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  • 1301.
    Wahlstedt, Fredrik
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Nilsson, Johannes
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Tillämpning av drönare för tillståndsbedömning av järnvägsterräng2018Independent thesis Basic level (degree of Bachelor), 180 hpOppgave
    Abstract [sv]

    Inom järnvägsunderhåll är tillståndsbedömning en viktig del för att kunna få ett mer effektivt förebyggande underhåll, samt uppfylla krav på säkerhet och tillgänglighet. Förvaltning av järnvägsinfrastrukturen är en del av Trafikverkets kärnverksamhet inom järnväg, ny och innovativ teknik är ett sätt att effektivisera förvaltningen där drönare är ett intressant exempel. Drönare är en ny tekniktillämpning som stöttar en digitaliserad anläggningsövervakning. Genom att använda sig av drönare vid inspektioner kan trafiken på järnvägarna gå som vanligt samtidigt som inspektioner utförs på ett snabbt och smidigt sätt. Syftet med arbetet är att skapa en kartläggning som visar möjligheter för att tillämpa drönare vid inspektion av järnväg och järnvägsinfrastruktur, samt utgöra en grund för drönartillämpningar inom Trafikverkets verksamhet inom tillståndsbedömning av järnvägsterräng. Målet är att göra en plan för hur Trafikverkets verksamhet kan använda drönare för att stötta tillståndsbedömning av järnvägsterräng. Delar av FMECA har använts för att se vilka möjligheter det finns vid tillämpning av drönare på järnväg samt att en SWOT-analys har utförts där det redogörs för vilka styrkor, svagheter, möjligheter och risker/hot det finns när drönare tillämpas vid inspektioner avjärnvägsterräng.

    Drönare har en stor begränsning då de enligt regler måste flygas inom synhåll för piloten. Om Trafikverket skulle få tillstånd att flyga drönaren utom synhåll skulle möjligheten att inspektera längre sträckor finnas. Om drönare implementeras i Trafikverkets verksamhet kan det innebära en stöttning till de nuvarande metoderna för tillståndsbedömning av järnvägsterräng. Genom analys av intervjuer, litteraturstudier och en fältstudie har resultatet blivit att drönare kan tillämpas för att utföra tillståndsbedömningar av järnvägsterräng och att möjligheter finns för inspektion av järnväg och järnvägsinfrastruktur. Implementering av drönare skulle möjliggöra en effektivisering av tillståndsbedömning av järnvägsterräng. Det kan även effektivisera förvaltningen samt stötta traditionella övervakningsmetoder och stötta uppfyllandet av leveranskvaliteter och författningsefterlevnad.

  • 1302. Wallin, Kjell
    et al.
    Emborg, Mats
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Jonasson, Jan-Erik
    Värme ett alternativ till kyla1997Rapport (Annet vitenskapelig)
  • 1303.
    Wallin, Rickard
    Luleå tekniska universitet, Institutionen för system- och rymdteknik.
    Blockkedjan: Organisationers möjligheter och utmaningar2019Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    Organizations wants to be at the top when it comes to using new technologies in order to retain a strong position on the market and also create innovative and unique service offerings. New technologies put pressure on organizations, that have to answer to its challenges. Blockchain is a new technology that is very well heard of, it is a complicated technology and is in constant development. The purpose of this study is to identify challenges that the blockchain technology brings to organizations as well what opportunities organizations are looking with the technology. There will also be discussions about potential opportunities that arise when organizations overcome the challenges and what the blockchain can contribute to digital services.

  • 1304.
    Wang, Chao
    et al.
    Southeast University, Nanjing.
    Wang, Zhilan
    Southeast University, Nanjing.
    Zhang, Jiwen
    Southeast University, Nanjing.
    Tu, Yong-Ming
    Southeast University, Nanjing.
    Grip, Niklas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Ohlsson, Ulf
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Elfgren, Lennart
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    FEM based research on the dynamic response of a concrete railway arch bridge2016Inngår i: IABSE CONGRESS, STOCKHOLM, 2016: Challenges in Design and Construction of an Innovative and Sustainable Built Environment / [ed] Elfgren, Lennart; Jonsson, Johan; Karlsson, Mats; Rydberg-Forssbeck, Lahja; Sigfid, Britt2016, CH - 8093 Zürich, Switzerland, 2016, s. 2472-2479Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The dynamic response of a concrete railway arch bridge is studied through a case study of the bridge over Kalix River, situated at Långforsen on the railway line between Kalix and Morjärv in northern Sweden. A simplified beam-element model, a spatial grillage-beam model and a refined shell-element model were built to analyze the bridge structure. A methodology was applied where measured static and dynamic responses were used to update finite element models of Långforsen Bridge. A multi-response objective function was presented, and the finite element method was proved feasible by comparison of predicted and measured response. In the paper comparative analyses were made of the time history displacement of three finite element models under three measured load cases. A standard train model from EUROCODE, HSLM-A 1, was applied and the dynamic responses under different speeds were studied. The results showed that a refined shell element model could accurately analyze dynamic responses of the concrete railway arch bridge in a better way than beam element and spatial grillage models. The dynamic analysis based on this type of shell model can give an optimized suggestion for the railway operation as well as for the design of high-speed railway bridges.

  • 1305.
    Wang, Chao
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand. South East University, Nanjing, China.
    Zhang, JIwen
    South East University, Nanjing, China.
    Tu, Yongming
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand. South East University, Nanjing, China.
    Sabourova, Natalia
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Grip, Niklas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Blanksvärd, Thomas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Elfgren, Lennart
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Fatigue Assessment of Reinforced Concrete Railway Bridge based on a Coupled Dynamic System2020Inngår i: Structure and Infrastructure Engineering, ISSN 1573-2479, E-ISSN 1744-8980Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper proposes a fatigue damage assessment methodology of a reinforced concrete bridge based on a train bridge coupled dynamic analysis system. This coupling system is composed of a vehicle a ballasted track and a bridge structure to realize a coupled vibration analysis during train passages. This methodology adopts the Palmgren Miner rule to linearly accumulate fatigue damage, and accomplishes fatigue assessment based on recommended SN relationships for reinforced concrete from various criteria. In this paper, the dynamic performances of a bridge structure are analyzed with two different vehicle models, a moving load model (and a moving spring mass damper model). Calculated dynamic stresses areused to evaluate the fatigue damage of critical positions in a reinforced concrete bridge. A case study is carried out of a railway arch bridge with a span of 89 m, Långforsen Bridge. It runs over Kalix River on the railway between Kalix and Morjärv in northern Sweden The fatigue assessment is made by combining the presented methodology with measurements. Furthermore, the effects of train speed and axle load on fatigue damage are investigated. The results indicate that good estimations of the fatigue damage assessment are made for four measured cases based on a train-bridge coupled dynamic analysis. For low speeds and light loads no difference could be seen in the cumulative fatigue damage for the two vehicle models. But high speeds and/or heavy load ssignificantly affect the fatigue damage.

  • 1306.
    Wang, Xiaodong (Alice)
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Hagman, Olle
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Björngrim, Niclas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Elfgren, Lennart
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Engineered wood in cold climate: application to monitoring of a new Swedish suspension bridge2013Inngår i: Advanced Materials Research, ISSN 1022-6680, E-ISSN 1662-8985, Vol. 639-640, s. 96-104Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Engineered wood is increasingly used in large structures in Europe, though little is known of its behavior in cold climate. This paper presents the structural health monitoring (SHM) system of a newly built suspension bridge with a deck of glulam timber as well as a bond stability study regarding cold climate performance of engineered wood. The bridge is located in Skellefteå in northern Sweden, and it connects two parts of the city situated on opposite shores of the Skellefteå river. In this ongoing study of the timber-bridge, a structural health monitoring system is employed to verify structural design and long-term performance. This 130m-span bridge is monitored using GNSS receivers, MEMS accelerometers, laser positioning systems, wireless moisture content sensors, strain gauges and weather stations. Data from the monitoring systems is analyzed regarding accuracy, complexity, costs and reliability for long time use. Engineered wood application in bridges, sports centers and timber buildings are discussed. Bond stability of glulam structures in cold climate is also examined in a range of experiments ranging from small glued wood joints to full size glulam bridge performance over time. From an engineered wood material point of view, the study is relevant to cold regions such as Scandinavia, Canada, Alaska, Russia, and the northern parts of China and Japan etc. The engineered wood constructions in these areas will be exposed to low temperature in a quite long period each year. The goal is to determine how engineered wood behaves when exposed to temperatures between 20 °C to -60 °C.

  • 1307.
    Westlund, Kristin
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    METHODS FOR STUDYING PUBLIC SPACES' IMPACT ON THEIR LIFE: How to understand and improve them for their purpose2018Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    The great impact urbanized cities have on its people has been studied since the 1960s. This has created new methods to measure this impact. However, because of lack of knowledge on how to use these methods they are rarely used in the planning process of new spaces in practice. By concluding what each method provides to our understanding of public spaces, and how they can be further developed, we can create a more holistic and efficient planning-process regarding public spaces, while aiming for the important goal “To create cities fit for people”. In this study the focus will be on two existing methods: Space syntax and Jan Gehl’s method of observation. The motivation for these particular methods is their differences in their approach.

    The purpose of this study is “to get a deeper understanding of already existing urban planning methods in order to improve them for their purposes”. The purpose has been divided into three questions that will be answered: What are the differences between Space syntax and Jan Gehl’s method of observation? What can they provide in the study of public spaces’ effect on public life? If, then how can they contribute to each other in order to improve the methods separately for their purposes in the study of public spaces? To answer these questions, the objective will be to measure the impact of two public spaces on their public life by using the two methods. The results will be interpreted, compared and discussed for potential further development.

    Regarding what is the difference between the methods, it can be described as space syntax using the perspective of space and Jan Gehl the perspective of life. This leads to space syntax being concerned about how much the space encourages usage of it while Jan Gehl’s method of observation is focusing on the behaviour of the people using the space, for example who they are and what they do. Different representations for the methods become a result of this.

    When discussing what each method can provide to the study of public spaces, space syntax usefulness for comparing spaces to each other and making prognosis makes it adapted to choose an appropriate location for a new project. Jan Gehl method with its high amount of details can show the success of a space in practice. 

    Regarding what the methods can provide to each other in order to improve them: Space syntax is not entirely accurate to the observed flow of people, mostly derived from lack of input about important destinations. Therefore, one suggestion for improvement is to introduce important destinations as a variable. 

    The efficiency of space syntax can be integrated to the quality measurements of Jan Gehl’s method. By using computer programs to measure people’s behaviours, the time spending to observe and catalogue can decrease. However, surveillance has in history been used without people’s knowledge by the government and therefore it is very important for ethical reasons to get the general public’s approval before using these strategies. 

  • 1308.
    Westman, Gustaf
    Luleå tekniska universitet.
    Basic creep and relaxation of young concrete1995Inngår i: Thermal cracking in concrete at early ages: proceedings of the international symposium held by RILEM at the Technical Univ. of Munich ..., Oct. 10-12, 1994 / [ed] Rupert Springenschmid, London: Spon press, 1995, s. 87-94Konferansepaper (Fagfellevurdert)
  • 1309.
    Westman, Gustaf
    Luleå tekniska universitet.
    Concrete creep and thermal stresses: new creep models and their effects on stress development1999Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis deals with the problem of creep in concrete and its influence on thermal stress development. New test frames were developed for creep of high performance concrete and for measurements of thermal stress development. Tests were performed on both normal strength and high performance concretes. Two new models for concrete creep are proposed. Firstly, a viscoelastic model, the triple power law, is supplemented with two additional functions for an improved modelling of the early age creep behaviour. Secondly, a new engineering creep model is proposed suited for design purposes. The basic feature of this model is based on the creep expressions in CEB/FIP Model Code 90. With both models good agreement were obtained with test results. The investigation on the influence of creep on thermal stress development showed that thermal stresses cannot be accurately evaluated without a correct consideration of the viscoelastic behaviour. Creep response during the three first days after load application seems to be the most important part of the creep spectra.

  • 1310.
    Westman, Gustaf
    Luleå tekniska universitet.
    Creep and relaxation of high performance young concrete1996Inngår i: Fourth International Symposium on Utilization of High Strength/High Performance Concrete: 29 - 31 May 1996, Paris, France; proceedings / [ed] F. de Larrard, Paris: Presses Ponts et Chaussées , 1996, Vol. 2, s. 367-376Konferansepaper (Fagfellevurdert)
  • 1311.
    Westman, Gustaf
    Luleå tekniska universitet.
    Temperaturspänningar i betong1995Inngår i: Bygg & Teknik, ISSN 0281-658X, nr 7, s. 19-21Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
  • 1312.
    Westman, Gustaf
    Luleå tekniska universitet.
    Thermal cracking in high performance concrete: viscoelastic models and laboratory tests1995Licentiatavhandling, monografi (Annet vitenskapelig)
  • 1313.
    Westman, Gustaf
    et al.
    Luleå tekniska universitet.
    Emborg, Mats
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    A visco-elastic model for the determination of creep in young concrete1995Inngår i: Proceedings of Nordic Symposium on Modern Design of Concrete Structures / [ed] Kirsten Aakjaer, Aalborg: Department of Building Technology and Structural Enginering, Aalborg University , 1995, s. 109-119Konferansepaper (Fagfellevurdert)
  • 1314.
    Westman, Gustaf
    et al.
    Luleå tekniska universitet.
    Emborg, Mats
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Development of a relaxations test-frame1994Inngår i: Nordic Concrete Research, ISSN 0800-6377, Vol. 15, s. 89-96Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper describes how relaxation tests on young concrete are performed at the Division of Structural Engineering at Luleá University of Technology. The development of a new test machine is presented and some results from pilot tests are given. The presented test method can be used to simulate different thermal stress conditions in the casting of massive concrete structures. This means that it may reduce the need for complicated and expensive full scale tests to ensure that no cracking takes place in newly cast concrete structures. A one meter long concrete beam is poured directly into a form in a steel frame. Temperated air is blown into a box containing the specimen and is circulated around it. In this way the specimen can be given a temperature development which is representative for a specific concrete structure. One of the short ends of the specimen is fixed in the steel frame and the other end is free to move in the longitudinal direction. The position of the free end of the specimen is kept within 0.2 µm from the initial position by a servo-hydraulic cylinder. In this way, nearly 100% restraint is obtained. The force acting on the cylinder is directly proportional to the stresses occurring in the concrete specimen.

  • 1315.
    Westman, Gustaf
    et al.
    Luleå tekniska universitet.
    Emborg, Mats
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Bernander, Stig
    Creep and relaxation of young concrete1993Inngår i: Proceedings: Nordic Concrete Research Meeting : Göteborg 1993, Oslo: Norsk Betongforening , 1993, s. 65-67Konferansepaper (Fagfellevurdert)
  • 1316.
    White, Harry
    et al.
    New York State Department of Transportation, Albany, NY.
    Pétursson, Hans
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Collin, Peter
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Integral abutment bridges: the European way2010Inngår i: Practice Periodical on Structural Design and Construction, ISSN 1084-0680, E-ISSN 1943-5576, Vol. 15, nr 3, s. 201-208Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Integral abutment bridges are becoming more popular in Europe, but the traditions differ from country to country. This leads to different technical solutions for the same problem in each country. A European survey was conducted in early 2007 to illustrate the design criteria used by each different country for integral abutment bridges. The survey requested information useful to a designer comparing the design requirements and restrictions of various European countries. As an added measure of comparison, these results were compared to some recently conducted surveys of state agencies within the United States. When looking at the results of the European survey responses and past surveys of U.S. transportation agencies, it is clear that there are many similarities in design assumptions and construction practices. Yet, there are also significant differences.

  • 1317.
    Wieckowski, Zdzislaw
    Luleå tekniska universitet.
    Finite deformation analysis of motion of bulk material in silo: application of finite element method1994Rapport (Annet vitenskapelig)
  • 1318.
    Wilsch, Gerd
    et al.
    BAM, Berlin, Germany.
    Weritz, F
    BAM, Berlin, Germany.
    Schaurich, D
    BAM, Berlin, Germany.
    Niederleithinger, Ernst
    Federal Institute for Materials Research and Testing, BAM, Berlin, Germany.
    Report on optimum set-up for a LIBS system for applicationon on site (Laser Induced Breakdown Spectroscopy): Sustainable Bridges Background document SB 3.122007Rapport (Fagfellevurdert)
    Abstract [en]

    In this report, the principal applicability of LIBS (Laser Induced Breakdown Spectroscop) for the quantitative determination of Chloride contents in concrete has been shown by preliminary results obtained on reference samples and concrete cores originating from real, contaminated sites.The physical background, the necessary components for a LIBS experiment and the measurement procedure are described. A suitable Chlorine spectral line is found at 837,6 nm. Linear calibration curves are obtained for reference samples made of cement and cementmortar with Chloride concentrations ranging between 0 wt% Cl up to 2,34 wt% Cl related to the total mass of the sample. LIBS results of concrete cores are in good agreement with chemical analysis. Further spectral lines in the investigated wave length region allow advanced interpretation of the measured data. The ratio of the intensity of the Calcium spectral line at at 849,9 nm and the Oxygen spectral line at 844,6 nm (Ca/O-ratio) is used for assignment of spectra to cement paste or aggregate, respectively. Therefore, both, the Chlorine content related to cementand the Chlorine content related to concrete is available.

    The laser must provide enough energy, at least 200 mJ/pulse, to create a plasma on concrete. The other laser parameters are not so crucial, so that a usual NdYAG laser with about 10 ns pulse duration, 1064 nm wave length and about 10 Hz repetition frequency is sufficient. Additionally the laser should have a compact geometry and low weight, no need for external water circulation and capable of normal power supplies. It should be robust against dust and impacts. Lasers with these specifications are commercially available and the laser in the BAM laboratory is suitable for on-site application.

  • 1319.
    Witakowski, Piotr
    Luleå tekniska universitet.
    The methodology of strain examining of the thin wall structures1994Rapport (Annet vitenskapelig)
  • 1320.
    Zeng, L.F.
    et al.
    Chalmers University of Technology.
    Wiberg, N-E
    Chalmers University of Technology.
    Bernspång, Lars
    Adaptive finite element procedure for 2D dynamic transient analysis using direct integration1992Inngår i: International Journal for Numerical Methods in Engineering, ISSN 0029-5981, E-ISSN 1097-0207, Vol. 34, nr 3, s. 997-1014Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An adaptive h-version finite element procedure is presented for a 2D elastodynamic transient analysis using direct integration. The procedure modifies the spatial discretization, i.e. the mesh, in time so that the spatial discretization error can be controlled in each time instant. We analyse an a priori error estimate for the total energy which shows that an a posteriori error estimate developed by Zienkiewicz and Zhu for linear elastostatics can reasonably be extended to dynamic transient analysis. For the time integration, both explicit and implicit time integration schemes can be coupled with the procedure. However, the study in this paper is confined to the use of the Newmark scheme. Numerical examples are used to study the performance of the error estimate and to illustrate the adaptive procedure. Obtained numerical results indicate that: (i) the extension of the Zienkiewicz-Zhu estimate to dynamic transient analysis is useful; (ii) the presented adaptive procedure can, in an efficient way, provide a finite element solution with a user-controlled accuracy.

  • 1321.
    Zirgulis, Giedrius
    et al.
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Svec, Oldrih
    Risø, DTU, Division of Building and Construction, Danish Technological Institute (DTI), Taastrup.
    Geiger, Mette
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Cwirzen, Andrzej
    Aalto University School of Engineering, Department of Civil and Structural Engineering, Finland.
    Kanstadt, Terje
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Variation in fiber volume and orientation in walls: experimental and numerical investigations2016Inngår i: Structural Concrete, ISSN 1464-4177, E-ISSN 1751-7648, Vol. 17, nr 4, s. 576-587Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Previous research with fibre-reinforced slab elements has shown that the surface roughness of formwork and the presence of rebars affect fibre orientation and fibre volume distribution. This paper discusses the orientation and volume distribution of steel fibres in wall elements cast from a single point. In particular, the effect of formwork tie bars on fibre orientation and distribution was studied. To quantify the fibre orientation and distribution, numerical simulations and X-ray computed tomography were applied, and the mechanical performance was determined using three-point bending tests on sawn beams. The Thorenfeldt model (applied in the Norwegian proposal of the new fibre-reinforced concrete guideline) was used to estimate the residual flexural tensile strength based on fibre orientation and distribution. The simulation results show that the fibre orientation can be related to the flow pattern. The results indicate a large variation in fibre orientation, which was experimentally confirmed. The fibre volume distribution was mostly uniform, except for an area with fewer fibres at the casting point. The large variation in fibre orientation was reflected by a large variation in residual flexural tensile strengths. Weak zones due to anisotropic fibre orientation caused by formwork tie bars were observed.

  • 1322.
    Zou, Zhongquan
    et al.
    Central South University of Forestry and Technology, Changsha.
    Enochsson, Ola
    He, Guojing
    Central South University of Forestry and Technology, Changsha.
    Elfgren, Lennart
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Finite element analysis of small span reinforced concrete trough railway bridge2009Inngår i: Key Engineering Materials, ISSN 1013-9826, E-ISSN 1662-9795, Vol. 400-402, s. 645-650Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The static behavior of a reinforced concrete trough railway bridge is analyzed by finite element method. The influences of load distribution fashion, supporting width of the bearings and the additional support beneath the girder are investigated; and the spatial effect of the stress distribution is studied as well. To confirm the analysis accuracy, the results are calibrated with the field load test results. It is found that the influence of load distribution fashion is minor and negligible, while those of supporting width and additional support are not negligible; and the spatial effect is significant.

  • 1323.
    Åström, Joakim
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Karlsson, Tobias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Sökandet på injekteringssamband: en utvärdering av injekteringskoncept vid Lunda bergtunnlar, Förbifart Stockholm2020Independent thesis Basic level (university diploma), 80 poäng / 120 hpOppgave
    Abstract [sv]

    Vid drivningen av Lunda bergtunnlar, en delsträcka på Förbifart Stockholm har inläckage av vatten orsakat problem. Uppsatta krav på tätheten i tunnlarna har visat sig vara svåra att uppnå, detta har resulterat i flertal produktionsstopp. Huvudförfarandet har varit att bedriva förinjektering, på grund av undermåliga resultat har ett omfattande efterinjekteringsarbete fått utföras. Efterinjektering är en svår och tidskrävande procedur att genomföra, därav vore en effektivisering av förinjekteringsarbetet önskvärd. Genom att sammanställa och utvärdera data tillhandahållen av Trafikverket och Implenia, har detta arbetet ämnat att finna ett samband mellan bruksåtgång, vattenförlust samt MWD. Ett potentiellt samband skulle kunna leda till en mer aktiv design av injekteringen, minskning av bruksåtgången samt en tidseffektivisering. Den utvärdering som gjorts har baserats på injekteringsprotokoll samt MWD-data från totalt nio injekteringsskärmar. Sammanställda data har komponerats på ett sätt som till synes enklast skulle kunna visa en korrelation mellan bruksåtgången, MWD-data och vattenförlusten. Studien finner ingen sådan korrelation varken genom att se till enstaka borrhål eller hela injekteringsskärmar. MWD-data och vattenförlusten tycks kunna påvisa att bruksåtgången kan bli högre i de områden där sprickor och hög vattenförlust uppmätts, framförallt vid borrhål som uppvisar samband.

  • 1324.
    Öhult, Leif
    Luleå tekniska universitet.
    Hur bygga i kallt klimat1991Licentiatavhandling, monografi (Annet vitenskapelig)
  • 1325.
    Östlund, Per-Olov
    et al.
    Luleå tekniska universitet.
    Elfgren, Lennart
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Inverkan av fleraxiell last och temperatur på betong1976Rapport (Annet vitenskapelig)
  • 1326.
    Žirgulis, Giedrius
    et al.
    Department of Structural Engineering, Norwegian University of Science & Technology (NTNU), Trondheim, Norway.
    Švec, Oldřich
    Division of Building & Construction, Danish Technological Institute (DTI), Taastrup, Denmark.
    Geiker, Mette Rica
    Department of Structural Engineering, Norwegian University of Science & Technology (NTNU), Trondheim, Norway.
    Cwirzen, Andrzej
    Department of Civil & Structural Engineering, Aalto University School of Engineering, Espoo, Finland.
    Kanstad, Terje
    Department of Structural Engineering, Norwegian University of Science & Technology (NTNU), Trondheim, Norway.
    Influence of reinforcing bar layout on fibre orientation and distribution in slabs cast from fibre-reinforced self-compacting concrete (FRSCC)2016Inngår i: Structural Concrete, ISSN 1464-4177, E-ISSN 1751-7648, Vol. 17, nr 2, s. 245-256Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Fibre orientation and volume distribution affect the post-cracking tensile strength, which is one of the main design parameters of fibre-reinforced concrete (FRC). This paper discusses the influence of unidirectional and grid reinforcement on fibre orientation and distribution in FRC slabs. Slabs without conventional reinforcing bars were used as a reference. The slab size was 1200 × 1200 × 150 mm. Numerical simulations were used to predict the fibre orientation and X-ray computed tomography (CT) to determine the actual fibre orientation and distribution. Beams were sawn from each slab, CT-scanned and tested in three-point bending tests in accordance with EN 14651. Both the numerical simulations and the CT results show that the rebars caused a more isotropic fibre orientation in the lower halves of the slabs. This was confirmed in the bending tests, where the lowest variation and highest residual tensile strengths were documented for beams sawn from slabs with grid reinforcement. Fibre migration from the upper layer to middle and lower layers of the slabs due to gravity was observed in all slabs, and in the reinforced slabs, migration also depended on the distance from the casting point. The reinforcement led to an accumulation of fibres above the rebars in the middle layer of each reinforced slab. A set of mechanisms is proposed to explain the experimental results.

  • 1327.
    Žirgulis, Giedrius
    et al.
    Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), Trondheim.
    Švec, Oldřich
    Division of Building and Construction, Danish Technological Institute (DTI), Taastrup.
    Sarmiento, Elena Vidal
    Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), Trondheim.
    Geiker, Mette Rica
    Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), Trondheim.
    Cwirzen, Andrzej
    Aalto University School of Engineering, Helsinki.
    Kanstad, Terje
    Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), Trondheim.
    Importance of quantification of steel fibre orientation for residual flexural tensile strength in FRC2016Inngår i: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 49, nr 9, s. 3861-3877Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The orientation of steel fibres affects the flexural performance of fibre-reinforced concrete. In this paper, selected experimental methods for the characterization of fibre orientation are evaluated and the relationship between residual flexural tensile strength and fibre orientation is discussed. To illustrate the applicability of the methods, the impact of the formwork surface on fibre orientation in slabs cast with fibre-reinforced self-compacting concrete (slump-flow class SF1 according to EN206) was investigated for the cases of formwork surfaces with slip, semi-slip and rough condition. The comparison of fibre orientation quantification methods showed good agreement between X-ray computed tomography and image analysis of sections from sawn beams. The variation in fibre orientation over the slab thickness was strongly influenced by the flow and the roughness of the formwork surface. The Thorenfeldt model for the impact of the fibre orientation factor on residual flexural tensile strength (used in the Norwegian proposal for fibre concrete guidelines) was verified and showed good agreement.

  • 1328. Elfgren, Lennart ()
    Fracture mechanics of concrete structures: From theory to applications: Report of the Technical Committee 90-FMA Fracture Mechanics to Concrete/Applications, RILEM (the International Union of Testing and Research Laboratories for Materials and Structures)1989Rapport (Annet vitenskapelig)
    Abstract [en]

    Ductile and durable concrete structures are the goal of all designers. In order to achieve such goals it is necessarry to know the laws that govern the behaviour of materials and structures.This report explains how cracking, ductility and brittleness are influenced by dimensions (size effects) and material properties such as tensile strength, stiffness (modulus of elasticity) and fracture energy. This is done with the help of models of fracture mechanics. The different models that have emerged during the last ten years are first presented and accomodated inside a common frame. Practical applications are then presented in a variety of fields. The report should be of interest to persons engaged in design, development, research and teaching in the field of Concrete structures. It was prepared by RILEM Technical Committee 90-FMA 'Fracture Mechanics of Concrete - Applications' during 1986-1988.

  • 1329. Fransson, Lennart ()
    Ice mechanics and shipping in ice-infested waters2008Rapport (Annet vitenskapelig)
    Abstract [sv]

    Följande rapport ingår i projektet "Ismekanikk og havnedrift i islagte farvann" (delprogrammet Nordkalotten INTERREG III A Nord). Denna rapport är huvuddokumentet där alla delrapporter inom projektet sammanställts. Övriga rapporter som ingår är följande: - Nonlinear finite element simulations of ice forces on offshore structures - Mätning av islaster med isbrytare - Ice Induced Vibrations of Slender Structures - Isförhållanden längs svenska kusten, Bottenviken, Bottenhavet och Barents hav - Ice Control Measures in Swedish Harbours - Database Norströmsgrund

  • 1330. Collin, Peter ()
    Hällmark, Robert ()
    Nilsson, Martin ()
    International workshop on prefabricated composite bridges2009Rapport (Annet vitenskapelig)
  • 1331. Elfgren, Lennart ()
    Round Robin analyses and tests of anchor bolts in concrete structures: RILEM Technical Committee 90-FMA, Fracture Mechanics of Concrete - Applications1998Rapport (Annet vitenskapelig)
  • 1332. Enochsson, Ola ()
    Stål- och samverkansbroar: seminarieuppgifter i doktorandkurs 20042005Rapport (Annet (populærvitenskap, debatt, mm))
    Abstract [sv]

    Luleå tekniska universitet, LTU och Kungliga tekniska högskolan, KTH anordnade under 2004 en doktorandkurs i stål- och samverkansbroar. Kursen gavs inom det Vinnova stödda FOU-konsortiet Väg/Bro/Tunnel. Kursens syfte var att deltagarna skulle få en inblick i stål- och samverkansbroar genom föreläsningar och studiebesök, samt även få chansen att träna upp sina egna konstruktionsfärdigheter genom att själv välja och göra en konstruktionsuppgift. Kursen genomfördes med tre 2-dagars kurstillfällen antingen på KTH eller på LTU, samt med ett avslutande seminarium och studiebesök i Paris.

  • 1333. Elfgren, Lennart ()
    Noghabai, Keivan ()
    Luleå tekniska universitet.
    Tension of reinforced concrete prisms: round robin analysis and tests on bond : a report from an investigation arranged by RILEM technical committee 147-FMB fracture mechanics to anchorage and bond2001Rapport (Annet vitenskapelig)
    Abstract [en]

    Results are presented from a RILEM Round Robin Investigation. It deals with tension stiffening of reinforcement bars embedded in concrete tie elements. Seven groups of researches have performed some 50 tests and analyses. Parameters discussed are: cover thickness, crack spacing, bar size, tension stiffening of naked reinforcing bars, and influence of concrete strain softening. Similar trends were seen in the different tests and most of the applied theoretical models give reasonable results. The general behaviour is similar, although there seems to be some differences between the tested cracking loads. The models used are able to predict the bond behaviour in a correct way: analytical models based on the tension softening of concrete; bond-slip relations; as well as finite element methods with inner softening bands. The CEB-FIP Model Code can be used for design purposes and gives straight-forward predictions. The following new and/or refined insights were obtained from the tests: Cover thickness and crack spacing. - The number and spacing of visible cracks are more or less proportional to the thickness of the concrete cover. Bar diameter size effect. - There is a small tendency to a proportionally lower tension stiffening effect for larger bar sizes but the scatter is too large to secure definite conclusions. Longitudinal splitting and yielding of reinforcement. - Longitudinal splitting cracks occurred close to and after yielding of the reinforcement. Tension stiffening of naked reinforcing bars. - A new hypothesis of a tension stiffening of the bare reinforcing bar has been presented. Concrete strength and strain softening - The crack opening resistance is given by the tension softening curve of the concrete. By addition of fibres to the concrete matrix, the curve is changed, and the crack opening resistance is improved without necessarily changing other properties of the concrete. The chosen amount and type of fibers do not necessarily have much influence on the tensile strength, and the same crack patterns will be obtained on elements with the same geometry. The shape of the load-deformation curve, however, is considerably changed compared to that of the plain concrete. This is due to the enhanced crack-opening resistance, whereas the stiffening effect seems to depend on the crack spacing and consequently on the cover thickness and the degree of confinement it provides.

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