| 1. |
- Crocetti, Roberto, et al.
(författare)
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Stress-laminated-timber decks: state of the art and design based on Swedish practice
- 2016
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Ingår i: European Journal of Wood and Wood Products/Holz als Roh - und Werkstoff. - : Springer Science and Business Media LLC. - 1436-736X .- 0018-3768. ; 74:3, s. 453-461
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Tidskriftsartikel (refereegranskat)abstract
- Stress-laminated-timber (SLT) bridge decks area valid alternative to conventional short- and medium-spanbridges in terms of cost and performance. SLT decks aremade from a number of planks or glulam beams positionedside by side and stressed together using high-strength steelbars. A concentrated load can therefore be distributed fromthe loaded beams onto adjacent beams due to the resistingfriction caused by the pre-stressing of all beams in thedeck. This paper describes the state of the art of SLT bridgedecks, with special emphasis on Swedish practice. Theeffect of butt joints on deck deflection and solution appliedto accommodate the loss of pre-stress are shown. Simpledesign tools for the preliminary design of road bridges areillustrated. Best practice with regard to some detailing,water protection and durability is also discussed. Finally,possible developments of SLT bridges are discussed.
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| 2. |
- Blomfors, Martin, et al.
(författare)
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Reliability analysis of corroded reinforced concrete beam with regards to anchorage failure
- 2019
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Ingår i: Life-Cycle Analysis and Assessment in Civil Engineering. - : CRC Press/Balkema. - 9781138626331 - 9781351857574 ; , s. 337-344, s. 337-344
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Konferensbidrag (refereegranskat)abstract
- Reinforcement corrosion is a common problem in reinforced concrete infrastructure today, and it is expected to increase in the future. To simply replace the corroded structures with new ones requires large resources, both in financial and environmental terms. Therefore it is important that existing structures are used to their full potential, also after the onset of corrosion. This paper presents a reliability study of the anchorage capacity of a reinforced concrete beam including reinforcement corrosion. The sensitivity of the different input parameters is also studied. As expected, the results show that the reliability is reduced with corrosion; the magnitude depends to a large extent on the modelling uncertainty used for the bond model for corroded reinforcement. The sensitivity analysis shows an influence of corrosion also on the sensitivities of the input parameters, which is expected based on the properties of the underlying bond model. This paper demonstrates that probabilistic evaluations give valuable insight of the reliability, which can be used to prolong the service-life of existing infrastructure and save both money and the environment.
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| 3. |
- Blomfors, Mattias, 1990, et al.
(författare)
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Partial safety factors for the anchorage capacity of corroded reinforcement bars in concrete
- 2019
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Ingår i: Engineering structures. - : Elsevier BV. - 0141-0296 .- 1873-7323. ; 181, s. 579-588
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Tidskriftsartikel (refereegranskat)abstract
- Many reinforced concrete bridges in Europe and around the world are damaged by reinforcement corrosion and the annual maintenance costs are enormous. It is therefore important to develop reliable methods to assess the structural capacity of corroded reinforced concrete structures and avoid unnecessary maintenance costs. Although there are advanced models for determining the load carrying capacity of structures, it is not obvious how they should be used to verify the performance of existing structures. To confidently assess the bond of corroded reinforcement in concrete, for example, the calculation model must give a sufficient safety margin. When designing new structures, semi-probabilistic approaches (such as the partial safety factor method) are adopted to achieve the target reliabilities specified in structural design codes. This paper uses probabilistic methods to develop partial factors for application in an existing bond model, to assess the safety of corroded reinforced concrete structures. The response of the bond model was studied using Monte Carlo (MC) simulations for several design cases, with probability distributions fitted to the results. Partial factors were then derived, based on these distributions. Furthermore, an MC-based simulation technique called “importance sampling” was used to study the reliability of several deterministic bond assessments conducted using these partial factors. The results show that deterministic assessments which use the proposed partial factors lead to a safety level at least equal to the target value. The results presented in this paper will support the assessment of reinforced concrete structures with anchorage problems and give a reasonable approximation of the anchorage capacity with sufficient safety margin. When generalised to cover other failure modes and structural configurations, this will enable better utilisation of damaged structures and lead to major environmental and economical savings for society.
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| 4. |
- Haghighatafshar, Salar, et al.
(författare)
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Hydroeconomic optimization of mesoscale blue-green stormwater systems at the city level
- 2019
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694. ; 578
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Tidskriftsartikel (refereegranskat)abstract
- The development of tools to help cities and water utility authorities communicate and plan for long-term sustainable solutions is of utmost importance in the era of a changing and uncertain climate. This study introduces a hybrid modeling concept for the cosimulation of mesoscale blue-green stormwater systems and conventional urban sewer networks. The hybrid model successfully introduces the retention/detention effects of mesoscale blue-green stormwater systems to the hydraulic dynamics of the sewer network. The cosimulation package was further facilitated with a cost-oriented multiobjective optimization algorithm. The aim of the scalar multiobjective optimization was to minimize the total cost comprising both flooding costs and action costs – both parameters solely representing the financial components of cost – through optimal placement of mesoscale blue-green systems of optimal size. The suggested methodology provides a useful platform for sustainable management of the existing sewer networks in cities from a hydroeconomic perspective.
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| 5. |
- Persson, Peter
(författare)
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Vibrations in a Built Environment : Prediction and Reduction
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Vibrations in a built environment can exceed the requirements for sensitive equipment in a building or can cause annoyance to residents. Hence, there is often a need for reducing such vibrations. The vibrations can originate from ambient sources such as motorway traffic, or from internal sources such as people walking inside the building. Disturbing vibrations can be reduced by reduction measures. Vibration-reduction measures can be evaluated numerically, with for instance the finite element method, to avoid construction of expensive mock-ups. In the thesis, large finite element models involving several physical domains (e.g. road, soil, bedrock, and building parts) were developed to study the effect of vibration-reduction measures.Ground vibrations can be reduced by installing a wave barrier between an external source and a receiver. As concluded in the thesis, an empty barrier (i.e. a trench) installed in the soil has the ability to reduce the ground-vibration level by approximately 60%. If the barrier contains a solid material, however, the level of reduction is reduced to approximately 30%. At long distances, at around 500 m and longer, from the vibration source, an amplification in vibration is observed. At such distances, moreover, the ground motion follows the motion of the bedrock. Another example of a wave obstacle that is studied in the thesis involves shaping the landscape surrounding a building. The topsoil that is usually transported from the construction site can be used to construct hills and valleys that constitute the shaped landscape. However, this can result in anything from an appreciable reduction to an appreciable amplification in the ground-vibration levels, depending on how the landscape is formed. If constructed properly, the reduction in the level of vibration can reach approximately 35%. Vibrations from both external and internal sources can be reduced by modifying the properties of the concrete slabs and the soil underneath. The soil properties can be improved by mixing the soil with a binder, in order to stiffen the soil. Is is shown in the thesis that by using stabilised soil underneath a concrete slab, vibrations originating from motorway traffic can be reduced by almost 60%, and up to 80% for an internal pedestrian load. By using a time-efficient numerical model developed in the thesis, the effect by using different positions for the supports of a water-pipe system on vibrations transmitted to other parts of buildings was studied. Because frequency peaks can be avoided, a marked change of vibration characteristics can be achieved. A reduction of more than 60% in the transmitted vibrations was observed. The general methods and measures presented in the thesis are exemplified by the conceptual design process of the MAX IV Laboratory, a vibration-sensitive research facility. This laboratory exhibited the phenomena needed for selecting it as a comprehensive example case.
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| 6. |
- Arvidsson, Björn, et al.
(författare)
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A methodological approach for mapping and analysing cascading effects of flooding events
- 2023
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Ingår i: International Journal of River Basin Management. - : Informa UK Limited. - 1814-2060 .- 1571-5124. ; 21:4, s. 659-671
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Tidskriftsartikel (refereegranskat)abstract
- Current local or regional flood risk assessments, as required by the EU flood risk directive, rarely account for cascading effects due to interdependencies between critical infrastructures. However, it is essential to consider these effects, as they may severely impact areas outside the immediate flood risk area. The main purpose is to present and problematize a method (AB-CEM) for mapping and analysing cascading effects due to floods, aiming at also being relevant for other spatially widespread hazards. The method development and the pilot study, in Sweden, reveal that there is a prominent practical need for methods for mapping and analysing critical infrastructure interdependencies and cascading effects. Another key finding is that the method process and its results can serve as an important basis for decision-making about proactive and reactive efforts related to geographically extensive hazards. We further conclude that there is a recurring problem regarding sensitive and secret data. More specifically, the conflicting interests of information availability and information security concerning critical infrastructures, which needs to be resolved at the national level and communicated through clear guidelines. The method is a much-needed step towards accounting for cascading effects of floods in practice.
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| 7. |
- Nik, Vahid, 1979
(författare)
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Making energy simulation easier for future climate - Synthesizing typical and extreme weather data sets out of regional climate models (RCMs)
- 2016
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Ingår i: Applied Energy. - : Elsevier BV. - 1872-9118 .- 0306-2619. ; 177, s. 204-226
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Tidskriftsartikel (refereegranskat)abstract
- Higher availability of future climate data sets, generated by regional climate models (RCMs) with fine temporal and spatial resolutions, improves and facilitates the impact assessment of climate change. Due to significant uncertainties in climate modeling, several climate scenarios should be considered in the impact assessment. This increases the number of simulations and size of data sets, complicating the assessment and decision making. This article suggests an easy-to-use method to decrease the number of simulations for the impact assessment of climate change in energy and building studies. The method is based on synthesizing three sets of weather data out of one or more RCMs: one typical and two extremes. The method aims at decreasing the number of weather data sets without losing the quality and details of the original future climate scenarios. The application of the method is assessed for an office building in Geneva and the residential building stock in Stockholm.Results show that using the synthesized data sets provides an accurate estimation of future conditions. Variations and uncertainties of future climate are represented by the synthesized data. In the case of synthesizing weather data using multiple climate scenarios, the number of simulations and the size of data sets are decreased enormously. Combining the typical and extreme data sets enables to have better probability distributions of future conditions, very similar to the original RCM data.
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| 8. |
- Rydén Sonesson, Tove, et al.
(författare)
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Modeling National Interdependent Critical Infrastructures : Application and Discussion for the Swedish Power and Internet Backbone
- 2019
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Ingår i: Proceedings of the 29th European Safety and Reliability Conference (ESREL). - Singapore : Research Publishing Services. - 9789811127243 ; , s. 3358-3365
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Konferensbidrag (refereegranskat)abstract
- Critical Infrastructures (CIs) have a vital role in the functioning and development of our modern societies. To accurately understand the potential consequences of critical infrastructure disruptions, dependencies and potential cascading effects between CIs have to be considered in risk governance. As a step towards creating a system-of-systems model of Sweden’s national technical CIs, this paper presents a generic modelling approach that extends on current topological approaches by also incorporating capacity flow constraints to capture the salient properties of technical infrastructures. The model is exemplified for Sweden’s national electric transmission system, a national backbone information and communication infrastructure, and their interdependencies. The model is populated with real-life data, such as topology, capacities, spatial orientation and the population’s dependence on the provided services. The modelling approach is complemented with a discussion on the challenges and opportunities with creating a system-of-system model of national infrastructures and how such a model can guide cross-sector decision making.
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| 9. |
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| 10. |
- Björnsson, Ivar, et al.
(författare)
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Decision support framework for bridge condition assessments
- 2019
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Ingår i: Structural Safety. - : Elsevier BV. - 0167-4730 .- 1879-3355. ; 81
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Tidskriftsartikel (refereegranskat)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.
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