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.

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>

Bridges are an important element of the infrastructure today. The technical competence has reached high levels in most countries and the limits given to a bridge designer are set by economic restrictions rather than technical skill. The ever lasting chase for more economic solutions and procedures includes both a wish for cheaper constructions as well as for a decrease in the following maintenance costs. The roller bearings used in conventional bridges are known to generate high costs both during construction and due to maintenance, and the possibility to remove these bearings and accompanying expansion joints are therefore investigated since several years. In Sweden, the absence of bridges built with integral abutments has made it difficult to test and evaluate this solution. In 2005, an international project called Intab was launched with the explicit aim to look at different solutions possible to use if joints and bearings are excluded. One of the most common discussed problems concerning bridges built without expansion joints is the accommodation of longitudinal elongation due to temperature variations. A bridge built with integral abutments is often supported by piles made of steel or concrete. The longitudinal elongation of the superstructure induces a displacement and a moment in these piles, which in time may cause a fatigue failure. Therefore it is of big interest to look at the amplitude of these strains. Within the Intab project, a pilot object was built in Nordmaling, ~50 km south of Umeå. It is a 40 meter long and 5 meter wide composite bridge with two steel girders and a concrete deck. The steel piles in this bridge is equipped with strain gauges who are used both for longterm and shortterm measurements. The sampled data from longterm measurement is collected on a computer on site, and then downloaded through a traditional modem. The data from the shortterm measurement is sampled and collected immediately during the test. The shortterm test is performed during both summer and winter conditions, and consists of a lorry passing the bridge while different measurements are done. The result from the measurement is also compared to calculations and a 2-D FE-model. It seems that short-term measurements performed during warmer months, May and October, show better agreement with the FE-simulations than the tests performed during the winter. The used FE-model is based on restrictions from Bro 2004. Regarding the long-term measurements, the obtained strain values are not in a range where fatigue can be considered as a severe problem. / Godkänd; 2008; 20080212 (ysko)

No description available.

No description available.

Sverige har tillsammans med samtliga medlemsstater i FN ingått i vad som benämns Agenda 2030. Målet med Agenda 2030 är att leda världen mot en mer rättvis och hållbar framtid genom 17 globala delmål. Ett av dessa delmål beaktar klimatförändringar och de åtgärder som krävs för att minska dess utveckling. Byggbranschen producerar idag 21% av Sveriges totala utsläpp av växthusgaser och tillverkningen av cement producerar cirka 2–3 % av byggbranschens totala utsläpp. I dagens läge genomför Cementa, Sveriges enda producent av cement, forskning som ämnar att minska uppkomsten av växthusgaser vid cementtillverkningen. Med målet att erhålla en helt koldioxidneutral cementproduktion. Bara i Sverige genereras 12 miljoner ton rivningsavfall per år som kan härledas till byggbranschen. Genom att utveckla möjligheterna för återbruk av betongkonstruktioner förväntas återbruksprocessen minska mängden rivningsavfall och dessutom minska behovet av nyproducerad betong. Initialt kan implementering av återbrukbara betongkonstruktioner generera ett större klimatavtryck i förhållande till konventionellt producerade konstruktioner. Men att ett sådant, utökat klimatavtryck, kan försummas vid genomfört återbruk. Det är främst i byggnader där upprepande planlösning och vanligt förekommande konstruktioner använts som återbruksmöjligheterna bör beaktas. Avvikande och unika byggnader förväntas varken projekteras med hänsyn till återbruk eller erhålla ett utbud av byggnadselement som motsvarar efterfrågan. I dag dimensioneras bärverk av betong med en betydligt kortare livslängd än vad betongens tekniska livslängd förväntas vara. Därav rivs byggnader utan att dess tekniska livslängd överskridits. Exempelvis var 25% av alla rivna byggnader i Sverige år 1980 30 år eller yngre. Demonteringsprocessen för en byggnad förknippas starkt med uppförandet, både genom projektering och produktion. Genom att hämta inspiration från andra branscher som bil- och teknikindustrin, där produkter produceras med komponenter som kan demonteras och bytas ut, kan även hela byggnader producerats för att möjliggöra demontering och underhåll. Då fallstudien genomförs beaktas sex olika betongpelare som genom Eurokod 2 och EKS 11 testas för återbruk som balkar. Beroende av pelarnas längd bestäms antalet fack som beaktas efter återbruket. Pelarna kontrolleras i både brott- och bruksgränstillstånd med varierande upplagsvillkor i brottgränstillståndet. Det upplagsvillkor som i brottgränstillståndet tillåter störst belastning beaktas vidare i bruksgränstillståndet. Vidare kontrolleras även pelarnas faktiska lastupptagningsförmåga, då elementet brukas med avsett syfte. Då pelarna kontrolleras som balkar genomförs detta i linje med befintliga dimensioneringsnormer för betongbalkar. Därav ges en helhetsbild över de brister men även möjligheter som präglar återbruk av liknande konstruktioner. Samtliga pelare erhåller goda lastupptagande egenskaper, där indata för fyra av pelarna korrigeras för att klara ställda krav på tvärkraftsarmering. Differerade krav på tvärkraftsarmering mellan pelare och balkar genererar problem då minimiarmering använts för pelarens byglar. Vidare åskådliggörs vikten av att i projekteringsfasen beakta återbruksmöjligheterna samt att då generera goda förutsättningar för genomförandet. Detta genom implementering av mekaniska infästningar som underlättar demonteringsskedet, permanenta uppmärkningar som möjliggör identifiering och orientering av elementens innehåll samt tjockare täckskikt som möjliggör utökade livslängder.

In general, the main purpose of a structural control system is to apply powerful control techniques that improve the behaviour of civil structures under various kinds of dynamic loading. The first part of this thesis presents novel applications of posicast and input shaping control schemes that have never previously been applied in the field of structural control. Numerical simulations of a benchmark three-story building with an MR damper are used to verify the efficiency of the proposed control theories. The superiority and effectiveness of the suggested schemes at reducing the structure’s responses were demonstrated using six evaluation criteria and by comparison to results achieved with well-established classical control schemes. Moreover, a comprehensive procedure for generating scaled real ground motion records appropriate for a seismic analysis and design of structures using the linear spectrum matching technique is presented based on a seismic hazard study.To efficiently control a structure, it is necessary to estimate its real-life dynamical behaviour. This is usually done using the Structural Identification approach, which is also addressed in this thesis. Structural Identification is commonly utilized to bridge the gap between the real structure and its modeled behaviour. It can also be used to evaluate the structure’s health, detect damage, and assess efficiency. Despite the extensive development of parametric time domain identification methods, their relative merits and the accuracy with which they predict the behaviour of vibrating structures are largely unknown because there have been few comparative studies on their performance under diverse test conditions, and they have not been verified against real-life data gathered over extended periods of time.Thus, the second part of this thesis focuses on applications of parametric and non-parametric models based on the Structural Identification approach in order to clarify their potential and applicability. In addition, a new strategy is proposed that combines this approach with techniques based on Singular Value Decomposition (SVD) and Complex Mode Indicator Function (CMIF) curves to detect structural damage.The methods developed in this work are used to predict the vertical frequencies of the top storey in a multi-storey building prefabricated from reinforced concrete in Stockholm, and to detect and locate damage in a benchmark steel frame. In addition, the non-parametric structural identification approach is used to investigate variation in the modal characteristics (frequency, damping, and mode shapes) of a steel railway bridge. / <p>Godkänd; 2015; 20150303 (taredr); Nedanstående person kommer att disputera för avläggande av teknologie doktorsexamen. Namn: Tarek Edreees Saaed Alqado Ämne: Konstruktionsteknik/Structural Engineering Avhandling: Structural Control and Identification of Civil Engineering Structures Opponent: Professor Francesc Pozo, Department of Applied Mathematics III, Escola Universitària d’Enginyeria Tècnica Industrial de Barcelona (EUETIB), Universitat Politècnica de Catalunya Comte d’Urgell, Barcelona, Spanien Ordförande: Professor Jan-Erik Jonasson vid Avd för byggkonstruktion och produktion, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet Tid: Torsdag den 26 mars 2015, kl 10.00 Plats: C305, Luleå tekniska universitet</p>