Externally bonded fibre-reinforced polymer (FRP) systems have shown to be a robust and durable way to repair, or strengthen concrete structures. Epoxy, as the most common bonding agent, provides excellent force transfer, and bonds well to the base substrate to the as well as to the strengthening material. However, the epoxy-bonded systems exhibit certain inherent weaknesses, such as low compatibility with the concrete substrate, degradation in strength and stiffness around 85 °C, and toxicity both during application and when subjected to fire. Epoxies also require a minimum application temperature often above 10 °C, and create sealed surfaces, potentially resulting in moisture and freeze/thaw problems.In recent years, alternative, inorganic bonding agents have been in the focus of research. Cementitious bonding agents, when combined with the FRP, have the potential to become a high-performance strengthening system, without the drawbacks of the epoxy-bonded systems. Inorganic binders provide excellent protection to the FRP against UV-degradation, fire, or vandalism. Contrary to epoxy, they can be applied in colder temperatures or climates. They show a better compatibility with the base concrete in terms of chemical or thermal compatibility, shrinkage properties, and they do not create diffusion-closed surfaces.In this thesis, the mineral-based composite (MBC) strengthening system has been investigated, with focus on the tensile behaviour of the material. The MBC comprises of a carbon fibre polymer (CFRP) grid and an inorganic, mineral-based binder. Additionally, MBC has been placed in a wider context within the field of externally bonded, mineral-based strengthening systems. On the material side, MBC has been modified and enhanced by involving strain-hardening mortars. The experimental work presented in the thesis consists of two test series aiming to investigate the tensile behaviour. First, uniaxial tensile tests were carried out on dogbone-shaped specimens, to characterize the tensile properties of the bare composite strengthening material. Then, wedge-splitting tests were conducted to investigate the post-cracking behaviour, toughness, and ductility of the MBC, and the interaction between the MBC and the base concrete.The chosen test methods have proven to be suitable to characterize the tensile behaviour of the MBC. In all cases, the specimens failed with CFRP rupture, indicating good bond, both on the base concrete-mortar, and the mortar-CFRP interface. The MBC strengthening system performed excellent in terms of load-carrying capacity. Furthermore, the strain-hardening mortar has been found to enhance both the load bearing and in particular, the deformation capacity. It has also been shown that the pseudo-ductile mortar is capable to shift the overall behaviour from brittle towards a more ductile failure.The potential in such improved mineral-based strengthening systems is enormous. The ductility provided by the strain-hardening mortars together with the stiffness and strength from the FRP component could result in a high-performance strengthening material applicable in a range of different situations, from shear-sensitive structures through mining applications, such as tunnel linings.

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

The main aim of this thesis is to refine models for strength and heat development of the young concrete, and evaluate if developed models at Luleå University of Technology (LTU) for creep, autogenous shrinkage and thermal dilation needs refinement. These are of importance in hardening control and in crack control of a concrete structure.Strength development is one of the most important properties in concrete to consider when analysing concrete structures. The need of actions on site is different at various stages of hardening, from the fresh concrete to the hardened concrete. This thesis defines a model analysing maturity and associated strength growth within three important time periods. The model can be applied separately within each of these periods depending on test data available. Known is that the temperature plays an important role on the strength development of concrete structures. Not so well known is that, if the concrete temperature remains high, strength reduction at later ages often occurs compared to hardening at lower temperature. Both these phenomena have been implemented in the model for strength growth and the functionality of the model is demonstrated by evaluation of laboratory tests for five concrete mixes and two types of cement.As heat of hydration affects the temperature levels and several other properties of concrete structures it is important to document the parameters accurately. In the traditional semi-adiabat (TSA) the measured heat energy originates from the reaction between cement and water. This energy warms up the concrete sample and all the ambient materials of the equipment. In order to model these energies, the TSA setup is transformed into an associated sphere. A refined model using a correction factor is introduced, which accounts for energies lost to the TSA setup materials. Results show that the effect of this factor cannot be disregarded. An increased insulation amount gives a decreased cooling factor but an increased need for correction.Creep at constant temperature, both for moist sealed specimens and drying out conditions, are evaluated. The Linear Logarithmic creep Model (LLM) is shown to work well for basic creep, i.e. creep at moist sealed conditions. But, for creep during simultaneous moist drying, there is a need to adjust the current model or develop a new model to account for the increase of creep due to ongoing drying.Autogenous shrinkage and thermal dilation (free deformation) are evaluated from tests. For the free deformation of young concrete at variable temperature the existing models are satisfactory in modelling the thermal dilation, but in some cases the autogenous shrinkage cannot be adequately described. A new or refined model is needed that works for autogeneous shrinkage even at more complex temperature variations.

The thesis deals with the axial strength of axially and eccentrically loaded concrete walls with cut-out openings strengthened by fiber-reinforced polymers (FRPs).Background: Functional modifications of concrete structures are common because existing structures must often be adapted to comply with current living standards. Such modifications may include the addition of new windows or doors and paths for ventilation and heating systems, all of which require openings to be cut into structural walls. These openings are a source of weakness and can size dependently reduce the structures’ stiffness and load-bearing capacity, thus, requiring the element to be repaired.Aim and objectives: The main aim of this project was to develop a toolbox containing solutions for strengthening concrete walls with existing or newly created openings using FRP materials. The two immediate objectives sought are: (1) An assessment of the research level on concrete walls with and without openings; (2) An experimental and numerical investigation of the structural behavior of the FRP strengthened walls with openings.Methods of investigation: The experimental program was defined by reviewing therelevant tests performed to date. The literature review revealed research gaps that the current study aims to fill. Moreover, preliminary nonlinear finite element analyses were performed prior to the experimental program in order to gain insight into the structural behavior of these elements. Nine specimens designed to represent typical wall panels in residential buildings, at half-scale, were constructed for testing to failure. The two types of openings examined comprised symmetric halfscaled single door-type openings, and symmetric half scaled double door-type openings. The test matrix was divided into three stages, namely: (1) Reference specimens, (2) Pre-cracked specimens strengthened by FRP and (3) Un-cracked specimens strengthened by FRP. The strengthening method used was FRP confinement with the aid of mechanical anchorages.Results: The results indicate that the 25% and 50% reductions in cross-sectional area of the solid wall caused by introducing the small opening and large opening reduced its load carrying capacity by nearly 36% and 50%, respectively. The application of the FRP confinement increases the capacity and the stiffness of the specimens with cut-out openings. The axial strengths were between 85 94.8% and 56.5-63.4% for specimens having a small and large opening, respectively, of that of a solid wall.Conclusion: The FRP-confinement together with the mechanical anchorages was able to partly restore the capacity of a solid wall. Better results might have been possible if longitudinal FRP strips or bi-directional fibers were used. The effects of steel anchorages were not investigated and it is believed that they might have had positive influences. However, the optimal distance between the anchors should be further investigated. Moreover, the influence of the prestressing force of the anchorages may also be an important parameter that has led to an increase in capacity. Keywords: Strengthening, Fiber-reinforced polymers, Concrete walls, Openings, Axial load, Eccentricity, Out-of-plane behavior, Two-Way

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

Mining at great depths has become the reality for the mining industry in Sweden, that faces challenges in terms of increasing seismic events and sometimes intrinsically related rock mass failure. Kiirunavaara mine is owned by LKAB (located at north Sweden) and the company has been dealing with seismicity in a daily basis once the mine has been regarded as seismically active since 2007-2008 and presently has the largest seismic monitoring system in the world. Several authors have studied the characteristics of seismicity at Kiirunavaara mine, but still a closer look into the factors that influence mining-front related seismicity has yet not been performed. In this sense, the present master thesis aimed to investigate the influential contexts on mining-front seismicity in Kiirunavaara mine from a production point of view (mucking data, mining-front geometry and mining sequence) and to point out probable triggers to seismic events and practical guideline measures to partly mitigate the seismic risk. For this the large seismic events (local magnitude ML ≥ 1.5) from 2011 to 2021 classified by previous studies as mining-front related have been analyzed. 63 events were initially investigated individually, combining mucking data, production data and mine geometry from GironPlot 2D and 3D views and the seismic data from software mXrap. The aim was to find patterns of contexts (in terms of mucking data, mining-front geometry and mining sequence) that are likely influential to the occurrence of large seismic events. The results allowed to reclassify the number of mining-front related seismic events to 52, and these were pointed to be probably triggered by blasting (25 events) or mucking (27 events). The events were further classified in 7 categories of probable influential contexts. Most of the events were categorized as related to the Longitudinal Mining category (19 events) and to the Stage I category (17 events). The Stage I category presents a critical scenario of stress concentration in the intact rock pillar that exists between sublevels on the initial stage of production of a level, when no connection to the cave above has been established yet. The high number of events related to the Longitudinal Mining category reinforces the suggestion of not using this type of geometry in the mine. Other categories show the relevance of having proper strategies in terms of mining sequence and mining rate between production blocks. The work brings forward relevant discussions for the future of mining in high stressed environments, e.g. how to enhance the early production stage in terms of providing better preconditioning to the cave and also highlight the importance of investigating and developing tools that could allow to increase the understanding of mucking on the mining-front related seismicity at Kiirunavaara mine.

Mitt förslag på ett Hus för Folket är ett Träningscenter beläget mellan bostadsområdet Nickstahöjden och pendelstationen Nynäsgård Station, som är Nynäshamns nordligaste pendelstation. Båda platserna, och skärningspunkten mellan dem, medför förutsättningar som både är relevanta för mitt projekt, och som jag anser gör mitt projekt relevant på just den här platsen.  Målsättningen med projektet har varit att skapa förutsättningar för ett program som sträcker sig utanför byggnadens gränser. Tranan är utöver ett förslag på ett träningscenter också ett förslag som ämnar interagera med staden på en större skala än den enskilda byggnadens. Min huvudsakliga ambition har varit att föreslå en hybrid mellan en byggnad och en infrastruktur. / Mitt förslag på ett Hus för Folket är ett Träningscenter beläget mellan bostadsområdet Nickstahöjden och pendelstationen Nynäsgård Station, som är Nynäshamns nordligaste pendelstation. Båda platserna, och skärningspunkten mellan dem, medför förutsättningar som både är relevanta för mitt projekt, och som jag anser gör mitt projekt relevant på just den här platsen.  Målsättningen med projektet har varit att skapa förutsättningar för ett program som sträcker sig utanför byggnadens gränser. Tranan är utöver ett förslag på ett träningscenter också ett förslag som ämnar interagera med staden på en större skala än den enskilda byggnadens. Min huvudsakliga ambition har varit att föreslå en hybrid mellan en byggnad och en infrastruktur.

Fotogrammetri är en metod där man kan skapa tredimensionella modeller genom att ta flertal bilder på objektet med en kalibrerad kamera. Fotogrammetri har på senare år blivit ett alltmer populärt verktyg som används i många olika branscher eftersom processen att skapa tredimensionella modeller har förenklats genom att kunna ta bilder med vanliga konsumentkameror. För underjordskonstruktioner så finns det många möjligheter för fotogrammetri. Exempelvis kan fotogrammetri användas under byggnation för geologer för att förankra sin kartering hos en annan geolog på distans men kan också användas som en relationshandling för ett framtidsyfte som i besiktningen för att utvärdera vart förstärkningen har brustit om det har med geologin att göra.   Västlänken är ett stort järnvägsprojekt som kommer gå under Göteborg stad. Här drivs stora delar av projektet i berg. Korsvägen är en delentreprenad av Västlänken. Här använder sig entreprenören sig av laserskanning för att uppfölja mängder, till exempel mängdning av sprutbetong och för att visa den aktuella bergprofilen jämfört med den teoretiska. Men där laserskanning är i huvudsak för att skanna geometrier, så kan fotogrammetri också skapa imaginära modeller där sprickor, strukturer och andra intressanta föremål framgår i fotografisk kvalitet.   Syftet med detta examensarbete är att ta reda på följande; Kan fotogrammetri med kamera användas för skanning av tunnelprofiler för bland annat bedömning av tjocklek av förstärkningselement?  Det utfördes två olika försökstudier under examensarbetets gång. Det första var ett pilotförsök där det utvärderades om systemet fungerade som det var tilltänkt. Det andra försökstudien var i aktuell produktion i en av arbetstunnlarna i korsvägen. Det har visat sig att ett av resultaten visar att fotogrammetri är ett bra komplement för att kunna mäta geometrier i tunnlar om man kan acceptera en viss noggrannhet på ner till 90% jämfört med laserskanning med totalstation. Vid mätningar av volymer så kan det vara så lågt som 3% jämfört med laserskanning.  Resultat från undersökningen visar att implementering av fotogrammetri-systemet med det etablerade arbetssättet skulle fungera som underlag för relationshandlingar. Nästan alla anläggningsarbeten använder sig utav tredimensionell modellering i projektering och entreprenörer använder sig utav dessa modeller när de bygger. Så att implementera dessa fotogrammetrimodeller kopplade till projekteringsmodeller passar väldigt bra att få in som del i relationshandlingarna. Utmaningen är storlekarna på filerna som skapas och vilket filformat som ska användas.

<p>Godkänd; 1990; 20080404 (ysko)</p>

Cracks can occur due to temperature induced movements during the hardening phase of concrete. Thermal cracks are not decisive for the load-bearing capacity but cause costs for repair and may reduce the life of the structure. The risk of cracking can be judged through safety values, (partial coefficients) given in building codes. In the thesis, partial coefficients for thermal cracking problems are determined with a probabilistic model. One crucial parameter influencing the risk of cracking is the restraint. In the report, methods are derived and presented for the determination of the restraint. Rotational boundary restraint from elastic foundations is treated as well as the restraint in internal points in the structures. For the determination of the rotational boundary restraint coefficient, applicable and simple graphical tools are presented. The restraint in internal points is based on a so-called plane-section restraint coefficient, a resilience factor for structures with length to height ratios smaller than seven, and a factor for slip failures in joints between the young and old parts. Four experiments of walls cast on slabs are presented in the thesis. On a precast slab, concrete walls are cast and loaded by restraint stresses induced by the temperature during the hydration. Different boundary restraint situations are used for the structure as well as different amount of reinforcement in the joint between the walls and the slab. The restraint and the amount of reinforcement are investigated regarding the risk of through cracking of the wall. The phenomenon of slip failure in joints has been shown in the tests. / <p>Godkänd; 2000; 20070318 (ysko)</p>