| 1. |
- Desivyana, Nindya, 1997, et al.
(author)
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Challenges in the adoption of sustainable criteria in the Swedish property development industry
- 2023
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In: Procedia Computer Science. - : Elsevier BV. - 1877-0509. ; 219, s. 1752-1759
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Conference paper (peer-reviewed)abstract
- The construction industry is facing an increased focus on sustainability and climate neutrality, causing property developers to implement new requirements into the procurement documents, which are also driven by the national agenda. This study explores the current state of sustainability practice among Swedish property developers and identifies the main obstacles to expand further the implementation of the sustainability criteria. How the property developers define and implement sustainability requirements has been assessed through qualitative semi-structured interviews, focusing on sustainability certification systems, Life Cycle Assessment (LCA), and social sustainability. The results show usage of sustainability certification systems for marketing purposes and high awareness and practice of LCA, even though the accuracy of LCA was questioned. This study also identified guideline gaps for circular economy and social sustainability measurements, which could relate to low initiatives from the certification systems.
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| 2. |
- Rempling, Rasmus, 1976, et al.
(author)
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Utmattning
- 2021
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In: Betonghandbok material - Hårdnad betong, fysikaliska egenskaper och beständighet. - 9789179170882 ; , s. 485-510
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Book chapter (other academic/artistic)
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| 3. |
- Mathern, Alexandre, 1986
(author)
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Addressing the complexity of sustainability-driven structural design: Computational design, optimization, and decision making
- 2021
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Doctoral thesis (other academic/artistic)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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| 4. |
- Hellwig, Runa T., et al.
(author)
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The potential of the adaptive thermal comfort concept in long-term actively conditioned buildings for improved energy performance and user wellbeing
- 2020
-
In: IOP Conference Series: Earth and Environmental Science. - : IOP Publishing. - 1755-1307 .- 1755-1315. ; 588:3
-
Conference paper (peer-reviewed)abstract
- Technological progress in conditioning practice combined with prevailing thermal comfort criteria, created stable, tightly controlled indoor temperature bands. Research shows indoor temperatures to be increasing in the heating period, leading to higher building energy use than planned. Field studies provide proof that occupants not in control of their indoor climate are more dissatisfied and report problems in wellbeing. Widening temperature bands could be an effective measure leading to energy conservation, increasing satisfaction and, as shown recently, helping to mitigate health problems related to our way of life. The adaptive approach to thermal comfort postulates that people's thermal comfort perception adapts to the indoor and outdoor climatic conditions they normally experience. However, according to standards, the adaptive model is applicable only to passively conditioned (free-running) buildings, even though the adaptive principles may well apply also to actively conditioned buildings. Our review found studies demonstrating positive health effects and energy conservation potential in permanently or seasonally conditioned buildings. On this basis, the potential of the adaptive approach and translations into concrete design or operation solutions for actively conditioned buildings are discussed in this paper. We conclude that the adaptive concept offers a potential for indoor climate control in actively conditioned buildings in the temperate and cold climates.
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| 5. |
- Johansson, Pär, 1986, et al.
(author)
-
Aerogelbaserad puts för energieffektivisering av äldre och kulturhistoriskt värdefulla byggnader (webinar)
- 2021
-
Other publication (other academic/artistic)abstract
- I denna webinar i samarbete med Energimyndighetens program Spara och Bevara introduceras aerogelbaserad puts och vi beskriver hur materialet kan bidra till renovering och energieffektivisering. I webinariet presenteras också helt färska forskningsresultat. Många äldre byggnader är svåra att renovera för att uppnå en god energibesparing. Detta gäller speciellt för kulturhistoriska byggnader där det finns begränsningar i möjliga praktiska och tekniska lösningar. Byggnadernas karaktärsdrag, begränsningar i tillåten väggtjocklek i bygglov och risker for fuktrelaterade skador är bara några exempel. I ett forskningsprojekt på Chalmers studeras en ny typ av isolerande puts. Denna puts är baserad på aerogelpartiklar som möjliggör fler tekniska lösningar vid renovering och energieffektivisering än konventionell puts. Aerogelbaserad puts är kalk- eller cementbaserad och innehåller aerogel som är ett superisolerande material. Dess värmekonduktivitet är under 0,020 W/m·K, ungefär hälften av mineralullsisolering. Aerogelpartiklarna ger den aerogelbaserade putsen isolerande egenskaper jämförbara med konventionella isoleringsmaterial. Förutom bättre isolerande egenskaper jämfört med vanlig puts är den aerogelbaserade putsen fuktdiffusionsöppen och har en hög fuktkapacitet. Detta är fördelaktiga egenskaper för att uppnå en fuktsäker konstruktion. Aerogelbaserad puts kan vara en del av lösningen på utmaningarna för att renovera kulturhistoriska byggnader, utan att förvanska utseendet, samtidigt som tjockleken på isoleringen kan minska. Nu utvärderas materialet ur värme- och fuktsynpunkt för användning i svenska byggnader och klimatförhållanden.
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| 6. |
- Johansson, Pär, 1986, et al.
(author)
-
Interior insulation using super insulation materials: saving energy and space
- 2020
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In: IOP Conference Series: Earth and Environmental Science. - : IOP Publishing. - 1755-1307 .- 1755-1315. ; 588:5
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Conference paper (peer-reviewed)abstract
- Interior insulation can be used in buildings where the exterior characteristics may not be altered due to cultural heritage protection. This is common for many buildings in Sweden from the period before 1941. Energy efficiency, thermal comfort and building performance are all affected by an interior insulation. Super insulation materials present novel opportunities to save both energy and space. The aim of this study is to investigate the benefits and drawbacks of using super insulation materials as interior insulation. A field study building was investigated for feasibility, which, together with interviews with professionals in the field of architecture, cultural heritage and building consultants, give a general overview. In conclusion, there are both benefits and drawbacks with interior insulation. Super insulation provides increased flexibility in terms of interior detailing and possibility to preserve characteristic elements. On building level interior super insulation could reduce the energy use by up to 20%. This gives energy savings of 0.5 TWh on national level and a reduction of 0.7% of the total CO2 emissions for heating the Swedish building stock. A drawback is that there are few examples and little experience from building with super insulation materials among both architects and other decision makers.
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| 7. |
- Karim, Ali Naman, 1992, et al.
(author)
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Aerogelbaserad puts- Superisolering för framtiden
- 2020
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In: Husbyggaren. ; :6, s. 8-11
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Journal article (other academic/artistic)abstract
- I ett forskningsprojekt på Chalmers studeras en aerogelbaserad puts med mycket bra isolerande egenskaper. Förhoppningen är att användningen av den så kallade superisolerande putsen ska bidra till att minska byggsektorns energianvändning, både för existerande och nya byggnader. Superisolerande puts kan, förutom att spara energi, dessutom resultera i funktionella väggar med mindre tjocklek. Detta bidrar i sin tur till att öka mängden uthyrningsbar golvyta inomhus, yta som annars skulle tagits upp av väggens isolering. I denna artikel vill vi informera om vad vi planerar att göra i projektet och berätta om den superisolerande putsens egenskaper.
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| 8. |
- Karim, Ali Naman, 1992, et al.
(author)
-
Super insulation plasters in renovation of buildings in Sweden: energy efficiency and possibilities with new building materials
- 2020
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In: IOP Conference Series: Earth and Environmental Science. - : IOP Publishing. - 1755-1307 .- 1755-1315. ; 588:4
-
Conference paper (peer-reviewed)abstract
- Super insulation plasters are new and high energy efficient plasters mixed with aerogel particles. Aerogel is a porous and low-density material with very low thermal conductivity compared to the traditional insulation materials. Today, approximately 27% of Sweden’s multi-family houses have a plaster façade. Plaster is commonly used in many other European countries as well. In this paper, numerical simulations are utilized to estimate the total magnitude of energy and CO2 emissions that can be saved annually in Sweden by using super insulation plasters. In additional, possibilities and challenges in conjunction with the introduction of new techniques and materials in the building sector have been addressed, through interviews and literature review. The annual energy use and CO2 emissions can be reduced by 74±48 GWh and 1000 ±600 ton respectively if 10% of Sweden’s multi-family houses are externally insulated by super insulation plaster. Based on the interviews it is evident that distinct information and documentation about a new building material, concerning the material properties and long-termperformance, needs to be provided by the producer before usage of the material on industrial scale. Another important issue is the cost of a new technique and that it has to be economically motivated. Implementation of the super insulation plaster in Swedish buildings can contribute to achieving the sustainable development goals numbers 7, 8 and 9 by 2030, by increasing the energy efficiency of buildings and productivity on construction sites.
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| 9. |
- Mathern, Alexandre, 1986, et al.
(author)
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Lessons learned from the construction, inspection, and defect assessment of reinforced concrete foundations for wind turbines
- 2022
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In: Applied Sciences (Switzerland). - : MDPI AG. - 2076-3417. ; 12:3
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Journal article (peer-reviewed)abstract
- Foundations of wind turbines are subject to challenging conditions during their service life as they support ever larger wind turbines under complex loading situations. There have been numerous reports of cracked concrete foundations of wind turbines. Cracking can impair the durability and serviceability of the foundations, thereby leading to very expensive repairs or even to premature failure of the structure. To avoid cracking-related problems and improve the quality of concrete foundations, it is important to gather information and experience from the production stage and its outcome. However, although problems and defects in the construction of wind turbine foundations are widespread, they have very seldom been documented and reported, in particular from a contractor’s perspective. This article analyses and critically reviews data collected during the production, inspection, diagnosis, and repair activities conducted in relation to the construction of foundations for a wind farm project in Sweden. The extent of defects observed on individual foundations is assessed and used to investigate the eventual relation between the observed deviations and different production aspects. Investigation methods to determine the importance of these defects and their consequences and possible remediation measures are also discussed. Finally, recommendations are proposed to improve the quality control of wind turbine foundations.
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| 10. |
- Stephen, Jake, et al.
(author)
-
Internal thermal environment and futureproofing of a newly built, naturally ventilated UK school
- 2020
-
In: IOP Conference Series: Earth and Environmental Science. - : IOP Publishing. - 1755-1307 .- 1755-1315. ; 588:3
-
Conference paper (peer-reviewed)abstract
- Research indicates that school children have lower comfort levels than adults and this exacerbates the challenge of tackling the risks of summer overheating in schools without resorting to air conditioning. UN SDG 13 calls for climate action to strengthen the resilience of our cities and reduce the impact of climate change. In this work, a modern, naturally ventilated school in Southampton, UK was used to evaluate single, "hard", passive retrofit measures and "soft", building management solutions that could increase the wellbeing of students and reduce current and future demand for cooling. The school was selected as it represents the current standardised design guidance for schools released in 2012 by the Department of Education (DfE). The research presents air temperature observations collected during the summer of 2015. Dynamic thermal modelling was undertaken to evaluate passive retrofit and "soft" solutions to reduce the overheating risk. The model was validated with temperature data collected from the school classrooms. The results indicate that (a) such school buildings have high likelihood of overheating, based on children's comfort temperatures and (b) passive retrofits focused on shading and ventilation could help to reduce the classroom temperature when required. It is recommended that "soft" adaptive solutions will prove effective to reduce future air conditioning demand, but this will require a radical change in established practices. Achieving the UN Sustainable Development Goals by 2030 will require to rethink and redesign urban living and city infrastructures.
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| 11. |
- Teli, Despoina, 1980, et al.
(author)
-
Teaching the concept of adaptive thermal comfort in building design education
- 2020
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In: 16th Conference of the International Society of Indoor Air Quality and Climate: Creative and Smart Solutions for Better Built Environments, Indoor Air 2020.
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Conference paper (peer-reviewed)abstract
- Traditional building design education in the disciplines of building services, civil engineering, mechanical engineering, etc. focusses on quantifiable factors, i.e. factors which can be subject of calculation, simulation and dimensioning. Since non-quantifiable factors are not part of calculation or simulation models, there is a tendency that they are not adequately considered in education and, as a result, in building planning and operation. In the case of human thermal comfort, building professionals are required to understand the mechanisms and impact of non-quantifiable factors related to human thermal comfort and health, most of which are part of the adaptive thermal comfort concept. This paper identifies the challenges in teaching the concept of adaptive thermal comfort through a collection of lived experiences of the authors. The paper then proposes appropriate intended learning outcomes and teaching methods to equip students with the background knowledge, understanding and skills required to consider human adaptation in their designs. It is widely accepted that integrated design is a precondition for a building design that functions well, offers sufficient comfort for their users and can be operated in a sustainable way. Integrated building design requires that different disciplines work closely together and understand and respect their different focus areas and languages. Herein the case of human thermal comfort requires engineers who understand the mechanisms and impact of non-quantifiable factors on human well-being indoors. Within the work of Annex 69: “Strategy and practice of adaptive thermal comfort in low energy buildings” we developed a framework and a guideline for adopting adaptive thermal comfort principles in design and operation of buildings, which may serve as a complementary tool in an integrated design process and inclusion of adaptive thermal comfort in education.
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| 12. |
- van Eldert, Jeroen, 1987-, et al.
(author)
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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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In: Rock Mechanics and Rock Engineering. - : Springer. - 0723-2632 .- 1434-453X. ; 53:3, s. 1349-1358
-
Journal article (peer-reviewed)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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| 13. |
- Jockwer, Robert, 1984, et al.
(author)
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Design for adaption - making timber buildings ready for circular use and extended service life
- 2021
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In: World Conference on Timber Engineering 2021, WCTE 2021.
-
Conference paper (peer-reviewed)abstract
- The use of timber and the implementation of the concept of circularity in the process of the construction of buildings potentially has a high sustainability impact, both from the perspective of material and construction technique. The three most effective ways to ensure the benefit of the circularity in the building sector in general are (1) maintain the service life of structures and buildings materials as long as possible to avoid unnecessary emissions and costs for demolition and reconstruction (2) conserve the quality of materials as long as possible to avoid unnecessary emissions and costs for the replacement and processing of new materials and (3) recycle and repurpose only the parts and materials which cannot function any more for technical and/or socio-cultural reasons. In this paper an approach is discussed towards a more sustainable built environment by making buildings adaptable to the changes of demands and requirements to building functions and thus leading to an extended use of buildings in a maximum of life cycles. This design for adaption may enhance economic, social and environmental benefits to various stakeholders and key players related to the building process, i.e. developers, building owners, users, municipality and others.
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| 14. |
- Täljsten, Björn, 1961-, et al.
(author)
-
Assessment of prestressed concrete bridges - challenges
- 2020
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In: IABSE Symposium, Wroclaw 2020. - Zürich : International Association For Bridge And Structural Engineering (IABSE). ; , s. 487-494
-
Conference paper (peer-reviewed)abstract
- Prestressed concrete bridges are important parts of our infrastructure. They are susceptible to different kinds of deterioration processes. Examples of damages and deficiencies are cracking, corrosion, voids, bond loss, reduction of cover layer, delamination, fatigue and loss of stiffness and strength. This necessitates methods to continuously assess their condition in order to avoid problems that might lead to shorter service life or reduction of structural integrity. Many of the existing prestressed bridges in Europe are now approaching their design life length. However, with proper and continuous inspection, monitoring and assessment, we may plan proactive maintenance and the structural safety can be assured or – if necessary - increased. This will save both money and decrease the environmental impact of the structure.
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| 15. |
- El Houssami, M., et al.
(author)
-
Fire safety of interior materials of buses
- 2023
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In: Fire and Materials. - : John Wiley and Sons Ltd. - 0308-0501 .- 1099-1018. ; 47:7, s. 910-
-
Journal article (peer-reviewed)abstract
- This study provides an analysis on the fire safety of passengers and the fire protection of coaches and buses. A brief review of major bus fire incidents, an overview of current regulations in Europe, and their limitations are presented. The study finds that the current small-scale fire test methods described in UN ECE Reg No. 118 need to be replaced by test methods that can assess the reaction to fire of materials when exposed to ignition sources of varying sizes. To address these shortcomings, the study proposed an expert recommendation to update the material fire safety requirements and testing for buses. Additional measures are proposed, derived from objectives and strategies applied in other transport sectors, and can be tested through existing European and international standards, which are widely used by several industries. These measures aim to extend the time with tenable conditions for a safe evacuation in case of fire, reduce the degree of damage to buses, reduce the risk for fast and excessive thermal exposure on modern energy carriers needed for a more sustainable transport sector. © 2023 The Authors.
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| 16. |
- Femenias, Paula, 1966, et al.
(author)
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Om-renovering: Möjligheter för energieffektivisering och återskapande av kulturvärden när flerbostadshus renoveras på nytt
- 2020
-
Reports (other academic/artistic)abstract
- Projektet har undersökt möjligheterna att återskapa estetiska och historiska karaktärsdrag av flerbostadshus som blivit förändrade i samband med tidigare energisparprogram samtidigt som nya energieffektiviseringar kan genomföras, en process som vi valt att kalla för om-renovering. En om-renovering skapar möjligheter för energieffektivisering men också att uppnå mål om en god bebyggd och gestaltad livsmiljö. Projektet har studerat om-renovering ur ett helhetsperspektiv vilket inkluderat energibesparingar, arkitektur och kulturvärden, genomförbarhet samt sociala värden. Studien har fokuserat på flerbostadshus uppförda före 1946 i Göteborg. Flera metoder och angreppsätt har använts i fyra delstudier. En första delstudie var en inventering av ungefär en tredjedel av flerbostadshusen uppförda före 1946 i Göteborg. Målet var att undersöka hur husen har renoverats och deras status idag, med fokus på yttre synliga ändringar. Till inventeringen lades information från energideklarationer om energiprestanda vilket gjort det möjligt att undersöka samband mellan energiprestanda och renoveringar. Inventeringen visar att det är svårt att fastställa generella samband mellan tidigare renoveringar och energiprestanda med de sammanställda data. Slutsatsen är att inventeringar på fastighets- eller byggnadsnivå är nödvändiga för att ta rätt beslut vid nya energieffektiviseringar. I en andra delstudie gjordes fallstudier av fyra fastigheter med landshövdingehus, tre som omrenoverats och en som genomgått en första större renovering. Fallstudierna beskriver motiv för återställande av träfasader och ambitioner för energibesparingar. Det finns inga krav på återställande vid bygglov. De motiv som framkommer pekar istället på ekonomiska och estetiska drivkrafter för om-renoveringar. Energieffektivisering var bara ett uttalat mål i ett fall och energibesparingarna blev lägre än vad som krävs för att uppnå våra svenska energimål. Om-renoveringarna är en kompromiss mellan vad som uppfattats som estetiskt tilltalande och vad som varit ekonomiskt eller tekniskt genomförbart. Översyn från myndighetshåll av energieffektiviseringar och kulturvärden framstår som bristfällig. En tredje delstudie har studerat de boendes syn på kulturvärden i boendemiljön i tre av de ovan nämnda fallen. Studien visar ett statistiskt samband mellan trivsel och uppskattning av kulturvärden. De boende känner till sitt hus’ historia och uppskattar den. En del boende, särskilt de som bott länge på samma ställe, har en egen relation till husets och områdets historia. För andra, här representerat av flera yngre som bor i en äldre fastighet, är äktheten inte lika viktig vid ett återskapande som atmosfären. Slutligen, i en fjärde delstudie undersöktes energi- och klimatpåverkan från om-renoveringen i en av fallstudierna. Studien pekar på att återbetalningstiden för den inbyggda energi- och klimatpåverkan är strax under 25 år och därmed kortare än livslängden för material och komponenter som använts (om renoveringen antas ha en livslängd på 50 år). En jämförelse mellan en återställd träfasad och en fasad med moderna fibercementplattor är till träfasadens fördel ur ett klimatperspektiv men inte vad gäller inbyggd energi. Rapporten avslutas med rekommendationer för konsulter, fastighetsägare och handläggare på kommuner och andra myndigheter som arbetar med frågor kring om-renovering.
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| 17. |
- Hagentoft, Carl-Eric, 1958, et al.
(author)
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Mathematical Expressions for Prediction of the Effective Thermal Conductivity of Perfectly Packed Two-phase Mixtures
- 2023
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In: Environmental Science and Engineering (Subseries: Environmental Science). - 1863-5520. ; , s. 767-774
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Conference paper (peer-reviewed)abstract
- This paper introduces new and handy mathematical expressions for predicting and understanding the effective thermal conductivity of two-phase homogeneous mixtures. In a two-phase mixture, particles of the dispersed phase are mixed in the matrix of the second phase. A primary purpose of the proposed model is to predict and understand the effective thermal conductivity of high porous thermal insulation materials, for which many other similar analytical models offer less accuracy. The presented expressions assume a perfectly packed mixture and consider the thermal conductivity of the two phases, the proportion and the particle size of the dispersed phase. The proposed model includes non-dimensional heat loss factors, calculated by two and three-dimensional numerical simulations. In the continuation of the work presented, an experimental study is planned to evaluate the accuracy of the model, compared to other existing analytical solutions, and the validity of the assumptions made.
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| 18. |
- Jockwer, Robert, 1984
(author)
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Eurocode 5 – Eingeklebte Gewindestangen
- 2022
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In: Forum Holzbau International - Aus der Praxis - Für die Praxis. - 9783906226484 ; 1, s. 277-291
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Conference paper (other academic/artistic)
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| 19. |
- Jockwer, Robert, 1984, et al.
(author)
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Long-term deformation behaviour of timber columns: Monitoring of a tall timber building in Switzerland
- 2021
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In: Engineering Structures. - : Elsevier BV. - 1873-7323 .- 0141-0296. ; 234
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Journal article (peer-reviewed)abstract
- Knowledge on the short and long term deformation behavior of highly loaded components in tall timber buildings is important in view of improving future design possibilities with respect to serviceability, both in the construction and in the operational state. In this paper, we present the results of a monitoring case-study on a tall timber-hybrid building in Switzerland, a 15 storey and 60 m high office building completed in 2019. A fibre-optic measuring system showed an increase of the deformation with increasing load during the construction phase of highly stressed spruce-GLT and beech-LVL columns. However, the highest strain values were not reported in the columns themselves but at the ceiling transitions and in the area near their supports. The measurements on the columns were compared with model calculations for long-term deformation of timber elements in order to differentiate single components of the total deformation caused by load, time, and changes in climate during the construction. Over a monitoring period of a year, good agreement of the modelled deformations could be confirmed, which indicates that such models could be well suited for future usage in serviceability design of tall timber buildings.
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| 20. |
- Johansson, Morgan, 1971, et al.
(author)
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Numerical modelling of vibrational effects on buildings from blasting
- 2023
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In: 12th EFEE World Conference on Explosives and Blasting. - 9780955029080 ; :3.-Blast-Vibration-and-Seismology, s. 243-250
-
Conference paper (peer-reviewed)abstract
- It is well known that blasting in rock may cause structural damages to nearby buildings. There are various national standards that regulate acceptable blast induced vibration levels. These standards are sometimes criticized for being outdated with a need of revision. Such a revision should be based on deeper knowledge on the various aspects that causes damages to buildings from vibrations; either based on distance, frequency or some other measures. It is thus of importance to develop more reliable numerical predictions on ground and structural vibrations from blasting in rock, as this enables a more efficient rock excavation process that may lead to both economic and environmental savings. The present work is a continuation of [1] where numerical simulations are carried out based on the finite element method with both two-dimensional and three dimensions models. The numerical simulations have been used to carry out parameter studies on simplified buildings exposed to vibration loads. Parameters that are varied in these studies have been geometry, material and load characteristics in the form of load frequency and wave propagation speed in the ground. Comparisons are made with experiments carried out in Norway by NGI. The work concludes several features that have notable influence on the structural vibration: • The parameters and modelling related to the ground-building interaction are important: o Both vertical and horizontal coupling effects should be captured. o The damping properties of the ground-building interaction need to be taken into account. • Simplified two-dimensional models generally capture the lowest fundamental vibrational modes of the building. • Global effects (eigenfrequencies and vibrational modes) and local effects (stress concentrations near corners etc.) are coupled in an intricate manner.
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| 21. |
- Karim, Ali Naman, 1992, et al.
(author)
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Determination of the Effective Thermal Conductivity of Aerogel-based Coating Mortars Using Numerical Simulations- Random Packing
- 2023
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In: Environmental Science and Engineering (Subseries: Environmental Science). - 1863-5520. ; , s. 757-765
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Conference paper (peer-reviewed)abstract
- Aerogel-based coating mortars have declared thermal conductivities of 0.03-0.05 W/(m∙K), similar to those of conventional thermal insulation materials. Due to the high porosity and fragility of aerogel granules, the material obtains a reduced mechanical strength compared to conventional mortars. Recently, there has been a large research effort on developing new mixtures with improved thermal and mechanical properties. This paper presents and evaluates two-dimensional numerical simulations, based on the random packing technique, as an alternative method to laboratory measurements in predicting the effective thermal conductivity of these mortars. Experimental data from the literature, on thermal conductivity of aerogel-based coating mortars containing 50-90 vol- % aerogels were used to validate the simulation results. In this preliminary validation study, a relative error of 6-10 % was observed. Future work can focus on improving the accuracy and including the prediction of mechanical properties in the suggested model.
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| 22. |
- Karim, Ali Naman, 1992, et al.
(author)
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Moisture absorption of an aerogel-based coating system under different wetting scenarios
- 2023
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In: Building and Environment. - 0360-1323. ; 245
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Journal article (peer-reviewed)abstract
- Aerogel-based coating mortars (ACM-systems) provide energy-efficient retrofitting solutions for masonry buildings, with thermal conductivities (30-50 mW/(m·K)) comparable to traditional insulation materials. However, limited knowledge on their moisture absorption under rainwater wetting hinders the moisture-safe design of building envelopes incorporating these mortars. Thus, this study investigated the moisture absorption of an ACM-system under three laboratory-created wetting scenarios. A small-scale setup was developed to simulate runoff wetting based on typical wind-driven rain intensities in Sweden, enabling continuous monitoring of moisture conditions during wetting and drying. Two complementary capillary suction experiments under zero (free suction) and elevated hydrostatic pressure explored additional wetting scenarios. The impact of water-repellent paint and surface cracks was also assessed, as previous testing focused on undamaged ACM-systems. Among the three wetting scenarios, runoff wetting resulted in the lowest moisture absorption by the undamaged ACM-system. Water-repellent paint (sd=0.01 m) reduced moisture uptake by up to 15% during runoff and 50% during free capillary suction for the same system. Horizontal or vertical surface cracks of 1±0.5 mm width increased water absorption by 3-5 times during prolonged runoff wetting, comparable to suction at elevated hydrostatic pressure. Furthermore, a trial was done to verify a simplified numerical moisture transport model using the runoff experiment. The results highlighted the necessity for future model refinement and advanced moisture transport modeling in the ACM-system. The developed small-scale setup facilitated easy use and real-time monitoring of moisture conditions during wetting and drying. Future development should include wind-driven rain simulation alongside the existing runoff wetting scenario.
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| 23. |
- Karim, Ali Naman, 1992, et al.
(author)
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Superisolerande puts ett steg närmare verklighet i Sverige – erfarenheter från fältförsök
- 2022
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In: Bygg och teknik. - 0281-658X. ; :2, s. 46-48
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Journal article (other academic/artistic)abstract
- Aerogelbaserad puts skapar nya möjligheter vid energieffektivisering av putsade fasader. Detta kan ha särskild betydelse vid renovering av kulturhistoriskt värdefulla byggnader där putsen ger en energieffektivisering utan att förvanska byggnaden. Putsen kan dessutom ersätta isoleringen i fasaden och därmed minska tjockleken på konstruktionen. I ett forskningsprojekt på Chalmers testas nu materialet ur ett fuktsäkerhetsperspektiv för användning i Sverige. Denna artikel beskriver putssystemet med aerogelbaserad puts och presenterar de praktiska erfarenheterna från det första pågående fältförsöket i Sverige.
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| 24. |
- Karim, Ali Naman, 1992
(author)
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Wetting and drying of aerogel-based coating mortars in Swedish climates
- 2023
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Doctoral thesis (other academic/artistic)abstract
- Aerogel-based coating mortars (ACMs) have emerged as energy-efficient wall finishes with thermal conductivities of 30–50 mW/(m∙K). These coating mortars represent a promising alternative to traditional thermal insulation materials for retrofitting uninsulated building envelopes particularly in culturally significant structures. Although previously used in Central Europe, their moisture absorption under rainwater wetting, early-stage drying, and long-term hygrothermal performance in other climates remain inadequately explored. This gap in knowledge presents challenges in designing moisture-safe solutions and evaluating in-field thermal insulation performance in regions characterized by high moisture loads and limited drying potential. Therefore, an investigation was conducted to increase knowledge of the moisture performance of coating systems with ACMs. This investigation combined field and laboratory-based measurements with numerical hygrothermal simulations to study their moisture absorption under diverse wetting scenarios and evaluate their drying performance. Furthermore, the impact of surface water-repellent properties and surface cracks was assessed. The laboratory studies employed a newly developed small-scale test setup designed to simulate runoff wetting caused by typical wind-driven rain intensities in Sweden. Moreover, two supplementary capillary suction experiments under zero (free suction) and elevated hydrostatic pressure (created by Karsten tube) were conducted to explore additional wetting scenarios. A 15-month field test in Gothenburg, Sweden, combined with hygrothermal simulations were utilized to evaluate the early-stage drying and long-term hygrothermal performance of the coating system with ACM for four Swedish cities. The laboratory measurements demonstrated minimal moisture absorption in the undamaged coating system with ACM, even during prolonged 24-h runoff wetting. As expected, applying water-repellent paint (sd = 0.01 m) to the exterior of the coating system effectively reduced the water absorption while maintaining the drying capacity. Conversely, coating systems with a 1 ± 0.5 mm wide surface crack had 3–5 times amplified water intrusion due to hydrostatic pressure from the created water film on the surface. This could increase the risk of local moisture accumulation. Capillary suction tests of the ACM revealed a substantial increase in water absorption after repeated wetting exposure. Meanwhile, the same tests on the complete coating system showed a consistently stable water absorption. Field measurements indicated that the built-in moisture in the ACM dried out within six months. Hygrothermal simulations for four Swedish cities revealed an early-stage drying period ranging from 134 to 336 days based on the climate and time of application. Over time, the ACM exhibited no hygroscopic moisture accumulation; however, walls highly exposed to wind-driven rain could experience elevated relative humidity within the ACM, thereby resulting in an average increase in thermal conductivity of up to 9%. The findings show that the examined coating system with ACM presents a moisture-safe solution for retrofitting external homogenous concrete and masonry structures, preventing moisture accumulation from rainwater wetting. However, considering the information regarding the anticipated early-stage drying time and the moderate elevation in thermal conductivity is crucial when evaluating the in-field hygrothermal performance of the coating system.
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| 25. |
- Nasrollahi, Kourosh, 1991
(author)
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Differential railway track settlement in a transition zone – Field measurements and numerical simulations
- 2023
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Licentiate thesis (other academic/artistic)abstract
- In a transition zone between two different railway track forms, there is a discontinuity in track structure leading to a gradient in track stiffness. Examples include transitions between different superstructures, e.g., slab track to ballasted track, and/or between different substructures, e.g., embankment to a bridge or tunnel structure. Differences in loading and support conditions at the interfaces between track superstructure and substructure on either side of the transition may lead to differential track settlement and an irregularity in longitudinal rail level soon after construction because of densification of ballast and consolidation in the subsoil. This results in an amplification of the dynamic traffic loading along the transition. To ensure the safety of railway operation and reduce maintenance costs, it is necessary to monitor the condition of the transition zone and detect any operational change at an early stage. A methodology for the simulation of long-term differential track settlement, the development of voided sleepers leading to a redistribution of rail seat loads, and the evolving irregularity in vertical track geometry at a transition between two track forms, is presented. For a prescribed traffic load, the accumulated settlement is predicted using an iterative approach. It is based on a time-domain model of vertical dynamic vehicle–track interaction to calculate the contact forces between sleepers and ballast in the short term. These are used in an empirical model to determine the long-term settlement of the ballast and subgrade below each sleeper. Gravity loads and state-dependent track conditions are accounted for. The methodology is applied to a transition zone between a ballasted track and a slab track that is subjected to heavy haul traffic. The influence of higher axle loads and the implementation of under sleeper pads on sleeper settlement is assessed. Based on fibre Bragg grating sensors, a setup for in-situ long-term condition monitoring of track bed degradation in a transition zone has been developed and implemented to provide data for verification and calibration of the simulation model. The system is designed for measurements in an operational railway track in harsh conditions in the north of Sweden. The instrumentation along the transition comprises four clusters, each with an optical strain gauge array on the rail web in one sleeper bay, and an accelerometer and a displacement transducer on the sleeper end. Two additional accelerometers are installed far from the transition zone to measure a reference state. Combined, the data should not only provide details on long-term settlements, but also the change in dynamic response it underpins.
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