviewed)abstract
- This paper investigates accidental loading in the form of heavy goods vehicle (HGV) collisions to bridge supporting structures. Structures adjacent to roads are normally strong enough to resist collisions from light vehicles, while it may not be feasible for such structures to resist collisions from all HGVs (greater than 3,5 tons). In this paper a probabilistic model is used to determine these collision forces while Bridge Weigh In Motion (B-WIM) measurements performed on Swedish highways form the foundation for the calculated results. The probabilistic model is evaluated using Monte-Carlo simulations in which approximately 60 thousand B-WIM measurements are included. The results are compared with values given in the design codes and the implications of using codified prescriptive approaches in Eurocode 1-7 (CEN 2006) are discussed. It is found that the tabulated values given in the code are significantly lower than the values determined from the simulations. It can be questioned whether these loads are intended to provide adequate safety with respect to the intensity and weights of HGV vehicles in today’s traffic environment.
|
|
| 10. |
- Björnsson, Ivar, et al.
(author)
-
Suitable degree of crudeness in engineering practice
- 2019
-
In: IABSE Symposium, Guimaraes 2019. - : International Association for Bridge and Structural Engineering (IABSE). - 9783857481635 ; , s. 1592-1599
-
Conference paper (peer-reviewed)abstract
- Practicing structural engineers may be familiar with the main principles of structural reliability but may not necessarily be experts in using such methods. This may lead to a lack in understanding the effect of uncertainties on the ensuing structural safety and to sub-optimization of more traditional structural engineering aspects. The aim of the current paper is to highlight the importance of considering risks and uncertainties in design and to improve the awareness of practicing engineers to such considerations. The importance of a consistent treatment of uncertainties in structural engineering is brought to attention with focus on the modelling approaches which often underlie decisions. Different aspects discussed are: decision making in light of uncertainty, principles of consistent crudeness and the influence of engineering performance in practice on the safety of structures. A simplified model, considering strategies for improving engineering models, is considered and examples, based on simplified decision models, are also provided.
|
|
| 11. |
- Honfi, Daniel, et al.
(author)
-
A practical approach for supporting decisions in bridge condition assessment and monitoring
- 2019
-
In: 20th Congress of IABSE, New York City 2019. - : International Association for Bridge and Structural Engineering (IABSE). - 9783857481659 ; , s. 2137-2142, s. 2137-2142
-
Conference paper (peer-reviewed)abstract
- 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).
|
|
| 12. |
- Honfi, Daniel, et al.
(author)
-
Decision support for bridge condition assessment
- 2017
-
In: SMAR 2017 Proceedings.
-
Conference paper (peer-reviewed)abstract
- The paper presents the first steps of the development of a theoretical framework for a rational yet practical decision making process concerning the condition assessment of existing bridges in Sweden. The main focus is on how to choose the appropriate level of enhanced conditions assessment considering aspects of model sophistication, uncertainty consideration and knowledge content utilisation. A conceptual case study is presented exemplifying how the framework can be used to structure the assessment actions of a steel bridge subjected to fatigue deterioration.
|
|
| 13. |
- Honfi, Daniel, et al.
(author)
-
Decision support for maintenance and upgrading of existing bridges
- 2017
-
In: IABSE Conference, Vancouver 2017. - : International Association for Bridge and Structural Engineering (IABSE). - 9783857481536 ; , s. 336-345, s. 336-345
-
Conference paper (peer-reviewed)abstract
- Maintenance of transportation infrastructure assets can be relatively expensive, since it does not only include the direct cost of interventions, but also the indirect consequences of traffic disruptions. To make optimal decisions about maintenance actions, including rehabilitation and upgrading, reliable information about the performance of existing structures is needed. However, obtaining such information might require significant efforts and can be done in various ways. The purpose of an ongoing Swedish research project BIG BRO is to develop a framework for a decision support methodology that can be used for implementing maintenance strategies for bridges on a rational basis. The present paper provides a brief overview about the project as well as describes some of the ongoing work.
|
|
| 14. |
- Honfi, Daniel, et al.
(author)
-
Informed successive condition assessments in bridge maintenance
- 2020
-
In: Journal of Civil Structural Health Monitoring. - : Springer. - 2190-5452 .- 2190-5479. ; 10:4, s. 729-737
-
Journal article (peer-reviewed)abstract
- 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.
|
|
| 15. |
- Honfi, Daniel, et al.
(author)
-
Inspection and monitoring of bridges in Sweden
- 2018
-
Reports (other academic/artistic)abstract
- This report provides an overview about recent research activities and current practice concerning inspection and monitoring of the structural performance of bridges and the related decision-making process. A brief review of common methods of collecting information on structural performance of bridges is presented, followed by a description of the use of the information collected in structural analysis and maintenance planning. An overview about the state of the art is given including recent scientific developments. Finally, the current Swedish practice for bridge management is presented.
|
|
| 16. |
- Klasson, Anders, et al.
(author)
-
Design for lateral stability of slender timber beams considering slip in the lateral bracing system
- 2018
-
In: Structures. - : Elsevier BV. - 2352-0124. ; 16, s. 157-163
-
Journal article (peer-reviewed)abstract
- The present study investigates the significance of potential slip in the bracings of simply supported slender timber members. Three bracing configurations are considered. The first case is that of a timber beam braced at one point at mid-span, the second one braced at two points and the third one braced at three points. Possible slip in the bracing members can for example be due to joint deformation, initial crookedness of purlins and slack (or relaxation) of cables in the stabilizing bay (catenary action). In this study, it is shown that slip in the bracing system can result in a reduced load-bearing capacity (due to larger beam stresses) of the beams. Also, the greater the slip, the greater lateral deflections and consequent bracing forces of the braced member. A simplified approach, using a larger initial geometrical imperfection, to account for potential slip in bracings is also evaluated. This approach is found to work reasonably well in terms of stresses and bracing forces, but underestimates the lateral displacements.
|
|
| 17. |
- Klasson, Anders, et al.
(author)
-
Slender Roof Structures - Failure Reviews and a Qualitative Survey of Experienced Structural Engineers
- 2018
-
In: Structures. - : Elsevier BV. - 2352-0124. ; 15, s. 174-183
-
Journal article (peer-reviewed)abstract
- Many slender roof structures have collapsed due to snow loading and instability. Although accurate stability calculations can be performed using theoretical models, these calculations may not always reflect the behaviour of real structures as a result of the uncertainties relating to e.g. loading, material behaviour, geometry, initial imperfections and the actual boundary conditions of the structure. As a result, the approach to stability design requires subjective decisions by the structural engineer concerning loading and modelling assumptions. This paper investigates the significance of these types of decisions made by structural engineers in designing slender roof structures. This investigation is based on a review of previous failure studies together with a survey of 17 experienced structural engineers. The results of this investigation indicate that most structural failures are a result of human errors; thus, a suitable strategy for avoiding errors is through quality control and design checking. Moreover, a significant discrepancy was observed concerning design assumptions made by the engineers in the study. Some of these assumptions, e.g. a non-conservative choice of the buckling length of a beam, have a significant negative impact to structural safety. It is therefore recommended that the structural engineers involved in the design of a structure have adequate experience and a holistic mindset. Another recommendation is that both drawings and design calculations are thoroughly reviewed before construction. Also, temporary bracing to be used during construction should be included in design. Finally, it is important that the communication between different partners in the design of a structure is satisfying.
|
|
| 18. |
- Kling, Peter, 1968, et al.
(author)
-
A homologous salmonid leptin radioimmunoassay indicates elevated plasma leptin levels during fasting of rainbow trout
- 2009
-
In: General and Comparative Endocrinology. ; 162:3, s. 307-312
-
Journal article (peer-reviewed)abstract
- The present study was conducted to establish a homologous radioimmunoassay (RIA) for quantifying plasma leptin (Lep) levels in salmonid species, and to study Lep levels in relation to nutritional status. A part of the Lep peptide, a 14 amino acid long sequence, identical between a Salmo and an Oncorhynchus species was synthesised. Polyclonal antibodies were raised in rabbit against this antigen and both were subsequently used in the development of a RIA protocol for assessing plasma Lep levels. The limit of detection of the assay was 0.3 nM, and intra- and interassay coefficient of variation (CV) were 8.4% and 13%, respectively. Apart from Atlantic salmon and rainbow trout, the assay exhibits measuring parallelism for a range of fish species, including arctic char, Atlantic cod and turbot, suggesting that the established RIA is useful for quantifying Lep levels in several fish species. The RIA indicates that Lep is found in salmonid plasma at levels of 0.5–5 nM, which is comparable with other peptide hormones, and well within the measuring range of the RIA. A study of fed and fasted rainbow trout showed elevated plasma Lep levels during fasting. In addition there was no correlation between Lep levels and condition factor. These data suggest that the relation between circulating Lep levels and energy status differs from that in mammals. While Lep is linked to energy balance, it may not act as an adiposity signal in salmonids, possibly pointing to functional divergence among ectothermic and endothermic vertebrates.
|
|
| 19. |
- Kling, Peter, 1968, et al.
(author)
-
The role of GH in lipid homeostasis, energy utilization and partitioning in rainbow trout: interactions with ghrelin, leptin and insulin-like growth factor I
- 2012
-
In: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480. ; 175:1, s. 153-162
-
Journal article (peer-reviewed)abstract
- The growth-promoting effects of in vivo growth hormone (GH) treatment were studied in relation to size and lipid content of energy stores including liver, mesentery, white muscle and belly flap in rainbow trout. In order to elucidate endocrine interactions and links to regulation of growth, adiposity and energy metabolism, plasma levels of GH, insulin-like growth factor I (IGF-I), leptin (Lep) and ghrelin, were assessed and correlated to growth and energy status. In addition tissue-specific expression of lepa1 mRNA was examined. Juvenile rainbow trout were implanted with sustained-release bovine GH implants and terminally sub-sampled at 1, 3 and 6 weeks. GH increased specific growth rate, reduced condition factor (CF) and increased feed conversion efficiency resulting in a redistribution of energy stores. Thus, GH decreased mesenteric (MSI) and liver somatic index (LSI). Lipid content of the belly flap increased following GH-treatment while liver and muscle lipid content decreased. Independent of GH substantial growth was accompanied by an increase in muscle lipids and a decrease in belly flap lipids. The data suggest that the belly flap may function as an energy buffering tissue during episodes of feeding and lean growth. Liver and muscle lipids were positively correlated to body weight, indicating a size-dependent change in adiposity. Hepatic lepa1 mRNA positively correlated to MSI and CF and its expression decreased following GH treatment, coinciding with decreased hepatic lipid content. Plasma Lep was positively correlated to MSI and belly flap lipid content, suggesting that Lep may communicate energy status. In summary, the observed GH tissue-specific effects on lipid metabolism in rainbow trout highlight the complex physiology of the energy reserves and their endocrine control.
|
|
| 20. |
|
|
| 21. |
|
|
| 22. |
- Larsson Ivanov, Oskar, et al.
(author)
-
The practical value of structural health information for time dependence in bridge maintenance
- 2021
-
In: Structure and Infrastructure Engineering. - : Informa UK Limited. - 1573-2479 .- 1744-8980. ; , s. 1-16
-
Journal article (peer-reviewed)abstract
- 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.
|
|
| 23. |
- Leander, John, et al.
(author)
-
A decision support framework for fatigue assessment of steel bridges
- 2018
-
In: Engineering Failure Analysis. - : Elsevier BV. - 1350-6307 .- 1873-1961. ; 91, s. 306-314
-
Journal article (peer-reviewed)abstract
- Many bridges are approaching or have already passed their expected service life. For steel bridges, fatigue is often the decisive degradation phenomenon that theoretically puts restrictions on a continued use. At the same time, fatigue is also afflicted with large uncertainties on the resistance side as well as on the action effect side. An accurate assessment of the service life will require measures outside the governing regulations but understanding what steps to take and how to consider the outcome for decisions on interventions can be a difficult task for a non-expert. This paper presents possible assessment actions and a decision support framework for rational decisions on interventions to extend the theoretical service life of existing bridges. A case study of a critical railway bridge is incorporated to demonstrate the framework. The aim is to provide a tool for bridge managers on how to evaluate and procure different assessment actions.
|
|
| 24. |
- Leander, John, et al.
(author)
-
Risk-based planning of assessment actions for fatigue life prediction
- 2017
-
In: 2nd International Conference on Structural Integrity, ICSI 2017, 4-7 September 2017, Funchal, Madeira, Portugal. - : Elsevier. ; 5, s. 1221-1228
-
Conference paper (peer-reviewed)abstract
- It is vital to extend the service life of existing bridges as far as possible as a means for improved sustainability leading to reduced economic cost and resource consumption. This requirement is especially valid for bridges which are critical components of highly vulnerable infrastructure systems. Achieving this aim requires enhanced methods involving various actions and methods influencing different aspects of the assessment process. A framework is presented in this paper based on three common factors used to describe the assessment actions of existing bridges; (i) model sophistication, (ii) uncertainty consideration, and (iii) knowledge content. The framework elucidates the influence of different decisions on the assessment process and facilitates the planning of appropriate assessment actions. Furthermore, it provides a basic scheme for a risk-based decision analysis for determining suitable assessment actions or activities. A fatigue assessment of an existing bridge detail is used to demonstrate the application of the framework in practical cases.
|
|
| 25. |
- Molnár, Miklós, et al.
(author)
-
Energy efficient buildings by use of reinforced masonry walls : An experimental study
- 2021
-
Reports (other academic/artistic)abstract
- Användning av ytförstärkning har undersökts som ett led i att förbättra murade ytterväggars energiprestanda. De experimentella undersökningarna genomförda vid Lunds tekniska högskola visar att genom användning av ytförstärkning kan tjockleken på den bärande delen i en yttervägg minskas med mellan 30 - 50 procent jämfört med dagens väggtyper. Väggarnas bärförmågan kan samtidigt bibehållas eller rentav ökas. Det insparade utrymmet kan nyttjas till mer termisk isolering, vilket medför att ytterväggens energiprestande förbättras utan ytterligare ökning av dess totala tjocklek.
|
|
| 26. |
- Moosmayer, Stefan, et al.
(author)
-
KALK study: ultrasound guided needling and lavage (barbotage) with steroid injection versus sham barbotage with and without steroid injection - protocol for a randomized, double-blinded, controlled, multicenter study
- 2017
-
In: BMC Musculoskeletal Disorders. - : BIOMED CENTRAL LTD. - 1471-2474. ; 18
-
Journal article (peer-reviewed)abstract
- Background: For the treatment of calcific tendinitis of the shoulder a variety of treatment regimes exist. Commonly used treatment measures include medication with oral analgesics, corticosteroid injections, extracorporeal shockwave therapy, ultrasound guided needling and lavage, and surgical treatment. Earlier cohort studies suggest that patients may benefit from these treatments, but there are few randomized studies and conflicting evidence about the effectiveness of the various treatments. In the present study we aim to compare the effectiveness of ultrasound guided needling and lavage (barbotage) together with a steroid injection to sham barbotage with and without an additional steroid injection. Methods: The study will be performed in six secondary-care institutions in Norway and Sweden. It is designed as a pragmatic, randomized, three-arm, parallel group, double-blinded, sham-controlled clinical trial with a 2-year follow-up. It will be performed on 210 patients, aged 30 years or older, presenting with painful arc, positive impingement sign and a calcium deposit amp;gt; 5 mm. Randomization to one of the three treatment options will be performed by using an online central randomization system. The three treatment groups are barbotage together with a subacromial steroid injection (the barbotage group), sham barbotage together with a subacromial steroid injection (the steroid group) or sham barbotage without a subacromial steroid injection (the placebo group). In the placebo group the steroid injection will be replaced by a short-acting local anaesthetic. Standardized home-based post-treatment physiotherapy will be performed by all patients for 8 weeks. Follow-ups are at 2 and 6 weeks, 4, 8, 12 and 24 months after treatment was given and will be performed with the patients and the outcome assessors blinded for group assignment. Primary outcome will be the Oxford shoulder score at 4 month follow-up. Secondary outcome measures are the QuickDASH upper extremity score, the EQ-5D-5L general health score and visual analogue scales for pain at rest, during activity, and at night. Discussion: The scientific evidence from this placebo-controlled trial will be of importance for future treatment recommendations in patients with calcific tendinitis.
|
|
| 27. |
- Moosmayer, Stefan, et al.
(author)
-
Ultrasound guided lavage with corticosteroid injection versus sham lavage with and without corticosteroid injection for calcific tendinopathy of shoulder: randomised double blinded multi-arm study
- 2023
-
In: BMJ. British Medical Journal. - : BMJ PUBLISHING GROUP. - 0959-8146 .- 0959-535X. ; 383
-
Journal article (peer-reviewed)abstract
- Objective To compare treatment effects between ultrasound guided lavage with corticosteroid injection and sham lavage with and without corticosteroid injection in patients with calcific tendinopathy of the shoulder. Design Pragmatic, three arm, parallel group, double blinded, sham controlled, randomised, superiority trial with repeated measurements over 24 months. Setting Six hospitals in Norway and Sweden. Participants 220 adults with calcific tendinopathy of the shoulder, persistent for at least three months. Interventions Ultrasound guided deposit lavage plus subacromial injection of 20 mg triamcinolone acetonide and 9 mL 1% lidocaine hydrochloride (lavage+steroid); sham lavage plus subacromial injection of 20 mg triamcinolone acetonide and 9 mL 1% lidocaine hydrochloride (sham lavage+steroid); or sham lavage plus subacromial injection of 10 mL 1% lidocaine hydrochloride (sham). All patients received a physiotherapeutic treatment regimen consisting of four home exercises. Main outcome measures The primary outcome was the result on the 48 point scale (0=worst; 48=best) of the Oxford Shoulder Score (OSS) at four month follow-up. Secondary outcomes included measurements on the short form of the Disabilities of the Arm, Shoulder and Hand questionnaire (QuickDASH) and of pain intensity up to 24 months. The influence of the size of the deposit at baseline and of the persistence or disappearance of the deposit was investigated. Results Data from 218 (99%) participants were included in the primary analysis. Differences between groups on the OSS at four months were not significant: lavage+steroid versus sham 0.2 (95% confidence interval -2.3 to 2.8; P=1.0); sham lavage+steroid versus sham 2.0 (-0.5 to 4.6; P=0.35); lavage+steroid versus sham lavage+steroid -1.8 (-4.3 to 0.7; P=0.47). After four months, 143 patients with insufficient treatment effect received supplementary treatment. At 24 months, none of the study procedures was superior to sham. No serious adverse events were reported. Conclusions This study found no benefit for ultrasound guided lavage with a corticosteroid injection or for sham lavage with a corticosteroid injection compared with sham treatment in patients with calcific rotator cuff tendinopathy of the shoulder.th calcific rotator cuff tendinopathy of the shoulder.
|
|
| 28. |
- Nasr, Amro, et al.
(author)
-
A qualitative prioritization of the risks imposed on bridges due to climate change
- 2019
-
In: IABSE Symposium, Guimaraes 2019. - : International Association for Bridge and Structural Engineering (IABSE). - 9783857481635 ; , s. 80-87
-
Conference paper (peer-reviewed)abstract
- 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.
|
|
| 29. |
- Nasr, Amro, et al.
(author)
-
A review of the potential impacts of climate change on the safety and performance of bridges
- 2021
-
In: Sustainable and Resilient Infrastructure. - : Informa UK Limited. - 2378-9689 .- 2378-9697. ; 6:3-4, s. 192-212
-
Research review (peer-reviewed)abstract
- An overabundance of evidence, both observational and from model projections, indicate that changes to the climate system are taking place at unprecedented rates. Although the magnitudes of these changes involve large uncertainties, the fact that our climate is changing is unequivocal. To ensure an unimpaired functionality of our societies,it is therefore of crucial importance to study the potential climate change impacts on infrastructure. Taking into account that bridges have a considerably long service life, it is of direct relevance to ascertain their reliable performance against climate change risks. This paper synthesizes the findings of over 190 research articles to identify the potential risks climate change may pose on bridges. Over 30 potential risks, supported by pertinent previous bridge damage (or failure) cases, are identified, categorized, and linked to the projected future climate changes. The identified risks can be used as a basis for future risk prioritization by bridge managers.
|
|
| 30. |
- Nasr, Amro, et al.
(author)
-
Bridges in a changing climate : a study of the potential impacts of climate change on bridges and their possible adaptations
- 2019
-
In: Structure and Infrastructure Engineering. - : Taylor and Francis Ltd.. - 1573-2479 .- 1744-8980. ; 16:4, s. 738-749
-
Journal article (peer-reviewed)abstract
- 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.
|
|
| 31. |
- Nasr, Amro, et al.
(author)
-
Climate change impact on safety and performance of existing and future bridges
- 2018
-
In: Proceedings of the Sixth International Symposium on Life-Cycle Civil Engineering (IALCCE 2018). ; , s. 1735-1741, s. 1735-1741
-
Conference paper (peer-reviewed)abstract
- Recent decades have seen an increased attention towards the threat of climate change to our built environment and not least our 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. This paper presents the initial findings of a new research project which is concerned with establishing an improved management of the risks to our infrastructure, especially bridges, in light of a changing climate. In this paper, a preliminary survey of the climate change related risks on bridges is conducted. Timely consideration of these impacts is of utmost importance to ensure a satisfactory performance of our bridges in the future. The interplay between the different risks and how the occurrence of one risk may influence other risks is also briefly discussed. The future stages of the project are mentioned as well. The authors would like to acknowledge the support of the Swedish Transport Administration. Any opinions, findings, or conclusions in this work are those of the authors and are not necessarily in accordance with those of the Swedish Transport Administration.
|
|
| 32. |
|
|
| 33. |
|
|
| 34. |
- Nasr, Amro, et al.
(author)
-
Climate change risks and bridge design
- 2023
-
In: Adapting the Built Environment for Climate Change : Design Principles for Climate Emergencies - Design Principles for Climate Emergencies. - 9780323953368 - 9780323953375 ; , s. 109-131
-
Book chapter (peer-reviewed)abstract
- Climate change can have substantial impacts on the safety and performance of infrastructure systems. Understanding these impacts is of paramount importance, especially for long-lived infrastructure elements, such as bridge structures. This chapter focuses on discussing the impacts of climate change to bridges and describes a conceptual framework as a guide for bridge designers on how to consider these impacts in bridge design. Several existing challenges are, however, highlighted that hinder the application of such a framework in practical contexts (e.g., climate change data availability and uncertainty). Overcoming these challenges is necessary to facilitate a rational consideration of climate change impacts in the design of bridge infrastructure. Although the current chapter mainly addresses bridges, the identified risks and proposed framework can be extended to other types of infrastructures and infrastructure elements.
|
|
| 35. |
- Nasr, Amro, et al.
(author)
-
Klimatförändringars inverkan på broars säkerhet och prestanda : En översyn av potentiella effekter och anpassningsåtgärder
- 2019
-
Reports (other academic/artistic)abstract
- Vår infrastruktur kommer att påverkas av klimatförändringar, både nu och i framtiden.För att kunna säkerställa infrastrukturens funktion och uppfylla de säkerhetskrav somfinns kommer det därför att krävas investeringar i anpassningsåtgärder. Men åtgärder börinte tas på utifrån bristfällig kunskap, det är därför väsentligt att i förväg kartlägga vilkatyper av påverkan som kan förväntas och vilka åtgärder som är rimliga att genomföra.Denna rapport sammanfattar resultat från studier av risker med klimatförändringar ochdess potentiella effekter på broar, då dessa konstruktioner kan komma att påverkas avolika ändringar i klimatet. I studierna har 243 forskningsartiklar och rapporter från helavärlden gåtts igenom för att identifiera potentiella risker för broar på grund av ändringari klimatet. Det bör nämnas att resultaten i rapporten inte är fokuserade på Sverige utanhar ett internationellt perspektiv; de flesta av de identifierade riskerna är dock relevantaför svenska förhållanden, medan andra är mer relevanta i andra delar av världen.Totalt har 31 olika risker identifierats och kategoriserats i sju olika huvudkategorier enligtföljande:• Beständighet (riskgrupp D),• Funktion (riskgrupp S),• Geoteknik (riskgrupp G),• Ökad belastning (riskgrupp I),• Olyckslaster (riskgrupp A),• Extrema naturhändelser (riskgrupp E)• Drift (riskgrupp O).Utöver dessa riskkategorier har även en kortare analys av samverkande händelser gjorts,dvs. händelser där två eller flera klimatfaktorer eller effekter samverkar och ger en störresammantagen effekt än om de inträffar var för sig. En avslutande del om möjligaanpassningsåtgärder har även inkluderats, där metoder funna i litteraturen för att hanterade olika riskerna som identifierats beskrivs.Den viktigaste slutsatsen i rapporten är att ett stort antal risker finns för broar.Föreliggande rapport bidrar därmed till att lyfta fram dessa risker och synliggöra desseffekter. De två klimatfaktorer som påverkar flest risker för broar är temperaturhöjningoch ökad eller minskad nederbörd, de kan individuellt eller kombinerat påverka 25 av de31 identifierade riskerna. Beroende på förutsättningarna för en specifik bro (dvs.geografiskt läge, platsegenskaper, konstruktivt system, etc.) varierar de potentiellaklimateffekterna och deras möjliga konsekvenser. En bedömning av sannolikheten för enviss risk att inträffa, eller en prioritering av de olika riskerna, tas därmed inte upp irapporten. Sådana mer detaljerade kontextspecifika studier pågår och kommer attredovisas framöver inom ramen för projektet.
|
|
| 36. |
- Nasr, Amro, et al.
(author)
-
National-Level Analysis of the Impact of Climate Change on Local Scour under Bridge Piers in Sweden
- 2023
-
In: Journal of Infrastructure Systems. - 1076-0342. ; 29:2
-
Journal article (peer-reviewed)abstract
- Scour is an important cause of bridge failures. This article investigates the impact of climate change on bridge-pier scour in all 246 Swedish catchment areas. Although a few previous studies assessed the impact of climate change on bridge-pier scour in other countries, none of those studies identified the locations within a certain country where climate change is projected to have the highest impacts on bridge scour. A novel national-level method, based on possibility theory, is proposed herein for addressing this gap. The proposed method provides answers to the following questions: For which catchment areas is the projected increase in pier-scour depth highest or lowest? What is the percentage of catchment areas where climate change is projected to have either a positive or negative impact on scour risk in all scenarios? Which climate change scenarios cause the highest or lowest increase in equilibrium scour depth? Although these questions are addressed particularly for Sweden, the proposed method is generally applicable for any other location. The catchment area Riebnesströmmen (located in the northernmost county in Sweden) was identified to have the highest increase in the equilibrium scour depth in all considered reference periods (up to ∼25% increase), whereas the catchment area with the lowest increase varied depending on the considered reference period. The answers to the second question depended on the reference period and ranged from ∼5% to ∼10% and ∼8% to ∼14% for positive and negative impacts on scour risk, respectively. Interestingly, for the third question, it was found that higher-emission scenarios are not always more critical than lower-emission ones. These findings demonstrate the importance of performing national-level analyses of climate change impacts on infrastructure considering the different scenarios. The proposed method enables an efficient allocation of resources for adapting bridges to the increased scour risk due to climate change. Additionally, it can serve as a useful tool for quickly estimating the impact of climate change on bridge-pier scour for a certain location.
|
|
| 37. |
- Nasr, Amro, et al.
(author)
-
Probabilistic analysis of climate change impact on fungal decay of timber elements in ground contact and their long-term structural performance
- 2022
-
In: Wood Material Science and Engineering. - : Informa UK Limited. - 1748-0272 .- 1748-0280.
-
Journal article (peer-reviewed)abstract
- Climate change can substantially affect infrastructure performance and safety. In this article, the impact of climate change on fungal decay of wooden infrastructure in ground contact is investigated. For this purpose, projections of three different climate change scenarios are used to assess the impact of climate change on fungal decay rate of untreated clear wood elements in ground contact in Sweden. The highest increase in the average decay rate is observed for four counties located in mid-Sweden, i.e. Örebro, Värmland, Västmanland, and Gävleborg. Furthermore, two illustrative examples are presented to demonstrate the impact of the increased decay rates on the structural performance and long-term reliability of timber elements in four selected counties, Skåne (southernmost Sweden), Örebro, Värmland, and Västmanland. In the first illustrative example, the impact of climate change on the bending moment capacity of untreated timber utility poles is assessed while in the second the impact on the long-term reliability of axially loaded untreated columns is investigated. In the four studied counties, it is found that climate change can have considerable impacts on the structural performance and long-term reliability of timber elements in ground contact.
|
|
| 38. |
- Nasr, Amro, et al.
(author)
-
Quantitative assessment of the impact of climate change on creep of concrete structures
- 2021
-
In: Proceedings of the 31st European Safety and Reliability Conference (ESREL 2021). - Singapore : Research Publishing Services. - 9789811820168 ; , s. 1318-1325
-
Conference paper (peer-reviewed)abstract
- Creep of concrete structures is in most cases regarded as a serviceability problem that may have impacts on maintenance and repair costs but cannot lead to structural collapse. However, several structural collapses during the past decades have been, at least partly, attributed to excessive creep deformations. Recent studies suggest that concrete creep may be further exacerbated by climate change. The current study demonstrates how this effect can be quantitatively assessed. For this purpose, six different creep models (i.e, Model Code 1999, Model Code 2010, MPF, B3, B4, and B4s models) are used under considerations of historical and future climatic conditions in southernmost Sweden as given by a regional climate model. Furthermore, two different simulations were performed as follows: 1) considering only climate uncertainty represented by the climate model, and 2) considering climate uncertainty, parameter uncertainty, and creep model uncertainty. The highest impact of climate change on end of century creep coefficient is observed using model B4 where the 75th percentile of the increase in creep coefficient is found to range from 8% to ∼14% depending on the climate scenario. The results of the assessment in this article show that the uncertainty related to climate change on creep of concrete structures (higher effect in RCP8.5 than in RCP2.6 and RCP4.5 which have very similar results) is much smaller than uncertainties resulting from creep modelling.
|
|
| 39. |
- Nasr, Amro, et al.
(author)
-
Risk-based multi-criteria decision analysis method for considering the effects of climate change on bridges
- 2023
-
In: Structure and Infrastructure Engineering. - : Informa UK Limited. - 1573-2479 .- 1744-8980. ; 19:10, s. 1445-1458
-
Journal article (peer-reviewed)abstract
- Recent studies have identified many potential climate change impacts on bridges. Considering the sheer number of these potential impacts, how can a bridge owner prioritise which impacts to consider, and for which bridges? This paper proposes a risk-based multi-criteria decision analysis method for systematically addressing these two questions simultaneously. The proposed method can be used to address both extreme and non-extreme impacts as opposed to focussing solely on extreme impacts as has been done in previous prioritisation studies related to climate change risks. The proposed method is based on four main components of risk: hazard, impact, vulnerability and consequences. Several indices characterising these components are used to address the previous two questions. To reflect the uncertainty in the analysis, the different indices are assessed optimistically and pessimistically. Additionally, to ensure a more transparent decision-making process the inclusion of a strength of evidence assessment is also proposed. The applicability of the method is then demonstrated on three illustrative case studies for three different potential climate change impacts. It is concluded that the proposed method is both feasible and appropriately fulfils its purpose. Nevertheless, the proposed method should be more elaborately tested on practical bridge case studies to further establish its applicability.
|
|
| 40. |
- Nasr, Amro, et al.
(author)
-
The need for nonuniform risk acceptability across climate change scenarios
- 2024
-
In: Risk Analysis. - 0272-4332.
-
Journal article (peer-reviewed)abstract
- Climate change risk assessment studies focus on identifying and analyzing different risks considering several climate change scenarios and on evaluating the cost-effectiveness of different adaptation measures. However, risk acceptability is often not reflected on in the context of climate change risk studies. Noting that the different climate change scenarios depict drastically contrasting images of the future in terms of population growth, economic development, and changes to life expectancy, this article uses risk acceptance criteria that are based on socioeconomic considerations to highlight the need for nonuniform risk acceptability across climate change scenarios. For this purpose, the optimum implied cost of averting a fatality derived based on the life quality index concept and the value of a quality-adjusted life year derived based on the time principle of acceptable life risk are assessed in three different climate change scenarios for Sweden. Additionally, an illustrative example that assesses the acceptable probability of failure of a steel rod under axial tension in the different climate change scenarios is presented. It is shown that risk acceptance criteria can vary considerably across the different climate change scenarios (e.g., more than 190% variation in the acceptable probability of failure for Sweden in the considered example). This article demonstrates that the ability of societies to afford risk-reducing measures may vary considerably across the different climate change scenarios. Hence, it can be concluded that (1) in the context of climate change risk assessments, risk acceptance criteria need to be developed to account for the different climate change scenarios, and (2) these criteria may vary considerably across the different climate change scenarios. Finally, relevant challenges and research needs are also provided.
|
|
| 41. |
- Nasr, Amro, et al.
(author)
-
Towards a conceptual framework for built infrastructure design in an uncertain climate : Challenges and research needs
- 2021
-
In: Sustainability (Switzerland). - : MDPI AG. - 2071-1050. ; 13:21
-
Journal article (peer-reviewed)abstract
- The potential risks of climate change on the built environment involve large uncertain-ties. 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.
|
|
| 42. |
- Nasr, Amro, et al.
(author)
-
Towards a holistic prioritization of climate-change risks for bridges
- 2019
-
In: 13th International Conference on Applications of Statistics and Probability in Civil Engineering, ICASP13. - 9791196712501
-
Conference paper (peer-reviewed)abstract
- Although the projected changes in the climate include considerable uncertainties, especially with downscaling, there is irrefutable evidence that the climate is changing at an unprecedented and alarming rate. In recent studies, some of the potential climate-change risks on bridges have been identified. The sheer number of these potential risks provokes two questions. Firstly, for a certain risk of interest (e.g. increased scour rate) which bridges should be prioritized from an inventory of bridges? Secondly, for a specific bridge, which of these risks are more critical? This paper proposes a method that can be used for addressing these two questions while considering the uncertainties intrinsic to the problem. Although this paper focuses on addressing the first question, a discussion on how the proposed method can be used for answering the second is also presented. The suggested method is based on four risk components
|
|
| 43. |
|
|
| 44. |
- Ronnestad, Ivar, et al.
(author)
-
Leptin and leptin receptor genes in Atlantic salmon: Cloning, phylogeny, tissue distribution and expression correlated to long-term feeding status
- 2010
-
In: GENERAL AND COMPARATIVE ENDOCRINOLOGY. - 0016-6480. ; 168:1, s. 55-70
-
Journal article (peer-reviewed)abstract
- The present study reports the complete coding sequences for two paralogues for leptin (sLepA1 and sLepA2) and leptin receptor (sLepR) in Atlantic salmon. The deduced 171-amino acid (aa) sequence of sLepA1 and 175 aa sequence for sLepA2 shows 71.6% identity to each other and clusters phylogenetically with teleost Lep type A, with 22.4% and 24.1% identity to human Lep. Both sLep proteins are predicted to consist of four helixes showing strong conservation of tertiary structure with other vertebrates. The highest mRNA levels for sLepA1 in fed fish (satiation ration = 100%) were observed in the brain, white muscle, liver, and ovaries. In most tissues sLepA2 generally had a lower expression than sLepA1 except for the gastrointestinal tract (stomach and mid-gut) and kidney. Only one leptin receptor ortholog was identified and it shares 24.2% aa sequence similarity with human LepR, with stretches of highest sequence similarity corresponding to domains considered important for LepR signaling. The sLepR was abundantly expressed in the ovary, and was also high in the brain, pituitary, eye, gill, skin, visceral adipose tissue, belly flap, red muscle, kidney, and testis. Fish reared on a rationed feeding regime (60% of satiation) for 10 months grew less than control (100%) and tended to have a lower sLepA1 mRNA expression in the fat-depositing tissues visceral adipose tissue (p < 0.05) and white muscle (n.s.). sLepA2 mRNA levels was very low in these tissues and feeding regime tended to affect its expression in an opposite manner. Expression in liver differed from that of the other tissues with a higher sLepA2 mRNA in the feed-rationed group (p < 0.01). Plasma levels of sLep did not differ between fish fed restricted and full feeding regimes. No difference in brain sLepR mRNA levels was observed between fish fed reduced and full feeding regimes. This study in part supports that sLepA1 is involved in signaling the energy status in fat-depositing tissues in line with the mammalian model, whereas sLepA2 may possibly play important roles in the digestive tract and liver. At present, data on Lep in teleosts are too scarce to allow generalization about how the Lep system is influenced by tissue-specific energy status and, in turn, may regulate functions related to feed intake, growth, and adiposity in fish. In tetraploid species like Atlantic salmon, different Lep paralogues seems to serve different physiological roles.
|
|
| 45. |
- Sarmiento, Silvia, et al.
(author)
-
COMPARISON AND JOINT EVALUATION OF IMPORTANCE, REDUNDANCY AND ROBUSTNESS INDICATORS APPLIED TO AGING PRESTRESSED CONCRETE BRIDGES
- 2024
-
Journal article (other academic/artistic)abstract
- The use of an adequate approach to assess and design large-scale structures, such as bridges, may prevent early structure failures and provide economical solutions throughout the service life. 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 properly 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; however, they 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. This points out the necessity to create more uniform formulations and to agree on target values that can help with the redundancy and robustness interpretation.
|
|
