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  • 1.
    Ríos Bayona, Francisco
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Analytical and numerical approaches to estimate peak shear strength of rock joints2019Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    In Sweden, there exists a large number of dams. Many of them are founded on rock masses normally affected by the presence of sub-horizontal rock fractures, which makes sliding along rock joints under the dam foundation one of the most critical failure mechanism. Various attempts have been made to relate the peak shear strength of rock joints to measurable parameters. However, the uncertainty in the determination of the shear strength of rock joints is nonetheless still significant.The main aim of this thesis is to investigate, develop and apply analytical and numerical techniques for estimation of peak shear strength of natural and unfilled rock joints. In a first step, the peak shear strength of several natural and unfilled rock joint was calculated by using surface aperture measurements from high-resolution optical scanning and a modified version of the analytical criterion previously developed by Johansson and Stille in 2014. In a second step, PFC2D was utilised to perform numerical shear tests on two-dimensional profiles selected from high-resolution optical scanning on unweathered and perfectly mated tensile induced rock joints.The results from the analytical approach show that the calculated peak shear strengths of the analysed samples are in good agreement compared with the laboratory investigations. Conversely, the obtained results from the numerical approach show lower peak shear strengths in the analysed two-dimensional profiles compared with the conducted laboratory shear tests.The analytical approach together with the advanced techniques to measure surface roughness available today, may be a possible way forward towards a methodology to determine peak shear strength of large-scale natural rock joints in-situ.

  • 2.
    Bekele, Abiy
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Application of Automated Non-contact Resonance Testing for Low Temperature Behavior of Asphalt Concrete2019Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Impact resonance testing is a well-documented non-destructive testing method and its applications on asphalt concrete have also been implemented successfully. The test is carried out manually by inducing an impact in order to excite the test specimen and taking measurements of the vibrational response. In an effort to improve the manual procedure of impact resonance testing, an automated non-contact methodology is developed and its applicability with regards to low temperature behaviors of asphalt concrete is investigated. Results from this work show that repeatable fundamental resonance frequency measurements can be performed on a disc shaped specimen in an automated manner without the need to open the thermal chamber. The measurements obtained from the new method have been verified by taking similar resonance frequency measurements using an instrumented impact hammer. It has also been shown in this work that the proposed method is suitable to investigate the lone effects of cyclic thermal conditioning on asphalt concrete without any other possible biasing effects associated with contact in the conventional testing. A hysteretic behavior of stiffness modulus is obtained on three different asphalt concrete specimens subjected to repeated low temperature cyclic conditioning. Reduced modulus values at each temperature are obtained in all the tested specimens after a low temperature stepwise conditioning at temperatures from 0oC to -40 oC. This observed behavior shows that the dynamic modulus of the tested specimens is affected by low temperature conditioning. The norm of the complex modulus decreases and the phase angle or damping ratio increases after low temperature conditioning. Hence, valuable and practical low temperature characteristics of different asphalt concrete mixtures can possibly be obtained by using the proposed methodology.

  • 3.
    Shamu, John
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    On the measurement and application of cement grout rheological properties2019Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The rheological properties of cement-based grouts play a key role in determining the final spread in grouted rock formations. Rheologically, cement grouts are known to be complex thixotropic fluids, but their steady flow behavior is often described by fitting the simple Bingham constitutive law to flow curve data. The resultant Bingham parameters are then used in grouting design of e.g. tunnels, to estimate the penetration length. Since cement grouts are thixotropic suspensions, the interpretation of their flow curves as obtained from flow sweeps in concentric cylinder rotational rheometers is often complicated by: the presence of wall slip, sedimentation and unstable flow at low shear rates. A systematic approach to study these effects within the constraints of the concentric cylinder geometry (Couette) and for different cement grout concentrations was carried out as part of the Licentiate research work. Of particular interest was the influence of geometry and flow sweep measurement interval on flow curves, including the characteristic unstable flow branch that appears at applied shear rates that are below the critical shear rate. The unstable flow branch observed below the critical shear rate has been described as a characteristic feature in the flow curves of thixotropic suspensions, e.g. cement grouts, laponite. From a practical standpoint, this information can then be readily used to improve rheological measurements of cement grouts. The existence of the critical shear rate below which no stable flow occurs, plus the complex wall slip phenomenon are then discussed by considering how they affect actual spread in rough and smooth rock fractures.

    Another major part of the research presented in this thesis relates to the measurement of model yield stress fluid (YSF), i.e. Carbopol, velocity profiles within the radial flow geometry. Radial flow between parallel plates, is an idealized fundamental flow configuration that is often used as a basis for grout spread estimation in planar rock fractures. Compared to other flow configurations with YSFs, e.g. channels, only a limited amount of work has presented analytical solutions, numerical models and especially experimental work for radial flow. Thus, as a first step towards more systematic studies of the plug flow region of YSFs in radial flow the current work presents the design, manufacture and for the first time velocity profile measurements that were conducted by using the pulsed Ultrasound Velocity Profiling (UVP) technique. The current observations for tests carried out with different disk spacings and flow rates show a distinct plug region, coupled with wall slip effects for the Carbopol model YSF fluid that was used. The theoretically predicted velocity profiles and the measured ones agree reasonably well, and the main discrepancies are discussed. Future studies, would then be targeted at improving the current experimental setup, for detailed measurements of the plug flow region along the radial length, which remains a challenging issue for studies on YSFs and engineering applications such as rock grouting design.

  • 4.
    Cebecauer, Matej
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Transport planning.
    Short-Term Traffic Prediction in Large-Scale Urban Networks2019Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    City-wide travel time prediction in real-time is an important enabler for efficient use of the road network. It can be used in traveler information to enable more efficient routing of individual vehicles as well as decision support for traffic management applications such as directed information campaigns or incident management. 3D speed maps have been shown to be a promising methodology for revealing day-to-day regularities of city-level travel times and possibly also for short-term prediction. In this paper, we aim to further evaluate and benchmark the use of 3D speed maps for short-term travel time prediction and to enable scenario-based evaluation of traffic management actions we also evaluate the framework for traffic flow prediction. The 3D speed map methodology is adapted to short-term prediction and benchmarked against historical mean as well as against Probabilistic Principal Component Analysis (PPCA). The benchmarking and analysis are made using one year of travel time and traffic flow data for the city of Stockholm, Sweden. The result of the case study shows very promising results of the 3D speed map methodology for short-term prediction of both travel times and traffic flows. The modified version of the 3D speed map prediction outperforms the historical mean prediction as well as the PPCA method. Further work includes an extended evaluation of the method for different conditions in terms of underlying sensor infrastructure, preprocessing and spatio-temporal aggregation as well as benchmarking against other prediction methods.

  • 5.
    Leffler, David
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Transport planning.
    Simulation based evaluation of flexible transit2019Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Transport authorities are faced with the challenge of making effective use of existing transportation infrastructure under increasing needs of transport accessibility, sustainability, and safety. The ongoing growth and adoption of shared mobility options, the anticipation of automated vehicles, and the increased availability of real-time data brought on with the developments of Intelligent Transport Systems, have all inspired many innovations in public transit design. The integration of these technologies in existing public transit holds great potential for operational planning and control, but is also notoriously difficult to evaluate. In the included papers, flexible operational policies that make use of real-time data and connected vehicles are developed and assessed through the extension of an existing public transit simulation framework, BusMezzo.

    Paper I explores the incorporation of flexibility in fixed urban transit via real-time short-turning, a fleet management strategy not often studied in a real-time context. In this paper, a decision rule for when and where a short-turn should occur based on predicted passenger costs is developed and evaluated in a case study of a bidirectional urban bus line in Stockholm, Sweden.

    Paper II focuses on the design and analysis of an automated feeder service. In this paper an extension of BusMezzo with a module for simulating a variety of flexible transit operations is presented. Estimated reductions in on-board crew costs with vehicle automation motivate a case study of two vehicle fleets where a fully demand-responsive operational policy is compared against fixed route and schedule operations.

  • 6.
    Lövqvist, Lisa
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Towards frost damage prediction in asphaltic pavements2019Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Roads are subjected to mechanical loads from the traffic as well as deteriorating mechanisms originating from the surrounding environment and climate. The damage arising is particularly severe during the winter season, when for example raveling, pot holes and cracks can emerge on the surfaces of asphaltic roads. These winter related damages are difficult to characterize and predict, partly due to the complexity of the asphalt material and partly since they cannot be linked to one single phenomenon but several, such as the (long term) existence of moisture, frost damage and frost heave, low temperature cracking and the embrittlement of the mastic at low temperatures. Further adding to the complexity is the combination of these phenomena which may accelerate the emergence and evolution of the damage mechanisms. This licentiate research project is mainly focusing on the emergence and development of frost damage in the asphalt layer but will include the effect of other damage mechanisms in its continuation. The goal of the project is to develop a multiscale model able to predict the damage development in an asphalt pavement during a desired period of time, to enhance maintenance predictions as well as pavement design choices. This licentiate thesis is the first part of this project and aims to lay the foundation of the multiscale model. To achieve this, a micromechanical model of frost damage in asphalt mixtures has been developed. This model couples the moisture and mechanical damage happening on the short and long term, caused by the infiltration of moisture and the expansion of water turning into ice during temperature drops. Both possible adhesive damage in the mastic-aggregate interface and cohesive damage in the mastic is included. In addition to the developed micromechanical model, this thesis presents the overall concept for the formulation of the multiscale model as well as discusses about its motivations and advantages.

  • 7.
    Liu, Fangzhou
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Dynamic analysis of hollow core concrete floors2018Licentiate thesis, comprehensive summary (Other academic)
  • 8.
    Zangeneh Kamali, Abbas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. ELU Konsult AB.
    Dynamic Soil-Structure Interaction Analysis of Railway Bridges: Numerical and Experimental Results2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The work reported in this thesis presents a general overview of the dynamic response of short-span railway bridges considering soil-structure interaction. The study aims to identify the effect of the surrounding and underlying soil on the global stiffness and damping of the structural system. This may lead to better assumptions and more efficient numerical models for design.A simple discrete model for calculating the dynamic characteristics of the fundamental bending mode of single span beam bridges on viscoelastic supports was proposed. This model was used to study the effect of the dynamic stiffness of the foundation on the modal parameters (e.g. natural frequency and damping ratio) of railway beam bridges. It was shown that the variation in the underlying soil profiles leads to a different dynamic response of the system. This effect depends on the ratio between the flexural stiffness of the bridge and the dynamic stiffness of the foundation-soil system but also on the ratio between the resonant frequency of the soil layer and the fundamental frequency of the bridge.

    The effect of the surrounding soil conditions on the vertical dynamic response of portal frame bridges was also investigated both numerically and experimentally. To this end, different numerical models (i.e. full FE models and coupled FE-BE models) have been developed. Controlled vibration tests have been performed on two full-scale portal frame bridges to determine the modal properties of the bridge-soil system and calibrate the numerical models. Both experimental and numerical results identified the substantial contribution of the surrounding soil on the global damping of short-span portal frame bridges. A simplified model for the surrounding soil was also proposed in order to define a less complicated model appropriate for practical design purposes.

  • 9.
    Zäll, Emma
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Footbridge Dynamics: Human-Structure Interaction2018Licentiate thesis, monograph (Other academic)
    Abstract [en]

    For aesthetic reasons and due to an increased demand for cost-effective and environmentally friendly civil engineering structures, there is a trend in designing light and slender structures. Consequently, many modern footbridges are susceptible to excessive vibrations caused by human-induced loads. To counteract this, today's design guidelines for footbridges generally require verification of the comfort criteria for footbridges with natural frequencies in the range of pedestrian step frequencies. To ensure that a certain acceleration limit is not exceeded, the guidelines provide simplified methodologies for vibration serviceability assessment.

    However, shortcomings of these methodologies have been identified. First, for certain footbridges, human-structure interaction (HSI) effects might have a significant impact on the dynamic response. One such effect is that the modal properties of the bridge change in the presence of a crowd; most importantly, the damping of the bridge is increased. If this effect is neglected, predicted acceleration levels might be overestimated. Second, as a running person induces a force of greater amplitude than a walking person, a single runner might cause a footbridge to vibrate excessively. Hence, the running load case is highly relevant. These two aspects have in common that they are disregarded in existing design guidelines.

    For the stated reasons, the demand for improvements of the guidelines is currently high and, prospectively, it might be necessary to require the consideration of both the HSI effect and running loads. Therefore, this licentiate thesis aims at deepening the understanding of these subjects, with the main focus being placed on the HSI effect and, more precisely, on how it can be accounted for in an efficient way.

    A numerical investigation of the HSI effect and its impact on the vertical acceleration response of a footbridge was performed. The results show that the HSI effect reduces the peak acceleration and that the greatest reduction is obtained for a crowd to bridge frequency ratio close to unity and a high crowd to bridge mass ratio. Furthermore, the performance of two simplified modelling approaches for consideration of the HSI effect was evaluated. Both simplified models can be easily implemented and proved the ability to predict the change in modal properties as well as the structural response of the bridge. Besides that, the computational cost was reduced, compared to more advanced models.

    Moreover, a case study comprising field tests and simulations was performed to investigate the effect of runners on footbridges. The acceleration limit given in the design guideline was exceeded for one single person running across the bridge while a group of seven people walking across the bridge did not cause exceedance of the limit. Hence, it was concluded that running loads require consideration in the design of a footbridge.

  • 10.
    Lundberg, Joacim
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials. VTI - Statens Väg- och Transportforskningsinstitut.
    Non-Exhaust PM10 and Road Dust2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Non-exhaust PM10 is an issue in the urban environment linked to health issues. Emissions of non-exhaust PM10 is relatable to pavement properties. Also of importance is resuspension of road dust stored from surfaces. This depends on the traffic and metrological conditions. Given this, the purpose of the thesis was to give an overview limited to Sweden and the Nordic countries regarding non-exhaust PM10 emissions and road dust.

    The overview includes how particles are related to human health. Also included is the principle of how particles are emitted from road surface and tyre interaction, both directly and through resuspension of road dust. This thesis also includes an overview of how the use of studded tyres impact on asphalt surfacings and how the properties of the materials used impact on the abrasion wear. This is then linked to the emissions of non-exhaust particles. Further described is how measurements can be done of ambient particles and road dust, followed on two major models for road abrasion wear and non-exhaust PM prediction. Also included is how road operation, e.g. traction sanding and dust binding, influence the particle emissions together with other options to reduce the emissions through, e.g. limiting the use of studded tyres.

    One special issue discussed in this thesis is the lack of holistic view regarding the environmental problems in the urban environment with focus on particle emissions and road noise emissions, both from the road surface and tyre interaction. Currently the most problematic issue is prioritized and the resulting solution to that specific problem might increase other problems.

    This thesis shows that much knowledge is available regarding non-exhaust PM10 emissions and road dust, but also that several knowledge gaps exists. Several suggestions on further studies is given together with a brief overview on the continued work forward from this thesis.

  • 11.
    Eriksson, Daniel
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Numerical models for degradation of concrete in hydraulic structures due to long-term contact with water2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The durability of concrete is of major concern in all types of concrete structures where the combined effect of exposure conditions and the type and quality of the concrete material usually determines the rate of degradation. Furthermore, there are synergy effects between different deterioration mechanisms, which means that the combined rate of degradation is higher than the sum of the individual rates of each mechanism. Therefore, to accurately predict the residual service life of existing structures or when designing new structures, it is essential to consider all these aspects. This means that various chemical and physical processes, as well as how these interact, must be taken into account in models aiming to be used for service life predictions.

    This thesis presents the first part of a research project with the aim to investigate common deterioration mechanisms of concrete in hydraulic structures, and to improve the knowledge how these and other related phenomena can be described using mathematical models. The objective is also to study how different mechanisms interact and to find suitable approaches to account for these interactions in the models. To this end, a literature survey on commonly detected damage in hydraulic structures is presented. In addition, it also addresses in what types of and where in hydraulic structures the various damage types are usually observed. The mathematical models presented in this part of the project are focused on long-term water absorption in air-entrained concrete as well as on freezing of partially saturated air-entrained concrete. Both models are based on a multiphase description of concrete and poromechanics to describe the coupled hygro-thermo-mechanical behaviour. The thesis also presents some of the basic concepts of multiphase modelling of porous media, including discretization of the models using the finite element method (FEM). Furthermore, it covers the simplifications that are usually introduced in the general macroscopic balance equations for mass, energy and linear momentum when modelling cement-based materials.

    To verify the developed models and to show their capabilities, simulation results are compared with experimental data, in situ measurements and other simulations from the literature. The results indicate that both models perform well and can be used to predict long-term moisture conditions in hydraulic structures as well as freezing-induced strains in partially saturated air-entrained concrete, respectively. Even though no interactions with other deterioration mechanisms are included in the models, the development and use of these have given insights to which parameters that are important to consider in such extensions. Furthermore, based on the insights gained, the complexity of describing the full interactions between several mechanisms in mathematical models is also discussed. It is concluded that models aiming to be used for service life predictions of hydraulic structures in day-to-day engineering work need to be simplified. However, the type of advanced models presented in this thesis can serve as a basis to study which aspects and parameters that are essential to consider in simplified prediction models.

  • 12.
    Johansson, Ingrid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Transport Planning, Economics and Engineering.
    Simulation Studies of Impact of Heavy-Duty Vehicle Platoons on Road Traffic and Fuel Consumption2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The demand for road freight transport continues to grow with the growing economy, resulting in increased fossil fuel consumption and emissions. At the same time, the fossil fuel use needs to decrease substantially to counteract the ongoing global warming. One way to reduce fuel consumption is to utilize emerging intelligent transport system (ITS) technologies and introduce heavy-duty vehicle (HDV) platooning, i.e. HDVs driving with small inter-vehicle gaps enabled by the use of sensors and controllers. It is of importance for transport authorities and industries to investigate the effects of introducing HDV platooning. Previous studies have investigated the potential benefits, but the effects in real traffic, both for the platoons and for the surrounding vehicles, have barely been explored. To further utilize ITS and optimize the platoons, information about the traffic situation ahead can be used to optimize the vehicle trajectories for the platoons. Paper I presents a dynamic programming-based optimal speed control including information of the traffic situation ahead. The optimal control is applied to HDV platoons in a deceleration case and the potential fuel consumption reduction is evaluated by a microscopic traffic simulation study with HDV platoons driving in real traffic conditions. The effects for the surrounding traffic are also analysed. Paper II and Paper III present a simulation platform to assess the effects of HDV platooning in real traffic conditions. Through simulation studies, the potential fuel consumption reduction by adopting HDV platooning on a real highway stretch is evaluated, and the effects for the other vehicles in the network are investigated.

  • 13.
    Vieira, Tiago
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials. VTI.
    Tyre-road Interaction: a holistic approach to noise and rolling resistance2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Energy dissipation, fuel consumption, real-estate property prices and health issues are some of the aspects related to the tyre/pavement interaction and its functional properties of rolling resistance and noise. The first two aspects are affected by the tyre/road interaction as energy is dissipated mostly by hysteretic losses as the tyre is subjected to dynamic deformations when contacting the pavement surface. The other effect of this contact system that is analysed in this thesis is noise. Excessive noise exposure leads to a decrease in real-estate property values and even health issues such as increased blood pressure, sleep disturbance, cognitive impairment in children, among others.

    To mitigate such issues, a good understanding of the underlying causes is crucial and therefore a holistic approach was used to analyse the contact interaction in a more comprehensive way, encompassing the pavement, tyre, environmental and contact media (contaminations). Both noise and rolling resistance were analysed after subjecting the contact system to controlled interventions in one variable while maintaining the other variables constant and then comparing to a reference condition. In the first part of the investigative work, different tyres were tested while maintaining the pavement, environment and contact media constant, allowing an evaluation of the impact of winter tyres on noise and rolling resistance. In the second part, an intervention in the pavement was applied while maintaining the other variables constant. allowing an evaluation of the impact of surface grinding on noise and rolling resistance.

    The first part quantified how noisier studded tyres are in comparison to non-studded tyres, yet no substantial difference in rolling resistance was found. The second part revealed the potential of the horizontal grinding to reduce noise and rolling resistance, having a limitation, on the duration of such effects, especially for Swedish roads where studded tyres are used.

  • 14.
    Sjölander, Andreas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Analyses of shotcrete stress states due to varying lining thickness and irregular rock surfaces2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Shotcrete is sprayed concrete applied pneumatically under high pressure and was invented in the beginning of the 1900's. This new technique decreased the construction time and since steel fibres were introduced in the shotcrete during the 1970's, shotcrete has been the primary support method for tunnels.

    Tunnels excavated with the drill and blast method creates a highly irregular rock surface which results in a shotcrete lining with varying thickness. The structural behaviour as well as the loads acting on the shotcrete lining depends on the interaction between the shotcrete, rock and rock bolts. There are several parameters influencing this interaction, e.g. bond strength, the stiffness of the rock and thickness of the shotcrete. All of these parameters are difficult to predict accurately which makes the structural design of the lining to a complex problem.

    This thesis present the first part of a research project with the long-term goal to improve the understanding of the structural behaviour of the shotcrete lining. To achieve this, numerical modelling have been used to study the build up of stresses and cracking of shotcrete when subjected to restrained loading caused by e.g. temperature differences and drying shrinkage. The response in the lining when subjected to a gravity load from a block has also been studied. The model is capable of describing the non-linear deformation behaviour of both plain and fibre reinforced shotcrete and uses presented in situ variations in thickness to more accurately account for the effects of expected variations in thickness. The thesis discuss and demonstrate the effect of important loads that acts on the shotcrete lining and how the irregular geometry of the rock surface in combination with the varying thickness of the shotcrete affect the development of stresses in the lining. It is also discussed how a full or partial bond failure affect the structural capacity of a shotcrete lining.  

     

  • 15.
    Teng, Penghua
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Hydraulic Engineering.
    CFD MODELLING OF TWO-PHASE FLOWS AT SPILLWAY AERATORS2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Due to the high-speed flow in a chute spillway, cavitation damages often occur. This undesired phenomenon threatens the safety of the structure. For the purpose of eliminating the damages, an aerator is often installed in the spillway. To understand its characteristics, physical model tests are a popular method. To complement the model tests, computation fluid dynamics (CFD) simulations are used to study aerator flows. To represent the two-phase flows, multiphase models should be employed. This thesis examines two of them, namely, the Volume-Of-Fluid model (VOF) and Two-Fluid model.

    Based on the background of the Bergeforsen dam, the aerator flow is modelled by means of the VOF model. The simulated spillway discharge capacity is in accordance with the experimental data. Compared with the results, empirical formulas fail to evaluate the air supply capacity of aerator as it is wider than the conventional width. A hypothetical vent modification is proposed. For the original and proposed layouts, the study illustrates the difference in the air-flow conditions. The results show that a larger vent area is, for a large-width aerator, preferable in the middle of the chute.

    To study the flip bucket-shaped aerators in the Gallejaur dam, physical model tests and prototype observations are conducted. The results lead to contradicting conclusions in terms of jet breakup and air entrainment. A CFD model is, as an option, employed to explain the reason of the discrepancy. The numerical results coincide with the prototype observations. The jet breakup and air entrainment are evaluated from air cavity profiles; the air-pressure drops are small in the cavity. The discrepancy is due to overestimation of the surface-tension effect in the physical model tests.

    Based on the experimental data of an aerator rig at the Laboratory of Hydraulics, Hydrology and Glaciology (VAW), ETH Zurich, the Two-Fluid model is used to predict air concentration distributions in the aerated flow. The model includes relevant forces governing the motion of bubbles and considers the effects of air bubble size. The numerical results are conformable to the experiments in the air cavity zone. Downstream of the cavity, the air concentration near the chute bottom is higher, which is presumably caused by the fact that the interfacial forces in the Two-Fluid model are underestimated.

  • 16.
    Elgazzar, Hesham
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    End-Shield Bridges for High-Speed Railway: Full scale dynamic testing and numerical simulations2017Licentiate thesis, monograph (Other academic)
    Abstract [en]

    The increasing need for High-Speed Railway (HSR) to reduce the travelling time requires increasing research within this field. Bridges are main components of any railway network, including HSR networks, and the optimization of their design for this purpose would contribute to a faster and more cost effective development of the HSR network. The initial investment, the running and maintenance costs of the bridges can be decreased through better understanding of the their dynamic behaviour.

    This thesis studies the dynamic behaviour of end-shield railway bridges under HSR operation. 2D beam analysis is used to study the effect of the distribution of the train’s axle load. Relatively accurate 3D FE-models are developed to study the effect of Soil-Structure Interaction (SSI) and the dynamic response of the bridges. Modelling alternatives are studied to develop an accurate model. A full scale test of a simply supported Bridge with end-shields using load-controlled forced excitation was performed and the results were used to verify the theoretical models.

    A manual model updating process of the material properties of the 3D FE-model is performed using FRFs from the field measurements. A Simple 2D model is also developed, where a spring/dashpot system is implemented to simplify SSI, and updated to reproduce the field measured responses.

    The conclusions of the project emphasize the importance of SSI effects in the dynamic analysis of end-shield bridges for predicting their dynamic behaviour.

    The conclusions also show that the modelling of the surrounding soil and the assumption of the soil material parameters have significant effect on the dynamic response. Even the boundary conditions, bedrock level and the ballast on the railway track affects the response. The results also show that the bridge’s concrete section behaves as uncracked section under the studied dynamic loading.

  • 17.
    Al-Ayish, Nadia
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology.
    Environmental Impact of Concrete Structures - with Focus on Durability and Resource Efficiency2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Concrete is essential for the construction industry with characteristic properties that make it irreplaceable in some aspects. However, due to the large volumes consumed and the energy intense cement clinker production it also has a notable climate impact. In order to reach the international and national sustainability goals it is therefore important to reduce the climate impact of concrete structures.

    There are many ways to influence the environmental impact of concrete and a detailed analysis is one of the actions that could push the industry and the society towards a sustainable development. The purpose of this research is to evaluate the environmental impact of concrete structures and the built environment and to highlight the possibilities to reduce that impact with choice of concrete mix and innovative design solutions.

    A life cycle assessment (LCA) was carried out to analyze the environmental impact of two thin façade solutions with innovative materials and to evaluate influences of different greenhouse gas reducing measures on concrete bridges. The influence of supplementary cementitious materials (SCM) in terms of climate impact and durability was also analyzed.

    The results indicate that SCMs have a twofold effect on the climate impact of reinforced concrete structures. Not only do they reduce the greenhouse gases through cement clinker replacement but also by an improvement of durability regarding chloride ingress. Currently, this is not considered in the regulations, which makes it difficult to foresee in LCA at early design stages. The results also show great possibilities to reduce the climate impact through different measures and design alternatives and the need for further development of products and solutions.

  • 18.
    Bjureland, William
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    On reliability-based design of rock tunnel support2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Tunneling involves large uncertainties. Since 2009, design of rock tunnels in European countries should be performed in accordance with the Eurocodes. The main principle in the Eurocodes is that it must be shown in all design situations that no relevant limit state is exceeded. This can be achieved with a number of different methods, where the most common one is design by calculation. To account for uncertainties in design, the Eurocode states that design by calculation should primarily be performed using limit state design methods, i.e. the partial factor method or reliability-based methods. The basic principle of the former is that it shall be assured that a structure’s resisting capacity is larger than the load acting on the structure, with high enough probability. Even if this might seem straightforward, the practical application of limit state design to rock tunnel support has only been studied to a limited extent.

    The aim of this licentiate thesis is to provide a review of the practical applicability of using reliability-based methods and the partial factor method in design of rock tunnel support. The review and the following discussion are based on findings from the cases studied in the appended papers. The discussion focuses on the challenges of applying fixed partial factors, as suggested by Eurocode, in design of rock tunnel support and some of the practical difficulties the engineer is faced with when applying reliability-based methods to design rock tunnel support.

    The main conclusions are that the partial factor method (as defined in Eurocode) is not suitable to use in design of rock tunnel support, but that reliability-based methods have the potential to account for uncertainties present in design, especially when used within the framework of the observational method. However, gathering of data for statistical quantification of input variables along with clarification of the necessary reliability levels and definition of “failure” are needed.

  • 19.
    Solat Yavari, Majid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Slab Frame Bridges: Structural Optimization Considering Investment Cost and Environmental Impacts2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This research encompasses the automated design and structural optimization of reinforced concrete slab frame bridges, considering investment costs and environmental impacts. The most important feature of this work is that it focusses on realistic and complete models of slab frame bridges rather than on optimization of only individual members or sections of a bridge. The thesis consists of an extended summary of publications and three appended papers. In the first paper, using simple assumptions, the possibility of applying cost-optimization to the structural design of slab frame bridges was investigated. The results of the optimization of an existing constructed bridge showed the potential to reduce the investment cost of slab frame bridges. The procedure was further developed in the second paper. In this paper, automated design was integrated to a more refined cost-optimization methodology based on more detailed assumptions and including extra constructability factors. This procedure was then applied to a bridge under design, before its construction. From the point of view of sustainability, bridge design should not only consider criteria such as cost but also environmental performance. The third paper thus integrated life cycle assessment (LCA) with the design optimization procedure to perform environmental impact optimization of the same case study bridge as in the second paper. The results of investment cost and environmental impact optimization were then compared. The obtained results presented in the appended papers highlight the successful application of optimization techniques to the structural design of reinforced concrete slab frame bridges. Moreover, the results indicate that a multi-objective optimization that simultaneously considers both environmental impacts and investment cost is necessary in order to generate more sustainable designs. The presented methodology has been applied to the design process for a time-effective, sustainable, and optimal design of concrete slab frame bridges.

  • 20.
    Neves, Cláudia
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Structural Health Monitoring of Bridges: Model-free damage detection method using Machine Learning2017Licentiate thesis, monograph (Other academic)
    Abstract [en]

    This is probably the most appropriate time for the development of robust and reliable structural damage detection systems as aging civil engineering structures, such as bridges, are being used past their life expectancy and beyond their original design loads. Often, when a significant damage to the structure is discovered, the deterioration has already progressed far and required repair is substantial. This is both expensive and has negative impact on the environment and traffic during replacement. For the exposed reasons the demand for efficient Structural Health Monitoring techniques is currently extremely high. This licentiate thesis presents a two-stage model-free damage detection approach based on Machine Learning. The method is applied to data gathered in a numerical experiment using a three-dimensional finite element model of a railway bridge. The initial step in this study consists in collecting the structural dynamic response that is simulated during the passage of a train, considering the bridge in both healthy and damaged conditions. The first stage of the proposed algorithm consists in the design and unsupervised training of Artificial Neural Networks that, provided with input composed of measured accelerations in previous instants, are capable of predicting future output acceleration. In the second stage the prediction errors are used to fit a Gaussian Process that enables to perform a statistical analysis of the distribution of errors. Subsequently, the concept of Damage Index is introduced and the probabilities associated with false diagnosis are studied. Following the former steps Receiver Operating Characteristic curves are generated and the threshold of the detection system can be adjusted according to the trade-off between errors. Lastly, using the Bayes’ Theorem, a simplified method for the calculation of the expected cost of the strategy is proposed and exemplified.

  • 21.
    Tell, Sarah
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Vibration mitigation of high-speed railway bridges: Application of fluid viscous dampers2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    At the moment of writing, an expansion of the Swedish railway network has started, by constructions of new lines for high-speed trains. The aim is to create a high-speed connection between the most populous cities in Sweden - Stockholm, Göteborg and Malmö, and the rest of Europe. Thereby, the likelihood of faster, longer and heavier foreign trains crossing the Swedish lines is increased. However, this could be problematic since the dynamic response in railway bridges and, consequently, the risk of resonance increases with increasing train speeds.

    Bridges are usually designed based on contemporary conditions and future requirements are rarely considered, due to e.g. cost issues. Prospectively, the dynamic performance of existing bridges may become insufficient. Hence, the current expansion of the high-speed railway network results in an increased demand of innovative design solutions for new bridges and cost-efficient upgrading methods for existing lines.

    The aim of the present thesis is to propose a vibration mitigation strategy suitable for new and existing high-speed railway bridges. The main focus is a retrofit method with fluid viscous dampers installed between the bridge superstructure and the supports, which is intended to reduce the vertical bridge deck acceleration below the European design code limits. Furthermore, the intention is to investigate the efficiency of such a system, as well as to identify and analyse the parameters and uncertainties which could influence its functionality.

    In order to examine the applicability of the proposed retrofit, case studies, statistical screenings and sensitivity analyses are performed and analysed. Two different models, a single-degree-of-freedom system and a finite element model, are developed and compared. From the different models, it is possible to study the influence from the damper parameters, the variability of the material properties and different modelling aspects on the bridge response. After the installation of the fluid viscous dampers, it is found that the acceleration level of the bridge deck is significantly reduced, even below the design code requirements.

  • 22.
    Hassanie, Samer
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Service and Energy Systems.
    A Systematic Approach to Integrated Building Performance Assessment and Visualisation2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The aim of this project was to develop a holistic approach to building-performance assessment without limiting it to energy use (usually expressed in kWh/m2/year), but rather include more parameters that represent the following aspects: Economic, environmental, and quality of service provided to the occupant/client. If it can be shown that buildings can be operated not only in an energy-efficient way, but also in a way that takes into consideration the needs of the occupants, a case could be built that a higher quality of indoor environment does not necessarily mean a higher economic impact. It is also important to show that having access to high-quality building-performance data leads to high-quality analysis and visualisation, and consequently to a chance to detect faults and improve building operation. To answer these questions, a large office building in Stockholm, Sweden was used as a case study. The building was equipped with energy meters and 1,700 sensor points, uniformly distributed over the occupied areas, that measured room temperature, duct temperature, occupancy presence/absence and supply airflow, in addition to other states. The data was processed using RStudio, and various types of visualisation plots were used, including carpet plots, masked scatter plots, bar plots, line graphs, and boxplots. The data pointed to some interesting results. First, just knowing the energy use is not sufficient for understanding the quality of the service provided to the occupants. Second, performing a thorough analysis of room unit data can detect faults. Third, using carpet plots for energy-data visualisation is effective for energy-use pattern recognition. Finally, visualising the building performance parameters in a parallel coordinate plot is a more informative representation of integrated building performance compared to the energy performance certificates typically used today. 

  • 23.
    Nejad Ghafar, Ali
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    An Experimental Study to Measure And Improve the Grout Penetrability2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    An essential demand in any underground facility is to seal it against the water ingress to reduce the time and cost of the construction and the corresponding environmental hazards. To achieve this, obtaining sufficient grout spread is of great importance. Among the grouts, cement grouts with lower costs and environmental issues have been more reliable, whereas their main problem is filtration that restricts the grout spread. Several investigations have been therefore aimed to develop instruments to measure the grout penetrability as a fundamental means to improve the grout spread. Due to the difference in assumptions, limitations, and test conditions, and the deficiency in design their results are occasionally in contradiction. The question here is how to measure the grout penetrability more realistic? To answer this, two of the most frequently used instruments, Filter pump and Penetrability meter, were adjusted to approach the test conditions in Short slot. The results were discussed with respect to the origins of contradictions to better evaluate the reliability and functionality of the instruments.

    Among the influencing parameters on grout spread, applied pressure is a key element. The stepwise pressure increment is the method currently used to improve the grout spread in rock. Application of dynamic grouting has been studied as a solution to improve the grout spread for almost three decades. Despite some promising results, the method has not been yet industrialized due to the limited efficiency and issues in the type and frequency of the applied pressure, and the geometry of the test equipment. Therefore, finding a more efficient alternative of the applied pressure was the second goal of this study. A pneumatic pressure control system was consequently employed to examine the efficiency of the method in Short slot. The results conclusively revealed the effectiveness of the method and provided a strong basis for further development of the dynamic grouting.

  • 24.
    Abbasiverki, Roghayeh
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Analysis of underground concrete pipelines subjected to seismic high-frequency loads2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Buried pipelines are tubular structures that are used for transportation of important liquid materials and gas in order to provide safety for human life. During an earthquake, imposed loads from soil deformations on concrete pipelines may cause severe damages, possibly causing disturbance in vital systems, such as cooling of nuclear power facilities. The high level of safety has caused a demand for reliable seismic analyses, also for structures built in the regions that have not traditionally been considered as highly seismically active. The focus in this study is on areas with seismic and geological conditions corresponding to those in Sweden and Northern Europe. Earthquakes in Sweden for regions with hard rock dominated by high-frequency ground vibrations, Propagation of such high-frequency waves through the rock mass and soil medium affect underground structures such as pipelines.

    The aim of this project is investigating parameters that affect response of buried pipelines due to high-frequency seismic excitations. The main focus of the study is on reinforced concrete pipelines. Steel pipelines are also studied for comparison purposes. The effects of water mass, burial depth, soil layer thickness and non-uniform ground thickness caused by inclined bedrock are studied. The results are compared to those obtained for low-frequency earthquakes and the relationship between strong ground motion parameters and pipelines response is investigated. It is shown that, especially for high frequency earthquake excitations, non-uniform ground thickness due to inclined bedrock significantly increase stresses in the pipelines. For the conditions studied, it is clear that high-frequency seismic excitation is less likely to cause damage to buried concrete pipelines. However, the main conclusion is that seismic analysis is motivated also for pipelines in high-frequency earthquake areas since local variation in the ground conditions can have a significant effect on the safety.

  • 25.
    Prästings, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Aspects on probabilistic approach to design: From uncertainties in pre-investigation to final design2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Geotechnical engineering is strongly associated with large uncertainties. Exploring a medium (soil) that is almost entirely and completely hidden from us is no easy task. Investigations can be made only at discrete points, and the majority of a specific soil volume is never tested. All soils experience inherent spatial variability, which contributes to some uncertainty in the design process of a geotechnical structure. Furthermore, uncertainties also arise during testing and when design properties are inferred from these tests. To master the art of making decisions in the presence of uncertainties, probabilistic description of soil properties and reliability-based design play vital roles. Historically, the observational method (sometimes referred to as the “learn-as-you-go-approach”), sprung from ideas by Karl Terzaghi and later formulated by Ralph Peck, has been used in projects where the uncertainties are large and difficult to assess. The design approach is still highly suitable for numerous situations and is defined in Eurocode 7 for geotechnical design. In paper I, the Eurocode definition of the observational method is discussed. This paper concluded that further work in the probabilistic description of soil properties is highly needed, and, by extension, reliability-based design should be used in conjunction with the observational method. Although great progress has been made in the field of reliability-based design during the past decade, few geotechnical engineers are familiar with probabilistic approaches to design. In papers II and III, aspects of probabilistic descriptions of soil properties and reliability-based design are discussed. The connection between performing qualitative investigations and potential design savings is discussed in paper III. In the paper, uncertainties are assessed for two sets of investigations, one consisting of more qualitative investigations and hence with less uncertainty. A simplified Bayesian updating technique, referred to as “the multivariate approach”, is used to cross-validate data to reduce the evaluated total uncertainty. Furthermore, reliability-based design was used to compare the two sets of investigations with the calculated penetration depth for a sheet-pile wall. The study is a great example of how a small amount of both time and money (in the pre-investigation phase) can potentially lead to greater savings in the final design.

  • 26.
    Veganzones Muñoz, José Javier
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Bridge Edge Beams: LCCA and Structural Analysis for the Evaluation of New Concepts2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Bridge edge beams in Sweden may involve up to 60% of the life-cyclemeasure costs incurred along the road bridge’s life span. Moreover, usercosts as means of traffic disturbances are caused. Consequently, the SwedishTransport Administration started a project to find better alternativeedge beam design proposals for the society.The goal of this thesis is to contribute to the development of bridgeedge beam solutions that can result better for the society in terms of totalcost and still fulfill the functional requirements, through the evaluation ofnew concepts. A life-cycle cost analysis was carried out to assess the proposedalternatives. The results served as a guidance to identify alternativesthat could qualify for more detailed studies. One such proposal wasa solution without edge beam. Since the edge beam is known to distributeconcentrated loads, the removal of such member could lead to loss ofrobustness of concrete bridge deck slabs. Thus, a structural analysis todetermine the influence of the edge beam was performed through nonlinearfinite-element modelling validated from experimental evidenceavailable in the literature. An assessment of the existing calculationmethods for the overhang slab is also presented.The results show that the edge beam behaves as a load-carrying memberwhich contributes to a wider distribution of shear forces. An increasedload resisting capacity for reinforced concrete bridge deck overhang slabswas documented. The removal of the edge beam would imply loss of robustnessin the bridge, which might have to be counteracted by an increaseof the thickness of the deck slab.

  • 27.
    Gasch, Tobias
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Concrete as a multi-physical material with applications to hydro power facilities2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    During its lifetime, a concrete structure is subjected to many different actions, ranging from mechanical loads to environmental actions. To accurately predict its integrity from casting and throughout its service life, a modelling strategy is required that considers mechanical loading but also implicitly accounts for physical effects such as temperature and moisture variations. This is especially true for large concrete structures found in many infrastructure applications such as bridges, nuclear power plants and dams. Modelling concrete as a multi-physical material is becoming an increasingly used approach for which large research efforts are being made, including the development of more refined mathematical and numerical methods as well as considering more physical and chemical variables in the coupled model.

    The research project, of which this licentiate thesis is the first phase, aims at investigating aging concrete structures at hydro power facilities, with focus on the internal structures of the power plants. This thesis presents a review of advanced mathematical methods and concepts for modelling aging concrete found in the literature which can later be applied to study such structures. The focus is on models that describe the deformational behaviour of concrete where aspects such as aging, cracking, creep and shrinkage are investigated. However, in order to accurately describe such phenomena, a multi-physical approach is adopted where moisture and temperature variations in the concrete are studied. Also, models that describe the chemical behaviour related to hydration and thus in extension aging, are also reviewed and introduced in the multi-physical framework. The use of such models are discussed in the context of the finite element method (FEM), in which coupled models are implemented, verified and applied in the appended papers using two different FE codes.

    Several verification examples are presented covering different aspects of the implemented models, both in isolation and coupled in a multi-physical setting. By comparing the numerical results with experimental data from the literature it can be shown that it is possible to predict most aspects of aging concrete that have been of interest here. While these examples are all on a laboratory scale, numerical examples and case studies are also provided that exemplify how the models can be applied on a structural scale. By using the developed analysis tools, valuable information and insights can be gained on aging concrete structures and these tools will in the next phase of the research project be applied to large concrete structures at hydro power facilities.

  • 28.
    Khan, Abdullah
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Fundamental investigation to improve the quality of cold mix asphalt2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Cold mix asphalt (CMA) emulsion technology could become an attractive option for the road industry as it offers lower startup and equipment installation costs, energy consumption and environmental impact than traditional alternatives. The adhesion between bitumen and aggregates is influenced by diverse parameters, such as changes in surface free energies of the binder and aggregates or the presence of moisture or dust on the surface of aggregates, mixing temperatures, surface textures (including open porosity), nature of the minerals present and their surface chemical composition, as well as additives in the binder phase. The performance of cold asphalt mixtures is strongly influenced by the wetting of bitumen on surfaces of the aggregates, which is governed by breaking and coalescence processes in bitumen emulsions. Better understanding of these processes is required. Thus, in the work this thesis is based upon, the surface free energies of both minerals/aggregates and binders were characterized using two approaches, based on contact angles and vapor sorption methods. The precise specific surface areas of four kinds of aggregates and seven minerals were determined using an approach based on BET (Brunauer, Emmett and Teller) theory, by measuring the physical adsorption of selected gas vapors on their surfaces and calculating the amount of adsorbed vapors corresponding to monolayer occupancy on the surfaces. Interfacial bond strengths between bitumen and aggregates were calculated based on measured surface free energy components of minerals/aggregates and binders, in both dry and wet conditions.

    In addition, a new experimental method has been developed to study bitumen coalescence by monitoring the shape relaxation of bitumen droplets in an emulsion environment. Using this method, the coalescence of spherical droplets of different bitumen grades has been correlated with neck growth, densification and changes in surface area during the coalescence process. The test protocol was designed to study the coalescence process in varied environmental conditions provided by a climate-controlled chamber. Presented results show that temperature and other variables influence kinetics of the relaxation process. They also show that the developed test procedure is repeatable and suitable for studying larger-scale coalescence processes. However, possible differences in measured parametric relationships between the bitumen emulsion scale and larger scales require further investigation.

    There are several different research directions that can be explored for the continuation of the research presented in this thesis. For instance, the rationale of the developed method for analyzing coalescence processes in bitumen emulsions rests on the assumption that the results are applicable to large-scale processes, which requires validation. A linear relationship between the scales is not essential, but it is important to be able to determine the scaling function. Even more importantly, qualitative effects of the investigated parameters require further confirmation. To overcome the laboratory limitations and assist in the determination of appropriate scaling functions further research could focus on the development of a three-dimensional multiphase model to study coalescence processes in more detail, including effects of surfactants, pH and other additives such as mineral fillers and salts. Additionally, better understanding of the breaking process and water-push out could help significantly to optimize CMA mix design. Different methods, both numerical and experimental could be explored for this.

  • 29.
    de Frias Lopez, Ricardo
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Granular Materials for Transport Infrastructures: Mechanical performance of coarse–fine mixtures for unbound layers through DEM analysis2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Granular materials are widely used as unbound layers within the infrastructure system playing a significant role on performance and maintenance. However, fields like pavement and railway engineering still heavily rely on empirically-based models owing to the complex behaviour of these materials, which partly stems from their discrete nature. In this sense, the discrete element method (DEM) presents a numerical alternative to study the behaviour of discrete systems with explicit consideration of the processes at particulate level governing the macroscopic response.

     This thesis aims at providing micromechanical insight into the effect of different particle sizes on the load-bearing structure of granular materials and its influence on the resilient modulus and permanent deformation response, both of which are greatly influenced by the stress level. In order to accomplish this, binary mixtures of elastic spheres under axisymmetric stress are studied using DEM as the simplest expression for gap-graded materials, which in turn also can be seen as a simplification of more complex mixtures.

    First, the effect of the fines content on the force transmission at contact level was studied. Results were used to define a soil fabric classification system where the roles of the coarse and fine fractions were defined and quantified in terms of force transmission.

    A behavioural correspondence between numerical mixtures and granular materials was established, where the mixtures were able to reproduce some of the most significant features regarding the resilient modulus and permanent strain dependency on stress level for granular materials.

    A good correlation between soil fabric and performance was also found. Generally, higher resilient modulus and lower deformation values were observed for interactive fabrics, whereas the opposite held for instable fabrics.

    Mixtures of elastic spheres are far from granular materials, where numerous additional factors should be considered. Nevertheless, it is the author’s belief that this work provides insight into the soil fabric structure and its effect on the macroscopic response of granular materials.

  • 30.
    Döse, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures. CBI Betonginstitutet.
    Ionizing Radiation in Concrete and Concrete Buildings: Empirical Assessments2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    One of the major issues with radiation from the natural isotopes 40K, 226Ra (238U) and 232Th and their decay products is the forthcoming legislation from the European Commission in relation to its Basic Safety Directive (2014). The European legislation is mandatory and could not be overthrown by national legislation. Hence, even though the BSS is still a directive it is foreseen as becoming a regulation in due time.

    The reference value of the natural isotopes, from a radiation point of view, set for building materials is 1 mSv per year (EC, 2014). Earlier recommendations (The Radiation Protection Authorities in Denmark, Finland, Iceland, Norway and Sweden, 2000) within the Nordic countries set an upper limit at 2 mSv per year of radiation from building materials.

    The main objective within the frame of the thesis was to investigate gamma radiation in relation to Swedish aggregates and their use as final construction products and the applicability and use of a model (EC, 1999) for building materials to calculate the effective dose within a pre-defined room. Part of the thesis also investigates different methodologies that can be used to assess the radiation in a construction material made up of several constituents (building materials) and aims to show that for some purposes as for the construction industries (precast concrete), that a hand-held spectrometer can be used with good accuracy, even though the object is limited in thickness and size. Secondly, the author proposes a simplified way of assessing the radiation in a construction material by use of correlation coefficient of a specified recipe by use of a hand-held spectrometer. Moreover, an understanding of the different building materials´ contribution to the finalized construction product, e.g. concrete is demonstrated, and how to achieve a good control of the radiation levels in the concrete building.

  • 31.
    Wang, Cong
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Service and Energy Systems.
    Optimal Design of District Energy Systems: a Multi-Objective Approach2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The aim of this thesis is to develop a holistic approach to the optimal design of energy systems for building clusters or districts. The emerging Albano university campus, which is planned to be a vivid example of sustainable urban development, is used as a case study through collaboration with the property owners, Akademiska Hus and Svenska Bostäder. The design addresses aspects of energy performance, environmental performance, economic performance, and exergy performance of the energy system. A multi-objective optimization approach is applied to minimize objectives such as non-renewable primary energy consumptions, the greenhouse gas emissions, the life cycle cost, and the net exergy deficit. These objectives reflect both practical requirements and research interest. The optimization results are presented in the form of Pareto fronts, through which decision-makers can understand the options and limitations more clearly and ultimately make better and more informed decisions. Sensitivity analyses show that solutions could be sensitive to certain system parameters. To overcome this, a robust design optimization method is also developed and employed to find robust optimal solutions, which are less sensitive to the variation of system parameters. The influence of different preferences for objectives on the selection of optimal solutions is examined. Energy components of the selected solutions under different preference scenarios are analyzed, which illustrates the advantages and disadvantages of certain energy conversion technologies in the pursuit of various objectives. As optimal solutions depend on the system parameters, a parametric analysis is also conducted to investigate how the composition of optimal solutions varies to the changes of certain parameters. In virtue of the Rational Exergy Management Model (REMM), the planned buildings on the Albano campus are further compared to the existing buildings on KTH campus, based on energy and exergy analysis. Four proposed alternative energy supply scenarios as well as the present case are analyzed. REMM shows that the proposed scenarios have better levels of match between supply and demand of exergy and result in lower avoidable CO2 emissions, which promise cleaner energy structures.

  • 32.
    Mohammadi Mohaghegh, Ali
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures. NTNU i Ålesund.
    Use of Macro Basalt Fibre Concrete for Marine Applications2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Deterioration of concrete structures due to the corrosion of embedded steel is a well-known universal problem. Norway with its numerous bridges, ports, offshore and floating structures along its coastline, is also encountered with corrosion degradation. The harsh environment of the Norwegian Sea regarding its low temperature, wind, and waves, makes the design and construction of marine structures more demanding. In recent years, usage of sustainable composite materials in the field of structural engineering has been rising. The usage of natural fibre reinforced polymer materials in the form of reinforcement bars or macro fibres with a low density, high strength, and excellent corrosion resistance, gives us better choices for the design and construction of marine structures. Our knowledge about the fibre reinforced self-compacting concrete has increased as a result of introducing it as a building material some decades ago. However, more research is still needed when it comes to the application of new types of fibres. This thesis is a result of this need, whereby the author has done two series of experimental programmes regarding the subject. In the first series, the flow characteristics of fresh state, conventional and self-compacting macro basalt fibre concrete were studied. In the second series, mechanical properties of high performance and medium strength macro basalt fibre concrete including the post-cracking behaviour, compressive strength and electrical resistivity were in focus. The findings were presented in three appended papers and the extended summary composing this thesis. Additionally, the thesis presents an overview of the design procedure of floating concrete structures and the possibility of using macro basalt fibre concrete via a case study. The author’s literature review shows that basalt fibres have an adequate resistance against alkali environment of the concrete matrix and corrosive environment of seawater.

  • 33.
    Onifade, Ibrahim
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Development of a Morphology-based Analysis Framework for Asphalt Pavements2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The morphology of asphalt mixtures plays a vital role in their properties and behaviour. The work in this thesis is aimed at developing a fundamental understanding of the effect of the asphalt morphology on the strength properties and deformation mechanisms for development of morphology-based analysis framework for long-term response prediction. Experimental and computational methods are used to establish the relationship between the mixture morphology and response. Micromechanical modeling is employed to understand the complex interplay between the asphalt mixture constituents resulting in strain localization and stress concentrations which are precursors to damage initiation and accumulation. Based on data from actual asphalt field cores, morphology-based material models which considers the influence of the morphology on the long-term material properties with respect to damage resistance, healing and ageing are developed. The morphology-based material models are implemented in a hot-mix asphalt (HMA) fracture mechanics framework for pavement performance prediction. The framework is able to predict top-down cracking initiation to a reasonable extent considering the variability of the input parameters. A thermodynamic based model for damage and fracture is proposed. The results from the study show that the morphology is an important factor which should be taken into consideration for determining the short- and long-term response of asphalt mixtures. Further understanding of the influence of the morphology will lead to the development of fundamental analytical techniques in design to establish the material properties and response to loads. This will reduce the empiricism associated with pavement design, reduce need for extensive calibration and validation, increase the prediction capability of pavement design tools, and advance pavement design to a new level science and engineering.

  • 34.
    Albrektsson, Joakim
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures. SP Technical Research Institute of Sweden.
    Durability of fire exposed concrete: Experimental Studies Focusing on Sti„ffness & Transport Properties2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Road and rail tunnels are important parts of the modern infrastructure. High strength concrete (HSC) is commonly used for tunnels and other civil engineering structures, since it allows high load carrying capacity and long service life. In general, Swedish road and rail tunnels should be designed for a service life of 120 years. However, HSC has shown to be sensitive to severe fires in the moist tunnel environment, i.e., fire spalling may occur. Extensive research shows that addition of polypropylene (PP) fibres in the fresh concrete mix significantly reduces the risk of fire spalling. The durability of a concrete structure is mainly governed by the transport properties. Further, experimental studies aimed at understanding the protective mechanism of PP fibres indicate that fluid transport increases in connection with the melting temperature of such fibres. This might reduce the durability of fire exposed concrete with addition of PP fibres. This study aims to investigate whether the use of PP fibres has any significant effect on the durability of moderate fire exposed concrete structures.

    The experimental study focused on transport properties related to durability and stiffness reduction of fire exposed civil engineering concrete with and without addition of PP fibres. The study consists of three parts; (i) unilateral fire exposure in accordance with the standard time-temperature curve (Std) and a slow heating curve (SH), (ii) uniformly heating of non-restrained samples to 250oC, and (iii) moderate unilateral fire exposure, 350oC, of restrained samples. Changes in material properties caused by the fire exposure were studied by means of ultrasonic pulse velocity, full field-strain measurements during uniaxial compression core tests, polarization and fluorescence microscopy (PFM), water absorption and non-steady state chloride migration.

    The study shows that fire exposure influences different properties of importance for load carrying capacity and durability. To get a clear image of the fire damage one has to combine different test methods during damage assessments. Transport properties of concrete both with and without addition of PP fibres were considerably affected even at moderate fire exposure. Hence, the service life might be reduced. All series with addition of PP fibres exhibited higher water absorption compared to the series without PP fibres. The practical importance of this might, however, be small since also the water absorption of concrete without PP fibres was considerably affected for the fire scenarios considered in this study. Behind the fire exposed surface, i.e., between 30 and 60 mm, no change in water absorption was observed for concrete without PP fibres. However, higher water absorption of the series with addition of PP fibres was observed.

    Indicative fire tests aimed to evaluate the resistance to fire spalling during a subsequent severe fire was also conducted. The concretes with addition of PP fibres showed no signs of fire spalling, while progressive spalling was observed for the concrete without PP fibres.

  • 35.
    Gustafsson, Marcus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Energy efficient and economic renovation of residential buildings with low-temperature heating and air heat recovery2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    With the building sector accounting for around 40% of the total energy consumption in the EU, energy efficiency in buildings is and continues to be an important issue. Great progress has been made in reducing the energy consumption in new buildings, but the large stock of existing buildings with poor energy performance is probably an even more crucial area of focus. This thesis deals with energy efficiency measures that can be suitable for renovation of existing houses, particularly low-temperature heating systems and ventilation systems with heat recovery. The energy performance, environmental impact and costs are evaluated for a range of system combinations, for small and large houses with various heating demands and for different climates in Europe. The results were derived through simulation with energy calculation tools.

    Low-temperature heating and air heat recovery were both found to be promising with regard to increasing energy efficiency in European houses. These solutions proved particularly effective in Northern Europe as low-temperature heating and air heat recovery have a greater impact in cold climates and on houses with high heating demands. The performance of heat pumps, both with outdoor air and exhaust air, was seen to improve with low-temperature heating. The choice between an exhaust air heat pump and a ventilation system with heat recovery is likely to depend on case specific conditions, but both choices are more cost-effective and have a lower environmental impact than systems without heat recovery. The advantage of the heat pump is that it can be used all year round, given that it produces DHW.

    Economic and environmental aspects of energy efficiency measures do not always harmonize. On the one hand, lower costs can sometimes mean larger environmental impact; on the other hand there can be divergence between different environmental aspects. This makes it difficult to define financial subsidies to promote energy efficiency measures.

  • 36.
    Peñaloza, Diego
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Exploring climate impacts of timber buildings: The effects from including non-traditional aspects in life cycle impact assessment2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    There is an urgency within the building sector to reduce its greenhouse gas emissions and mitigate climate change. An increased proportion of biobased building materials in construction is a potential measure to reduce these emissions. Life cycle assessment (LCA) has often been applied to compare the climate impact from biobased materials with that from e.g. mineral based materials, mostly favouring biobased materials. Contradicting results have however been reported due to differences in methodology, as there is not yet consensus regarding certain aspects. The aim of this thesis is to study the implications from non-traditional practices in climate impact assessment of timber buildings, and to discuss the shortcomings of current practices when assessing such products and comparing them with non-renewable alternatives.

    The traditional practices for climate impact assessment of biobased materials have been identified, and then applied to a case study of a building with different timber frame designs and an alternative building with a concrete frame. Then, non-traditional practices were explored by calculating climate impact results using alternative methods to handle certain methodological aspects, which have been found relevant for forest products in previous research such as the timing of emissions, biogenic emissions, carbon storage in the products, end-of-life substitution credits, soil carbon disturbances and change in albedo. These alternative practices and their implications were also studied for low-carbon buildings.

    The use of non-traditional practices can affect the climate impact assessment results of timber buildings, and to some extent the comparison with buildings with lower content of biobased building materials. This effect is especially evident for energy-efficient buildings. Current normal practices tend to account separately for forest-related carbon flows and aspects such as biogenic carbon emissions and sequestration or effects from carbon storage in the products, missing to capture the forest carbon cycle as a whole. Climate neutrality of wood-based construction materials seems like a valid assumption for studies which require methodological simplification, while other aspects such as end-of-life substitution credits, soil carbon disturbances or changes in albedo should be studied carefully due to their potentially high implications and the uncertainties around the methods used to account for them. If forest phenomena are to be included in LCA studies, a robust and complete model of the forest carbon cycle should be used. Another shortcoming is the lack of clear communication of the way some important aspects were handled.

  • 37.
    Ignat, Razvan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Field and Laboratory Tests of Laterally Loaded Rows of Lime-Cement Columns2015Licentiate thesis, comprehensive summary (Other academic)
  • 38.
    Wadi, Amer
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Flexible culverts in sloping terrain: Research advances and application2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Although the construction of flexible culverts involves simplicity in comparison to similar concrete structures, the complexity of the beneficial interaction between soil and steel materials requires good understanding for their composite action and performance. Current design methods have certain validity limitations with regard to applicable slopes above the structures. Given the short construction time of flexible culverts, there is an urge to explore the feasibility and the constructability of such as cost-effective structures in sloping terrain, where they may function as an avalanche protection structure for a given road, a culvert under a ski slope, or even as a protection canopy for tunnel entrances.

    This report compiles the efforts carried out toward gaining knowledge about the different factors that may affect the behaviour of flexible culverts in sloping environment. The report includes an extended summary of the investigation, which is mainly presented in two appended papers. The study involved numerical simulation of three case studies to investigate their performances with regard to soil loading and avalanche loads as well. The height of cover, surface slope intensity, slope stability, soil support conditions, and avalanche proximity, were studied and discussed.

    The study results allowed realizing the susceptibility of flexible culverts to low heights of soil cover when built in sloping terrain, which is reflected in the deformation response and the incremental change in sectional forces, especially the bending moments. It is also found that increasing the depth of soil cover may feasibly improve the structural performance under asymmetrical soil loading and avalanche loads, where it subsequently help in reducing the bending moments in the wall conduit. The presence of a flexible culvert may affect adversely the soil stability in sloping terrain and thus need to be addressed in design. Furthermore, the flexural response of a flexible culvert is directly influenced by the soil support configuration at the downhill side of the structure. In addition, the report also attempts to highlight some general guidelines about the design aspects of flexible culverts in sloping terrain, and seeks to reflect some of the findings on the design methodology for flexible culverts used in Sweden.

  • 39.
    Lingwanda, Mwajuma
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    In-situ Penetration as Alternative to Extensive Boreholes and Lab Testing for Exploration in Sandy Soils2015Licentiate thesis, comprehensive summary (Other academic)
  • 40.
    Ghafoori Roozbahany, Ehsan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Investigation of asphalt compaction in vision of improving asphalt pavements2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Asphalt joints are potentially weakest parts of every pavement. Despite of their importance, reliable tools for measuring their mechanical properties for design and performance assessments are still scarce. This is particularly true for cold joints when attaching a new hot pavement to a cold existing one as in case of large patches for pavement repair. In this study, three static fracture testing methods, i.e. indirect tensile test (IDT), direct tension test (DTT) and 4 point bending (4PB), were adapted and used for evaluating different laboratory made joints. The results suggested that joints with inclined interfaces and also the ones with combined interface treatments (preheated and sealed) seemed to show more promising behaviors than the vertical and untreated joints. It was also confirmed that compacting from the hot side towards the joint improved the joint properties due to imposing a different flow pattern as compared to the frequent compaction methods. The latter finding highlighted the importance of asphalt particle rearrangements and flow during the compaction phase as a very little known subject in asphalt industry. Studies on compaction are of special practical importance since they may also contribute to reducing the possibility of over-compaction and aggregate crushing.

    Therefore, in this study, a new test method, i.e. Flow Test (FT), was developed to simulate the material flow during compaction. Initially, asphalt materials were substituted by geometrically simple model materials to lower the level of complexity for checking the feasibility of the test method as well as modeling purposes. X-ray radiography images were also used for capturing the flow patterns during the test. Results of the FT on model materials showed the capability of the test method to clearly distinguish between specimens with different characteristics. In addition, a simple discrete element model was applied for a better understanding of the test results as a basis for further improvements when studying real mixtures. Then, real mixtures were prepared and tested under the same FT configuration and the results were found to support the findings from the feasibility tests. The test method also showed its potential for capturing flow pattern differences among different mixtures even without using the X-ray. Therefore, the FT was improved as an attempt towards developing a systematic workability test method focusing on the flow of particles at early stages of compaction and was called the Compaction Flow Test (CFT).

    The CFT was used for testing mixtures with different characteristics to identify the parameters with highest impact on the asphalt particle movements under compaction forces. X-ray investigations during the CFT underlined the reliability of the CFT results. In addition, simple discrete element models were successfully generated to justify some of the CFT results.

  • 41.
    Dinegdae, Yared Hailegiorgis
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Reliability-based Design Procedure for Flexible Pavements2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Load induced top-down fatigue cracking has been recognized recently as a major distress phenomenon in asphalt pavements. This failure mode has been observed in many parts of the world, and in some regions, it was found to be more prevalent and a primary cause of pavements failure. The main factors which are identified as potential causes of top down fatigue cracking are primarily linked to age hardening, mixtures fracture resistance and unbound layers stiffness. Mechanistic Empirical analytical models, which are based on hot mix asphalt fracture mechanics (HMA-FM) and that could predict crack initiation time and propagation rate, have been developed and shown their capacity in delivering acceptable predictions. However, in these methods, the effect of age hardening and healing is not properly accounted and moreover, these models do not consider the effect of mixture morphology influence on long term pavement performance. Another drawback of these models is, as analysis tools they are not suitable to be used for pavement design purpose. The main objective of this study is to develop a reliability calibrated design framework in load resistance factor design (LRFD) format which could be implemented to design pavement sections against top down fatigue cracking.

    For this purpose, asphalt mixture morphology based sub-models were developed and incorporated to HMA-FM to characterize the effect of aging and degradation on fracture resistance and healing potential. These sub-models were developed empirically exploiting the observed relation that exist between mixture morphology and fracture resistance. The developed crack initiation prediction model was calibrated and validated using pavement sections that have high quality laboratory data and observed field performance history. As traffic volume was identified in having a dominant influence on predicted performance, two separate model calibration and validation studies were undertaken based on expected traffic volume. The predictions result for both model calibration and validation was found to be in an excellent agreement with the observed performance in the field.

    A LRFD based design framework was suggested that could be implemented to optimize pavement sections against top-down fatigue cracking. To achieve this objective, pavement sections with various design target reliabilities and functional requirements were analyzed and studied.  A simplified but efficient limit state equation was generated using a central composite design (CCD) based response surface methodology, and FORM based reliability analysis was implemented to compute reliabilities and formulate associated partial safety factors. A design example using the new partial safety factors have clearly illustrated the potential of the new method, which could be used to supplement existing design procedures.

  • 42.
    McCarthy, Richard
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Self-compacting concrete for improved construction technology2015Licentiate thesis, comprehensive summary (Other academic)
  • 43.
    Källbom, Susanna
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Surface characterisation of thermally modified spruce wood and influence of water vapour sorption2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Today there is growing interest within the construction sector to increase the proportion of biobased building materials made from renewable resources. By-products or residuals from wood processing could in this case be valuable resources for manufacturing new types of biocomposites. An important research question related to wood-based biocomposites is how to characterise molecular interactions between the different components in the composite. The hygroscopic character of wood and its water sorption properties are also crucial. Thermal modification (or heat treatment) of wood results in a number of enhanced properties such as reduced hygroscopicity and improved dimensional stability as well as increased resistance to microbiological decay.

    In this thesis, surface characteristics of thermally modified wood components (often called wood fibres or particles) and influencing effects from moisture sorption have been analysed using a number of material characterisation techniques. The aim is to increase the understanding in how to design efficient material combinations for the use of such wood components in biocomposites. The specific objective was to study surface energy characteristics of thermally modified spruce (Picea abies Karst.) under influences of water vapour sorption. An effort was also made to establish a link between surface energy and surface chemical composition. The surface energy of both thermally modified and unmodified wood components were studied at different surface coverages using inverse gas chromatography (IGC), providing information about the heterogeneity of the surface energy. The water vapour sorption behaviour of the wood components was studied using the dynamic vapour sorption (DVS) method, and their surface chemical composition was studied by means of X-ray photoelectron spectroscopy (XPS). Additionally, the morphology of the wood components was studied with scanning electron microscopy (SEM).

    The IGC analysis indicated a more heterogeneous surface energy character of the thermally modified wood compared with the unmodified wood. An increase of the dispersive surface energy due to exposure to an increased relative humidity (RH) from 0% to 75% RH at 30 ˚C was also indicated for the modified samples. The DVS analysis indicated an increase in equilibrium moisture content (EMC) in adsorption due to the exposure to 75% RH. Furthermore, the XPS results indicated a decrease of extractable and a relative increase of non-extractable compounds due to the exposure, valid for both the modified and the unmodified wood. The property changes due to the increased RH condition and also due to the thermal modification are suggested to be related to alterations in the amount of accessible hydroxyl groups in the wood surface. Recommendations for future work and implications of the results could be related to knowledge-based tailoring of new compatible and durable material combinations, for example when using thermally modified wood components in new types of biocomposites for outdoor applications.

  • 44.
    Wallin, Joakim
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Systematic planning and execution of finite element model updating2015Licentiate thesis, monograph (Other academic)
    Abstract [en]

    In design of bridges and for estimation of dynamic properties and load carrying capacity Finite Element Method (FEM) is often used as a tool. The physical quantities used in the Finite Element (FE) model are often connected to varying degrees of uncertainty. To deal with these uncertainties conservative parameter estimates and safety factors are used. By calibrating the bridge FE model to better fit with the response of the real structure, less conservative parameter values can be chosen. This method of comparing measured and response with estimates from a FE model and calibrating the model parameters is called Finite Element Model Updating (FEMU).

    In the present thesis different aspects of FEMU are investigated. The first part comprises a literature review covering all aspects of FEMU with special focus on the choice of updating parameters, objective functions for iterative updating procedures and the automatic pairing of modes. This part is concluded with a flowchart suggesting a systematic approach to a FEMU project.

    In the second part of the text two bridge case studies are presented. In the first case study a railway bridge in the north of Sweden is studied. A detailed FE bridge model from a previous project is used as a simulation model for extraction of modal data by eigenvalue analysis. Then simplified models are created and attempts to update these models are performed. The updating parameters are chosen based on a simple sensitivity analysis. Tests are performed to investigate the influence of chosen updating parameters and objective function on the computational cost and the quality of the updated model.

    Case study number two is more comprehensive and focuses on the sensitivity analysis for the choice of updating parameters and on the choice of objective function. A road bridge in the Stockholm area is used and as for case study one a detailed model from a previous project is used as simulation model. Also a new criteria for the automatic pairing of modes is presented and tested. In the end an attempt to verify two of the updated models is performed.

  • 45.
    Chen, Feng
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    The Future of Smart Road Infrastructure: A Case Study for the eRoad2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    In the future, physical roads will not only serve for the mobility of the vehicles but also have the capability of enabling different smart functionalities, such as car2road communication, energy harvesting or dynamic charging of electrical vehicles. To ensure the sustainability of these advances, the environmental, economic and social costs for the road infrastructure itself should not offset its possible advances. Additionally, the road infrastructure itself may also need to be modified to ensure the long-term performance of the new functionalities.

    This licentiate mainly focused on the electrified road (called ‘eRoad’) infrastructure, which can be a representative case of the future smart road. Specifically, a historical overview of the technology development towards the electrification of road transportation sector is presented, along with an overview of prospective technologies for implementing an eRoad’s charging infrastructure. Of these, the Inductive Power Transfer (IPT) charging technology is examined in further details.

    The potential knowledge gaps for a successful integration of IPT charging technology within actual road infrastructure are discussed. Some general recommendations are given throughout the licentiate thesis, regarding such as the appropriate design of eRoad structure and right selection of road materials, the cost-effective maintenance operations in the long term, and the eRoad’s role in the overall life cycle environmental impacts in the electrification of road transportation sector. This licentiate provides the basis for further focus in this field and outlines the potential research areas that need further investigation to ensure the future of systemically optimized smart road infrastructure. 

  • 46.
    Zhu, Jiqing
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Towards a Viscoelastic Model for Phase Separation in Polymer Modified Bitumen2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this thesis, a review is given on the most popular polymers used today for polymer modification of bitumen. Furthermore, the development of a model for phase separation in polymer modified bitumen (PMB) is proposed, that will enable a better control and understanding of PMB phase behaviour, allowing thus to enhanced long-term performance. PMB is hereby considered as a blend and focus is placed on its structure, its equilibrium thermodynamics and its phase separation dynamics. The effects of dynamic asymmetry on phase separation in PMB are analysed with related theories and some image data. Based on the discussion in this thesis, it is concluded that the effects of dynamic asymmetry between bitumen and polymer should be taken into consideration when studying phase separation in PMB. By analysing related literature and image data, it is found that some features of viscoelastic phase separation are shown during the phase separation process in some PMBs. It is therefore possible and useful to develop a viscoelastic model for PMB to describe its phase separation behaviour. In this, the stress-diffusion coupling is expected to play a key role in the model. Finally, recommendations are made towards the future research which is needed to realize the proposed model.

  • 47.
    Spross, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    A Critical Review of the Observational Method2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Building a sustainable structure in soil or rock that satisfies all predefined technical requirements implies choosing a rational and effective construction method. An important aspect is how the performance of the structure is verified. For cases when the geotechnical behaviour is hard to predict, the existing design code for geotechnical structures, Eurocode 7, suggests the so-called “observational method” to verify that the performance is acceptable. The basic principle of the method is to accept predefined changes in the design during construction, in order to accommodate the actual ground conditions, if the current design is found unsuitable. Even though this in theory should ensure an effective design solution, formal application of the observational method is rare. It is therefore not clear which prerequisites and circumstances that must be present for the observational method to be applicable and be the more suitable method.

    This licentiate thesis gives a critical review of the observational method, based on, and therefore limited by, the outcome of the performed case studies. The aim is to identify and highlight the crucial aspects that make the observational method difficult to apply, thereby providing a basis for research towards a more applicable definition of the method. The main topics of discussion are (1) the apparent contradiction between the preference for advanced probabilistic calculation methods to solve complex design problems and sound, qualitative engineering judgement, (2) the limitations of measurement data in assessing the safety of a structure, (3) the fact that currently, no safety margin is required for the completed structure when the observational method is applied, and (4) the rigidity of the current definition of the observational method and the implications of deviations from its principles.

    Based on the review, it is argued that the observational method can be improved by linking it to a probabilistic framework. To be applicable, the method should be supported by guidelines that explain and exemplify how to make the best use of it. The engineering judgement is however not lost; no matter how elaborate probabilistic methods are used, sound judgement is still needed to define the problem correctly. How to define such a probabilistic framework is an urgent topic for future research, because this also addresses the concerns regarding safety that is raised in the other topics of discussion.

  • 48.
    Wennström, Jonas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Life Cycle Costing in Road Planning and Management: A Case Study on Collision-free Roads2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Construction of infrastructure does not only mean large capital investments but also future costs to operate and maintain these assets. Decision making in planning and design of roads will impact the need of future operation and maintenance activities. Additionally, infrastructure management is often under increasing pressure of aging structures, limited budgets and increased demands from public which require transparency in the decision making. Life cycle costing is a methodology that takes into account costs throughout an asset’s life cycle including investment, operation, maintenance and disposal. Despite the methodology’s existence for more than 40 years, the practical application is often reported to be scarce in both private and public sectors. Implementation in road planning and management means a high complexity where the life cycle costing can to be applied from early planning, design, construction and management in which all influence life cycle cost. Life cycle costing can also be applied in many different ways, level of detail and for different type of studies.

    For effective implementation of life cycle costing in road planning, design and management, different considerations need to be understood. In this thesis the application of life cycle costing has been studied through case study research. The main case selected was an investment to convert a single carriageway road to a, so called, sparse collision-free road. Through widening and separation between driving directions the traffic safety is significantly improved. However, in recent years increased operation and maintenance costs have been associated with the road type. Especially concerns regarding increased road user cost during road works have been expressed. This case was examined in two case studies from different perspectives. The first one was to study the implications on project appraisal and the second one examined the possibility to optimise pavement design.

    Results from cost benefit analyses based on established road appraisal techniques indicated that operation and maintenance related costs had limited impact on profitability. The second study also indicated that future cost can be influenced differently depending on criteria for optimal alternative. Based on economic analyses using established techniques, increased operation and maintenance liabilities appear to be of limited concern, in contrary to the perception. In future research this need to be set in context of road management with refined analysis in order to study implications for future management.

  • 49.
    Rydell, Cecilia
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Seismic high-frequency content loads on structures and components within nuclear facilities2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Sweden is generally considered to be a low seismicity area, but for structures within nuclear power facilities, the safety level demand with respect to seismic events are high and thus, these structures are required to be earthquake-resistant. The seismic hazard is here primarily considered to be associated with near-field earthquakes. The nuclear power plants are further founded on hard rock and the expected ground motions are dominated by high frequencies. The design earthquake considered for the nuclear facilities has an annual probability of 10-5 events, that is, the probability of occurrence is once per 100 000 years. The focus of the study is the seismic response of large concrete structures for the nuclear power industry, with regard not only to the structure itself but also to non-structural components attached to the primary structure, and with emphasis on Swedish conditions. The aim of this licentiate thesis is to summarize and demonstrate some important aspects when the seismic load is dominated by high frequencies. Additionally, an overview of laws, regulations, codes, standards, and guidelines important for seismic analysis and design of nuclear power structures is provided.

    The thesis includes two case studies investigating the effect of seismic high-frequency content loads. The first study investigates the influence of gaps in the piping supports on the response of a steel piping system subjected to a seismic load dominated by high amplitudes at high frequencies. The gaps are found in the joints of the strut supports or are gaps between the rigid box supports and the pipe. The piping system is assessed to be susceptible to high-frequency loads and is located within the reactor containment building of a nuclear power plant. The stress response of the pipe and the acceleration response of the valves are evaluated. The second study investigates the effect of fluid-structure interaction (FSI) on the response of an elevated rectangular water-containing concrete pool subjected to a seismic load with dominating low and high frequencies, respectively. The pool is located within the reactor containment building of a boiling water reactor at a nuclear power plant. The hydrodynamic pressure distribution is evaluated together with the stress distribution in the walls of the tank.

    From the two case studies, it is evident that the response due to a seismic load dominated by high frequencies and low frequencies, respectively, is different. Although the seismic high-frequency load may be considered non-damaging for the structure, the effect may not be negligible for non-structural components attached to the primary structure. Including geometrical non-linear effects such as gaps may however reduce the response. It was shown that the stress response for most of the pipe elements in the first case study was reduced due to the gaps. It may also be that the inclusion of fluid-structure interaction effects changes the dynamic properties of a structural system so that it responds significantly in the high frequency range, thus making it more vulnerable to seismic loads dominated by high frequencies. In the second case study, it was shown that even for a seismic load with small amplitudes and short duration, but with dominating high-frequency content, as the Swedish 10-5 design earthquake, the increase of the dynamic response as fluid-structure interaction is accounted for is significant.

  • 50.
    Zhou, Pin
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    The Use of the Continuity Factor as a Tool to Represent Representative Elementary Volume in Rock Engineering Design2014Licentiate thesis, comprehensive summary (Other academic)
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