| 1. |
- Mathern, Alexandre, 1986, et al.
(författare)
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Concrete Support Structures for Offshore Wind Turbines: Current Status, Challenges, and Future Trends
- 2021
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Ingår i: Energies. - : MDPI AG. - 1996-1073 .- 1996-1073. ; 14:7
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Forskningsöversikt (refereegranskat)abstract
- Today’s offshore wind turbine support structures market is largely dominated by steel structures, since steel monopiles account for the vast majority of installations in the last decade and new types of multi-leg steel structures have been developed in recent years. However, as wind turbines become bigger, and potential sites for offshore wind farms are located in ever deeper waters and ever further from the shore, the conditions for the design, transport, and installation of support structures are changing. In light of these facts, this paper identifies and categorizes the challenges and future trends related to the use of concrete for support structures of future offshore wind projects. To do so, recent advances and technologies still under development for both bottom-fixed and floating concrete support structures have been reviewed. It was found that these new developments meet the challenges associated with the use of concrete support structures, as they will allow the production costs to be lowered and transport and installation to be facilitated. New technologies for concrete support structures used at medium and great water depths are also being developed and are expected to become more common in future offshore wind installations. Therefore, the new developments identified in this paper show the likelihood of an increase in the use of concrete support structures in future offshore wind farms. These developments also indicate that the complexity of future support structures will increase due to the development of hybrid structures combining steel and concrete. These evolutions call for new knowledge and technical know-how in order to allow reliable structures to be built and risk-free offshore installation to be executed.
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| 2. |
- Mathern, Alexandre, 1986
(författare)
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Addressing the complexity of sustainability-driven structural design: Computational design, optimization, and decision making
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Being one of the sectors with the largest environmental burden and high socio-economic impacts sets high requirements on the construction industry. At the same time, this provides the sector with great opportunities to contribute to the globally pursued sustainability transition. To cope with the increasing need for infrastructure and, at the same time, limit their sustainability impacts, changes and innovation in the construction sector are required. The greatest possibility to limit the sustainability impact of construction works is at the early design phase of construction projects, as many of the choices influencing sustainability are made at that point. Traditionally, an early choice of a preferred design is often made based on limited knowledge and past experience, considering only a handful of options. This preferred design is then taken on to the successive stages in the stepwise design process, leading to suboptimization. Alternatively, many different design choices could be considered and evaluated in a more holistic approach in order to find the most sustainable design for a particular application. However, finding design solutions that offer the best sustainability performance and fulfil all structural, performance and buildability requirements, require methods that allow considering different design options, analysing them, and assessing their sustainability. The aim of this thesis is to explore and develop methods enabling structural engineers to take sustainability objectives into account in the design of structures. Throughout this thesis, a number of methods have been explored to take sustainability aspects into account in the structural design process. As a first step, highly parameterized computer codes for sustainability-driven design have been developed. These codes interoperate with FE analysis software to automatically model and analyse design concepts over the whole design space and verify compliance with structural design standards. The codes were complemented with a harmonized method for life cycle sustainability performance assessment, in line with the state-of-the-art standards. Here, sustainability criteria were defined covering environmental, social, economic, buildability and structural performance for multi-criteria assessment of design concepts. To identify the most sustainable designs within the set, multi-objective optimization algorithms were used. Algorithms that address the high expense of constraint function evaluations of structural design problems were developed and integrated in the parameterized computer codes for sustainability-driven design. To ensure the applicability and validity of these methods, case studies based on real-world projects and common structural engineering problems were used in this thesis. Case studies for bridges and wind turbine foundations as well as a benchmark case of a reinforced concrete beam were investigated. The case studies highlight the potential of the methods explored to support the design of more sustainable structures, as well as the applicability of the methods in structural engineering practice. It is concluded that it is possible and beneficial to combine computational design, life cycle sustainability assessment, and multi-objective design optimization as a basis for decision making in the design phase of civil engineering projects. A wide adoption of such a sustainability-driven design optimization approach in structural engineering practice can directly improve the sustainability of the construction sector.
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| 3. |
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| 4. |
- Stolen, Reidar, et al.
(författare)
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Solcelleteknologi og brannsikkerhet
- 2018
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Bruken av solcelleteknologi er i stor vekst i Norge. I denne studien er branntekniske utfordringer ved bruk av solcelleteknologi undersøkt, med hensyn på brannstart, brannspredning og brannslokking. Studien danner et kunnskapsgrunnlag for å ivareta brannsikkerheten under montering, drift og under slokkeinnsats, samt for å utforme et enhetlig og tydelig regelverk. Resultatene fra studien viser:Brannstart: Solcelleinstallasjoner inneholder mange koblingspunkt, som kan være potensielle tennkilder, og en liten mengde brennbare materialer. Dermed er det som trengs til stede for å starte en brann. Det er viktig at alle kontaktpunkter i solcelleinstallasjonen er robuste og tåler den påkjenningen de blir utsatt for gjennom sin levetid uten at det oppstår dårlig kontakt som kan føre til brann.Brannspredning: For utenpåmonterte solcellemoduler er det ofte en åpen luftspalte mellom modul og bygning. Dersom det er en brann i denne luftspalten, vil varmen kunne bli akkumulert, noe som kan føre til raskere og større brannspredning enn om bygningsoverflaten ikke hadde vært tildekket. I fullskalaforsøk med solcellemoduler montert på tak spredte brannen seg under hele arealet som var dekket av moduler, men stoppet da den nærmet seg kanten av dette arealet. Dette illustrerer viktigheten av at områder med solceller utenpå en bygning blir seksjonert for å unngå brannspredning. Eventuelt kan det benyttes mindre brennbare materialer på taket under solcellemodulene for å motvirke den økte varmepåkjenningen som solcellemodulene gir. Luftspalten mellom modul og bygning kan potensielt også gi endringer i luftstrømningen langs bygget, som igjen kan påvirke brannspredningen.Brannslokking: Brannvesenet har behov for informasjon om det er solcelleinstallasjon i bygget og hvilke deler av det elektriske anlegget som kan være spenningssatt. Under slokkeinnsats må brannvesenet ta hensyn til berøringsfare, og fare for at det kan oppstå lysbuer og andre feil som kan føre til nye antennelsespunkt. Ferskvann kan brukes som slokkemiddel, dette må spyles fra minimum 1 meters avstand med spredt stråle og minimum 5 meters avstand med samlet stråle. Solcellemoduler kan komplisere brannslokking ved at de danner en fysisk barriere mellom brannvesenet og brannen, samt fordi det må tas hensyn til plassering av spenningssatte komponenter. Når disse punktene er tatt høyde for, bør ikke utenpåmonterte solcelleinstallasjoner være et problem.Videre arbeid: For utenpåmonterte solcelleinstallasjoner, er det lite forskning på vertikal montering (på fasader), og hvordan en eventuell endret branndynamikk kan påvirke brannspredning og slokking. Videre er det i dag økende bruk av bygningsintegrerte solcelleinstallasjoner, noe som gir mange mulige nye utfordringer for brannsikkerheten og for regelverk, ettersom solcellen da er en del av bygningskroppen, samtidig som den er en elektrisk komponent. Tysk statistikk tyder på at brannrisiko for slike installasjoner kan være større enn for utenpåmonterte solcelleinstallasjoner, og dette vil det derfor være viktig å undersøke nærmere.
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| 5. |
- Mathern, Alexandre, 1986, et al.
(författare)
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Experimental study of time-dependent properties of a low-pH concrete for deposition tunnels
- 2018
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Ingår i: fib Symposium. - 2617-4820. ; , s. 1726-1735
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Konferensbidrag (refereegranskat)abstract
- The Swedish Nuclear Fuel and Waste Management Company developed a method for the final disposal of canisters for spent nuclear fuel in tunnels at depths of about 500 meters. The concept for closure of the deposition tunnels is based on a bentonite seal supported by a spherical concrete dome structure. In order to fulfil the requirements specific to the repository concept, a special mix of low-pH self-compacting concrete was developed. A series of large-scale castings and laboratory tests were conducted to gain experience on this low-pH concrete mix, in conjunction with the full-scale demonstration test of an unreinforced concrete dome plug in the underground hard rock laboratory in Äspö, Sweden. The laboratory tests aimed at studying the creep properties under high sustained compressive stresses of the low-pH concrete mix, its shrinkage properties and the properties of the rock-concrete interface. This paper provides an overview of these tests and analyses the latest results of the recently completed creep tests, which include 6 years of measurements. These results allow to improve understanding of the structural behaviour of the concrete plug and to assess the effects of the very high pressure acting on the plug on its deformations, cracking and water tightness.
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| 6. |
- van Eldert, Jeroen, 1987-, et al.
(författare)
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Application of Measurement While Drilling Technology to Predict Rock Mass Quality and Rock Support for Tunnelling
- 2020
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Ingår i: Rock Mechanics and Rock Engineering. - : Springer. - 0723-2632 .- 1434-453X. ; 53:3, s. 1349-1358
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Tidskriftsartikel (refereegranskat)abstract
- A tunnelling project is normally initiated with a site investigation to determine the in situ rock mass conditions and to generate the basis for the tunnel design and rock support. However, since site investigations often are based on limited information (surface mapping, geophysical profiles, few bore holes, etc.), the estimation of the rock mass conditions may contain inaccuracies, resulting in underestimating the required rock support. The study hypothesised that these inaccuracies could be reduced using Measurement While Drilling (MWD) technology to assist in the decision-making process. A case study of two tunnels in the Stockholm bypass found the rock mass quality was severely overestimated by the site investigation; more than 45% of the investigated sections had a lower rock mass quality than expected. MWD data were recorded in 25 m grout holes and 6 m blast holes. The MWD data were normalised so that the long grout holes with larger hole diameters and the shorter blast holes with smaller hole diameters gave similar results. With normalised MWD data, it was possible to mimic the tunnel contour mapping; results showed good correlation with mapped Q-value and installed rock support. MWD technology can improve the accuracy of forecasting the rock mass ahead of the face. It can bridge the information gap between the early, somewhat uncertain geotechnical site investigation and the geological mapping done after excavation to optimise rock support.
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| 7. |
- Sundell, Jonas, 1984, et al.
(författare)
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Economic valuation of hydrogeological information when managing groundwater drawdown
- 2019
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Ingår i: Hydrogeology Journal. - : Springer Science and Business Media LLC. - 1431-2174 .- 1435-0157. ; 27:4
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Tidskriftsartikel (refereegranskat)abstract
- © 2019, The Author(s). A procedure is presented for valuation of information analysis (VOIA) to determine the need for additional information when assessing the effect of several design alternatives to manage future disturbances in hydrogeological systems. When planning for groundwater extraction and drawdown in areas where risks—such as land subsidence, wells running dry and drainage of streams and wetlands—are present, the need for risk-reducing safety measures must be carefully evaluated and managed. The heterogeneity of the subsurface calls for an assessment of trade-offs between the benefits of additional information to reduce the risk of erroneous decisions and the cost of collecting this information. A method is suggested that combines existing procedures for inverse probabilistic groundwater modelling with a novel method for VOIA. The method results in (1) a prior analysis where uncertainties regarding the efficiency of safety measures are estimated, and (2) a pre-posterior analysis, where the benefits of expected uncertainty reduction deriving from additional information are compared with the costs for obtaining this information. In comparison with existing approaches for VOIA, the method can assess multiple design alternatives, use hydrogeological parameters as proxies for failure, and produce spatially distributed VOIA maps. The method is demonstrated for a case study of a planned tunnel in Stockholm, Sweden, where additional investigations produce a low number of benefits as a result of low failure rates for the studied alternatives and a cause-effect chain where the resulting failure probability is more dependent on interactions within the whole system rather than on specific features.
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| 8. |
- Sundell, Jonas, 1984, et al.
(författare)
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Comprehensive risk assessment of groundwater drawdown induced subsidence
- 2019
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Ingår i: Stochastic Environmental Research and Risk Assessment. - : Springer Science and Business Media LLC. - 1436-3240 .- 1436-3259. ; 33:2, s. 427-449
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Tidskriftsartikel (refereegranskat)abstract
- © 2019, The Author(s). We present a method for risk assessment of groundwater drawdown induced land subsidence when planning for sub-surface infrastructure. Since groundwater drawdown and related subsidence can occur at large distances from the points of inflow, the large spatial extent often implies heterogeneous geological conditions that cannot be described in complete detail. This calls for estimation of uncertainties in all components of the cause-effect chain with probabilistic methods. In this study, we couple four probabilistic methods into a comprehensive model for economic risk quantification: a geostatistical soil-stratification model, an inverse calibrated groundwater model, an elasto-plastic subsidence model, and a model describing the resulting damages and costs on individual buildings and constructions. Groundwater head measurements, hydraulic tests, statistical analyses of stratification and soil properties and an inventory of buildings are inputs to the models. In the coupled method, different design alternatives for risk reduction measures are evaluated. Integration of probabilities and damage costs result in an economic risk estimate for each alternative. Compared with the risk for a reference alternative, the best prior alternative is identified as the alternative with the highest expected net benefit. The results include spatial probabilistic risk estimates for each alternative where areas with significant risk are distinguished from low-risk areas. The efficiency and usefulness of this modelling approach as a tool for communication to stakeholders, decision support for prioritization of risk reducing measures, and identification of the need for further investigations and monitoring are demonstrated with a case study of a planned railway tunnel in Varberg, Sweden.
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| 9. |
- Jalilzadehazhari, Elaheh, 1985-, et al.
(författare)
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Achieving a trade‐off construction solution using BIM, an optimization algorithm, and a multi‐criteria decision‐making method
- 2019
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Ingår i: Buildings. - Basel, Switzerland : MDPI. - 2075-5309. ; 9:4, s. 1-14
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Tidskriftsartikel (refereegranskat)abstract
- The Energy Performance of Building Directive obligated all European countries to reduce the energy requirements of buildings while simultaneously improving indoor environment quality. Any such improvements not only enhance the health of the occupants and their productivity, but also provide further economic benefits at the national level. Accomplishing this task requires a method that allows building professionals to resolve conflicts between visual and thermal comfort, energy demands, and life‐cycle costs. To overcome these conflicts, this study exploits the incorporation of building information modelling (BIM), the design of experiments as an optimization algorithm, and the analytical hierarchy process (AHP) into a multi‐criteria decision‐ making method. Any such incorporation can (i) create constructive communication between building professionals, such as architects, engineers, and energy experts; (ii) allow the analysis of the performance of multiple construction solutions with respect to visual and thermal comfort, energy demand, and life‐cycle costs; and (iii) help to select a trade‐off solution, thereby making a suitable decision. Three types of energy‐efficient windows, and five types of ground floors, roofs, and external wall constructions were considered as optimization variables. The incorporation of several methods allowed the analysis of the performance of 375 construction solutions based on a combination of optimization variables, and helped to select a trade‐off solution. The results showed the strength of incorporation for analyzing big‐data through the intelligent use of BIM and a simulation in the field of the built environment, energy, and costs. However, when applying AHP, the results are strongly contingent on pairwise comparisons
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| 10. |
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INNOTRACK: Concluding technical report
- 2010
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Samlingsverk (redaktörskap) (refereegranskat)abstract
- The track structure, rails, switches and crossings account for more than 50% of maintenance and renewal costs for the rail industry. To improve the competitiveness of rail transportation, the cost-efficiency of these areas needs to be addressed.This the background to INNOTRACK, an integrated research project funded by the European Commission’s 6th research framework pro- gramme. Running from September 2006 to December 2009, INN- OTRACK has developed a multitude of innovative solutions in the areas of track substructure, rails & welds, and switches & crossings. The solutions have been assessed from technical, logistics and life cycle cost point of views.This Concluding Technical Report of INNOTRACK includes an overview of the project. It further details implementable results, and clusters them into ”highlight” areas. In addition, the book acts as a ”key” to the vast amount of information from INNOTRACK: All sections refer to project reports where more information can be found.
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