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  • 1. Adell, Anton
    Innovativ tätning av läckande dilatationsfogar i betongdammar: Bentonit: Metoder, Utvärdering och Fallstudie2022Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Most of Sweden’s concrete dams were built during the 1900’s. Therefore, they are starting to reach the estimated end of their life-cycle; 50-160 years. Some of these concrete dams are used for hydroelectric purposes. Hydroelectric power is one of Sweden’s primary source for electricity, which approximately makes for 45% of our total electric production. Hence, the need for reparation is increasing for further management and maintaining our electricity production in these concrete dams. Concrete dams are linked by expansion joints. These expansion joints help to reduce the stress, during swelling and shrinking, in the concrete caused by temperature variation. Due to the placement of these expansions joint, they become difficult to repair as well as ensuring the success of a reparation.

    Inside the expansion joint there are dimbands. The dimbands can be sealed with bitumen to help their water stopping abilities. For every expansion joint that is sealed with bitumen the estimated climate impact is 0,5 to 1,5 kg CO2-e per joint. If the dimbands, inside the expansion joint, or the surrounding concrete gets damaged or breaks the bitumen varnishes downstream. This generates for an increased environmental and climate impact, due to the need for new bitumen and steel to fill and seal the leak and oils being released into the surroundings. Therefore, it is also of interest to reduce the usage of bitumen or remove it completely from these dimbands. To minimize the complexity and reduce the usage of bitumen this thesis will evaluate a reparation method with bentonite pellets. The reparation method consists of a borehole, which is then backfilled, with bentonite pellets. There are two concrete dams in Sweden which have used this method. Therefore, this thesis work also aims to evaluate how this reparation will last, regarding time, against other options and future expectations regarding the replacement of bitumen.

    To begin, the bentonite pellets where first evaluated based on their swelling capabilities and moisture absorption. These attributes were tested by new methods, which are partly based on previous standards. These new methods for the material properties also allowed for long-term evaluation. To evaluate how the bentonite pellets would react over time they were placed in a temperature change cabinet. Five days in these cabinets, were assumed to, correspond to the Northern Swedish climate changes that takes place over a year.  The bentonite pellets were then evaluated by the new methods after 1,5 and 3 years. The results, for both swelling and moisture absorption, showed a difference depending on the bentonite type. The pure Na-bentonite moisture absorption has better absorption capabilities over time, compared to chemically produced Na-bentonite. The results from swelling shows that, regardless of bentonite type, they all induce worse swelling capabilities over time. Although, if they begin thawing cycles at a lower water content their swelling capabilities increases due to the bentonite experiencing exsiccation. 

    After the first experimental part, and this newly gathered material knowledge, a miniature version of a concrete dams’ expansion joint were built. The background to this was to research how many altitude meters (mVp) the bentonite pellets could withstand before collapse. Vattenfalls engineers built the testrigg, expansion joint, which primarily consisted of steel. A splintered concrete cube, with a predrilled hole in the middle, was then placed in this steel cartridge. The hole was then filled with bentonite pellets. To see the sequence of the material reaction during pressure tests the testrigg had a top of plexiglass. A manometer was then attached to the plexiglass. The manometer, and a consistent flow of water, allowed for the pressure to be monitored and regulated. When the sedimented bentonite pellets collapses the pressure drops. 

    Results from the pressure tests show a correlation between the bentonite pellets declared swelling pressure and the externally supplied water pressure. Depending on the inflow the bentonite pellets can withstand a pressure between 5 to 12 meters of water height – where the exact value is given by the time it is allowed to sediment. These values only consider the initial expansion of the material. Further research is required to evaluate how much water pressure the material can withstand over time.

    Based on the findings of this study one of the previously repaired concrete dams’ bentonite seal will collapse in due time, since the reparation exceeds 12 meters in height.

    Based on the information provided in this thesis it is difficult to decide whether a bentonite seal will be beneficial for the concrete structure. Further research is required to ensure the sustainability of using bentonite inside concrete structures.

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  • 2.
    Agredo Chavez, Angelica Maria
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Gonzalez, Jaime
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Andersson, Kasper
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Leidzen, Jon
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Andersson, Erik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Petersson, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Häggström, Jens
    Swedish Traffic Administration, Luleå, Sweden.
    Cracking and Fatigue of Heavy Loaded Prestressed Concrete Bridge in Sweden2022In: IABSE Symposium Prague 2022: Challenges for Existing and Oncoming Structures - Report, International Association for Bridge and Structural Engineering / [ed] František Wald, Pavel Ryjáček, Zürich: International Association for Bridge and Structural Engineering, 2022, p. 792-799Conference paper (Refereed)
    Abstract [en]

    A prestressed concrete bridge was built in 1963 with BBRV cables. It has three spans and a total length of 134.8 m. Due to mining activities the bridge was loaded with trucks with a total weight of 90 ton during 2012-2014 and from 2019. Crack development has been monitored manually and from 2020 with strain gauges and LVDTs.

    Cracks normally vary between 0.1 to 0.3 mm in width and grow in length with time. In November 2020 some of the strain gauges on the concrete showed alarming growth and the bridge was closed for traffic. Additional strain gauges were installed on vertical reinforcement bars and an assessment was carried out of the fatigue capacity of the bridge. It was found that the new strain gauges did not indicate any growth in strain and that the fatigue capacity was sufficient. The bridge could be opened again for traffic after being closed for five weeks. Monitoring drift in the strain gauges and fatigue are discussed.

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  • 3.
    Agredo Chavez, Angelica Maria
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Gonzalez, Jaime
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Capacci, L.
    Politecnico di Milano, Milan, Italy.
    Biondini, F.
    Politecnico di Milano, Milan, Italy.
    Structural model updating of an existing concrete bridge based on load testing and monitoring data2023In: Life-Cycle of Structures and Infrastructure Systems / [ed] Fabio Biondini, Dan M. Frangopol, Taylor & Francis Group, 2023, Vol. 1, p. 3999-4006Conference paper (Other academic)
    Abstract [en]

    The backbone of European infrastructure was built after the end of the second World War and has reached, or is near to, the end of its nominal design life. This issue urges the development of structural assessment procedures that can provide infrastructure managers the information to make decisions for repairing, upgrading, or replacement. In this paper, a methodology based on load testing and Structural Health Monitoring (SHM) for the assessment of a 65- year-old prestressed concrete bridge located in Northern Sweden is presented. The retrieved data is used to develop and calibrate structural models with different levels of data completeness. The SHM procedure includes the evaluation of material properties by diagnostics, definition of the layout and installation of the instrumentation, test execution, and data analysis. A preliminary structural model is developed based only on the original design parameters, and it is sequentially updated with monitoring data retrieved during a performed proof loading test of the bridge.

  • 4.
    Agredo Chavez, Angelica Maria
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Gonzalez, Jaime
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Bianchi, Silvia
    Politecnico di Milano, Milan, Italy.
    Biondini, Fabio
    Politecnico di Milano, Milan, Italy.
    Kukay, Brian
    Montana Technological University, Montana, United States.
    Available Tests to evaluate Residual Prestressing Forces in Concrete Bridges2022In: IABSE Symposium Prague 2022: Challenges for Existing and Oncoming Structures - Report, International Association for Bridge and Structural Engineering / [ed] František Wald, Pavel Ryjáček, International Association for Bridge and Structural Engineering, 2022, p. 1123-1131Conference paper (Refereed)
    Abstract [en]

    The reduction of the structural capacity and eventual collapse of existing concrete bridges is often related to the loss of the initial prestressing forces. This loss can be associated to immediate or time dependent factors such as elastic shortening, creep, relaxation, loading, and cracking, among others. In addition, environmental factors can lead to corrosion of the strands with the subsequent reduction of their area, loss of bond with the concrete and additional cracking which in turn will influence the value of the residual prestress force and the bridge capacity. Therefore, the evaluation of such losses is critical in the decision-making process of defining a financial and environmental cost optimized intervention strategies (e.g., strengthening or replacement). In this paper, a detailed literature review regarding destructive and non-destructive methods for measuring the residual force in prestressed concrete bridges is carried out and used to develop a database of existing experimental tests.

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  • 5.
    Agredo Chavez, Angelica Maria
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Ulfberg, Adrian
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Gonzalez-Libreros, Jaime
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Data Validation of Strain-Based Monitoring Systems in Low Temperature Conditions, Case Study: The Kalix Bridge2023In: Building for the Future: Durable, Sustainable, Resilient - Proceedings of the fib Symposium 2023 - Volume 2 / [ed] Alper Ilki, Derya Çavunt, Yavuz Selim Çavunt, Springer, 2023, Vol. 2, p. 986-995Conference paper (Refereed)
    Abstract [en]

    Over the last decades, economic growth and sustained development have enforced the need to ensure reliable and long-lasting infrastructure network to guarantee serviceability and safety. Nevertheless, detrimental effects can lead over time to insufficient structural performance under increasing service loadings and extreme events. Hence, Structural Health Monitoring (SHM) arises as a solution to cope with the need of having timely and continuous data to assess the state of crucial structural assets, such as prestressed concrete bridges. On this matter, the validation of the retrieved data becomes essential for the risk-based decision making in the assessment of bridges, where selecting the most suitable monitoring system could allow to addressed main causes to the right phenomena of deterioration during the service life of the bridge. Consistently with these efforts, this paper deals with a comparative study between the data acquired by different strain-based sensors such as Fiber optic systems (FOS) and strain gauges that were installed to monitor a proof loading test developed on a 65-year-old balanced cantilever prestressed concrete bridge located in Northern Sweden. The monitored data led to establish main differences between emerging types of monitoring systems such as FOS to the well-based strain gauges when exposed to low temperature conditions. Conclusions regarding the influencing parameters between both retrieved data are drawn when evaluating the structural response under serviceability loading conditions is performed, supporting decision makers when different levels of structural assessment are required.

  • 6.
    Albarazi, Rayan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Evaluation of Roadway Embankment Under Repetitive Axial Loading Using Finite Element Analysis2020Independent thesis Advanced level (degree of Master (Two Years)), 80 credits / 120 HE creditsStudent thesis
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  • 7.
    Al-Douri, Yamur
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Hamodi, Hussan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Data imputing using genetic algorithms (GA): A case study of cost data for tunnel fans2017Conference paper (Refereed)
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  • 8.
    Al-Emrani, Mohammad
    et al.
    Chalmers University of Technology.
    Lukic, Mladen
    CTICM.
    Nilsson, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Bridge fatigue guidance: a European research project2009In: Sustainable infrastructure: environment friendly, safe and resource efficient ; proceedings of IABSE symposium, Bangkok, Thailand, Sept. 9 - 11, 2009 / [ed] Mahāvidyālăy Culālaṅkărṇ, Zürich: International Association for Bridge and Structural Engineering, 2009Conference paper (Refereed)
  • 9.
    Alganadi, Mohammed
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Produktivitet i anläggningsproduktion – mätningar, faktorer som påverkar och en förbättringsmetod2021Independent thesis Advanced level (professional degree), 300 HE creditsStudent thesis
    Abstract [en]

    Productivity in the construction industry has been criticized because the industry for a long time has had poorer productivity development compared to other industries, for example the manufacturing industry, but the Swedish construction industry has great opportunities to improve its productivity.

    The purpose of this study is to contribute to an increased understanding concerning productivity, measuring of productivity and factors which influence productivity, that in the long run can help companies in the construction industry to improve productivity. Furthermore, various factors that have an impact on productivity were studied, which were investigated in order to see if those factors can be used to increase productivity in construction production.

    A qualitative interview study has been conducted in a construction company. The empirical material collected is from introductory interviews and in-depth interviews which have then been compared with a literature study in order to then be able to draw conclusions.

    The results show that no particular productivity measurement is performed in all projects, but productivity is checked through regular comparisons against cost calculations and schedules. This study has also shown that planning is one of the most important factors affecting productivity. The lack of management, communication, inappropriate weather conditions, the availability of materials, lack of documents and changes in blueprints can be potential reasons for the reported decline in productivity growth in various ways. Further research on this topic is needed to better understand the different methods that measure productivity and how the factors that affect productivity can be used to increase productivity in the Swedish construction industry.

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  • 10.
    Al-Gburi, Majid
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Restraint Calculation in Concrete Culvert First Casting2014Report (Other academic)
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  • 11.
    Al-Gburi, Majid
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Restraint Calculation in Concrete Culvert Second Casting2014Report (Other academic)
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  • 12.
    Al-Gburi, Majid
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Restraint Effects in Early Age Concrete Structures2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    One of the widespread issues in concrete structures is cracks occurring at early age. Cracks that appear in the young concrete may cause early start of corrosion of rebars or early penetration of harmful liquids or gases into the concrete body. These situations could result in reduced service life and in significantly increased maintenance cost of structures. Therefore it is important for construction companies to avoid these cracks.Volumetric deformations in early age concrete are caused by changes in temperature and/or the moisture state. If such movements are restrained, stresses will occur. If the tensile stresses are high enough, there will be a damage failure in tension and visible cracks arise. These stresses are always resulting from a self-balancing of forces, either within the young concrete bodyalone, i.e. without structural joints to other structures, or from the young concrete in combination with adjacent structures through structural joints.The decisive situation within a young concrete body alone is typically high stresses at the surface when the temperature is near the peak temperature within the body. This situation occur rather early for ordinary structures, say within a few days after casting for structures up to about some meters thickness, but for very massive structures like large concrete dams, it might take months and even years to reach the maximum tensile stresses at the surface. Usually this type of cracks is denoted "surface cracks", and in some cases only a temperature calculation may give a good perception to make decisions of the risk of surface cracking.On the other hand, the decisive situation within a young concrete body connected to adjacent structures, might include both risk of surface cracking at some distance away from the structural joint and risk of through cracking starting in the neighborhood of the structural joint. If the young concrete body is small in accordance to the adjacent structure, or, in other words, if thereis an overall high restraint situation in the young concrete, the risk of early surface cracking might be out of question. So, restraint from adjacent structures represents one of the main sources of thermal and shrinkage stresses in a young concrete body.This study is mainly concentrated on establishing the restraint inside the young concrete body counteracted by adjacent structures, and how to estimate the risk of through cracking based on such restraint distributions. The restraint values in the young concrete are calculated with use of the finite element method, FEM. Any spatial structure may be analyzed with respect to the level of restraint. Calculations of risk of cracking are demonstrated with use of existing compensation plane methods, and a novel method denoted equivalent restraint method, ERM, is developed for the use of restraint curves. ERM enables the use of both heating ofthe adjacent structure and/or cooling of the young concrete, which are the most common measures used on site to reduce the risk of early cracking.In a design situation many parameters are to be considered, like type of cement, different concrete mixes, temperature in the fresh concrete, surrounding temperatures, temperature in the adjacent structure, measures on site (heating/cooling/insulation), sequence order of casting.Therefore, in general a lot of estimations concerning risks of cracking are to be performed. The main objective with the present study is to develop methods speeding up and shorten the design process.Furthermore, established restraint curves have been applied to the method of artificial neural networks (ANN) to model restraint in the slab, wall, and roof for the typical structure Tunnel. It has been shown that ANN is capable of modeling the restraint with good accuracy. The usage of the neural network has been demonstrated to give a clear picture of the relative importance of the input parameters. Further, results from the neural network can be represented by a series of basic weight and response functions, which enables that the restraint curves easily can be made available to any engineer without use of complicated software.A new casting technique is proposed to reduce restraint in the newly cast concrete with a new arrangement of the structural joint to the existing old concrete. The proposed technique is valid for the typical structure wall-on-slab using one structural joint. This casting method means that the lower part of the wall is cast together with the slab, and that part is called a kicker. It hasbeen proven by the beam theory and demonstrated by numerical calculations that there is a clear reduction in the restraint from the slab to the wall using kickers.Restraint is affected by casting sequence as well as boundary conditions and joint position between old and new concrete elements. This study discusses the influence of different possible casting sequences for the typical structure wall-on-slab and slab-on-ground. The aim is to identify the sequence with the lowest restraint to reduce the risk of cracking.

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  • 13.
    Al-Gburi, Majid
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Restraint formulation for wall on slab at early age concrete structures by using ANN2012Report (Other academic)
    Abstract [en]

    Existing restraint curves have been applied to the method of artificial neural networks (ANN) to model restraint in the wall for the typical structure wall-on-slab. It has been proven that ANN is capable of modeling the restraint with good accuracy. The usage of the neural network has been demonstrated to give a clear picture of the relative importance of the input parameters. Further, it is shown that the results from the neural network can be represented by a series of basic weight and response functions. Thus, the results can easily be made available to any engineer without use of complicated software.

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  • 14.
    Al-Gburi, Majid
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Restraint in structures with young concrete: Tools and estimations for practical use2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    One of the widespread issues in concrete structures is cracks occurring at early age. Cracks that appear in the young concrete may cause early start of corrosion of rebars or early penetration of harmful liquids or gases into the concrete body. These situations could result in reduced service life and in significantly increased maintenance cost of structures. Therefore it is important for construction companies to avoid these cracks. Restraint represents one of the main sources of thermal and shrinkage stresses at early age concrete. Paper I, deals with both the compensation plane method, CPM, and local restraint method, LRM, as alternative methods studying crack risks for early age concrete. It is shown that CPM can be used both for cooling and heating, but basic LRM cannot be applied to heating. This paper presents an improved equivalent restraint method, ERM, which easily can be applied both for usage of heating and cooling for general structures. Restraint curves are given for two different infrastructures, one founded on frictional materials and another on rock. Such curves might be directly applied in design using LRM and ERM.In Paper II, existing restraint curves have been applied to the method of artificial neural networks (ANN) to model restraint in the wall for the typical structure wall-on-slab. It has been proven that ANN is capable of modeling the restraint with good accuracy. The usage of the neural network has been demonstrated to give a clear picture of the relative importance of the input parameters. Further, it is shown that the results from the neural network can be represented by a series of basic weight and response functions. Thus, the results can easily be made available to any engineer without use of complicated software.Paper III, discusses the influence of five casting sequences for the typical structure slab-on-ground. The aim is to map restraints from adjacent structures for a number of possible casting sequences, and to identify the sequence with the lowest restraint. The paper covers both continuous and jumped casting sequences, which include one, two and three contact edges. The result shows that the best casting sequence is the continuous technique with one contact edge.

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  • 15.
    Al-Gburi, Majid
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Jonasson, Jan-Erik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Nilsson, Martin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Effect of casting sequences on the restraint in slab-on-ground2014Conference paper (Refereed)
    Abstract [en]

    One of the widespread issues in concrete structures is cracks occurring at early age. Cracks that appear in the young concrete may cause early start of corrosion of rebars or early penetration of harmful liquids or gases into the concrete body. These situations could result in reduced service life and in significantly increased maintenance cost of structures. Therefore it is important for construction companies to avoid these cracks. Restraint represents one of the main sources of thermal and shrinkage stresses at early age concrete. The casting sequence is affected by the restraint from adjacent structures. The present study discusses the influence of five casting sequences for the typical structure slab-on-ground. The aim is to map restraints for a number of possible casting sequences, and to identify the sequence with the lowest restraint. The study covers both continuous and jumped casting sequences, which include one, two and three contact edges. The result shows that the best casting sequence is the continuous technique with one contact edge.

  • 16.
    Al-Gburi, Majid
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Jonasson, Jan-Erik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Nilsson, Martin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Effect of the boundary conditions on the crack distribution in early age concrete2014In: Nordic Concrete Research, ISSN 0800-6377, Vol. 50, p. 347-351Article in journal (Refereed)
    Abstract [en]

    Restrained movement in early age concrete may cause cracking. The boundary conditions – restraint – influence the possible crack distribution. This study aims at highlighting the effect of such restraint on the crack distribution. This is done by using the “Cracking Model for Concrete” in ABAQUS/Explicit simulating the non-linear behaviour under and after cracking. In the study the typical case wall-on-slab was in focus using a structure previously been tested in laboratory with both fixed and free bottom slab. The result of the modelling shows fairly good agreement with the cracks observed in the tests.

  • 17.
    Al-Gburi, Majid
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. College of engineering, University of Mosul, Iraq.
    Jonasson, Jan-Erik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Nilsson, Martin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Prediction of Restraint in Second Cast Sections of Concrete Culverts using Artificial Neural Networks2018In: European Journal of Environmental and Civil Engineering, ISSN 1964-8189, E-ISSN 2116-7214, Vol. 22, no 2, p. 226-245Article in journal (Refereed)
    Abstract [en]

    Estimation of restraint is very important for accurately predicting the risk of early thermal and shrinkage cracking in concrete structures. The stress in young concrete is affected by changes in its dimensions during hydration and the restraint imposed by adjoining structures. In concrete culverts, the restraints from existing structures acting upon the first and second casting sections to be cast are different, causing them to exhibit different early cracking behaviour. This work presents a new method for predicting restraint in complex concrete structures using artificial neural networks (ANNs). Finite element calculations were performed to predict restraint in 108 slabs, 324 walls and 972 roofs from second sections of concrete culverts, and the results obtained were used to train and validate ANN models. The ANN models were then used to study the effects of varying selected parameters (the thickness and width of the roof and slab, the thickness and height of the walls, and the length of the culvert section) on the predicted restraint. Mathematical expressions for predicting restraint values in slabs, walls and roofs were derived based on the ANN models’ output and implemented in an Excel spreadsheet that provides a simple way of predicting restraint in practical applications. Restraint values predicted in this way agree well with the results of finite-element calculations

  • 18.
    Al-Gburi, Majid
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Jonasson, Jan-Erik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Nilsson, Martin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Reduction of Early Age Crack Risks in Concrete Walls by Using a New Casting Technique2016In: Structural Engineering International, ISSN 1016-8664, E-ISSN 1683-0350, Vol. 26, no 3, p. 216-224Article in journal (Refereed)
    Abstract [en]

    Volumetric changes in early age concrete that are restrained might lead to cracks. The degree of restraint is influenced by the casting sequence and the dimensions of the castings. In the current study a new casting technique is proposed to reduce restraint in the newly cast concrete with a new arrangement of the structural joint to the existing old concrete. The proposed technique is valid for the typical structure wall-on-slab using one structural joint. This casting method means that lower part of the wall is cast together with the slab, and that part is called a kicker. Hereby, the behavior of the structure changes from a typical case wall-on-slab to a typical case wall-on-wall. It has been proven by the beam theory and demonstrated by numerical calculations that there is a clear reduction in the restraint from the slab to the wall using kickers. In the paper different kicker heights are studied with the aim of determining the minimum restraint in the upper part of the wall cast in contact with the kicker. The technique using kickers is compared with common measures used in the field to avoid cracking, such as cooling pipes in the new casting and/or heating cables in the adjoining old concrete. The presented method is both cost and time effective, as it opens the possibility to use larger structural length of each casting sequence.

  • 19.
    Al-Gburi, Majid
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Jonasson, Jan-Erik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Nilsson, Martin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Using Artificial Neural Network to Predict the Restraint in Concrete Culvert at Early Age2015In: Structural Engineering International, ISSN 1016-8664, E-ISSN 1683-0350, Vol. 25, no 3, p. 258-265Article in journal (Refereed)
    Abstract [en]

    Estimation of restraint is very important for accurate prediction of the risk of concrete cracking at early age. The present study predicts the restraint in 324 walls and 972 roofs for a concrete culvert. A parametric study included the thickness and width of the roofs, thickness and height of the walls, thickness and width of the slab, and length of the structures. Each parameter increased or decreased the restraint in the walls and the roofs. The calculation of the restraint was done elastically by the finite-element method (FE). The results were used by an artificial neural network (ANN) tool, where firstly an influential percentage was investigated as input parameters on the restraint prediction. Equations have been derived by the ANN model to calculate the restraint in the walls and the roofs. It was then used in an Excel sheet to calculate the restraint and compare the result with the result from the finite-element calculations giving high accuracy between the ANN model and the FE calculations

  • 20.
    Al-Gburi, Majid
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Jonasson, Jan-Erik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Nilsson, Martin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Hedlund, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Hösthagen, Anders
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Simplified methods for crack risk analyses of early age concrete: Part 1: Development of Equivalent Restraint Method2012In: Nordic Concrete Research, ISSN 0800-6377, Vol. 46, no 2, p. 17-38Article in journal (Refereed)
    Abstract [en]

    The present study deals with both the compensation plane method, CPM, and local restraint method, LRM, as alternative methods studying crack risks for early age concrete. It is shown that CPM can be used both for cooling and heating, but basic LRM cannot be applied to heating. This paper presents an improved equivalent restraint method, ERM, which easily can be applied both for usage of heating and cooling for general structures. Restraint curves are given for two different infrastructures, one founded on frictional materials and another on rock. Such curves might be directly applied in design using LRM and ERM.

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  • 21.
    Al-Gburi, Majid
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Jonasson, Jan-Erik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Yousif, Salim T
    Mosul University.
    Nilsson, Martin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Simplified methods for crack risk analyses of early age concrete: Part 2: Restraint factors for typical case wall-on-slab2012In: Nordic Concrete Research, ISSN 0800-6377, Vol. 46, no 2, p. 39-56Article in journal (Refereed)
    Abstract [en]

    Existing restraint curves have been applied to the method of artificial neural networks (ANN) to model restraint in the wall for the typical structure wall-on-slab. It has been proven that ANN is capable of modeling the restraint with good accuracy. The usage of the neural network has been demonstrated to give a clear picture of the relative importance of the input parameters. Further, it is shown that the results from the neural network can be represented by a series of basic weight and response functions. Thus, the results can easily be made available to any engineer without use of complicated software.

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  • 22.
    Ali, Asma Mahdi
    et al.
    Civil Engineering Department, Engineering College, Mustansiriyah University, Baghdad, Iraq.
    Al-Taai, Salwa R.
    Civil Engineering Department, Engineering College, Mustansiriyah University, Baghdad, Iraq.
    Jaafar, Esraa Kamal
    Civil Engineering Department, Engineering College, Mustansiriyah University, Baghdad, Iraq.
    Al-Maliki, Hadi Naser Ghadhban
    Civil Engineering Department, Engineering College, Mustansiriyah University, Baghdad, Iraq.
    Madhloom, Huda M.
    Civil Engineering Department, Engineering College, Mustansiriyah University, Baghdad, Iraq.
    Al-Ansari, Nadhir
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nonlinear Simulation Analysis of Mechanical Behaviour of Rubberized Concrete2022In: International Journal of GEOMATE, ISSN 2186-2982, Vol. 22, no 90, p. 125-137Article in journal (Refereed)
    Abstract [en]

    The main objective is to simulate the representation of rubber concrete with different percentages (0, 20, 40, 60, 80, 100%) of rubber using a finite element approach with ANSYS V.15 software to evaluate the behavior of concrete under the influence of mechanical force by using a standard cylinder to calculate its compressive strength, elasticity modulus and displacements for comparison with the previous experimental study, which showed a very close agreement of 5 to 12% when compared between them. The results showed that when the percentage of rubber increases, it leads to a decrease in the compressive strength, that is, its resistance, and an increase in the corresponding displacements and deformations that occur in them, as a result of the concentration of these stresses in the rubber limits. The results also showed that the meshing distribution of the analyzed elements by the ANSYS gave higher values of compressive strength and a decrease in the corresponding displacements when they were regular i.e. homogeneous compared to the irregular ones. Finally, through statistical analysis, it was found that the mean and arithmetic mean were acceptable and close when comparing the theoretical and practical results.

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  • 23.
    Alkayal, Adam
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Laser scanning of overbreak and deformation for crosscuts at Malmbergetmine: uGPS Rapid Mapper™2020Independent thesis Advanced level (degree of Master (Two Years)), 80 credits / 120 HE creditsStudent thesis
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  • 24.
    Alm, Ove
    et al.
    Luleå University of Technology.
    Norin, Jonas
    Luleå University of Technology.
    Olofsson, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Experimentella bestämningar av mekaniska egenskaper för hårdmetallpulver: slutrapport över pilotstudie1982Report (Other academic)
  • 25.
    Alm, Ove
    et al.
    Luleå University of Technology.
    Olofsson, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Attempt to make accurate measurements of deformations of compressible soilds at high pressure and different states of stress1982In: High pressure in research and industry: 8th AIRAPT Conference, 19th EHPRG Conference, 17 - 22 August 1981, Institte of Physical Chemistry, University of Uppsala, Sweden ; proceedings / [ed] C.-M. Backman, Uppsala: Fysikalisk-kemiska inst., Univ , 1982, p. 619-622Conference paper (Refereed)
  • 26.
    Al-Maliki, Hadi Naser Ghadhban
    et al.
    Civil Engineering Department, Engineering College, Mustansiriyah University, Baghdad, Iraq.
    Al-Balhawi, Ali
    Civil Engineering Department, Engineering College, Mustansiriyah University, Baghdad, Iraq.
    Al-Taai, Salwa R.
    Civil Engineering Department, Engineering College, Mustansiriyah University, Baghdad, Iraq.
    Madhloom, Huda M.
    Civil Engineering Department, Engineering College, Mustansiriyah University, Baghdad, Iraq.
    Gamil, Yaser
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Structural Behavior Of Precast High Strength Reinforced Concrete Vierendeel Truss Walls: A Numerical Approach2021In: International Journal of GEOMATE, ISSN 2186-2982, Vol. 21, no 84, p. 137-150Article in journal (Refereed)
    Abstract [en]

    Reinforced concrete (RC) walls have been widely used in different types of civil engineering projects. Therefore, their behaviour under several kinds of loading is of utmost importance. In this study, the main objective is to investigate the behaviour of RC Vierendeel walls under the applied loads by employing numerical analyses for the studied walls. Several assumptions are adopted in these analyses to simulate the actual behaviour of Vierendeel walls, which were experimentally studied in previous investigations. The numerical results showed that the simulated numerical behaviour has a very good agreement with the experimental results of the tested models. Statically, this agreement is validated and verified in terms of the mean and standard deviation values. Therefore, the proposed numerical models and assumptions are the suitable ones to simulate the structural behaviour of these walls under the applied conditions. The structural behaviour is presented in terms of load capacity, crack pattern, deflection, and mode of failure. The results show that the reactive powder concrete (RPC) models have more resistance under the applied load in terms of deflection, cracks, and ductility index than the models of normal strength concrete (NSC). Also, the openings are the main reason for the diagonal cracking at the corners of the RC walls. The deflection in all models is a single curvature. The mode of failure for all models is shear.  

  • 27.
    Alnadish, Adham Mohammed
    et al.
    Department of Transportation and Geotechnical Engineering, National University of Sciences and Technology (NUST), Balochistan Campus, Quetta, Pakistan.
    Katman, Herda Yati Binti
    Department of Civil Engineering, Universiti Tenaga Nasional, Kajang, Malaysia.
    Ibrahim, Mohd Rasdan
    Department of Civil Engineering, Universiti Malaya, Kuala Lumpur, Malaysia.
    Gamil, Yaser
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Department of Civil Engineering, School of Engineering, Monash University Malaysia, Selangor, Malaysia.
    Mashaan, Nuha S.
    School of Engineering, Edith Cowan University, Perth, WA, Australia.
    A bibliometric analysis and review on the performance of polymer-modified bitumen2023In: Frontiers in Materials, E-ISSN 2296-8016, Vol. 10, article id 1225830Article, review/survey (Refereed)
    Abstract [en]

    The addition of polymer to a base binder has been documented as a successful approach in terms of improving physical and rheological properties of the base bitumen. However, the main drawbacks of polymer-modified bitumen are incompatibility and degradation of polymer due to aging. This article aims to introduce a bibliometric analysis and review on modifying bitumen with polymers. Additionally, this article intent to highlight the significant gaps and recommendations for future work. Furthermore, another objective of this article is to provide a worth attempt regrading reducing the negative impact of polymer’s drawbacks on the performance of polymer-modified base binder. The findings of this article demonstrated that the test of storage stability for polymer-amended bitumen should be modified, in which the softening point of aluminum tube centerpiece should be measured to introduce a better evaluation for the storage stability of polymer-amended bitumen. In addition, the effects of kinetic factors (mixing sequence, viscosity of blend, shear rate, and time of mixing) on the compatibility of polymer-amended bitumen should be investigated. Moreover, the addition of compatibilizers and stabilizers to polymer-modified binder is recommended to improve compatibility and reduce the effect of aging on degradation of polymer.

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  • 28.
    Al-Taie, Entidhar
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Al-Ansari, Nadhir
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Knutsson, Sven
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Saaed, Tarek Edrees
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Foundation assessment in different parts of Iraq using STAAD Pro v8i2013In: Journal of Civil Engineering and Architecture, ISSN 1934-7359, E-ISSN 1934-7367, Vol. 7, no 3, p. 273-281Article in journal (Refereed)
    Abstract [en]

    Foundation is considered as one of the main parts of any structure such as buildings, railways, bridges, etc. The type of foundation used is highly dependent on the type and properties of soil. The design of foundations requires many factors that should be defined such as the load that the foundation is going to hold, geological conditions of the soil under the foundation, type of soil and the local building code criteria.There are number of differences in the geological and soil conditions in Iraq. As a consequence, these differences are reflected on the type of foundation to be used. Despite these differences, same materials and style of buildings are used all over Iraq. The main problems of Iraqi soil are high gypsum content, salinity and shallow water table depth. These factors that influence the foundations are the soil properties and the amount of loads that transmitted by the superstructure.The situation had been analysed through a case study which illustrated the link between soil and foundation types in three different parts of Iraq (Mosul, Baghdad and Basra). One building was analysed using STAAD. Pro software in these regions. It is evident that Iraqi designers and engineers require local code to define all the loads, materials and design of the foundation to be used. The use of local materials might be very effective from both engineering and economic perspectives.

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  • 29.
    Amran, Mugahed
    et al.
    Department of Civil Engineering, College of Engineering, Prince Sattam Bin Abdulaziz University, 11942 Alkharj, Saudi Arabia.
    Onaizi, Ali M.
    School of Architecture and Built Environment, The University of Newcastle, University Drive, Callaghan, NSW 2308, Australia.
    Makul, Natt
    Department of Civil Engineering Technology, Phranakhon Rajabhat University, Bangkok 10220, Thailand.
    Abdelgader, Hakim S.
    Department of Civil Engineering, Faculty of Engineering, University of Tripoli, Tripoli, Libya.
    Tang, W. C.
    School of Architecture and Built Environment, The University of Newcastle, University Drive, Callaghan, NSW 2308, Australia.
    Alsulami, Badr T.
    Department of Civil Engineering, College of Engineering and Islamic Architecture, Umm Al-Qura University, Makkah 24382, Saudi Arabia.
    Alluqmani, Ayed Eid
    Department of Civil Engineering, Islamic University of Madinah, Madinah 41411, Saudi Arabia.
    Gamil, Yaser
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Department of Civil Engineering, School of Engineering, Monash University Malaysia, Jalan Lagoon Selatan, 47500 Bandar Sunway, Selangor, Malaysia.
    Shrinkage mitigation in alkali-activated composites: A comprehensive insight into the potential applications for sustainable construction2023In: Results in Engineering (RINENG), ISSN 2590-1230, Vol. 20, article id 101452Article, review/survey (Refereed)
    Abstract [en]

    The extant body of literature articulates a noticeable disparity in the susceptibility to cracking and concomitant material degradation between alkali-activated composites (AAC) and ordinary Portland cement (OPC), predominantly attributable to shrinkage and subsequent drying phenomena. This divergence derives from the nanoscopic porosity of AAC binders, which is substantially finer than their OPC counterparts. However, experimental research validates that the judicious incorporation of alternative cementitious materials and fibrous reinforcements enriches the shrinkage characteristics of AAC, thereby enhancing its overall structural performance. Given the crucial role of shrinkage in defining the material integrity of AAC, especially under constrained environmental conditions, an in-depth understanding of shrinkage mechanisms materializes as a necessity for conceiving efficient shrinkage-mitigating strategies. In light of the growing interest in optimizing AAC through various material integrations and methodological innovations aimed at shrinkage diminution, this scholarly review undertakes an extensive synthesis of the laboratorial investigations focused on AAC shrinkage behavior and mitigation. However, this article critically evaluates widespread strategies for shrinkage mitigation, explicating their operative mechanisms. Moreover, it is outlined gaps in the existing research paradigm, promoting for targeted scholarly endeavors to yield a more clear understanding of shrinkage dynamics and to facilitate the advancement of environmentally sustainable AAC composites. Meanwhile, this study intended to consolidate existing research on developing trends in order to gain a comprehensive understanding of the possible uses of AACs and identify viable strategies for addressing AAC shrinkages. By addressing the challenges related to micro-cracking and shrinkage, the long-term durability of AACs may be improved, leading to increased adoption of these materials as sustainable building options in the construction industry today.

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  • 30.
    An, Bolun
    et al.
    School of Civil Engineering, Beijing Jiaotong University, Beijing, China. Beijing Key Laboratory of Track Engineering, Beijing, China. Beijing Engineering Research Centre of Rail Traffic Line Safety and Disaster, Beijing, China.
    Gao, Liang
    School of Civil Engineering, Beijing Jiaotong University, Beijing, China. Beijing Key Laboratory of Track Engineering, Beijing , China. Beijing Engineering Research Centre of Rail Traffic Line Safety and Disaster, Beijing, China.
    Xin, Tao
    School of Civil Engineering, Beijing Jiaotong University, Beijing, China. Beijing Key Laboratory of Track Engineering, Beijing, China. Beijing Engineering Research Centre of Rail Traffic Line Safety and Disaster, Beijing, China.
    Lin, Jing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    An approach to evaluate wheel-rail match properties considering the flexibility of ballastless track: Comparison of rigid and flexible track models in wheel-rail profile matching2019In: International Journal of COMADEM, ISSN 1363-7681, Vol. 22, no 3, p. 5-13Article in journal (Refereed)
    Abstract [en]

    Many different wheel/rail profiles are used in the China high-speed railway, and vehicle operation safety and comfort will decrease if the inappropriate wheel-rail profile pair is used. To solve the problem of estimating the wheel-rail match, many numerical models, including vehicle system dynamic models and wheel-rail rolling contact models, have been established to analyse the wheel-rail dynamic responses. Both methods have less consideration of the flexibility and vibration characteristics of ballastless track, leading to deviations in the calculation of middle and high frequency vibration. This paper proposes a vehicle-flexible track coupling model and compares it with the vehicle dynamic model (vehicle-rigid track model). In the rigid track model, only the track irregularities are considered in the track module; the vibrations and deformations of rails, track slab and the foundation are considered in the flexible track model. Taking Chinese CRH3 series wheel profile S1002CN and rail profile CHN60 as examples and considering different track excitations, the two models are compared. The wheel-rail interaction forces, wheel-rail wear depths, wear volumes and vehicle accelerations are chosen as analysis indices for the comparative study.

    The results show that the wheel-rail forces of the flexible track model are larger than the rigid track model in the frequency range from 70 to 120Hz, while they decrease obviously in the frequency range above 150Hz. The differences in wear depths and volumes between the two models exceed 10%. Therefore, the flexible track model should be considered when studying the match properties of different wheel-rail pairs.

  • 31.
    Anandika, Rayendra
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Non-destructive measurement of near-surface cracks in railheads: with focus on ultrasonic inspections2021Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Near-surface cracks in railhead that caused by rolling contact fatigue (RCF) is one of a kind rail defects that degrade rail track quality. Dependent on the trail load, the cracks can reach to severe level quickly. From many studies, the crack growth can be summarized as follows: At the first phase, the crack is initiated at the rail surface due to shear stresses created by the interaction between wheel and rail. The crack then propagates at about 30⁰ angle underneath. After a certain period of transition, the cracks starts propagating horizontally, vertically, or branching. If they propagates horizontally, the cracks potentially cause rail spalling. If they propagates vertically, then the cracks become more severe and dangerous.

    To overcome such defects, the infrastructure manager remove the top of railhead by performing rail grinding periodically. Prior the grinding, rail tracks need to be inspected to figure out how deep the cracks are by performing non-destructive testing (NDT). Eddy current testing (ECT) is one of the common method to estimate rail surface crack depths. Most of the practices in the industry, ECT estimates only the crack depth, without analyzing any other crack parameters, such as crack angle propagation, crack length, crack area, crack branches, etc. It also has no ability to identify multi-leveled cracks, sub surface cracks, dense cracks etc. Since depth is the only crack parameter that can be provided from ECT, the inspector have no knowledge about how severe the surface crack is. Whereas, information of crack phase, that is known from the crack profile (crack angle, crack depth and crack length) is beneficial to determine whether the crack is in initial or severe level. It also helps to decide the right time for grinding and avoid severe cracks remain long in the rails.

    Motivated by the benefit of knowing crack parameters, in this study, phased array ultrasonic transducer (PAUT) was used to inspect rail surface cracks. Generally, ultrasonic testing is used to inspect defect of rails at the far-field of the surface, such as at the body or bottom of the rails. Ultrasonic testing is not used to inspect near-surface cracks since the existence of dead zone at the few mm front of the transducer that is caused by piezoelectric crystal ringing inside the transducer. In this study, by utilizing wedge, phased array technique, and setting the optimum gain at the calibration process could decrease the existence of the dead zone. Thus the surface cracks can be observed clearly from the breaking surface to the deepest tip. At the measurement result, crack profile (propagation angle, depth and length), crack branches and multi-level cracks could be observed well. 

    To verify the measurement result, the inspected railheads were sliced into pieces with uniform 0.65-mm thickness. From these pieces, 3D cracks networks were reconstructed. Complete information of crack profiles (angle, depth and length) of all cracks under the inspected surfaces were collected and well presented. From the reconstructed crack images, crack tips, multi-level cracks, and crack branches can be seen. These confirms that the measurement results could be used to observe crack profile well. For a brief description about the results, 3.5 mm crack tip depth and 6 mm crack length were estimated well with 8% and 4% error, respectively. Although the measurement system still have lack of detection for crack path that oriented sharply from the horizontal line parallel to the surface, since the ultrasonic waves could not be reflected back by these paths.

    At the end of this study, assessment about the potential of measurement speed of the used system when be applied to the rail field inspection was presented. The study is based on the state of the art available at this topic. The discussion is provided in order to motivate the application of the system to be chosen by the rail inspector to use it for the real rail field inspection. 

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  • 32.
    Andersson, Kasper
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Leidzén, Jon
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Cracking and Fatigue in the Prestressed Concrete Bridge at Autio2022Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In early 2020, cracks were discovered on the bridge crossing the Torne River at Autio. This resulted in an investigation being launched to determine the structural state of the bridge. In conjunction with this investigation, monitoring equipment was installed on the bridge, which enabled the collection of measured strain at four critical points on the bridge. 

    In this thesis the measured strain was used to approximate stresses in the prestressing cables and thereby calculate the effects of fatigue on the bridge. Two different structural standards were used to calculate the results: Eurocode 2, and fib Model Code 2010. Likewise, two different cycle-counting methods were used to calculate the results: the Rainflow-algorithm, and the largest-magnitude approach. 

    Regardless of structural standard or cycle-counting method, the results indicate that the effects of fatigue are neither an issue for the bridge, currently, nor will it be in the expected lifetime of the bridge.

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  • 33.
    Andersson, Max
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    Digitala verktyg för materialhantering i husbyggnadsprojekt2022Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Försörjningskedjan i byggprojekt konvergerar materialflödet mot byggarbetsplatsen. Där byggs materialet ihop till en enskild produkt. Materialhanteringen är en av de viktigaste faktorerna för hur byggprojekt presterar gällande kostnad, tid, säkerhet i planeringen och arbetsplatsolyckor. Att flera olika materialflöden hanteras i projektspecifika miljöer av projektspecifika organisationer innebär en komplicerad logistikhantering. Trots det är byggbranschen jämförelsevis dålig på att utnyttja expertis och moderna tekniker för att förbättra materialhanteringen.

    Ett effektivt informationsflöde är väsentligt för att kunna upprätthålla ett effektivt materialflöde. Men byggprojekt har många olika källor till information med olika nivåer av detaljrikedom. Det leder till bristande kommunikation vilket får flera negativa effekter.

    Tidigare studier (Xue, Wang, Shen & Yu, 2007; Donyavi & Flanagan 2009) har visat att det finns ett behov av digitala verktyg för styrning av försörjningskedjan till byggprojekt. Andra studier (Olsson, 2000; Samuelson & Björk, 2014; Blanco, Mullin, Pandya & Sribdhar, 2017) har visat att det sällan är en helt friktionsfri process att implementera nya rutiner och digitala verktyg i byggbranschen. Därför finns ett behov av att studera hur företag kan lyckas med implementering av digitala verktyg för materialhantering.

    Målen med studien är att undersöka framgångsfaktorer för implementering av digitala verktyg för materialhantering i husbyggnadsprojekt och vilka effekter lyckad implementering kan leda till. Syftet är att öka effektiviteten i materialflöden i byggproduktion.

    Den här studien har utförts som en flerfallsstudie på flerbostadsprojekt där ett digitalt verktyg för materialhantering använts. Fallstudien består av ett primärt fall och ett jämförande fall. I det primära fallet har en långsiktig implementering av det digitala verktyget misslyckats, till skillnad från i det jämförande fallet. Det digitala verktyget som ingår i fallstudien är Myloc Construction och det används bland annat för att koordinera transporter till byggarbetsplatsen. Fallstudien genomfördes som en intervjustudie. Utöver respondenter från de olika byggprojekten inkluderas även respondenter från utvecklaren av det digitala verktyget.

    Det digitala verktyget tillgängliggör information om bland annat leveranser och förflyttningar påbyggarbetsplatsen. Detta förenklar koordineringen av materialflödet på byggarbetsplatsen och på så sätt kan det bidra till ökad samordning, färre störningar, minskad trängsel och effektivare godsmottagning. Dessutom finns ett bokningssystem för lyftresurser vilket gör det enklare att anpassa materialflödet efter resurstillgången eller vice versa. Studien har identifierat tre nyckelfaktorer för implementeringen av digitala verktyg för materialhantering:

    • Planering - Förutsättningarna i produktionen måste anpassas efter hur logistiken och det digitala verktyget är tänkt att fungera.
    • Resurser – En enhet som driver implementeringen av det digitala verktyget bör ägna sig åt att öka följsamheten och att driva igenom förbättringar i hanteringen av det digitalaverktyget. Hur mycket resurser som krävs för detta beror på logistikuppläggets komplexitet.
    • Riktlinjer – Det krävs riktlinjer för hur det digitala verktyget ska hanteras. Dessa bör till stor del anpassas efter projektets förutsättningar. En riktlinje som är viktig oberoende av projektets utformning är att bestämma med vilken framförhållning som information ska matas in. Riktlinjerna kan antingen förmedlas via projektspecifika instruktioner eller via avtal.

    Två tidigare studier (Olsson, 2000; Sullivan, Barthorpe och Robbins, 2010) har beskrivit att byggentreprenörer inte är vana vid att lägga resurser på att förbättra logistiken. Den här studien har bekräftat att det till viss del fortfarande är så, men studien tyder också på att detta är något som håller på att bli bättre. Dessutom bekräftar studien att användarna generellt är positivt inställda till att testa ny teknik för att utveckla sitt arbete.

    En studie (Aloini, Dulmin, Mininno & Ponticelli, 2012) har visat att sen inblandning av aktörer, brist på samordnad utformning och bristfälligt urval av leverantörer är riskfaktorer för implementering av ett logistikkoncept som kallas Supply Chain Management. Studien som gjorts i detta examensarbete kunde identifiera att dessa riskfaktorer även hindrat implementeringen av det digitala verktyget för materialhantering.

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  • 34.
    Andren, Henrik
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Wennström, Joakim
    Luleå University of Technology.
    Analysis of replication casting of ice surfaces2007In: Proceeding of the 8th International Symposium on Cold Region Development, Tampere University of Technology, 2007Conference paper (Refereed)
    Abstract [en]

    The microscopic analysis of an ice surface is very difficult, due to the nature of the ice. The optically transparent, brittle and very environmentally sensitive surface is hard to analyze in a manner that does not render the results useless from damage or errors in measurements.The ice surface is ill suited for contact microscopy, like Atomic Force Microscopy (AFM) or other methods of sliding a probe over the surface. Furthermore the ice surface is transparent, so even cold room optical microscopy is not feasible. Due to the vacuous atmosphere Scanning Electron Microscope (SEM) is not an option. In this paper the authors look at some casting techniques to try and reproduce the surface with a substance much better suited for optical and mechanical measurements, as well as having a longer shelf life and being easier to handle. Different evaluations have been considered, where the frequency information is used as a measure of resolution, comparing the resolution loss of different casting materials.The casting materials used are different products from the dental industry, as well as polyvinyl formvar, a dissolved polymer that is very useful for casting of ice surfaces.

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  • 35.
    Andrén, Anna
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering. The Swedish Transport Administration, Borlänge, Sweden.
    Dahlström, Lars-Olof
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Field Observations of Water and Ice Problems in Railway Tunnels from a Maintenance Perspective2023In: Journal of Earth Sciences and Geotechnical Engineering, ISSN 1792-9040, E-ISSN 1792-9660, Vol. 13, no 1, p. 11-54Article in journal (Refereed)
    Abstract [en]

    During the winter season, ice causes major problems in many Swedish railway tunnels. Ice, rock and shotcrete in the roof and on the walls may come loose and fall down, installations and cables can break due to ice loads and the tracks can become covered with ice. To maintain safety and prevent traffic disturbances, many tunnels require frequent maintenance. The removal of ice, loose rock and shotcrete is expensive and potentially risky work for the maintenance workers. To reduce maintenance costs, it is important to improve our knowledge of frost penetration inside tunnels and investigate the effect of ice pressure and frost shattering on loadbearing constructions. The aim of this investigation was to gather information about the problems caused by water leakage and its effect on the degradation of a rock tunnel when subjected to freezing temperatures. There are many factors that determine whether frost or ice formations will appear in tunnels. To collect information on ice formation problems, field observations were undertaken in five of Sweden’s railway tunnels between autumn 2004 and summer 2005. For one of the tunnels, follow-up observations also took place in March during the years 2005, 2006 and 2007.

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  • 36.
    Anglöv, Alexander
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Strategisk linjering av prestationsmått: En fallstudie om utformning och implementering av produktionsmål inom anläggning2021Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Bygg- och anläggningsindustrin brottas med frågor kring produktivitetsutveckling, då inte önskad produktivitet alltid uppnås. För att kunna öka och utveckla produktiviteten bör anläggningsföretag kunna mäta och följa upp sina prestationer. Genom att kunna mäta prestationer skapas en förståelse över hur verksamheten går och i vilken riktning den är på väg. Det finns svårigheter med att ta fram ett tydligt arbetssätt kopplat till målarbete inom anläggning då alla projekt har unika förutsättningar att utgå ifrån. Fel inom anläggningsprojekt kan leda till stora ekonomiska konsekvenser för företaget, och utan en tydlig målbild med relevanta prestationsmått är det svårt att veta om arbetet som utförs ligger i linje med de satta målen eller ej. För att kunna bemöta problemen har forskning inom problemområdet föreslagit att det är viktigt att det finns ett linjerat arbetssätt genom hela organisationen, så kallad strategisk linjering. Då företag inom bygg- och anläggningsbranschen länge blivit kritiserade för sin långsamma utveckling är strategisk linjering av prestationsmått ett intressant område att studera. Det är även ett relativt outforskat område när det kommer till andra studier och speciellt fallstudier inom bygg- och anläggningssektorn. Syftet med examensarbetet är att bidra till en ökad kunskap om strategisk linjering av produktionsmål och prestationsmått och dess specifika implementering inom anläggning. Examensarbetet studerar ett konkret implementeringsarbete avseende strategisk linjering av produktionsmål och prestationsmått inom ett anläggningsföretag. Målet med studien är att, med utgångspunkt i litteratur inom ämnesområdet adressera följande två huvudfrågeställningar:

    1.     Hur kan ett anläggningsföretag implementera strategisk linjering mellan produktionsmål och prestationsmått?

    2.     Vad kan utgöra hinder respektive möjliggörare vid implementering av strategisk linjering av prestationsmått inom anläggning?

     

    Datainsamlingen har bestått av intervjuer, dokumentinsamling och observationer. Innan datainsamlingen påbörjades utfördes en litteraturstudie inom forskningsområdet strategisk linjering av prestationsmått som ligger till grund för den teoretiska referensramen och den framtagna analysmodellen.  

    För att möjliggöra implementering av strategisk linjering mellan produktionsmål och prestationsmått krävs en sammanhängande målnedbrytning från ett anläggningsföretags övergripande mål ned till specifika produktionsmål som sedan kan följas upp genom tydliga mätbara prestationsmått. Prestationsmåtten ska vara lätta att förstå och utföra, och vara linjerade med de specifika produktionsmålen som i sin tur är linjerade med anläggningsföretagets övergripande mål. Analysen av litteraturen sammanvägt med fallföretagets förutsättningar visar att det är av värde att ha prestationsmått som både indikerar på vad som sker just nu, och vad som har skett under en viss period för att både kunna vara proaktiva och reaktiva i sitt agerande kopplat mot målarbetet. De prestationsmått som återkommande nämns i litteratur kring strategisk linjering av prestationsmått och som är analyserade i studien för att uppfylla detta är key performance indicators (KPI), performance indicators (PI), result indicators (RI) och key result indicators (KRI). Då projekt inom anläggningsbranschen består av väldigt varierande förutsättningar finns det möjliggörare för att lyckas implementera strategisk linjering av prestationsmått, men det finns även en del hinder.  

    Det största hindret med strategisk linjering av prestationsmått som upptäcktes i studien är att lyckas få prestationsmåtten tydligt mätbara då olika aktiviteter i ett anläggningsprojekt mäts i olika enheter. Det har visat sig att vara viktigt att alla som ska använda prestationsmåtten har en förståelse varför de ska användas, och hur de ska användas för att få öka möjligheterna för ett gemensamt arbetssätt inom företaget. Ytterligare ett hinder är om prestationsmåtten tas fram utan anknytning till produktionsmål, kritiska framgångsfaktorer, strategi, övergripande mål och vision, vilket skulle bidra till en avsaknad av enhetlighet inom ett anläggningsföretags målarbete. Det sista hindret som studien visar är om prestationsmåtten används på fel sätt och enbart visar resultat på past performance. Möjliggörarna till strategisk linjering av prestationsmått har visat sig vara att tydligt utformade prestationsmätningar bidrar till ett gemensamt arbetssätt, och det blir enklare att kontinuerligt följa upp resultat över tid. Med tydligt utformade prestationsmått ökar sannolikheten att tidigt upptäcka avvikelser som i sin tur kan korrigeras i rätt tid innan problemet hinner växa sig större. Rekommendationerna till fallstudieföretaget och andra anläggningsföretag blir att tydliggöra hur prestationsmåtten ska mätas, och hur de ska följas under projekten. Nästa steg blir att tydligt sprida prestationsmåtten ut i verksamheten för att säkerställa att alla förstår hur de ska användas vilket kan leda till större möjlighet att styra processen i rätt riktning. 

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  • 37. Apleberger, Lennart
    et al.
    Cederwall, Krister
    Luleå University of Technology.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Massiva betongkonstruktioner i varmt klimat: fältmätningar och teoretisk analys av väggsektioner : D. 1 Rapportdel1985Report (Other academic)
  • 38. Apleberger, Lennart
    et al.
    Cederwall, Krister
    Luleå University of Technology.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Massiva betongkonstruktioner i varmt klimat: fältmätningar och teoretisk analys av väggsektioner : D. 2 Tabelldel1985Report (Other academic)
  • 39.
    Arason, Magnús
    et al.
    EFLA.
    Bie Gundersen, Espen
    Agder Fylkeskommunne.
    Collin, Peter
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Ramboll Sverige.
    Vestman, Victor
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Ramboll Sverige.
    Innovasjon i bruforsterkning i Agder2020In: Nyheter om stålbyggnad, ISSN 1404-9414, Vol. 2020, no 4, p. 24-26Article in journal (Other academic)
    Abstract [no]

    EFLA og Luleå Tekniska Universitet har bistått Agder fylkeskommune med forsterkning av to gamle stålbjelkebruer i Agder fylke, som dannet en flaskehals for vegtransport i området. I prosjekteringen er det brukt en metode som aldri har vært brukt i Norge før, og den har vist seg å være effektiv i forhold til kostnad, gjennomførbarhet og miljøpåvirkning. Prosjektet er et eksempel på vellykket nordisk samarbeid, og kan ha overføring til fremtidige prosjekter

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  • 40. Arwidson, Claes
    et al.
    Bernspång, Lars
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Verification of numerical forming simulation in high strength steels2004In: Proceedings of the Conference Innovations in metal forming, 2004Conference paper (Refereed)
  • 41.
    Aulestia, Shane
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Effect of increased vertical stress on the state of grains in tailings2023Independent thesis Advanced level (degree of Master (Two Years)), 80 credits / 120 HE creditsStudent thesis
    Abstract [en]

    Tailings storage facilities (TSFs) serve as structures for storing tailings, i.e., waste materials generated by the mining industry. In recent years, tailings dam failures and collapse of these constructions have been reduced due to the establishment of regulations to control these structures, nevertheless, the consequences are catastrophic when tailings dam failures occur. There are some different construction methods for tailings dams. One common construction method is the upstream method; where the dam is raised by constructing embankments on top of the tailings stored in the impoundment. Thus, it is essential to understand the mechanical and geochemical behavior of deposited tailings to be able to perform safety assessments of tailings dams.  Material properties must be assessed for the present time as well as over a longer time since aging and continuous deposition might change the mechanical behavior over time. Continuous deposition leads to continuous increased vertical stress on particles, and there is a need to study if increased vertical stress can lead to a possible change of the mechanical properties of tailings. Therefore, this study has investigated the characteristics of tailings particles after being subjected to vertical stepwise loading.

    This study focuses on investigating the impact of particle breakage (or crushing) on tailings by analyzing material recovered from a tailings dam in Sweden. The research was performed on disturbed tailings material from a borehole of approximately 40 m depth. The study was conducted on four samples recovered 10 m apart, developing a characterization of the material and laboratory tests on each of them. The characterization consisted of the determination of intrinsic properties such as particle size distribution, particle shape, and mineralogy before and after testing; while the laboratory tests were conducted by means of the odometer test. The laboratory tests employed the oedometer test, which applies a vertical load in slow increments under K0 conditions to simulate the behavior of tailings consolidated in the impoundment.

    The results obtained from the oedometer tests showed interesting observations regarding changes in particle size distribution (PSD) before and after testing. Based on this study it is hard to conclude if the change in PSD solely is caused by crushing. Three samples show a PSD after oedometer which have slightly more fines than before oedometer, while the last sample has neglectable change in PSD. Theoretically, this small change in PSD indicates that larger tailings particles exhibited a higher susceptibility to some degree of crushing, but since the change is so small it cannot be excluded that the changes origins from the accuracy of determining the PSD.

     The samples taken at different depths were prepared using the tamping method, and the oedometer testing indicated minimal differences in their compression characteristics, and since the soil fabric was destroyed under sampling and then reconstituted through tamping this is expected. To investigate the influence of particle arrangement on the compression and potential crushing, one of the samples was tested in a slurry configuration. This test demonstrated that particle arrangement appears to be a contributing factor to crushing, as it showed less deviation in particle size distribution compared to the tamped sample.

    To contextualize and validate the findings, the results were correlated, evaluated, and compared with previous studies conducted on tailings from the same tailings storage facility (TSF). Although future research on crushing in correlation of mineralogy respectively and changes in particle shape are needed, this comparative analysis has provided input that can contribute to enhanced understanding of tailings behavior under increased vertical load.

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  • 42.
    Axelsson, Kennet B. E.
    et al.
    Luleå University of Technology.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Grennberg, Torsten
    Luleå University of Technology.
    Horrigmoe, Geir
    Luleå University of Technology.
    Johansson, Bernt
    Institutionen för Anläggningsteknik. Verksamhetsberättelse 1987/881988Report (Other (popular science, discussion, etc.))
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  • 43.
    Axelsson, Kennet B. E.
    et al.
    Luleå University of Technology.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Grennberg, Torsten
    Luleå University of Technology.
    Horrigmoe, Geir
    Luleå University of Technology.
    Johansson, Bernt
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Institutionen för Anläggningsteknik, Verksamhetsberättelse 1988/891989Report (Other (popular science, discussion, etc.))
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  • 44.
    Axelsson, Kennet B. E.
    et al.
    Luleå University of Technology.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Grennberg, Torsten
    Luleå University of Technology.
    Horrigmoe, Geir
    Luleå University of Technology.
    Johansson, Bernt
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Institutionen för Anläggningsteknik. Verksamhetsberättelse 1989/901990Report (Other (popular science, discussion, etc.))
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  • 45.
    Axelsson, Kennet B. E.
    et al.
    Luleå University of Technology.
    Johansson, Bernt
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Grennberg, Torsten
    Luleå University of Technology.
    Horrigmoe, Geir
    Luleå University of Technology.
    Institutionen för Anläggningsteknik. Verksamhetsberättelse 1990/911991Report (Other (popular science, discussion, etc.))
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  • 46.
    Axelsson, Kenneth
    et al.
    Luleå University of Technology.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Bro1990In: Nationalencyclopedin, Höganäs: Bra Böcker , 1990, p. 320-324Chapter in book (Other academic)
  • 47.
    Azzam, Omar
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    Driver ackordssystemet produktivitet i byggproduktion?: En studie av byggentreprenörers uppfattning2021Independent thesis Advanced level (professional degree), 300 HE creditsStudent thesis
    Abstract [en]

    To achieve continuous growth in society, a way forward is to ensure increased efficiency and productivity, the same applies to the construction industry. Some reports show that productivity in the construction sector has been stagnant for 80 years. Furthermore, some measurements even show that there has been a consistent decline in the construction industry's productivity. The construction industry has thus had weak growth in productivity.

    Studies have shown that there are several factors that could theoretically have an impact on productivity, these are Effectiveness, Efficiency, Quality, Working Quality and Innovation. These factors have been described based on several known theories. The theories have mainly dealt with two areas, Wage forms and Motivation and driving forces. In the construction sector, piecework wages have long been used as a wage system to regulate the wages of skilled workers. A discussion that may therefore be interesting is about the impact of piecework wages on productivity.

     The overall aim of the project is to seek production-related descriptions of what may explain why productivity in the construction industry has a low development. The degree project, therefore, seeks explanations for which factors are considered in construction management to have an impact on productivity. Furthermore, it is investigated whether and what effect the piecework wages have on productivity.

     The degree project has been based on three studies. Initially, a literature study was carried out which aimed to both create a theoretical basis and create a reference based on scientific articles, journals and literature that can be used to analyze the results against. The second study was a web-based survey sent out to 390 site managers to create an idea of what factors people in construction management consider contributing to increased productivity, and to capture site managers' perception on the piecework wages has an impact on productivity. Besides, productivity and piecework wages were also described and defined by site managers. The response rate was 35%. Finally, an in-depth survey was conducted. The in-depth survey is a result of the analysis carried out on the first survey. The in-depth survey was sent to 10 site managers. The response rate was 60%.

     The study shows that:

    • About 80 % of respondents believe that productivity has remained unchanged or decreased over the past 10 years. 80 % of the respondents also see a correlation between the piecework system and productivity in construction management. Furthermore, about 75 % believe that piecework contributes positively to productivity.
    • Respondents believe that commitment is the most important factor in increasing productivity.
    • Innovation and industrialization are undervalued when it comes to increasing productivity.
    • The results also indicate that the construction industry today does not agree on the definition of the concept of productivity.
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  • 48.
    Bagge, Niklas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Assessment of Concrete Bridges: Models and Tests for Refined Capacity Estimates2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Optimising the strategy for repairing, upgrading and replacing bridges in the European Union, and elsewhere, is becoming increasingly important due to ageing of the bridge stock, continuously increasing load requirements and budgetary limitations. Thus, there is a clear need to identify or develop, and implement, refined methods for assessing existing bridges in order to determine the most cost-effective options and actions to extend their lives, increase their capacities or replace them.Thus, the objective of the research project partly reported in this licentiate thesis is to verify and calibrate methods for refined assessment of existing bridges, using information acquired in an extensive program of experimental studies. In addition to describing parts of the project, the thesis is intended to provide a basis for suggestions and a discussion of the author’s future research in the area. It includes presentations of two experimental studies designed to evaluate, and calibrate, assessment methods:1. A laboratory-based experimental study of 12 two-span continuous reinforced concrete beams conducted in Dublin, Ireland, in 2012. The tests particularly focused on the beams’ nonlinear overall behaviour and related redistribution of internal forces.2. A full-scale test of a 55 year-old post-tensioned girder bridge in Kiruna, Sweden, in 2014, focusing on: (a) failure loading of the main girders, (b) failure loading of the slab, (c) the condition of post-tension cables, and (d) two strengthening systems using carbon fibre reinforced polymers (CFRP).The continuous reinforced concrete beams behaved in a nonlinear manner from an early stage in the loading. This is not usually considered in either the design or assessment of existing bridges, but should be for the verification to be accurate at the serviceability and ultimate limit states (SLS and ULS, respectively). The results also indicated that there was more redistribution of internal forces at the ULS than stated in standards. Thus, use of refined methods to assess bridges or other reinforced concrete structures can be beneficial for avoiding unnecessary repairs, strengthening or replacement measures. In addition, the tests demonstrated the importance of taking into account the interaction between flexural moments and shear forces. This is not considered in shear force resistance models included in, for example, the European standard.To date, too few reinforced concrete bridges have been tested to failure to parameterise assessment models robustly with low uncertainty levels. Thus, a programme aimed for verification and calibration of models for assessing existing bridges was designed. The comprehensive programme is described in the thesis, which also provides suggestions and a discussion for future research based on the tests and associated monitoring.During the full-scale tests of the Kiruna Bridge, data were acquired that are relevant to investigations in several fields related to bridge assessment. For instance the obtained data provide foundations for future research concerning: (a) the robustness, ductility and bridge behaviour, (b) the shear force and punching resistance of bridge girders and slabs, (c) assessment of post-tensioned steel cables’ condition, (d) strengthening methods using CFRP, (e) updating finite element models, and (f) reliability-based analysis.

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  • 49.
    Bagge, Niklas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Structural assessment procedures for existing concrete bridges: Experiences from failure tests of the Kiruna Bridge2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Assessing existing bridges is an important task in the sustainable management ofinfrastructure. In practice, structural bridge assessments are usually conducted usingtraditional and standardised methods, despite knowledge that these methods oftenprovide conservative estimates. In addition, more advanced methods are available, suchas nonlinear finite element (FE) analysis, that are used for research purposes and cansimulate the structural behaviour of bridges more accurately. Therefore, it would beuseful to develop practical and reliable procedures for refined assessments using theseadvanced techniques.Focusing on the ultimate load-carrying capacity of existing concrete bridges, this thesispresents a procedure for structural assessments. The fundamental idea is to improve theassessment successively, as necessary to predict bridges’ structural behaviour adequately.The procedure involves a multi-level assessment strategy with four levels of structuralanalysis, and an integrated framework for safety verification. At the initial level (Level 1)of the multi-level strategy, traditional standardised methods are used, no failures arecovered implicitly in the structural analysis and action effects are verified using localresistances calculated using analytical models. In the subsequent enhanced levels (Levels2 – 4), nonlinear FE analysis is used for stepwise integration of the verification of flexural,shear-related and anchorage failures into the structural analysis. The framework for safetyverifications includes partial safety factor (PSF), global resistance safety factor (GRSF) andfull probabilistic methods. Within each of these groups, verifications of desired safetymargins can be conducted with varying degrees of complexity.To demonstrate and evaluate the proposed structural assessment procedure, comparativestudies have been carried out, based on full-scale tests of a prestressed concrete bridge.This was the Kiruna Bridge, located in the northernmost city in Sweden, which was duefor demolition as part of a city transformation project, necessitated by large grounddeformations caused by the large nearby mine. Thus, it was available for destructiveexperimental investigation within the doctoral project presented in this thesis. The bridgehad five continuous spans, was 121.5 m long and consisted of three parallel girders with a connecting slab at the top. Both the girders and slab were tested to failure to investigatetheir structural behaviour and load-carrying capacity. Non-destructive and destructivetests were also applied to determine the residual prestress forces in the bridge girders andinvestigate the in situ applicability of methods developed for this purpose. The so-calledsaw-cut method and decompression-load method were used after refinement to enabletheir application to structures of such complexity. The variation of the experimentallydetermined residual prestress forces was remarkably high, depending on the sectioninvestigated. There were also high degrees of uncertainty in estimated values, and thusare only regarded as indications of the residual prestress force.Level 1 analysis of the multi-level assessment strategy consistently underestimatedcapacity, relative to the test results, and did not provide accurate predictions of the shearrelatedfailure observed in the test. With linear FE analysis and local resistance modelsdefined by the European standard, Eurocode 2, the load-carrying capacity wasunderestimated by 32 % for the bridge girder and 55 % for the bridge deck slab. At theenhanced level of structural analysis (Level 3), nonlinear FE analyses predicted thecapacities with less than 2 % deviation from the test results and correctly predicted thefailure mode. However, for existing bridges there are many uncertainties, for instance,the FE simulations were sensitive to the level of residual prestressing, boundaryconditions and assumed material parameters. To accurately take these aspects intoaccount, bridge-specific information is crucial.The complete structural assessment procedure, combining the multi-level strategy andsafety verification framework, was evaluated in a case study. Experiences from theprevious comparative studies were used in an assessment of the Kiruna Bridge followingthe Swedish assessment code. The initial assessment at Level 1 of the multi-level strategyand safety verification, using the PSF method, indicated that the shear capacity of one ofthe girders was critical. The most adverse load case (a combination of permanent loads,prestressing and variable traffic loads) was further investigated through enhancedstructural analyses implicitly accounting for flexural and shear-related failures (Level 3).Nonlinear FE analysis and safety evaluation using the PSF method, several variants of theGRSF method and the full probabilistic analysis for resistance indicated that the permittedaxle load for the critical classification vehicle could be 5.6 – 6.5 times higher than thelimit obtained from the initial assessment at Level 1. However, the study also indicatedthat the model uncertainty was not fully considered in these values. The modeluncertainty was shown to have strong effects on the safety verification and (thus)permissible axle loads. The case study also highlighted the need for a strategy forsuccessively improving structural analysis to improve understanding of bridges’ structuralbehaviour. The refined analysis indicated a complex failure mode, with yielding of thestirrups in the bridge girders and transverse flexural reinforcement in the bridge deck slab,but with a final shear failure of the slab. It would be impossible to capture suchcomplexity in a traditional standardised assessment, which (as mentioned) indicated thatthe shear capacity of the girder limited permissible axle loads. However, nonlinear FEanalyses are computationally demanding, and numerous modelling choices are required.Besides a strategy for rationally improving the analysis and helping analysts to focus oncritical aspects, detailed guidelines for nonlinear FE analysis should be applied to reduce the analyst-dependent variability of results and (thus) the model uncertainty. Clearly, toensure the validity of bridge assessment methods under in situ conditions, theirevaluations should include in situ tests. This thesis presents outcomes of such tests, therebyhighlighting important aspects for future improvements in the assessment of existingbridges.

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  • 50.
    Bagge, Niklas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Bernspång, Lars
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Carolin, Anders
    Trafikverket, SE-972 42, Luleå, Sweden.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Full-Scale Test to Failure of a Prestressed Concrete Bridge in Kiruna2014In: Nordic Concrete Research, ISSN 0800-6377, Vol. 50, p. 83-86Article in journal (Refereed)
    Abstract [en]

    To calibrate methods for condition assessment of prestressed concrete (PC) bridges, tests areplanned for a 50 year old five-span bridge with a length of 121 m in Kiruna in northern Sweden.Both non-destructive and destructive full-scale tests will be performed. This paper summarisesthe test programme, which comprises evaluation of the structural behaviour of the bridge, theresidual forces in the prestressed steel, methods for strengthening using carbon fibre reinforcedpolymers (CFRP) and the shear resistance of the bridge slab.

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