hh.sePublikasjoner
Endre søk
Begrens søket
1234 1 - 50 of 152
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Treff pr side
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
Merk
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 1.
    Abdul Gabar, Allan
    et al.
    Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap.
    Protic, Dennis
    Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap.
    Kartläggning av arbetsledarens arbetsfördelning i byggproduktion: En undersökning av möjliga förbättringar inom yrkesrollen2017Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [en]

    Every company strives for maximum efficiency. The construction industry, which is complex while margins are small, makes efficiency an important issue. In the construction industry today,the high demand for production is to be delivering high quality projects as well as within certain timeframes. In order for this to be achieved, there is a great demand for work management in production. Therefore, we have chosen to analyze improvement areas within the supervisor’s role.The purpose of this report is to investigate the supervisor’s situation in the construction industry.Furthermore, the purpose is to identify work-related tasks in the professional role that have the potential for efficiency enhancement.A frequency study has been conducted in three different workplaces where we have followed three different supervisors for a total of nine days to get an insight into how the supervisors spend theirtime. Interviews have been conducted with supervisors for an even broader view of the study. Literature search has been made where we have found theories that we also present. During the course of the study we have found that there are a few improvement areas. As an enhancement, we think digitalization should be implemented, and everyone should keep order and clean up afterwards, more feedback to employees, and develop communication.

    Fulltekst (pdf)
    fulltext
  • 2.
    Abdulhalim, Mohammed
    et al.
    Högskolan i Halmstad, Sektionen för ekonomi och teknik (SET).
    Angmyr, Sebastian
    Tillämpning av Partnering vid ombyggnad av bostäder: Vad krävs för ett framgångsrikt partnering projekt?2013Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Fulltekst (pdf)
    bilaga
    Fulltekst (pdf)
    fulltext
    Fulltekst (pdf)
    fulltext
  • 3.
    Abrahamsson, Mickael
    et al.
    Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap.
    Berg, Simon
    Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap.
    Tillfälliga modulhus - en ekonomisk och kvalitetsmässig analys2016Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [en]

    The populations of Sweden are right now facing an acute housing shortage. One of the reasons of this is the huge amount of immigrants that have been taken in over recent years. The construction industry hasn’t been able to keep up with the rising demand and is right now looking for a solution. Modular housing is one solution that has been proposed by Boverket, the national board of housing, building and planning as it reduces construction times. The purpose of this paper is to analyze this method and the potential consequences/gains it has. In this paper we have used three different case studies were we have done 3 interviews in each.   This research concludes that the problem doesn’t lie within the quality or the costs associated with modular housing. It lies within the temporary building permits that are often used when time is of the essence. 

    Fulltekst (pdf)
    fulltext
  • 4.
    Adiego Abad, Sonia
    Högskolan i Halmstad, Sektionen för ekonomi och teknik (SET).
    Degree project:HOSTEL2011Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    A construction project including planning, cost estimation and design of a Hostel on a property in the city of Halmstad.

  • 5.
    Afkari, Arash
    Högskolan i Halmstad, Sektionen för ekonomi och teknik (SET).
    Sustainable Low-Cost Housing in Ethiopia: A Study of CSSB-Technology2010Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    This degree project is about sustainable low-cost housing in Ethiopia with a focus on CSSB-technology, which is one method of constructing houses. The project allowed me to visit Ethiopia during seven weeks in 2010, to observe, gather information and to perform tests regarding the specific subject. It is a sub-project to a larger research project initiated in 2002 at Halmstad University in an attempt to introduce low-cost housing technologies for the Kambaata Region in Ethiopia. The aim of the research project has been to develop and test new, sustainable, low-cost building technologies intended for the population, with regard to local traditions, needs and affordability.

    Fulltekst (pdf)
    FULLTEXT01
  • 6.
    Algeröd, Oskar
    et al.
    Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap.
    Davidsson, Tobias
    Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap.
    Hållfasthet i helväggselement av cementbunden träull2018Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    Cement bonded wood-wool as external walls have been used around the world since the 1980s. They can have different appearances, wood-wool slabs connected to each other into larger wall elements that are raised between concrete columns and beams. Another type is hollow wood-wool blocks that are stacked on each other and filled with concrete to make an external wall. In 2004 a new building system was launched in Sweden, large prefabricated wall elements of wood-wool. They are connected to each other with concrete columns and beams integrated in the elements to make an external wall. This report is looking into if the concrete beams and columns for the building system are needed. In the report three different tests were made to get the mechanical properties of the prefabricated wood-wool elements. Results showed that there was a large different in the density between the wall elements and it also showed that the modulus of rupture varied between 0.248-0.449 MPa on three identical wall elements. The characteristic modulus of rupture was three times higher than documented in previous reports of a similar wall. The conclusion of this report is that the concrete beams and columns should still be in the wall system.

    Fulltekst (pdf)
    fulltext
  • 7.
    Allerbo, Emma
    et al.
    Högskolan i Halmstad, Sektionen för ekonomi och teknik (SET).
    Waldemarsson, Hanna
    Högskolan i Halmstad, Sektionen för ekonomi och teknik (SET).
    Adobe - Technology of Everybody: Low Cost Housing in Ethiopia2013Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    The traditional building techniques in Ethiopia today contain a lot of wood. Because ofdeforestation the forest cover in the country has been decreased. A part of a solution would bethe exclusion of wood in construction and then the adobe technology is a good alternative. Adobe technology involves blocks made from local soil that mixed with water and straw asreinforcement. The sundried blocks can be bricked up to walls. As mortar the same wetmixture can be used.

    This report contains analyzed soil characteristics in the high altitude located Asella region todetermine its suitability for adobe blocks. The design of a kindergarten in Alem Maya is alsocarried out.

    Fulltekst (pdf)
    Adobe - Technology of Everybody: Low Cost Housing in Ethiopia
  • 8.
    Alzghoul, Ahmad
    et al.
    Högskolan i Halmstad.
    Hyseni, Burim
    Högskolan i Halmstad.
    Övergång till högre stålhållfastheter - konsekvensanalys2017Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Fulltekst (pdf)
    fulltext
  • 9.
    Andersen, Linn
    et al.
    Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap.
    Widell, Hanna
    Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap.
    En villaleverantörs möjlighet till etablering i Finland: analys av för- och nackdelar2015Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [en]

    The construction market has, as a result of the crisis in Europe been uncertain in recent years. During the year 2013, the construction will be stabilized, in particular Finland. The geographical proximity between Sweden and Finland and similarities in cultures and climates makes Finland a coveted market for many Swedish companies.

    Differences in national regulations and guidelines, which are produced by the authorities in different countries, are examples of barriers that may hamper the process, including for Swedish villa suppliers, to establish themselves on the Finnish market. It may be useful when facing a new export drive, to look up what similarities and differences there are between the countries building codes, to prevent mistakes and unnecessary costs to the project work.

    Fulltekst (pdf)
    fulltext
  • 10. Andersson, Mimmi
    et al.
    Andersson, Louise
    Ansvarsfrågan vid fuktspärrsarbete i våtutrymme2011Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    This final project is an investigation about the responsibility in rooms where the walls and floors are exposed or partly exposed to irrigation of water, as a bathroom, laundry room and WC.

     

    The cost for all water damage is valued for 5 000 000 000 SEK each year. How is this possible with all information about the problem and good materials? Who is responsible?

     

    Incites had been made in the subject throw reading reports and participation in courses about how to make a room mention above. Discussions have been made with workers in the trade of making the walls waterproof.

    The conclusion in the rapport is about who´s responsible for the damages and will pay the cost of the renovation. The responsibility is discussed between the contractor and the insurance company. If the room is waterproof system is made by the rules the insurance company pays. If it’s not the contractor is paying or if they don’t know how the carpenter is the owner has to pay for the new bathroom.

    Fulltekst (pdf)
    Ansvarsfrågan vid fuktspärrsarbete i våtutrymme
  • 11.
    Andreasson, Fredrik
    et al.
    Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap.
    Mårtensson, Johan
    Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap.
    Bascement i en samverkanskonstruktion: En fuktteknisk analys med inriktning på uttorkning2020Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [en]

    One of today’s biggest concerns in many industries is indubitably the environmental concern we arestanding against. Not least in the construction industry is this a big factor in creating and evolvingconstruction methods. The construction industry alone stands for 19 % of the greenhouse gas emissionsin Sweden.This has led to an increased use of wood in buildings and different construction details. Such as woodenframes in higher buildings and as in this study is very relevant, concrete composite slabs. The use of CLTconcretecomposite slabs utilizes the tensile strength from wood and the compression strength fromconcrete. While concrete has high carbon emissions this has led to development of Bascement which isa composition of Portlandcement and fly ash.This project will analyze the use of Bascement in composite slabs and how the impact of moistureevaporation from the hardening concrete will affect the CLT slab. These results will be compared with analready published study which analyzed the moisture properties and effects on a CLT-concretecomposition with standard Portland cement. By using the same model and parameters and onlychanging the cement the moisture is being measured in a 28-days timeframe with laboratory work forshort term vapor transmissions and an additional simulation for long term moisture content.

    Fulltekst (pdf)
    fulltext
  • 12.
    Angel, Linn
    Högskolan i Halmstad, Akademin för företagande, innovation och hållbarhet.
    Att bygga utifrån krav på konstruktion och hållbarhet: En jämförelse mellan dåtid och nutid2022Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [sv]

    I denna fallstudie jämförs en gammal gårdsbyggnad uppförd 1898 med kraven som ställs vid nybyggnation idag. För cirka 120 år sedan ställdes inte lika stränga krav på byggnationen som idag. De krav som undersöks handlar om hållbarhet och konstruktion. Syftet med studien är att skapa en bättre förståelse för varför dagens krav finns genom att undersöka en byggnad som är uppförd utan dessa krav.

    För att nå klimatmålen, som Sverige har antagit, finns det bland annat krav på byggnaders energieffektivitet som kan mätas genom att beräkna byggnadens primärenergital. Energieffektiviteten påverkas delvis av hur välisolerad en byggnad är varför kravet som ställs på en byggnads U-värde (värmegenomgångskoefficienten) också är intressant att undersöka. Gränsvärden på primärenergital och U-värde finns i Boverkets byggregler, BBR. Krav på konstruktionen finns i den internationella standarden Eurokod och de nationella valen i EKS.

    Beräkningar har gjorts på tak och bärande väggar för att kontrollera att de har tillräcklig bärighet. Även primärenergitalet och U-värden har räknats ut samt risken för fukt i den solida tegelväggen.

    Resultatet visar att konstruktionen klarar de krav som ställs i Eurokoderna och EKS och att byggnadens funktion bara uppfyller ett av de krav som ställs i BBR. Resultatet är i linje med tidigare forskning som har genomförts på energiprestanda hos gamla byggnader och visar på att det genom renovering, utan att skada byggnadens kulturvärde, är möjligt att uppnå dagens krav även om just den byggnaden som undersökts här inte når kraven.

    Fulltekst (pdf)
    fulltext
  • 13.
    Assad, Ibrahem
    et al.
    Högskolan i Halmstad, Akademin för företagande, innovation och hållbarhet.
    Majzoub, Mhd Nawras
    Högskolan i Halmstad, Akademin för företagande, innovation och hållbarhet.
    En jämförelse av energianvändning och klimatpåverkan av två olika byggnader2022Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [en]

    The composition will focus on valuations of energy during production, the construction process and the building's operation and with regards to climate impact and resource use.  In addition, energy performance in different buildings will be examined.  Another important factor that the work will focus on is energy consumption.  There is already a lot of research on energy efficiency in buildings and our work should be based on the latest research and new findings in this area.

    The first step in the work was to contact HFAB through telephone calls and email interviews. Furthermore, the energy efficiency has been calculated for the simulated villa. Later, climate calculations were made for Nerven 1, which is an apartment building. Data coming from HFAB applies to apartment buildings. Subsequently, environmental calculations have been made for the simulated villa, which showed a result that the villa is more environmentally friendly compared to apartment buildings. The main reason for this is the poor impact of concrete on the environment. Apartment buildings use significantly more concrete than the villa, which gives a bad environmental impact and results in the villa being friendlier. 

    Fulltekst (pdf)
    fulltext
  • 14.
    Augustsson, Emil
    et al.
    Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap.
    Jamel, Hussein
    Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap.
    Fukt i samverkanskonstruktioner: Bjälklag i KL-trä och betong2019Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [en]

    Timber-concrete composites is more and more frequently used in timber structures, as the structures grow taller and taller. This is due to its ability to increase the span of the slabs, improve the acoustic characteristics and improve the capacity of side loads, such as wind loads. The issue when executing this kind of composites is the different materials and how they react differently to moisture. Despite this, there is not much research on the subject. The purpose of this report is therefore to investigate what moisture contents to expect, both on short- and long-term, when different kind of executions of the timber-concrete slab is applied and what impact these values could lead to. The aim has been to contribute to a better understanding of what impact moisture in timber-concrete composites have, and how to handle this. To find out the moisture content, both laboratory tests and simulations has been carried out. From these tests we have been able to make calculations and assumptions in order to give suggestions on moisture barriers between the materials.

    Fulltekst (pdf)
    fulltext
  • 15.
    Balasini, Ali
    et al.
    Högskolan i Halmstad, Akademin för företagande, innovation och hållbarhet.
    Bekteshi, Enis
    Högskolan i Halmstad, Akademin för företagande, innovation och hållbarhet.
    Exoskelettets tillämpbarhet på byggarbetsplatsen utifrån ett arbetsmiljöperspektiv: - En undersökning om byggarbetares uppfattningar och erfarenheter2022Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

     

    Abstract

    MSD or musculoskeletal disorders and diseases that mainly occur in the joints, back and shoulders, affects a large number of construction workers. An innovation that could possibly prevent MSB is the exoskeleton. The purpose of this study is to address the applicability of the exoskeleton in the construction industry from a work environment perspective. Results from the studies showed that the majority of the participants experienced exoskeleton as a good aid, and they also considered using it continuously in their work, but only in some working steps like, workstep above shoulders. The conclusions that can be drawn from the study are that the majority of the participants had positive perceptions about the applicability of the exoskeleton in the construction industry. 

    Fulltekst (pdf)
    fulltext
  • 16.
    Bengtsson, Sofie
    et al.
    Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap.
    Göransson, Felix
    Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap.
    Branddimensionering av anslutning i KL-trä med inslitsad plåt och dymlingar2020Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Denna studie beskriver och analyserar de viktigare delarna kring branddimensionering för exponerat korslaminerat trä (utan beklädnad) med avseende på anslutningar med inslitsade plåtar och dymlingar. Det är dock brist på beräkningsmetoder för sådana anslutningar. Med fyra handböcker för limträ, kontra en för KL-trä, utgivna av Svenskt Trä finns det en hel del information om det materialet och dess anslutningar. Studien analyserar de två materialen för att undersöka om det finns möjlighet att nyttja forskning gällande beräkningar i limträ, för att därefter modifiera och applicera dem på KL-trä. Syftet med denna jämförelse vid brand av förband emellan grundas i att bredda kunskaperna inom området för KL-trä och eventuell kunna se intressanta samband. Målet för studien var att genom att identifiera dessa samband och tillföra nya aspekter relevant för KL- trä driva forskningen framåt. I studien gjordes en litteraturundersökning som visade att materialen har liknande egenskaper vid brand gällande brandens inledningsskede, förkolningsprocess, delaminering och de olika brott som kan ske under brand. Skjuvningsbrott i anslutningar med inslitsade plåtar och dymlingar anses vara det brott som bör dimensioneras för vid brand på grund av uppvärmda ståldelar och förkolning av träet. Därför samanställdes en beräkningsmetod för skjuvningsbrott i KL-trä med utgångspunkt i de befintliga beräkningarna för limträ enligt handboken Fire Safety in Timber Buildnigs - Technical Guideline for Europe. De två metoderna jämfördes och resultatet gav snarlika värden, vilket kan indikera på att utgångspunkten i limträ var rimlig men vidare studier krävs i form av undersökningar och eventuella brandtester. Andra typer av dolda anslutningar, t.ex sådana med självborrande skruvar, bör analyseras på liknande vis för att fastställa dess brandmotstånd.

    Fulltekst (pdf)
    fulltext
  • 17.
    Bergström, Gustav
    et al.
    Högskolan i Halmstad, Sektionen för ekonomi och teknik (SET).
    Åkeson, Axel
    Högskolan i Halmstad, Sektionen för ekonomi och teknik (SET).
    Sveriges första flerbostadshus med plusenergiteknik: Köldbryggors inverkan på energianvändningen, en jämförelse mellan plusenergiteknik och konventionellt byggande2014Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Fulltekst (pdf)
    fulltext
  • 18.
    Bernander, Frida
    et al.
    Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap.
    Lindhé, Kajsa
    Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap.
    Brandkrav, branddimensionering och brandskydd för trätakstolar: Ur ett konstruktörsperspektiv2018Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [en]

    This study contains a compilation and a clarification of the rules and requirements that can be applied to trusses and roof structures in consideration to fire. The different steps to decide the fire resistance of a truss or a roof construction is not that distinct and has to be combined with experience and subjective assessment. In case of fire the load combination for accidental load is used and in comparison with the ultimate limit state, the loads are reduced. Two different methods have been presented to determined the strength of construction timber, when exposed to fire. Both methods showed that construction timber, with a width of 45 mm, had a strength that correlate to a fire resistance of zero minutes. To improve the fire resistance of a roof construction different methods to protect the element has been presented. The most efficient ways to protect the construction is with gypsum boards and rockwool but for lower requirements wood covering can also be used. Fire retardant treatment (FTR) and fire protecting paint are also presented but are not applicable on wood trusses due to that FTR decreases the strength and fire protecting paint needs larger dimensions. In order to illustrate the different steps that are used when determining fire requirements of roof structures, two fictitious examples is presented. 

    Fulltekst (pdf)
    fulltext
  • 19.
    Björkman, Amelie
    Högskolan i Halmstad, Sektionen för ekonomi och teknik (SET).
    Hur uppnår vi god inomhusmiljö i förskolan idag?2014Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [en]

    Abstract:

    This thesis work has been conducted at the Real Estate Department in Halmstad.

    The department consists of a construction/project management-unit and an operation/management-unit.

    Like many other towns in Sweden, Halmstad has had a long lasting problem with indoor environment. Not at least at their preschools.

    Today they are constructing from current building regulations. They have learned from negative experiences which have occurred in the indoor environment in older buildings.

    Focus is now on healthy materials, like low emission value, energy efficiency and optimization of the building, but still with soft parameters such as cleaning, interior and choice of materials.

    The fixtures is provides by the real estate department and the furnishings are provides by the children and youth administration. Together they are trying to provide a great indoor environment.

    I have, together with the real estate department and the children and youth administration of Halmstad, investigated how to provide a good indoor environment in the preschools with small funds.

    In my thesis there is one theoretical part with a questionnaire survey of how the preschool staff is experiencing their indoor environment to determine where the problems often start. And a practical part with measurements to try and come down to a result that analysis the cause of the problems and also to make sure that the ventilation systems are fulfilling projected values.

    The measurements and the questionnaire surveys was made at Lokes preschool in Frösakull, Askens preschool in Oskarström and Gullbrandstorps preschool.

    There were some differences between the staff-responses at the three different preschools.

    At Askens preschool they feel that the premises are cleaned poorly.

    At Gullbrandstorps preschool they feel that the indoor-air is bad because they can´t open the windows. The only common factor is the problems they have with the noise the children makes, which unfortunately is normal and specific for the activity.

    The particle measurement shows that Askens preschool is the one with the most particles in the indoor-air, which can be the results of poor cleaning och materials that are hard to clean.

    The airflow measurements didn´t show any unusual values, at those preschools where the measurements went well.

    Fulltekst (pdf)
    Examensarbete140310
  • 20.
    Borgström, Karin Margaretha
    Högskolan i Halmstad, Akademin för företagande, innovation och hållbarhet, Centrum för innovations-, entreprenörskaps- och lärandeforskning (CIEL), Sustainability, Innovation and Management in Building (SIMB).
    Energy efficient buildings with a good indoor climate. An evaluation of actions taken at reconstruction2006Inngår i: 8th International Conference and Exhibition on Healthy Buildings 2006 (HB 2006) / [ed] E. de Oliveira Fernandes, M. Gameiro da Silva, J. Rosado Pinto, Herndon: International Society of Indoor Air Quality and Climate (ISIAQ) , 2006, Vol. 5, s. 231-234Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This study focuses on the importance to reduce the energy consumption when buildings are reconstructed, in order to decrease the environmental impacts. When reconstructing/renovating buildings it is important that the actions taken result in buildings with both low energy consumption and a good indoor climate. It is also important that all parts involved in the building process are aware of the close relationship between the use of energy in buildings and the indoor climate. This paper describes the actions taken in order to save energy when some buildings built between 1966 and 1970 in Halmstad, Sweden, were renovated/reconstructed, and how these actions have influenced the indoor climate. © Copyright 2013 Elsevier B.V., All rights reserved.

  • 21.
    Brembilla, Christian
    et al.
    Department of Applied Physics and Electronics, Umeå University, Umeå, Sweden.
    Lacoursiere, Claude
    High Performance Compting Center North (HPC2N), Umeå University, Umeå, Sweden.
    Soleimani-Mohseni, Mohsen
    Department of Applied Physics and Electronics, Umeå University, Umeå, Sweden.
    Olofsson, Thomas
    Department of Applied Physics and Electronics, Umeå University, Umeå, Sweden.
    Investigations of thermal parameters addressed to a building simulation model2015Inngår i: Proceedings of BS2015: 14th Conference of International Building Performance Simulation Association, Hyderabad, India, Dec. 7-9, 2015, India, Hyderabad: International Building Performance Simulation Association (IBPSA) , 2015, s. 2741-2748Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper shows the tolerance of thermal parameters addressed to a building simulation model in relation to the local control of the HVAC system. This work is suitable for a modeler that has to set up a building simulation model. The modeler has to know which parameter needs to be considered carefully and vice-versa which does not need deep investigations. Local differential sensitivity analysis of thermal parameters generates the uncertainty bands for the indoor air. The latter operation is repeated with P, PI and PID local control of the heating system. In conclusion, the local control of a room has a deterministic impact on the tolerance of thermal parameters.

    Fulltekst (pdf)
    FULLTEXT01
  • 22.
    Brembilla, Christian
    et al.
    Umeå University, Umeå, Sweden.
    Renman, Ronny
    Umeå University, Umeå, Sweden.
    Soleimani-Mohseni, Mohsen
    Umeå University, Umeå, Sweden.
    Östin, Ronny
    Umeå University, Umeå, Sweden.
    Olofsson, Thomas
    Umeå University, Umeå, Sweden.
    The impact of control strategies on space heating system efficiency in low-energy buildings2019Inngår i: Building Services Engineering Research & Technology, ISSN 0143-6244, E-ISSN 1477-0849, Vol. 40, nr 6, s. 714-731Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study efficiency factors measures the thermal energy performance for space heating. This study deals with the influence of control strategies on the effriciency factors of space heating and its distribution system. An adaptive control is developed and applied to two types of heating curves (linear and non-linear) for a low-energy building equipped with renewable energy sources. The building is modelled with a hybrid approach (law driven + data driven model). The design of the floor heating is calibrated and validated by assessing the uncertainty bands for low temperatures and mass flow rate. advantages and disavantages of linear and non-linear heating curves are highlighted to illustrate their impact on space heating thermodynamic behaviour and on the efficiency factors of the space heating system.

    Practical application: The study reveals that applying commercial building energy simulation software  is worthwhile to determine reliable performance predictions. Oversimplified building models, in particular when considering building thermal mass, are not capable of simulating the thermodynamic response of a building subjected to different control strategies. The application of different heating cuirves (linear and non-linear) to massless building models leaves the amount of mass flow rate delivered to the space heating unchanged when the building is subjected to sharp variations of the outdoor temperature. © The Chartered Institution of Building Services Engineers 2019

  • 23.
    Brembilla, Christian
    et al.
    Department of Applied Physics and Electronics, Umeå University, Umeå, Sweden.
    Soleimani-Mohseni, Mohsen
    Department of Applied Physics and Electronics, Umeå University, Umeå, Sweden.
    Olofsson, Thomas
    Department of Applied Physics and Electronics, Umeå University, Umeå, Sweden.
    Hybrid heating system for open-space office/laboratory2015Inngår i: Energy, Science and Technology 2015: The energy conference for scientists and researchers. Book of Abstracts, EST, Energy Science Technology, International Conference & Exhibition, 20-22 May 2015, Karlsruhe, Germany / [ed] Karlsruher Institut für Technologie (KIT), Karlsruhe: Karlsruher Institut für Technologie (KIT) , 2015, s. 315-315Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Open-space office/laboratory are quite common in Scandinavia and they are usually designed for multipurpose work. There are office area where is possible to work standing up and in the same time to work at the desk. For this purpose a hybrid heating system made by electric convectors and panel radiators is investigated. Two step response tests of the hybrid heating system are performed at the laboratory of Umeå University. The first test is executed during the week, disturbances from heat sources degrading the quality of the results. The second test is performed during week-end. The error analysis shows a maximum discrepancies of +0.6 °C between measured and simulated data. However, a thermal time constant of the room can be deducted and use it for controlling purposes.

    Fulltekst (pdf)
    FULLTEXT01
  • 24.
    Brembilla, Christian
    et al.
    Department of Applied Physics and Electronics, Umeå University, Umeå, Sweden.
    Soleimani-Mohseni, Mohsen
    Department of Applied Physics and Electronics, Umeå University, Umeå, Sweden.
    Olofsson, Thomas
    Department of Applied Physics and Electronics, Umeå University, Umeå, Sweden.
    Transient model of a panel radiator2015Inngår i: Energy, Science and Technology 2015: The energy conference for scientists and researchers. Book of Abstracts, EST, Energy Science Technology, International Conference & Exhibition, 20-22 May 2015, Karlsruhe, Germany / [ed] Karlsruher Institut für Technologie (KIT), Karlsruhe: Karlsruher Institut für Technologie (KIT) , 2015, s. 321-321Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper shows a detailed transient model of a panel radiator considered as a system of multiple storage elements. The experiment records the temperature surface of the panel in the process of heating up. The qualitative results of the experiment suggest the more appropriate technique for modelling this technology. The transient model performs the modelling with horizontal thermal capacitances connected in series. This model calculates the temperature of exhaust flow, heat emission towards indoor environment, temperature gradient on panel surface, dead and balancing time identified numerically on the chart.

    Fulltekst (pdf)
    FULLTEXT01
  • 25.
    Brembilla, Christian
    et al.
    Department of Applied Physics and Electronics (TFE), Umeå University, Umeå, Sweden.
    Östin, Ronny
    Department of Applied Physics and Electronics (TFE), Umeå University, Umeå, Sweden.
    Soleimani-Mohseni, Mohsen
    Department of Applied Physics and Electronics (TFE), Umeå University, Umeå, Sweden.
    Olofsson, Thomas
    Department of Applied Physics and Electronics (TFE), Umeå University, Umeå, Sweden.
    Paradoxes in understanding the Efficiency Factors of Space Heating2019Inngår i: Energy Efficiency, ISSN 1570-646X, E-ISSN 1570-6478, Vol. 12, nr 3, s. 777-786Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Efficiency factors are here defined as the thermal energy performance indicators of the space heating. Until recently, the efficiency factors were assumed as one value for space heating located in any climate. This study addresses the problem of how the outdoor climate affects the efficiency factors of a space heating equipped with 1D model of hydronic floor heating. The findings show how the efficiency factors, computed with two numerical methods, are correlated with the solar radiation. This study highlights the paradoxes in understanding the results of efficiency factors analysis. This work suggests how to interpret and use the efficiency factors as a benchmark performance indicator.

    Fulltekst (pdf)
    FULLTEXT01
  • 26.
    Callen, Ana Cruz
    Högskolan i Halmstad, Sektionen för ekonomi och teknik (SET).
    housing development2011Independent thesis Basic level (degree of Bachelor), 15 poäng / 22,5 hpOppgave
    Fulltekst (pdf)
    FULLTEXT01
  • 27.
    Cinthio, Nathalie
    et al.
    Högskolan i Halmstad, Sektionen för ekonomi och teknik (SET).
    Josefsson, Sandra
    Högskolan i Halmstad, Sektionen för ekonomi och teknik (SET).
    Chalmersmodellens applicering på starkt överkonsoliderad lera2009Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    In this master’s thesis real settlements for the over consolidated clay below Arenahallen in Halmstad are compared with two different models for settlement calculations; Chalmersmodellen without creep and Chalmersmodellen with creep. Chalmersmodellen with creep is based on Terzaghi’s consolidation theory with an addition to creep. The purpose has been to find out whether Chalmersmodellen with creep can be used for this clay or if Chalmersmodellen without creep should be used instead. The problem has been solved with detailed studies of literature, sampling of undisturbed flasks of clay with geotechnical boring trailer and tries of compression with an odometer of the flasks in question. Thereafter the evaluated results from the odometer were used in Chalmersmodellen.

    After complementary of the real settlement, where not all measurements exist, the results of our researches showed that Chalmersmodellen with creep were overestimating the settlement before the preconsolidation stress has been reached.

    Fulltekst (pdf)
    FULLTEXT01
  • 28.
    Dimashki, Alba
    Högskolan i Halmstad, Akademin för företagande, innovation och hållbarhet.
    Dimensionering av platta på mark: En jämförelse mellan hand- och datorberäkningar2022Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [en]

    The digital revolution has introduced several tools for structural engineers in the form of computer programs. These computer tools have partly transformed the role of structural engineers from their performing manual calculations to using different computer programs, evaluating the results, and checking codes. 

    Advanced computer-based calculation programs are often relied on when dimensioning structural parts. However, these are associated with certain consequences, especially when using black box software, which increases the need for an estimated model. 

    The purpose of this paper is to examine how the design of a concrete slab is estimated and how the results of such an estimate calculation relate to the results from computer calculations.

    The research method involves three main steps: gathering facts from references to learn how to design a concrete slab; developing a calculation model; and learning how to use PEPS, which is a type of black box software for performing calculations.

    In the analysis, PEPS is compared with manual calculations and the following conclusions are drawn based on the results:

    The estimate dimensioning of an edge-stiffened concrete slab can be simplified by using the equilibrium equation based on the edge beam. Results from this simplified method will differ from results produced by the computer program. 

    Simplified calculations are used to check the reasonableness of the PEPS results: Although PEPS indicates the cause of the bearing capacity of the concrete slab, the program fails to demonstrate how the results are calculated.

    Fulltekst (pdf)
    fulltext
  • 29.
    Ebead, U.
    et al.
    Qatar University, Doha, Qatar.
    Younis, Adel
    Qatar University, Doha, Qatar.
    Pull-off characterization of FRCM/Concrete interface2019Inngår i: Composites Part B: Engineering, ISSN 1359-8368, E-ISSN 1879-1069, Vol. 165, s. 545-553Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Fabric-reinforced cementitious matrix (FRCM) composites are usually surface-applied for strengthening reinforced concrete (RC) structures. The efficacy of the FRCM strengthening systems is dependent on the FRCM/concrete bond performance. This paper reports on the experimental results of FRCM/concrete bond characterization through pull-off tests. Six FRCM-strengthened RC slabs ( mm) were prepared and enabled conducting 72 FRCM/concrete pull-off tests. The parameters investigated included: (a) FRCM material (carbon or polyparaphenylene benzobisoxazole (PBO)); (b) level of substrate roughness (no/low/high roughening); and (c) specimen's test age (7, 28, 56, and 84 days). All FRCM systems were single-plied. The study revealed a significance of the surface preparation and test age of specimens on the FRCM/concrete pull-off strength. High-roughness specimens showed an average of 74% pull-off strength increase compared to those without roughening. Also, specimens tested at Day 84 showed 54% strength increase compared to those tested at Day 7, on average. PBO-FRCM system showed slightly higher pull-off strength than that of the carbon counterpart. The specimens showed two distinctive failure types at the (i) fabric/mortar interface and (ii) concrete/matrix interface: the latter was more prominent in carbon-FRCM. Nonetheless, the failure mode was most dependent on the fabric geometry and the substrate roughness. Based on a statistical analysis of the tested specimens, prediction models were proposed for the FRCM/concrete pull-off strength and failure mode.

  • 30.
    Ehlorsson, Viktor
    et al.
    Högskolan i Halmstad, Sektionen för ekonomi och teknik (SET).
    Palmqvist, Victor
    Högskolan i Halmstad, Sektionen för ekonomi och teknik (SET).
    Prefabricerade betongbroar - är det möjligt?2010Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    ”Prefabricerad broproduktion ger ett snabbt montage och stor möjlighet att styra produktionsprocessen”

    (En av de intervjuade)

    Vid traditionell produktion av betongbroar tillverkas bron på plats. Ingående arbeten såsom byggande och rivning av ställning, formsättning, armering samt gjutning av bron är tidskrävande moment som innefattar oergonomiska arbetsställningar för yrkesarbetarna, där de dessutom exponeras för ogynnsamma väderförhållanden och höga höjder. De flesta betongbroar som byggs i Sverige utförs fortfarande enligt traditionella metoder innehållande många tidskrävande och ogynnsamma arbetsmoment.

    I rapporten behandlas prefabricerade betongbroar som är ett konkurrenskraftigt alternativ vid broproduktion. Broelementen tillverkas på fabrik och monteras på plats, vilket leder till tidsvinster, minskade trafikstörningar, förbättrad arbetsmiljö och bättre kvalitet. Prefabricerade betongbroar kan ses som en del av industrialiseringen av byggprocessen där standardiserade lösningar och metoder används för att effektivisera byggandet.

    Intervjuer med personer verksamma inom anläggningsbranschen har gjorts för att få fram ett så relevant resultat som möjligt. Dessa gav oss en övergripande uppfattning om prefabricerade betongbroars fördelar och nackdelar samt anledningarna till det låga användandet i Sverige.

    Rapporten visar att prefabricerade betongbroar är en möjlig produktionsmetod vid brobyggnad. De kvalitetsproblem som förekommit har arbetats bort, istället uppnås idag en bättre kvalitet på den färdiga bron. Beställarna måste dock värdera tidsaspekten redan i upphandlingsfasen för att prefabricerade betongbroar ska anses fördelaktiga. Dessutom måste projekteringsprocessen förändras och en ny kompetens arbetas fram inom branschen. Förändras dessa faktorer är vi helt övertygade om att prefabricerande betongbroar har en ljus framtid i Sverige.

    Fulltekst (pdf)
    FULLTEXT01
  • 31.
    Eliasson, Daniel
    et al.
    Högskolan i Halmstad, Akademin för företagande, innovation och hållbarhet.
    Carlsson, Olle
    Högskolan i Halmstad, Akademin för företagande, innovation och hållbarhet.
    Undersökning av grundläggningsmetod, kantbalkar utförda med glas, polystyren och korslimmat-trä.2023Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Byggbranschen bidrar till stora utsläpp av växthusgaser, och det är därför viktigt att utforska hållbara material för att minska påverkan. Studien fokuserar på grundfundament för mindre trähus i Sverige, där betong i platta på mark ersätts med korslimmat trä (KLT) för att reducera klimatpåverkan. Eftersom betong har hög tryckhållfasthet gjordes analys av kantbalkens kapacitet. Fyra alternativ på kantbalkar undersöks: KLT/EPS400, KLT/Foamglas, KLT/EPS s100 och EPS400. Studien bedömer även den nuvarande dimensioneringen i hållfasthetsberäkningarna. Testdata för tryckhållfasthet används för att jämföra med förväntade resultat och avgöra om beräkningsmodellen ”2:1 metoden” är tillräcklig.Syftet är att bedöma möjligheterna för användning i två hustyper hos en ledande hustillverkare i Sverige. Miljöpåverkan av alternativen beräknas med IVL Svenska Miljöinstitutets verktyg, BM, där även en betonggrund jämförs. Det utförs även en enklare insikt i skillnader av produktion mellan en klassisk betonggrund och Klaragrunden. Studien visade att 1-plansvillan Lycke kan utföras med KLT och EPS s100, och att 1,5-plansvillan Tyresund kan se möjligheter med KLT och FoamglasT4+. Studien visade också att den bästa genomsnittliga grunden är KLT och EPS s400. Genom att byta ut betongen i en platta på mark med KLT, gör det möjligt att sänka grundens CO2 utsläpp med 65-68%.

    Fulltekst (pdf)
    fulltext
  • 32.
    Eltantawi, I.
    et al.
    Qatar University, Doha, Qatar.
    Alnahhal, W.
    Qatar University, Doha, Qatar.
    El Refai, A.
    Laval University, Quebec, Canada.
    Younis, Adel
    Linnaeus University, Växjö, Sweden.
    Alnuaimi, N.
    Qatar University, Doha, Qatar.
    Kahraman, R.
    Qatar University, Doha, Qatar.
    Bond performance of tensile lap-spliced basalt-FRP reinforcement in high-strength concrete beams2022Inngår i: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 281, artikkel-id 114987Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper investigates the bond between high-strength concrete (HSC) and tensile lap-spliced basalt fiber-reinforced polymer (BFRP) bars. Ten large-scale BFRP-reinforced concrete beams (300 × 450 × 3900 mm) were fabricated and tested under four-point loading until failure. The parameters investigated included the BFRP bar diameter (10, 12, and 16 mm), the splice length (400–1200 mm range), and the bar surface texture (sand-coated (SC) and helically wrapped (HW)). Test results demonstrated that the flexural capacity of the beams reinforced with SC-BFRP bars was almost similar to that of beams reinforced with HW-BFRP bars. However, SC-BFRP bars showed a slightly higher bond with concrete compared to that of helically wrapped counterparts. The bond strength of spliced BFRP bars was inversely related to the splice length. Also, BFRP bars with larger diameter bars require longer splice lengths to reach their maximum capacity. Finally, the experimentally estimated critical splice lengths were compared to those calculated by existing models and code-based equations. Both ACI 440.1R-15 and CSA S806-12 provisions were conservative in predicting splice length for BFRP bars. However, the CSA-S6-14 design code was more accurate in estimating the splice length for BFRP with bigger diameters. Though, it was not conservative with smaller diameters.

  • 33.
    Eriksson, Martin
    et al.
    Högskolan i Halmstad, Sektionen för ekonomi och teknik (SET).
    Eriksson - Karlsson, Jimmie
    Optimering av betong med Byggcement (CEM II) till håldäcksproduktion2011Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    This thesis has been developed inassociation with Strängbetong AB, Sweden.

    A few years backCementa AB introduced a new type of cement on the Swedish market: Byggcement,which is a Portland Limestone Cement. This type of cement is better for theenvironment and cheaper than Rapid Hardening Cement which is used today at SträngbetongAB.

    Strängbetong AB isvery interested in a change of cement in the factory and wants to know what ittakes to make a transition from Rapid Hardening Cement to Byggcement.

    This final projectaims at investigating how the workability and strength development are affectedby a transition from the existing cement to Byggcement and how we can change theproperties of the concrete by adding different types of superplasticizers. 

    Laboratory and factoryexperiments were made, to investigate the transition.

    Fulltekst (pdf)
    fulltext
  • 34.
    Gadd, Henrik
    et al.
    Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap, Bio- och miljösystemforskning (BLESS), Energivetenskap.
    Werner, Sven
    Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap, Bio- och miljösystemforskning (BLESS), Energivetenskap.
    Thermal energy storage systems for district heating and cooling2015Inngår i: Advances in Thermal Energy Storage Systems: Methods and Applications / [ed] Luisa F. Cabeza, Cambridge: Woodhead Publishing Limited, 2015, 1, s. 467-478Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    The context for this chapter is the current use and typical applications of thermal energy storages within contemporary district heating and cooling systems in the Nordic countries. Examples include a new assessment method, distributed heat storages, and hourly, daily, weekly, and seasonal heat and cold storages. Specific sizes have been estimated for 209 heat storages and 9 cold storages.

  • 35.
    Ghasemi, Yahya
    Luleå University of Technology, Luleå, Sweden.
    Aggregates in Concrete Mix Design2017Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The importance of studying the behaviour and properties of concrete can be highlighted by considering the fact that concrete is the most used man-made material in the world. The very first step in making concrete is its mix design and deciding the type and amount of constitutes used in the production of concrete which should fulfil the requirements of the final product. Mix design models are commonly used for the purpose of proportioning concrete ingredients while anticipating the properties of the final product. 

    The current document deals with the commonly used principals in mix design models namely particle packing theory and excess water/paste layer theories. The conducted studies includes an investigation on accuracy of particle packing models (Toufar, 4C, CPM) and also tries to address the issue with measurement of specific surface area of particles as an essential input to water/paste layer theories. 

    It has been observed that the particle packing models can predict the packing density with acceptable margin. However, it should be mentioned that the particle packing models by themselves are not mix design models but should be rather used as a part of a mix design. In addition, it was found that the accuracy of calculating the specific surface area of particles based on their size distribution curve can be further improved by assuming angular platonic solids as uniform shape of aggregate instead of traditional approach of assuming spheres for aggregates’ shape. 

  • 36.
    Ghasemi, Yahya
    Luleå University of Technology, Luleå, Sweden.
    Flowability and proportioning of cementitious mixtures2019Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Understanding the role of constituents of cementitious mixtures as the most globally used human-made material and their effect on the flowability of the blends is of great importance. A comprehensive understanding of the ingredients of mixtures allows for optimized proportioning of constituents and can lead to a reduction in cement and water demand of the blends.

    The thesis focuses on relating the flow of mixtures to the specific surface area of the particles through the concepts of excess water layer theory by assuming that the particles are enveloped by a thin film layer that separates the grains and lubricates their surfaces. However, in order to study the film thickness, it is inevitable to consider packing density and specific surface area of the particles. Both of the mentioned parameters and their influence on water requirement of mixtures were investigated as a part of the project.

    The theoretical part of the thesis includes background and explanation of the concepts and theories used in conducting the research including particle packing theory, specific surface area, and excess layer theories. In addition, the thesis attempts at defining and formulating terms and parameters such as representative shape, mixer efficiency, and optimal packing.

    The experimental part of the thesis consists of laboratory measurements of packing density in the loose state, estimation of specific surface area using microtomography and slump tests for mortar and concrete.

    The results of the thesis indicate that the available packing models can estimate the packing density with acceptable accuracy. In addition, it was shown that it is possible to estimate flowability of mixtures based on information about the specific surface area of the constituents. A mix design approach is introduced which predicts flow spread of slump test, a measure that is often used in laboratories and at the building sites.

    Moreover, the research revealed that the estimation of the specific surface area of particles can be improved by assuming a platonic solid shape for the particles instead of spheres. Furthermore, the mixer efficiency was quantified and optimization of mixtures against packing density and water requirement was explained.

    The finding of the project lays a foundation for a simple workability based mix design approach.

  • 37.
    Ghasemi, Yahya
    et al.
    Luleå University of Technology, Luleå, Sweden.
    Emborg, Mats
    Head of R&D Betongindustri, Luleå, Sweden; Betongindustri AB, Stockholm, Sweden.
    A method for obtaining optimum packing of aggregates for concrete at the onset of flow2017Inngår i: Nordic Concrete Research: Proceedings of the XXIII Nordic Concrete Research Symposium, Aalborg, Denmark 21-23 August, 2017 / [ed] Marianne Tange Hasholt, Oslo: Norsk Betongforening , 2017Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Particle packing models have been studied extensively during past decades and led to development of some complex and relatively accurate predictions of packing of granular materials. While the models are capable of calculating the packing density for different volumetric share of constitutes, the concept of optimum packing remains unclear. The study aims to define optimum packing based on particle packing theory and excess water layer theory. The approach makes it also possible to calculate amount of paste that is required to put a concrete mixture at the onset of flow. Some pilot tests conducted in the laboratory showed good agreement with calculated data.

  • 38.
    Ghasemi, Yahya
    et al.
    Luleå University of Technology, Luleå, Sweden.
    Emborg, Mats
    Luleå University of Technology, Luleå, Sweden.
    Particle Packing for Concrete Mix Design: Models vs. Reality2014Inngår i: Nordic Concrete Research, ISSN 0800-6377, Vol. 51, s. 85-94Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The packing density of aggregates is of great importance in concrete mix design as obtaining a higher packing density leads to less usage of cement paste which has technical, environmental and economic benefits. It is thus of interest to model particle packing correctly. Hence, in this study, packing densities of seven mixes of aggregate were attained in the laboratory using the loose packing method and were compared to values suggested by three models: 4C, Compressible Packing Model and Modified Toufar Model. Modified Toufar showed 1.72% mean difference from the laboratory values while CPM and 4C had mean differences of 1.79% and 1.84% respectively. In addition, it was found that some of the models are preferable in certain mixtures.

  • 39.
    Ghasemi, Yahya
    et al.
    Department of Civil, Environmental and Natural Resources Engineering, Luleå University of Technology, Luleå, Sweden.
    Emborg, Mats
    Department of Civil, Environmental and Natural Resources Engineering, Luleå University of Technology, Luleå, Sweden.
    Cwirzen, Andrzej
    Department of Civil, Environmental and Natural Resources Engineering, Luleå University of Technology, Luleå, Sweden.
    Effect of water film thickness on the flow in conventional mortars and concrete2019Inngår i: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 52, nr 3, artikkel-id 62Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Mortar and concrete can be divided into two phases of solids and water where water fills the voids between the grains and also coats the surface of particles. The current study investigates the influence of the thickness of coating water on flow spread of mortars and concretes. The article aims at correlating consistency of concretes to consistency of mortars. It was found that the flow behavior of granular mixtures can be directly related to the average water film thickness that envelops the particles. The concept was tested on mortar and concrete mixtures with different cement types, aggregate grading, aggregate shape, fineness and proportioning; proving water film thickness to be the most critical parameter affecting the flow. The results of the study indicate the possibility of predicting the flowability of mixtures by knowing the enveloping water film thickness. In addition, the relation between flowability of mixtures measured in different sizes of slump cone is explored to enable translating flow of mortars measured in mini-slump cone to flow of concrete obtained from Abram’s cone. © 2021 Springer Nature Switzerland 

  • 40.
    Ghasemi, Yahya
    et al.
    Department of Civil, Environmental and Natural Resources Engineering, Luleå Technical University, Luleå, Sweden.
    Emborg, Mats
    Department of Civil, Environmental and Natural Resources Engineering, Luleå Technical University, Luleå, Sweden.
    Cwirzen, Andrzej
    Department of Civil, Environmental and Natural Resources Engineering, Luleå Technical University, Luleå, Sweden.
    Estimation of specific surface area of particles based on size distribution curve2018Inngår i: Magazine of Concrete Research, ISSN 0024-9831, E-ISSN 1751-763X, Vol. 70, nr 10, s. 533-540Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Workability in the fresh state is one of the most important factors in design and production of concrete and can be related to the water demand of the mixture, which in addition to other factors is a function of the particle shape of aggregates and binders and their specific surface area. While it is known that the shape of fine particles has a significant effect on the water demand, there are uncertainties regarding how the various shape parameters would affect the specific surface area, mainly because up to now many of the shape parameters have not yet been clearly defined and there are no commonly accepted methods for their measurement and/or estimation. In this research, the actual particle shapes were replaced with regular convex polyhedrons to calculate the total specific surface area using the size distribution curves of the samples. The obtained results indicate that while, in some cases, the assumption of a spherical particle shape leads to an acceptable estimation of the specific surface area when compared with Blaine test results, the specific surface area of powders with more angular particles could be calculated more accurately with the assumption of a polyhedron shape rather than a sphere. Copyright © ICE Publishing 2021

  • 41.
    Ghasemi, Yahya
    et al.
    Department of Civil, Environmental and Natural Resources Engineering, Luleå Technical University, Sweden.
    Emborg, Mats
    Department of Civil, Environmental and Natural Resources Engineering, Luleå Technical University, Sweden.
    Cwirzen, Andrzej
    Department of Civil, Environmental and Natural Resources Engineering, Luleå Technical University, Sweden.
    Exploring the relation between the flow of mortar and specific surface area of its constituents2019Inngår i: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 211, s. 492-501Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Mortars can be studied as mixtures of solid and flowable phases. The volume of the flowable phase required for deformation depends on the solid phase surface area according to excess layer theories. This paper examines the relation between the specific surface area of constituents in mortars and their flow. The flowable phase volume was divided by the solid phase surface area to obtain the layer thickness surrounding the surface of the particles. The results suggested that the amount of water and paste needed to ensure flow could be estimated from the packing density and specific surface area of the particles. © 2019 Elsevier Ltd

  • 42.
    Ghasemi, Yahya
    et al.
    Högskolan i Halmstad, Akademin för företagande, innovation och hållbarhet, Rydberglaboratoriet för tillämpad naturvetenskap (RLAS). Luleå University of Technology, Luleå, Sweden.
    Emborg, Mats
    Luleå University of Technology, Luleå, Sweden.
    Cwirzen, Andrzej
    Luleå University of Technology, Luleå, Sweden.
    Quantification of the shape of particles for calculating specific surface area of powders2016Inngår i: International RILEM Conference Materials Systems and Structures in Civil Engineering 2016 (MSSCE 2016) on Fresh Concrete, Paris: Rilem publications, 2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The concepts of particle packing and water/paste layer theory are commonly used for basis of concrete mix design models. While particle packing insists on achieving fewer voids in aggregate matrix by adding fine aggregate, water/paste layer theories state that increasing the amount of fines will lead to higher water demand since the specific surface area of particles will increase. In order to calculate the thickness of excess paste, it is essential to quantify the shape of particles. However, there are uncertainties regarding how the various shape parameters would affect the packing and specific surface, mainly because up to now many of the shape parameters are not yet clearly defined and there are no commonly accepted methods for their measurement. In addition, the term “shape” needs to be defined, some research suggest that for obtaining an appropriate shape factor several parameters need to be measured e.g. flakiness, elongation, sphericity, convexity etc. The paper aims to derive a shape factor based on variation of packing from the packing of ideal spheres with the same particle size distribution as the studied aggregate and to apply the shape factor to calculate an approximate specific surface area value.

  • 43.
    Ghasemi, Yahya
    et al.
    Structural and Construction Engineering, Luleå Universtiy of Technology, Luleå, Sweden.
    Johansson, Niklas
    Structural and Construction Engineering, Luleå Universtiy of Technology, Luleå, Sweden.
    Particle packing of aggregates for concrete mix design: Models and methods2014Inngår i: Nordic Concrete Research, ISSN 0800-6377, nr 50, s. 109-112Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An optimized aggregate particle packing density used as a base for concrete mix design provides economic, environmental and technical advantages. The particle packing density can be determined by many methods and predicted by different models. This paper reviews common packing and procedures and compares predictions of three common packing models to each other. It was found that the models tend to show different packing densities and percentage of ingredients for the same mixture. A test setup is proposed to determine the accuracy of each model’s prediction

  • 44.
    Ghasemi, Yahya
    et al.
    Department of Civil, Environmental and Natural Resources Engineering, Luleå Technical University, Luleå, Sweden.
    Rajczakowska, Magdalena
    Department of Civil, Environmental and Natural Resources Engineering, Luleå Technical University, Luleå, Sweden | Faculty of Civil Engineering, Wroclaw University of Science and Technology, Wroclaw, Poland.
    Emborg, Mats
    Department of Civil, Environmental and Natural Resources Engineering, Luleå Technical University, Luleå, Sweden | RandD Betongindustri AB, Stockholm, Sweden.
    Cwirzen, Andrzej
    Department of Civil, Environmental and Natural Resources Engineering, Luleå Technical University, Luleå, Sweden.
    Shape-dependent calculation of specific surface area of aggregates versus X-ray microtomography2020Inngår i: Magazine of Concrete Research, ISSN 0024-9831, E-ISSN 1751-763X, Vol. 72, nr 2, s. 88-96Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The specific surface area (SSA) of constituents in a concrete mixture has a significant effect on its workability in the fresh state. Excess layer theories relate the SSA to the flow behavior of mixtures and can be used as part of an approach to the mix design. However, measurement of SSA is complex and includes several issues, and thus is commonly replaced by mathematical estimation of the parameter. The mathematical approximation of surface area is based on the assumption of a spherical shape for the particles, which leads to failure of taking into account the effect of shape and the square-cube law. The article explores the possibility of replacing the assumption of a spherical shape with that of Platonic solids as the representative shape to account for the angularity of aggregates. The calculation was conducted based on information on the particle size distribution (PSD) obtained from the dry sieving method. A calculated surface area on the assumption of a dodecahedron shape for natural aggregates and a cubical shape for crushed aggregates showed good agreement with SSA measurements conducted by X-ray microtomography. Furthermore, the effect of changes in PSD on the accuracy of the approach was also studied. It was found that the estimated value of SSA was improved in comparison with the traditional way of calculation on the assumption of a spherical shape. © 2018 ICE Publishing: All rights reserved.

  • 45.
    Gustafsson, Herman
    et al.
    Högskolan i Halmstad, Sektionen för ekonomi och teknik (SET).
    Albertsson, Martin
    Högskolan i Halmstad, Sektionen för ekonomi och teknik (SET).
    Standardisering av snöröjningsplan: Instruktioner, råd och tips för snöröjning av tak med stora spännvidder2012Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    The Swedish winters 2009/10 and 2010/11 were rich in snow and many roofs collapsed, mainly largespan frames. Investigations were made and the amount of snow was not the primary cause, insteadthere were several other causes. One of these was that in some cases roofs were shoveled in anunfavorable manner which affected the load patterns negatively, so causing the roofs to collapse.Most people lack the knowledge of how shoveling will affect the roof. Had there been an increasedunderstanding regarding shoveling, some roofs could have been prevented from collapsing.

    Through both qualitative and quantitative research in the form of interviews and calculations thetheoretically best ways to shovel a selection of roof types is presented in the report. The roofstructures covered are 3-compartment, continuous and Gerberspliced metal roof decks. Thecalculations only concern the bending moments in the decks. The results show that differentmethods are required depending on the type of structure. Therefore it is very important to knowwhat kind of a building is to be shoveled.

    To ensure that this information should be easy to understand and apply, a template has beendesigned with tips and advice for the structural engineer on how to establish a plan for shoveling.The plan for shoveling should then be passed on to the property owner with instructions, tips andadvice on how to attend to his property before, during and after the snow has fallen.

    Fulltekst (pdf)
    fulltext
  • 46.
    Gustafsson, Matilda
    et al.
    Högskolan i Halmstad, Sektionen för ekonomi och teknik (SET).
    Nilsson, Martin
    Högskolan i Halmstad, Sektionen för ekonomi och teknik (SET).
    Övergången till Eurokod 2: En konsekvensanalys2010Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Från och med den 1 januari 2011 kommer Sverige att gå över från Boverkets konstruktionsregler (BKR) till de, för den europeiska gemenskapen, gemensamma beräkningsreglerna Eurokoderna. De kommer att vara obligatoriska för alla bärande konstruktioner. Övergången kommer att innebära stora förändringar främst i konstruktörens vardag men man kommer även att se spår av den inom bland annat prefab-industrin. Rapportens tyngdpunkt ligger i att se på de faktorer som direkt berör betongelementindustrin. För att bättre förstå vilka förändringar övergången kommer att medföra för dels betongkonstruktören men också de konkreta förändringarna vad gäller armeringsmängd, sprickbreddsberäkningar och förankringslängder har dels ett ingående studium av de nya normerna samt en beräkningsjämförelse normerna emellan utförts.

    Normerna skiljer sig åt, men det är inte någon revolutionerande förändring då de båda bygger på samma dimensioneringsmetod. Den största skillnaden är att man, enligt Eurokoderna, lägger hela säkerheten på lastsidan.

    Huruvida armeringsmängden kommer, som man befarar, att öka är svårt att säga, även om mycket tyder på det. Dock skall påpekas att Eurokoderna ger en möjlighet att utföra vissa bärverk oarmerade eller lätt armerade.

    Sprickbreddskraven är de samma men dimensioneringsgången är något annorlunda. Vidare ges utrymme för att kontrollera huruvida kravet uppfylls utan att utföra beräkningar.

    Dimensionerandet av förankringslängder är mycket likt, normerna emellan. Men även här finns det möjlighet för konstruktören utföra dimensioneringen praktiskt taget utan beräkningar.

    Fulltekst (pdf)
    FULLTEXT01
  • 47.
    Hagelin, Christoff
    et al.
    Högskolan i Halmstad, Sektionen för ekonomi och teknik (SET).
    Karlsson, Erik
    Högskolan i Halmstad, Sektionen för ekonomi och teknik (SET).
    Dimensionering av fästplåtar enligt Eurokod2011Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    I dagsläget finns ingen bearbetad beräkningsmodell för fästplåtar enligt Eurokod. Syftet med detta examensarbete är att utforma en fungerande och lättförståelig beräkningsmodell för dessa fästplåtar. Arbetet har begränsats till fästplåtar med fyra och sex förankringar bestående av varmvalsat stål samt armeringsstänger som förankring. Beräkningsmodellen är uppbyggt med hjälp av studier på gamla beräkningar samt nya aspekter som anses vara relevanta som sedan översatts till Eurokod.  Fästplåten har analyserats utifrån normalkraft, tvärkraft och moment samt samverkan mellan dessa krafter. Varje ingående konstruktionsdels kraftkapacitet har kontrollerats och sedan sammanställts till en totalt tillåten kraft. För att ytterligare underlätta beräkningsmodellen har ett beräkningsprogram i Excel utarbetats. För att slutligen verifiera beräkningsmodellen har verkliga tester utförts.  

    Fulltekst (pdf)
    Dimensionering av fästplåtar enligt Eurokod
  • 48.
    Hamid, S.
    et al.
    Qatar University, Doha, Qatar.
    Naji, K.
    Qatar University, Doha, Qatar.
    Younis, Adel
    Linnaeus University, Växjö, Sweden.
    Ebead, U.
    Qatar University, Doha, Qatar.
    Material performance and cost effectiveness of seawater-mixed rubberized concrete2021Inngår i: Case Studies in Construction Materials, E-ISSN 2214-5095, Vol. 15, artikkel-id e00735Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The combined use of seawater and recycled tire aggregate (RTA) in concrete is potentially a way forward towards sustainable construction. It can help control harvesting of natural aggregates, manage waste tires, mitigate freshwater consumption and desalinationimpacts. The current paper aims at investigating the material performance and cost effectiveness of concrete mixed with seawater and RTA. The paper consists of two parts. The first part studies the characteristics (fresh and hardened) of concrete mixed with seawater and RTA. Thirteen concrete mixtures, varying in mixing water (seawater/freshwater) as well as fine and coarse aggregates (at 0%, 5%, 10%, and 20% replacement levels), were investigated. An extensive experimental program was conducted to compare the thirteen mixtures in terms of physical properties, workability, strength, water absorption, and chloride permeability. The second part of the paper performs a life cycle cost analysis (LCCA) for a 20-story building over a 100-year analysis period to verify the cost effectiveness of a proposed sustainable concrete that combines seawater, RTA (at 5% replacement level), and glass fiber-reinforced polymer (GFRP) reinforcement. A sensitivity analysis was performed to investigate the effect of the discount rate on the LCCA results.

  • 49. Hansson, Carl
    et al.
    Langvall, John
    Vertikalarmering i tegelbalkar ur arbetsmiljöperspektiv2014Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [en]

    Statistics of occupational injuries show that bricklayers are among the most exposed, with heavy lifting by far the most common cause of long-term sick leave. Prefabricated brick beams create yet another risk of injuries that can be prevented by auxiliary equipment or alternative solutions. From articles, interviews with masons and from a survey carried out in conjunction with this report, it appears that there are frequently difficulties in the use of available means for lifting and handling. Previous studies on the subject of transverse reinforcement in masonry beams indicate a viable method for bridging large openings in masonry walls. This bachelor thesis delves into whether the idea could be realized in today's brick construction with a view to improving occupational health and safety. Within the project a method, applicable in today's manufacturing of pre-stressed brick beams enabling mounting of vertical reinforcement, was developed and tested.

    Fulltekst (pdf)
    fulltext
  • 50.
    Hassanzadeh, Ali Sina
    et al.
    Högskolan i Halmstad, Akademin för företagande, innovation och hållbarhet.
    Alkhouli, Alaa Eddin
    Energieffektivisering av småhus: En fallstudie på hur renovering påverkar energiförbrukning, ekonomi och klimat2023Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Energianvändningen har ökat markant globalt sedan 1971, vilket har påverkat klimatet och orsakat global uppvärmning. För att minska energiförbrukningen och dess påverkan på klimatet har Sverige fastställt energi- och klimatmål fram till år 2030. Sektorn för bygg- och fastigheter har en stor roll att spela i att minska utsläppen av växthusgaser eftersom den stod för 15,9 miljoner ton koldioxidekvivalenter år 2020. Syftet med denna studie är att undersöka möjliga alternativa lösningar och åtgärder som kan minska både energiförbrukningen och kostnaderna samtidigt som klimatpåverkan från byggnader minskas. Fokus ligger på att tillämpa dessa åtgärder på ett småhus i Markaryd. I studien användes litteraturstudier, intervjuer och beräkningsprogram som Bidcon, energiberäkning.se och pay off-metoden. Resultaten visar att renoveringsåtgärder, såsom fönster- och dörrbyte, tilläggsisolering av vinden och installation av ett mekaniskt ventilationssystem, minskade energiförbrukningen och var ekonomiskt fördelaktiga när de kombinerades med andra åtgärder. Undersökningen visar att trä och cellulosa hade lägre klimatpåverkan än aluminium och glasull i skedena A1-A5. Renoveringsåtgärder, med rätt val av material, kan således minska energiförbrukningen och klimatpåverkan samtidigt som de är ekonomiskt fördelaktiga, vilket leder till positiva effekter för både miljön och ekonomin.

    Fulltekst (pdf)
    fulltext
1234 1 - 50 of 152
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf