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1
Kevern, John Tristan. "Advancements in pervious concrete technology." [Ames, Iowa : Iowa State University], 2008.
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Hardon, Roger G. "Technology of repair for corroded reinforced concrete." Thesis, Aston University, 1989. http://publications.aston.ac.uk/14268/.
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A number of factors relating to various methods of repair for chloride initiated corrosion damage of reinforced concrete have been studied. A novel methodology has been developed to facilitate the measurement of macro and micro-cell corrosion rates for steel electrodes embedded in mortar prisms containing a chloride gradient. The galvanic bar specimen comprised electrically isolatable segmental mild steel electrodes and was constructed such that macro-cell corrosion currents were determinable for a number of electrode combinations. From this, the conditions giving rise to an incipient anode were established. The influence of several reinforcement and substrate primer systems upon macro-cell corrosion, arising from an incipient anode, within a patch repair have been investigated. Measurements of electrochemical noise were made in order to investigate the suitability of the technique as an on-site means of assessing corrosion activity within chloride contaminated reinforced concrete. For this purpose the standard deviation of potential noise was compared to macro-cell galvanic current data and micro-cell corrosion intensity determined by linear polarisation. Hydroxyl ion pore solution analyses were carried out on mortar taken from cathodically protected specimens. These specimens, containing sodium chloride, were cathodically protected over a range of polarisation potentials. Measurement of the hydroxyl ion concentrations were made in order to examine the possibility of alkali-silica reactions initiated by cathodic protection of reinfored concrete. A range of mortars containing a variety of generic type additives were examined in order to establish their resistances to chloride ion diffusion. The effect of surfactant addition rate was investigated within a cement paste containing various dosages of naphthalene sulphonate.
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Catley, David Gerald. "Thermal curing of concrete with conductive polymer technology." Thesis, Sheffield Hallam University, 2009. http://shura.shu.ac.uk/19431/.
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Concrete is used on the majority of all construction projects. It is manufactured using the core constituents of a cement binder, typically Portland Cement, proportions of coarse and fine aggregates and water. The strength development of concrete is achieved by the addition of water that reacts with the binder in the form of a hydration reaction. This hydration reaction or strength development is dependant on two primary curing factors, time and temperature. Increasing the rate of strength development of concrete by elevating the curing temperature at early ages has advantages of maximising concrete production and reducing manufacturing time. Increasing the temperature of early age concrete up to 70 deg C is used in precast plants where it is critical for a minimum strength to be achieved within a certain time period to allow the removal of the concrete sections from moulds and forms. Various practices are adopted by precast concrete manufacturers to achieve the early strengths required to maximise production, both thermal and non-thermal. These include heating the various mix constituents of the concrete, using unnecessarily high cement contents within the mix, using large quantities of chemical admixtures or by increasing the ambient temperature of plants within which the elements are manufactured. In precast concrete plants the use of steam to elevate the curing temperature of the concrete is the most commonly adopted technique. However, it is inefficient and rarely provides controlled temperatures to the concrete as recommended in approved codes of practices and standards. This research programme has investigated the use of an alternative heating technology for concrete curing, optimising a unique Conductive Polymer Technology (CPT). The application and optimisation of the CPT material to provide heat curing to concrete within the laboratory, in-situ and within precast concrete plants has been investigated. The electrical properties of the CPT were investigated to determine their relationship with the size of the concrete elements. This was done for various CPT materials with different Characteristic Resistances. Having gained an in depth understanding of the electrical properties of the CPT, various heating Jackets were designed and manufactured to thermally cure concrete elements at early ages. The Jackets were designed with various outer protective materials. The effect of CPT curing on the strength and shrinkage, both at early ages and long-term, was determined. The thermal performance of the heating jackets was determined for each application including the uniformity of the heating provided into the concrete element. The interaction of the heat generated by hydration and CPT heating for larger elements was also investigated. The results showed that the CPT materials varied depending upon their manufacture and required target resistance. The thermal blankets had the capability to uniformly heat concrete elements at various ambient temperatures, to temperatures required by standards and approved codes of practice for accelerated curing of concrete. This uniform heating resulted in greater compressive strength of laboratory scale concrete elements with reduced shrinkage. The research identified the important parameters for CPT jacket design andmaterials selection e.g. the importance of the contact between CPT heating elements and the concrete element and the selection of appropriate insulation materials. The test programme also investigated the durability of CPT under different exposure conditions. The results from testing the CPT material under conditions such as freeze thaw, heating & cooling and wetting & drying showed that wetting and drying had the most significant affect on the CPTs resistance, altering by 10%. Other tests of durability included punching holes of various sizes into the CPT samples to determine their effect on the CPT's resistance. This was found to be directly linked to the area of CPT material removed. The manufacture, performance and operation of the CPT materials has also been investigated to provide an understanding of its mode of heating and its effect on concrete curing. The concept of maturity has been used to determine relationships between strength development and thermal curing and energy requirement for thermal curing when using CPT.
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Rezaei, Ehsan. "Vibrations of partly supported concrete railway sleeper." Thesis, Linköping University, Solid Mechanics, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-57679.
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Analytical and finite element solutions to the problem of a vibrating beam on an elastic foundation are presented. An application example is a concrete railway sleeper embedded in an elastic medium (the ballast). The sleeper is also elastically connected to the rails. Eigenfrequencies are calculated and vibration modes are discussed. The beam (sleeper) is divided into sections where each section may or may not be supported by the elastic foundation. The elastic connections to the rails are situated at the two joinings of the three sleeper sections.
Some conclusions are that Euler-Bernoulli beam theory can be used to calculate two, or maximum three, eigenfrequencies of the sleeper. The foundation stiffness influences the lowest bending-mode eigenfrequency the most; higher eigenfrequencies are practically unaffected by the foundation stiffness. The influence of railpad (and rail) stiffness on the sleeper eigenfrequencies is negligible.
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Altobelli, Frank Robert. "An innovative technology in concrete construction--semi-automated rebar tying." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/45703.
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KING-NYGREN, ELIAS. "Analysis of Complex 3D-Concrete Casting." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-299789.
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Concrete is the second most used material in the world and is primarily used within the construction industry. It is however also used for making decorative and functional smaller products within various industries. Manufacturing with concrete can be done with different manufacturing techniques, the most common technique being concrete casting in molds. This project was conducted at Arclight AB in Stockholm, a company on the verge of starting production of molds for casting concrete products. With many different manufacturing techniques at their disposal, it is however difficult for them to know which manufacturing technique should be used for which type of mold. The goal of this project is to compare the available manufacturing techniques at Arclight and see which are most suitable for mold manufacturing. The background research and preparation resulted in three segments of the casting process which needed to be analyzed: choice of concrete, choice post-processing technique, and choice of manufacturing technique. Results from the trails of these three segments gave invaluable information for the project. Concrete trails resulted in a recommendation of a concrete with high compression strength and high water content to make the concrete viscous and flow easily into the mold. Post-processing trials resulted in different optimal post-processing techniques based on the mold material and manufacturing technique. Manufacturing trails gave in-depth information on processing larger molds and the potential problems associated with casting complex large concrete products. The final result of the project is a spreadsheet which recommends an optimal manufacturing technique based on the geometry type and number of products to be cast. Maximum cost per product, maximum machine time for manufacturing and maximum total production time for the concrete products are also stated to find the optimal manufacturing technique for each specific concrete casting project. Before using this spreadsheet as a basis for manufacturing, it should be formatted for easier use. Additional tests with applying epoxy and polyurethane resin for post-processing molds should be conducted, in addition to testing materials for manufacture of master molds for vacuum forming.Betong är det näst mest använda råmaterialet i världen och används primärt inom byggindustrin. Det används även för tillverkning av estetiska och funktionella mindre produkter inom andra industrier. Betongprodukter kan tillverkas med flera olika tillverkningstekniker, där den vanligaste är gjutning av betong i gjutformar. Detta projekt var utfört hos Arclight AB i Stockholm, ett företag som är i början av att starta produktion av gjutformar för gjutning av betongprodukter. Med så många olika tillverkningstekniker hos företaget är det svårt att veta vilken tillverkningsteknik som är bäst lämpad för vilken typ av gjutform. Målet med detta projekt är att jämföra de olika tillverkningstekniker Arclight har och se vilka är mest lämpade för tillverkning av gjutformar. Bakgrundsforskningen och förberedandet resulterade i tre segment av gjutprocessen som behövde analyseras; val av betong, val av ytbehandlingsteknik, och val av tillverkningsteknik. Testerna inom dessa tre segment gav ovärderlig information för projektet. Resultatet av betongtesterna var en rekommendation av betong med hög tryckhållfasthet och en stor mängd vatten i betongen för lättare hällning i gjutformen. Resultatet av ytbehandlingstesterna var olika optimala ytbehandlingar beroende på material för gjutformen, samt tillverkningsteknik. Resultatet av tillverkningstesterna gav information om stora gjutformar bäst hanteras och eventuella problem associerade med att gjuta stora komplexa betongprodukter. Slutgiltiga resultatet av projektet är ett kalkylblad vilket rekommenderar optimala tillverkningsmetoden baserat på geometritypen av produkten som ska gjutas samt antalet produkter att tillverka. Maximal kostnad per produkt, maximal maskintid för tillverkning och maximal total tillverkningstid för produktion av betongprodukterna bestäms även för att finna optimala tillverkningstekniken för varje specifikt betonggjutningsprojekt. Innan detta kalkylark används för tillverkning borde det formateras så det är mer användarvänligt. Ytterligare ytbehandlingstester med epoxyresin och polyuretanresin bör göras på gjutformar, samt även att testa material för tillverkning av formverktyg för vakumforming.
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Cortis, Michael. "Numerical modelling of braided fibres for reinforced concrete." Thesis, University of Glasgow, 2016. http://theses.gla.ac.uk/7763/.
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Fire has been always a major concern for designers of steel and concrete structures. Designing fire-resistant structural elements is not an easy task due to several limitations such as the lack of fire-resistant construction materials. Concrete reinforcement cover and external insulation are the most commonly adopted systems to protect concrete and steel from overheating, while spalling of concrete is minimised by using HPFRC instead of standard concrete. Although these methodologies work very well for low rise concrete structures, this is not the case for high-rise and inaccessible buildings where fire loading is much longer. Fire can permanently damage structures that cost a lot of money. This is unsafe and can lead to loss of life. In this research, the author proposes a new type of main reinforcement for concrete structures which can provide better fire-resistance than steel or FRP re-bars. This consists of continuous braided fibre rope, generally made from fire-resistant materials such as carbon or glass fibre. These fibres have excellent tensile strengths, sometimes in excess of ten times greater than steel. In addition to fire-resistance, these ropes can produce lighter and corrosive resistant structures. Avoiding the use of expensive resin binders, fibres are easily bound together using braiding techniques, ensuring that tensile stress is evenly distributed throughout the reinforcement. In order to consider braided ropes as a form of reinforcement it is first necessary to establish the mechanical performance at room temperature and investigate the pull-out resistance for both unribbed and ribbed ropes. Ribbing of ropes was achieved by braiding the rope over a series of glass beads. Adhesion between the rope and concrete was drastically improved due to ribbing, and further improved by pre-stressing ropes and reducing the slacked fibres. Two types of material have been considered for the ropes: carbon and aramid. An implicit finite element approach is proposed to model braided fibres using Total Lagrangian formulation, based on the theory of small strains and large rotations. Modelling tows and strands as elastic transversely isotropic materials was a good assumption when stiff and brittle fibres such as carbon and glass fibres are considered. The rope-to-concrete and strand-to-strand bond interaction/adhesion was numerically simulated using newly proposed hierarchical higher order interface elements. Elastic and linear damage cohesive models were used effectively to simulate non-penetrative 'free' sliding interaction between strands, and the adhesion between ropes and concrete respectively. Numerical simulation showed similar de-bonding features when compared with experimental pull-out results of braided ribbed rope reinforced concrete.
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El-Dharat, A. A. G. "The structural behaviour of composite reinforced concrete trough floors." Thesis, University of Salford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356194.
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Coyle, Neil Robert. "Development of fully composite steel-concrete-steel beam elements." Thesis, University of Dundee, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270046.
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Steel-Concrete-Steel (SCS) composite construction consists of two relatively thin steel plates with the space between filled with concrete. Various forms of this construction exist, using overlapping shear studs and single bar connectors to provide shear reinforcement to the concrete and provide a shear transfer at the interface. The problem with current systems that rely purely upon shear studs or bar connectors is that they are prone to slip between the steel faceplates and concrete core. This slip leads to a loss of composite action causing a loss of stiffness and a reduced fatigue life. An extensive experimental programme consisting of 32 beam specimens and 34 other small scale specimens formed the basis for the study of the behaviour of surfaced SCS specimens under a variety of load conditions. The results of this test program showed that surfaced SCS specimens behaved in a more composite manner. This increase in composite action manifested itself in a number of ways. • Reduced slip between steel plate and concrete core • Increased stiffness of specimen • More even crack distribution This extensive experimental study was backed up with an analytical study to understand and predict the behaviour of the surfaced SCS elements. This study has led to a new method of predicting the capacity of such sections, to a greater degree of accuracy than current methods allow. Further to this a FE parametric study was carried out to investigate the sensitivity of the elements to changes in the main geometrical and material variables.
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Dennington, Simon P. J. "The effect of carboxylated acrylic polymer latices on the hydration kinetics of ordinary Portland cement." Thesis, University of Bristol, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390101.
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Rajczakowska, Magdalena. "Self-Healing Concrete." Licentiate thesis, Luleå tekniska universitet, Byggkonstruktion och brand, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-76527.
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Concrete is a brittle material prone to cracking due to its low tensile strength. Crack repairs are not only expensive and time-consuming but also increase the carbon footprint. Designing a novel concrete material possessing the ability to self-repair cracks would enhance its sustainability. Self-healing can be defined as a material’s ability to repair inner damage without any external intervention. In the case of concrete, the process can be autogenous, based on an optimized mix composition, or autonomous, when additional capsules containing some healing agent and/or bacteria spores are incorporated into the binder matrix. The first process uses unhydrated cement particles as the healing material while the other utilizes a synthetic material or bacteria precipitating calcite which are released into the crack from a broken capsule or activated by access to water and oxygen. The main disadvantages of the autonomous method are the loss of the fresh concrete workability, worsened mechanical properties, low efficiency, low survivability of the capsules and bacteria during mixing and the very high price. On the other hand, the autogenous self-healing was found to be more efficient, more cost effective, safer, and easier to implement in full-scale applications. Knowledge related to mechanisms and key factors controlling the autogenous self-healing is rather limited. Therefore, the aim of this research work was to better understand the autogenous self-healing process of concrete and to optimize the mix design and exposure conditions to maximize its efficiency. This licentiate thesis summarizes the main findings of the first 2.5 years of the PhD project. Several factors affecting autogenous self-healing were studied, including the amount of unhydrated cement, mix composition, age of material, self-healing duration and exposure conditions. The process was investigated both externally, at the surface, and deeper inside of the crack, by evaluating the crack closure and chemical composition of formed self-healing products. In addition, the flexural strength recovery was also studied. It was observed that a large amount of cement in the concrete mix does not ensure an efficient autogenous self-healing of cracks. A very dense and impermeable binder microstructure limited the transport of calcium and silicone ions to the crack and diminished the precipitation of the healing products. Addition fly ash increased the crack closure ratio close to the crack mouth, but its presence did not support the recovery of the flexural strength, presumably due to a very limited formation of load bearing phases inside the crack. Calcium carbonate was detected mainly at the crack mouth, whereas calcium silicate hydrate (C-S-H) and ettringite were found deeper inside the crack. The formation of C-S-H and ettringite presumably resulted in a regain of the flexural strength. On the other hand, calcite crystals formed close to the surface of the specimen controlled conditions inside the crack through its external closure. Healing exposure based on pure water appeared to be inefficient even despite the application of different temperature cycles and water volumes. The application of a phosphate-based retarding admixture in the curing water resulted in the highest self-healing efficiency. The admixture presumably inhibited the formation of a dense hydration shell on the surface of the unhydrated cement grains and promoted the precipitation of calcium phosphate compounds inside the crack. In addition, water mixed with microsilica particles caused a regain of the flexural strength through formation of C-S-H in the crack.
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Wiberg, Anders. "Strengthening of concrete beams using cementitious carbon fibre composites." Doctoral thesis, KTH, Civil and Architectural Engineering, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3582.
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The research described in this thesis deals with the use ofcement-based carbon fibre reinforced composites forstrengthening of existing structural concrete.
There is a large world-wide need for simple and reliablemethods to repair and strengthen aging infrastructure andbuildings. The use of cementitious fi- bre composites offersseveral advantages over the existing methods. No other work onstrengthening of structural concrete with cementitiouscomposites reinforced with continuous high strength fibres wasidentified when the present work started in 1998. At presenttime, 2003, it still is a new technique and very littleresearch has been internationally reported. This work includesa literature survey describing the state of the art of thestrengthening of structural concrete with cement based fibrereinforced composites.
Due to the novelty of this technique no specially adaptedmaterials are available and ready for use in cementitiouscomposites. In order to make many small scale tests to optimizethe composite, a new test beam has been developed. Severalparameter studies have been done in this work to determine howdifferent parameters, for example fineness of grading of thecement, additives, and fibre configuration affect thecomposite.
Large scale tests of ordinary concrete beams strengthenedwith a cementitious fibre composite are reported. The compositeused was made of a polymer modified mortar and a unidirectionalsheet of continuous carbon fibres, applied by hand. Bothflexural strengthening and shear strengthening were tested. Arelatively new method for measuring strains with digitalcameras was used on the shear strengthenings with a goodresult. It is concluded that the large scale tests have proventhat this method works and has great potential for futureuse.
Design methods for strengthenings were studied andevaluated. It is concluded that design methods formulated forstrengthening of structural concrete with carbon fibrereinforced polymers can be adapted also to cementitiouscomposites by introducing an efficiency factor.
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Gendy, S. S. F. M. "Explicit second-order mixed formulation of reinforced concrete structures under impact loading." Thesis, City, University of London, 2018. http://openaccess.city.ac.uk/19116/.
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Most available research on analysis of reinforced concrete structures under impact loads focuses on using continuum models such as membrane and solid elements, which renders the problem expensive in terms of computational effort. Therefore, a gap exists in the available literature, as no simple finite element has sufficient capabilities to deal with impact and shock problems while considering detailed local parameters. Meanwhile, the objective of this research is to develop several non-linear planar finite element models capable of accurately predicting the response of reinforced concrete structures subjected to impact dynamic loading. A mixed and displacement- based element that use an explicit time integration method and consider large deformations are being developed together with a third force-based first-order element that employs the explicit time integration method. A new algorithm that eliminates the need for iterations at the element level is proposed. The strain rate effect is accounted for in the material constitutive models. The developed explicit fibre beam models, particularly the force-based and mixed elements, represent a simple yet powerful tool for simulating the nonlinear complex effect of impact loads on structures accurately while using very few finite elements. The elements can particularly model fibrous slender reinforced concrete structures and steel concrete panels under impact loading. A simplified procedure is also developed to employ the planar elements in solving three-dimensional problems where the load is applied in the out-of-plane direction. The proposed elements are validated using benchmark experiments available from the literature. The results of the numerical studies proved the newly developed elements are capable of providing accurate and computationally efficient estimates of structural demands under severe impact loading conditions.
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Dry, Carolyn. "Design of systems for time delayed activated internal release of chemicals in concrete from porous fibers, aggregates of prills, to improve durability /." This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-05222007-091330/.
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Saevarsdottir, Thorbjoerg. "The structural, serviceability and durability performance of variable density concrete panels." Thesis, University of Canterbury. Civil Engineering, 2008. http://hdl.handle.net/10092/1237.
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Conventional concrete is a poor insulating material but has good thermal mass, while lightweight concrete provides good insulation at the price of thermal mass. Precast concrete wall systems have not been widely used in residential homes due to poor thermal and acoustic performance, despite being high quality products that are easy to construct. The variable density concrete panel was designed to combine good thermal storage, insulation and high quality precast concrete. It is produced from a single concrete mix which is vibrated to get a lightweight top layer and a normal/heavyweight bottom layer. The lightweight layer is the wall exterior, having low thermal conductivity providing good thermal insulation while the normal/heavyweight layer is the dense wall interior, having high specific heat to provide good thermal mass and sufficient strength for construction handling and to withstand service loads. The intention of this research was to estimate the hardened performance; that is the structural, serviceability and durability performance of the variable density concrete panel. Further developments to the mix design were made where the fresh properties were measured and thermal performance estimated on hardened specimens. Most of the major technical concerns were proved not being as severe as first thought, making the production of variable density concrete panels promising. To ensure that the variable density concrete would stratify, the concrete mix had to have defined fresh properties. Defined rheological ranges gave a good indication of the stratification potential, but the degree of stratification was also found to be dependent on the intensity and time of vibration. Slump flow had to be within a certain range to achieve good stratification but this alone did not guarantee stratification. Variable density concrete was found to have adequate strength capacity both in axial compression and in tension for likely service loads but the strength required to withstand handling loads at early ages was not assessed. The strength of the variable density concrete was found to be affected by several factors such as; degree of stratification, relative strength and thickness of the layers, curing environment and amount of defects. As the stratification of the concrete increased the thermal insulation improved whereas the strength decreased. Warping was found not to significantly affect the serviceability of panels despite differential shrinkage within the element. The amount of warping was mainly related to the degree of stratification. Warping decreased with better stratification as more stress and strain was relieved in the lightweight layer. The lightweight concrete was significantly weaker as well as being less stiff than the structural concrete and therefore creeps to follow the structural concrete. The thermal properties aimed for were generally not reached, but these mixes were not designed to optimise the thermal performance and were tested before the concrete was fully dried. This increased thermal conductivity and therefore reduced the measured R-values. Stratified concrete had good absorption resistance, poor permeability properties and was highly porous. If the concrete was over-vibrated it tended to have a rough surface finish that would require a coating. Delamination of the panels was not assessed in this research but is a likely mode of failure.
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Nilsson, Isak, and Leonard Sandström. "Behavior prediction of concrete dams." Thesis, KTH, Betongbyggnad, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-289385.
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As many dams were built around 1950, the expected life span of these dams are about tobe reached. With this, the need for monitoring and increased understanding of the damsstructural integrity increases. In order to prevent failures, two warning signals are defined;alert and alarm. The main difference being that the first indicates an unexpected changein behavior that needs to be addressed and evaluated in the near future, while the otherrequires that immediate action must be taken to ensure the safety of the dam.This report aims to evaluate the applicability of different models for designing alert values.In order to achieve this goal, two case studies have been performed. The first being onSchlegeis, an arch dam in Austria, and the second Storfinnforsen, a concrete buttress damin Sweden. The methods used are finite element modelling as well as data-based models.Data-based models work on the presumption that the dam behaviour is governed by variationsin environmental conditions such as temperature and water level. The report hasevaluated two commonly used data-based models, hydrostatic thermal time (HTT) and hydrostaticseasonal time (HST), as well as two machine learning based models artificial neuralnetworks (ANN) and boosted regression trees (BRT).The programs used in this report are BRIGADE plus for finite element method and MATLABfor the multi-linear regression analyses HTT and HST, as well as boosted regressiontrees. The neural networks were constructed in Python using TensorFlow and Keras API.The result from the case studies is that the commonly used data-based models HST andHTT perform well enough for creating predictions and alert levels when given a sufficientamount of historical data, approximately 3-5 years. Machine learning such as artificial neuralnetworks while comparable in prediction quality does not further increase the understandingof the dam behaviour and can due to the complexity of designing an appropriate networkstructure be less suited for this type of analysis. Finite element models can also capturethe behavior of the dam rather well. It is however not as accurate as data-based modelswhen sufficient data is available. An FE-model should be used for definition of alert valueswhen insufficient data exists after the dam conditions have been significantly altered, orwhen newly constructed. The main advantage that machine learning provides is that theyperform better for non-linear behavior than multi-linear regression.
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Fahy, Caroline. "A discrete transport-mechanical approach for modelling the durability of concrete." Thesis, University of Glasgow, 2014. http://theses.gla.ac.uk/5761/.
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Reinforced concrete is one of the most commonly used structural materials in the world and is used for buildings and many different types of civil engineering structures, such as bridges, tunnels and airports. The majority of these structures are required to remain in service for at least 50 years while some are expected to last well over 100 years. Fracture of these structures leads to an increase in the permeability of the concrete which in turn can result in increased ingress of water and other aggressive agents, such as chlorides or carbon dioxide, that accelerate the deterioration of these structures. Likewise, the mechanical properties of the concrete can be affected by the transport of moisture into the structure. The increase in moisture can lead to a reduction of the strength and the stiffness of the material. The costs arising from structural failure are extremely high and in practice repair work tends to be implemented even when it is not entirely necessary. Therefore reliable approaches that can describe the interaction between the transport and mechanical properties of concrete and predict resulting structural degradation are of great benefit for practising engineers. Numerical models, such as the one proposed in this work, could be used for predicting when a repair is really necessary. In this work, a transport-mechanical lattice approach to modelling the durability of concrete is proposed. The discretisation of the specimen domain is based on a dual Delaunay and Voronoi tessellation in which the edges of the Delaunay triangles form the mechanical elements and the transport elements are placed along the edges of the Voronoi polygons. The mechanical response of the concrete is described using an isotropic damage constitutive law, while the transport of moisture through the specimen is described using constitutive laws developed for mass transport through porous materials. Both the mechanical and the transport models are assessed individually before the coupling ii between the two models is implemented. The accuracy of the proposed coupled approach is validated through the analysis of an elastic thick-walled cylinder, in which the numerical results are compared with an analytical solution derived as part of this work. The proposed coupled approach is then applied to the case of corrosion-induced cracking of reinforced concrete structures. In this approach, the corrosion products are assumed to behave as a fluid and therefore values of fluid properties are required. A value of viscosity is determined based on the analysis of a concrete specimen containing a single reinforcement bar. Finally, the proposed approach is applied to a concrete specimen containing four reinforcement bars to assess the approach as a predictive model. As expected with the concrete specimen containing a single reinforcement bar, very good agreement between numerical and experimental results is obtained. In the case of a specimen containing four reinforcement bars, it is observed that for small attack penetration depths the proposed approach is in very good agreement with experimental results. As the analysis continued, however, the numerical approach under-estimated the crack width when compared to experimental results.
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Denton, Stephen Richard. "The strength of reinforced concrete slabs and the implications of limited ductility." Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274164.
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Hall, Robin. "Impact sound insulation of flooring systems with polyurethane foam on concrete floors." Thesis, Sheffield Hallam University, 1999. http://shura.shu.ac.uk/3135/.
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The problem of unwanted noise in buildings has grown continuously over the last twenty years and impact noise through separating floors has been identified as a particularly important problem. One accepted method for improving impact sound insulation is to use floating floors in which the walking surfaces are isolated from the supporting structure by a resilient layer. Traditionally the resilient layers comprise mineral or glass fibre quilts but other materials such as flooring grade polystyrene are increasingly used. Recently, shallow profile floating floors comprising flexible open cell polyurethane foam resilient layers have been developed. These systems are attractive for refurbishment projects since they can simply be placed on existing floors in order to improve their impact sound insulation whilst raising the existing floor level less than systems comprising fibre quilts. Shallow profile floating floors with thin layers of flexible open cell polyurethane foam are the subject of investigation as part of this research work. This thesis reviews the previous research on polyurethane foams and evaluates the usefulness of the Standard Tests on these materials for assisting in the selection of foam for use as resilient layers under lightweight floors. Both the static and dynamic behaviour of flexible open cell polyurethane foam are investigated and recycled polyurethane foam is shown to be particularly useful for use under floating floors Its characteristic behaviour under compressive strain is described for the first time. This thesis shows that by modifying the Standard Method for the determinaf on of the dynamic stiffness of resilient layers under floating floors (BS EN 29052-1), the effect of the air contained in the open cell foam specimens can be included in the Standard laboratory test. The modification makes it possible to evaluate the dynamic stiffness of low airflow resistivity resilient polyurethane resilient layers using the apparatus described in BS EN 29052-1 for the first time. Field measurements of impact sound pressure level conducted using sections of lightweight shallow profile floating floor on a concrete supporting floor are described. The measured improvements in impact sound insulation achieved by using the sections of floating floor are compared with the improvements predicted using the results from the modified Standard laboratory tests on the foams used as resilient layers. It is shown that by compensating for the mass impedance of the Standard tapping machine hammers good correlation between predicted and measured data is achieved. A simple method for predicting the weighted standardised impact sound pressure level (L'nT,w) in the receiving room is proposed which shows excellent correlation with L'nT,w obtained from the measured data. The work shows that BS EN 29052-1 is more widely applicable than the Standard itself states and for the first time identifies a method of predicting the performance of lightweight shallow profile floating floors with polyurethane foam resilient layers. Finally the use of the ISO tapping machine for assessing the impact sound insulation of the very lightweight floating floors of interest to this research is considered. Different methods of correlating perceived and measured the impact sound insulation of floors are reviewed. Experimental results conducted in this research programme, along with searches of the literature confirm that the tapping machine is a suitable source for measuring the impact sound insulation of these floors.
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Cauthen, Stephen Michael. "Vacuum assisted resin transfer molding in the repair of reinforced concrete bridge structures." Birmingham, Ala. : University of Alabama at Birmingham, 2008. https://www.mhsl.uab.edu/dt/2008m/cauthen.pdf.
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Loijos, Alex (Alexander Nikos). "Life cycle assessment of concrete pavements : impacts and opportunities." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/65431.
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Thesis (S.M. in Technology and Policy)--Massachusetts Institute of Technology, Engineering Systems Division, Technology and Policy Program, 2011.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student submitted PDF version of thesis.
Includes bibliographical references (p. 118-121).
The concrete pavement network in the United States plays a crucial role in the economy by enabling the transport of people and goods, but it also leads to resource consumption and environmental impacts. This thesis is fundamentally motivated to reduce the impact that concrete pavements have on climate change. The principal methodology that is used is life cycle assessment (LCA), which comprehensively includes all five primary phases of the life cycle: materials extraction and production, pavement construction, pavement rehabilitation, the use phase, and end-of-life recycling and disposal. This work informs the reduction of life cycle greenhouse gases (GHGs) through a three-pronged approach to: 1) comprehensively quantify GHG emissions for structures representing all primary pavement types in the US, 2) establishes a benchmark for GHG emissions from all concrete pavements in the US constructed annually, and 3) identifies five reduction strategies and measures the GHG reduction that is obtainable through these strategies, both at the project-level for different road classes and at the national level. This provides a portfolio of GHG reduction options to national and regional policymakers, transportation agencies, and pavement engineers.
by Alex Loijos.
S.M.in Technology and Policy
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Niven, Robert A. J. "Physiochemical investigation of CO₂ accelerated concrete curing as a greenhouse gas mitigation technology." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99193.
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There is an emerging demand for natural and engineered CO2 sinks to combat the effects of global warming. Carbon capture and storage (CCS) processes are expected to play a predominant role within a broad portfolio of technical innovations to mitigate greenhouse gas (GHG) emissions. A range of CCS methods will be required to provide GHG control technologies for the broad scope of industrial sectors. Within this class of technologies carbon dioxide accelerated concrete curing has the global potential to permanently and safely sequester up to 550 Mt CO2/yr while producing non-reinforced concrete products with improved physical properties and in less time than traditionally cured products. Previous research has exhibited shallow CO 2 penetration depth and modest CO2 uptake in grout and concrete samples despite using severe process conditions such as high pressures, temperatures and long experimental durations. Chemical and microstructural changes during carbonation were investigated to clarify the previously unexplained limitations in CO2 uptake and provide solutions to enhance CO2 storage. Loss of exposed particle surface area was identified as the most significant factor limiting complete carbonation of cement grout samples. The findings were applied to design a bench scale, flow-through carbonation curing reactor that sequestered CO2 at an average of 8.3 wt % of the cured cement with complete depth of penetration. The sequestration results were achieved with ambient temperature (20°C), 40% relative humidity, atmospheric pressure (1 atm), as-captured flue gas CO2 partial pressure (0.20) and low flow (1 Lpm) in less than 60 minutes.
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Hussin, Manal Kamil. "Identification of prestress force in prestressed concrete box girder bridges using ultrasonic technology." Thesis, Queensland University of Technology, 2018. https://eprints.qut.edu.au/117669/8/Manal_Hussin_Thesis.pdf.
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This research was aimed to develop an ultrasonic technology to identify the prestressing force in new and exciting prestressed concrete box girder bridges. The research study included finite element analysis and laboratory testing of a scaled down prestressed concrete box-girder bridge model. New approaches for ultrasonic testing and prestressed force identification were developed and tested successfully.
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Malek, Amir Masoud 1959. "Analytical study of reinforced concrete beams strengthened with fiber reinforced plastic plates (fabrics)." Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/282316.
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Epoxy-bonding a composite plate to tension face, is an effective technique for repair and retrofit of reinforced concrete beams. Experiments have indicated local failure of the concrete layer between the plate and longitudinal reinforcement in retrofitted beams. This mode of failure is caused by local stress concentrations at the plate end, as well as at the flexural cracks. A method has been presented for calculating shear and normal stress concentrations at the cut-off point of the plate. Stress concentrations predicted by this method have been compared to both finite element method and experimental results. The analytical models provide closed form solutions for calculating stresses at the plate ends and can easily be incorporated in design equations. The ultimate capacity of the reinforced concrete beams strengthened by composite plates bonded to the tension face, is controlled by either compression crushing of concrete, rupture of the plate, local failure of concrete at the plate end, or debonding of the plate. These failure modes have been considered in developing design guidelines for flexural strengthening of reinforced concrete beams using fiber composite plates. Bonding composite plates (fabrics) to the web of reinforced concrete beams can increase the shear and flexural capacity of the beam. An analytical model has been developed to calculate the stress distribution in the strengthened beam, and the shear force resisted by the composite plate before cracking and also after formation of flexural cracks. Parametric study has been performed to reveal the effect of important parameters such as fiber orientation, and plate thickness. The ultimate shear capacity of reinforced concrete beams is also increased by epoxy-bonding composite plates to the side faces of the beam. Truss analogy and compression field theory have been used to determine the effect of the composite plate on the crack inclination angle and the shear capacity of reinforced concrete beams at ultimate state. The effects of important parameters such as plate thickness and fiber orientation angle on the crack inclination angle and the shear capacity of the strengthened beam have been investigated through a parametric study.
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El-Nemr, Amr Maher. "Serviceability of concrete members reinforced with FRP bars." Thèse, Université de Sherbrooke, 2013. http://hdl.handle.net/11143/6124.
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La détérioration des infrastructures au Canada due à la corrosion des armatures est l'un des défis majeurs de l'industrie de la construction. Les progrès récents dans la technologie des polymères ont conduit au développement d'une nouvelle génération de barres d'armature à base de fibres renforcées de polymères (PRF), (en particulier les fibres de verre). Ces barres, résistant à la corrosion, ont montré un grand potentiel d'utilisation pour mieux protéger les infrastructures en béton armé contre les effets dévastateurs de la corrosion. Avec la publication du nouveau code S807-10 "Spécifications pour les polymères renforcés de fibres" et la production de barres en PRF de très haute qualité, celles-ci représentent une alternative réaliste et rentable par rapport à l'armature en acier pour les structures en béton soumises à de sévères conditions environnementales. La conception des éléments en béton armé de barres en PRF est généralement gouvernée par l'état de service plutôt que l'état ultime. Par conséquent, il est nécessaire d'analyser les performances en flexion et le comportement en service en termes de déflexion et de largeur de fissures des éléments en PRF sous charges de service et de vérifier que ces éléments rencontrent les limites des codes. Aussi, de récents développements dans l'industrie des PRF ont conduit à l'introduction des barres en PRF avec des configurations de surface et des propriétés mécaniques différentes. Ces développements sont susceptibles d'affecter leur performance d'adhérence et, par conséquent, la largeur des fissures dans les éléments en PRF. Cependant, les codes de conception et les guidelines de calcul fournissent une valeur unique pour le coefficient d'adhérence (k[indice inférieur b]) en tenant compte des configurations de surface et en négligeant le type de barre en PRF, le diamètre de la barre, et le type de béton et de sa résistance. En outre, le code canadien S807-10 "Spécifications pour les polymères renforcés de fibres" fournit une étape en classant les barres en PRF par rapport à leur module d'élasticité (E[indices inférieurs frp]). Ces classifications ont été divisées en trois classes : Classe I (E[indices inférieurs frp]<50 GPa), Classe II (50 GPa [plus petit ou égal] E[indices inférieurs frp]< 60 GPa) et Classe III (E[indices inférieurs frp] [plus grand ou égal] 60 GPa). Ce programme de recherche vise à étudier expérimentalement le comportement en flexion des éléments en béton en service armé avec différents paramètres sous charges statiques. Le programme expérimental est basé sous plusieurs paramètres, dont les différents ratios de renforcement, différents types de barres (différentes classes comme classifiées par le CAN/CSA S807-10), le diamètre et la surface de la barre, la configuration ainsi que la résistance du béton. De plus, les recommandations actuelles de design pour les valeurs de k[indice inférieur b] et la vérification de la dépendance des valeurs de k[indice inférieur b] sur le type de barres (verre ou carbone), le diamètre des barres et le type de béton et sa résistance ont été étudiées. Le programme expérimental comprenait la fabrication et les essais sur 33 poutres à grande échelle, simplement appuyées et mesurant 4250 mm de long, 200 mm de large et 400 mm de hauteur. Vingt et sept poutres en béton ont été renforcées avec des barres en PRF à base de verre, quatre poutres en béton ont été renforcées avec des barres de PRF à base de carbone, et deux poutres ont été renforcées avec des barres en acier. Toutes les poutres ont été testées en flexion quatre points sur une portée libre de 3750 mm. Les paramètres d'essai étaient: le type de renforcement, le pourcentage d'armature, le diamètre des barres, configurations de surface et la résistance du béton. Les résultats de ces essais ont été présentés et discutés en termes de résistance du béton, de déflection, de la largeur des fissures, de déformations dans le béton et l'armature, de résistance en flexion et de mode de rupture. Dans les trois articles présentés dans cette thèse, le comportement en flexion et la performance des poutres renforcées de barres en PRFV et fabriquées avec un béton normal et un béton à haute performance ont été investigués, ainsi que les différentes classes de barres en PRFV et leurs configurations de surface. Les conclusions des investigations expérimentales et analytiques contribuent à l'évaluation des équations de prédiction de la déflection et des largeurs de fissures dans les codes de béton armé de PRF, pour prédire l'état de service des éléments en béton renforcés de PRF (déflection et largeur de fissures). En outre, à la lumière des résultats expérimentaux de cette étude, les équations de service (déflection et largeur des fissures) incorporées dans les codes et guidelines de design [ACI 440.1R-06, 2006; ISIS Manual No.3, 2007; CAN/CSA-S6.1S1, 2010; CAN/CSA-S806, 2012] ont été optimisées. En outre, les largeurs de fissures mesurées et les déformations ont été utilisées pour évaluer les valeurs courantes de k[indice inférieur b] fournies par les codes et les guidelines de calcul des PRF. En outre, les conclusions ne prennent pas en charge la valeur unique de k[indice inférieur b] pour les barres en PRF de types différents (carbone et verre) avec des configurations de surface similaires et s'est avéré être dépendant du diamètre de la barre.
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Lewis, Zachary Ludon. "Evaluation of thermal variations on concrete pavement using three dimensional line laser imaging technology." Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50406.
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Jointed Plain Concrete Pavements (JPCP) are some the most popular forms of concrete pavement that are used in the state of Georgia. Each year the Georgia Department of Transportation (GDOT) inspects and surveys their highways to determine what condition the pavement is in and if any rehabilitation is required to maintain the integrity of the highway. These annual surveys include the JPCP and the key concrete pavement characteristics that are used to determine the condition of the JPCP are the faulting at the joints and the roughness of the section. Since it is well known that concrete will exhibit slight movement when subjected to thermal variations it is possible that the these minor movements could have an impact on the measured slab properties used to rate the JPCP section. The focus of this research is to develop a methodology to use three dimensional technologies to capture JPCP surface data under a variety of thermal conditions, to develop a procedure to collect and analyze concrete temperature data, to develop a method to analyze the surface data and how to correlate all of the data that was collected. Three test sites were chosen that covered a total of 6 test sections that were composed of 25 slabs and 26 joints each. This provided a total of 150 slabs and 156 joints that were used for analysis.
A single slab was selected as a test specimen to install thermal logging devices into so that the temperature distributions through the slab could be investigated. Three positions were monitored to determine if the position that the temperature gradient was measured was critical. It was found that the temperature followed a similar trend for all of the positions with the profiles being slightly shifted from each other. It was also concluded that the temperature in the bottom of the slab was approximately the same as the temperature in the base. It was discovered that the maximum positive temperature gradient occurred simultaneously with the maximum ambient air temperature and the maximum surface temperature. The results showed that the surface temperature followed a trend similar to the ambient air temperature. However the surface temperature was greater throughout the day.
The faulting analysis results indicated that out of the 156 joints inspected only 15 showed a variation in the average faulting that was greater than the 0.5 mm (0.02 in) accuracy of the sensors used to collect the JPCP surface data. Further investigation revealed that there was no clear trend between the temperature change and the average faulting variation. It was concluded that if there was a change in the average faulting due to temperature it is smaller than what can be depicted by the sensing vehicle and it is less than the 1 mm (0.04 in) measurement accuracy that is specified in the American Association of State Highway and Transportation Officials (AASHTO) R36-04 specification which governs the accuracy requirements for automated faulting measurement methods.
The International Roughness Index (IRI) was the method used to measure the roughness on each test site for each data collection run. This resulted in 336 IRI values that were inspected to determine whether there was an impact from the temperature variations. The IRI results showed that the roughness of the test sections did vary through the day. After it was found that the IRI did vary through the day the IRI distributions were compared to the temperature distribution and 7 out of the 12 distributions studied showed a weak correlation between the temperature and the IRI. The amount of variation in the IRI was not quantified because the exact accuracy of the IRI values attained from the sensing vehicle was unknown. However it was attempted to validate the system and determine the accuracy but one of the validation test sections showed disappointing results while the other two showed promising results. Further research is required to fully evaluate the sensing vehicles ability and accuracy when measuring the IRI.
A procedure was also developed to extract the longitudinal and transverse curvature of the concrete pavement slabs. Three test slabs were selected at one of the test sites and curvature results were generated using the developed procedure. The curvature results were visually and quantitatively assessed. The visual analysis indicated that the curvature profiles measured by the 3D line lasers did change throughout the data collection, but the patterns did not follow what was expected and a correlation could not be created with the temperature. The quantitative results for the longitudinal curvature revealed that one of the slabs did show a pattern that followed the temperature changes during the data collection, but it did show as much as 4.65 mm (0.183 in) of change between consecutive data collection runs. The longitudinal curvature results for the other two slabs did not show a trend and exhibited unlikely changes in the curvature measured between consecutive data collection runs, which in some instances the deviation was as much as 12.09 mm (0.480 in). For the transverse curvature one of the slabs indicated that the curvature did not change during the data collection, while the other two showed sudden changes as high as 2.16 mm (0.085 in) between consecutive data collection runs. The developed procedure is only preliminary and needs to be further evaluated and refined for it to be able to adequately measure the curvature of as slab. The results also need to be verified using actual measured ground truth curvatures to determine the validity of using the developed procedure and the 3D line laser data to measure the curvature of concrete slabs. Once the procedure is proven to produce reliable results it should be compared to other curvature computation methods, such as those that utilize road profilers or LIDARs, to determine which method is the best.
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Alzuhairi, Fatin, and abdulfata Fatah. "Environmentally improved concrete is compared with ordinary concrete with respect to estimated environmental impact." Thesis, KTH, Byggteknik och design, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-296542.
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Swedish buildings account for a large part of Sweden's greenhouse gas emissions, which is why the construction industry within the framework of the concrete initiative has produced a Roadmap for Climate Neutral Concrete. The climate neutral targets meant that Sweden will have net carbon emissions of carbon dioxide in the atmosphere by 2045. In order to achieve the national environmental goals, it is important to reduce the climate impact from concrete construction. Today, the concrete industry is facing a major challenge in minimizing the consumption of concrete, while at the same time the need for new buildings is increasing as a result of the increase in land populations.Concrete lifecycle analysis shows that 90 percent of carbon dioxide emissions come from the manufacturing process of cement clinker that is included in the cement binder. For this reason, the concrete industry has researched and developed various alternatives that contribute to reducing the environmental impact caused by concrete by reducing carbon dioxide emissions.The purpose of this thesis is to evaluate the environmental impact of different types of concrete and to investigate two factors that contribute to reducing carbon dioxide emissions in the atmosphere. The factors being investigated are choice of optimized concrete recipe by reducing proportion of cement and choice of concrete composition by replacing cement with alternative binders.A survey study was conducted to analyze the environmental impact of different types of concrete with different amounts of cement, water percentage and exposure class. In addition, a comparison study between ordinary concrete and climate-enhanced concrete was performed to analyze the climate impact of climate-enhanced concrete with different improvement steps compared to ordinary concrete. To carry out this study, a study of ordinary concrete has been carried out with documents (concrete quantity, strength class and water cement figures) from a reference project obtained by Specialfastigheter, and then replaced with climate-enhanced concrete in various improvement steps.The results show that concrete with lower cement volume and higher water cement numbers give a marked reduction in the building's climate impact. By reducing the amount of cement in the concrete, the proportion of cement clinkers included in the cement binder is lowered, which in turn reduces the climate impact. In addition, a comparison study also shows that the building's climate impact can be reduced between 10, 25 and 52 percent through the use of climate-enhanced charm. This is because climate-enhanced concrete is being replaced by some cement with alternative binders.The conclusion is that this study provides greater opportunity for the construction industry to gain additional knowledge and a better understanding of how environmental impact can be reduced by choosing the right type of concrete. Choosing concrete with lower strength, higher water cement ratio and higher proportion of alternative binders contributes to lower climate impact from concrete.Svenska byggnader står till svars för en stor del av Sveriges utsläpp av växthusgaser, därför har byggbranschen inom ramen för betonginitiativet tagit fram Färdplan för Klimatneutral betong. Klimatneutralmålen innebär att Sverige ska uppnå nettonollutsläpp av koldioxid i atmosfär år 2045. För att kunna nå de nationella miljömålen är det viktigt att sänka klimatpåverkan från betongkonstruktion. Idag befinner sig betongbranschen inför stor utmaning att minimera konsumtion av betong, samtidigt som behovet av nybebyggelse ökar till följd av att jordbefolkningen ökar.Betonglivscykelanalys visar att 90 procent av koldioxidutsläpp kommer från tillverkningsprocess av cementklinker som ingår i bindemedlet cement. Av denna anledning har betongbranschen undersökt och utvecklat olika alternativ som bidrar till minskning av miljöpåverkan orsakad av betong genom att reducera koldioxidutsläpp.Syftet med detta examensarbete är att utvärdera miljöpåverkan från olika betongssorter samt att undersöka två faktorer som bidrar till minskning av koldioxidutsläpp i atmosfären. De faktorer som ska undersökas är val av optimerat betongsrecept och alternativa bindemedel. Det optimerade betongrecept sker genom minskning av andel av cement och val av betongsammansättning där cement ersätts med alternativa bindemedel.En undersökningsstudie utfördes för att analysera miljöpåverkan av olika betongssorter med olika cementsmängd, vattencementtal och exponeringsklass. Dessutom utfördes en jämförelsestudie mellan vanlig betong och klimatförbättrad betong för att analysera klimatpåverkan av klimatförbättrad betong med olika förbättringssteg jämfört med vanlig betong. För att genomföra denna studie har olika betongsmängder, hållfasthetsklass och vattencementtal undersökas. Betonginformation hämtas från ett referensprojekt erhållna av Specialfastigheter för att sedan ersättas med klimatförbättrad betong i olika förbättringssteg.Resultaten visar att betong med lägre cementmängd och högre vattencementtal ger uppmärksammade minskning av byggnadens klimatpåverkan. Genom att minska cementmängden i betongen sänks andelen av cementklinker som ingår i bindemedlet cement, vilket i sin minskar klimatpåverkan. Dessutom visar även jämförelsestudien att byggnadens klimatpåverkan kan minskas mellan 10, 25 och 52 procent genom användning av klimatförbättrad betog. Detta beror på att klimatförbättrad betong ersätter en del av cement med alternativa bindemedel.Slutsatsen är att denna studie ger större möjlighet för byggbranschen att få ytterligare kunskap samt bättre förståelse om hur miljöpåverkning kan minskas genom att välja rätt betongtyp. Att välja betong med lägre hållfasthet, högre vattencementtal och högre andel av alternativa bindemedel bidrar till lägre klimatpåverkan från betong.
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DALLA, ROSA LEONARDO. "Structural Health of a concrete tunnel lining under complex in situ loading." Thesis, KTH, Bro- och stålbyggnad, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-255537.
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Supporting structures were designed for a utility tunnel in hard rock which was to be intersectedby some road tunnels. With the intersections involving partial overlapping between the idealcross-sections, a concrete lining and post-tensioned steel cables were added to support theutility tunnel prior to the excavation of the road tunnels. The objectives in this work wereto identify the structural behaviour of the system, assess the present state of the supportingstructures and suggest an effective monitoring strategy. Preliminary information was collectedfrom the original drawings, technical specifications as well as from site visits. Using on thefinite elements software Comsol Multiphysics, suitable models were built to represent thetunnel intersections and to test hypotheses. The significant uncertainties in the problem wereaddressed by studying limit cases and discussing their results. A measure of validation wasgained from comparing cracks in concrete on site with cracking hotspots predicted by themodel. It was concluded that the behaviour of the lining is not compatible with that of cablesuspended structures and that concrete is subject to relatively high state of stress. Monitoringcable forces was found to be an ineffective strategy for identifying changes in the structuralsystem. Monitoring the evolution of cracks in concrete was found to be the most feasiblestrategy.
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Watase, Azusa. "Non-Destructive Evaluation of Concrete Structures Using High Resolution Digital Image and Infrared Thermography Technology." Master's thesis, University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5885.
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As existing bridge structures age, they are susceptible to the effects of deterioration, damage and other deleterious processes. These effects hamper the capacity and efficiency of transportation networks and adversely impact local, regional and national economic growth. As a result, bridge authorities and other professionals have become more sensitive to maintenance issues related to this aging infrastructure. While highway bridge condition have been monitored by visual inspection, non-destructive evaluation (NDE) technologies have also been developing and they are expected to be utilized for effective management of highway bridges or other civil infrastructure systems. Efficient use of these technologies saves time spent or bridge inspections, and also helps the bridge authorities for management decision-making. One of the NDE technologies is the image-based technology. In this thesis research, image-based technologies using high resolution digital images (HRDI) and infrared thermography image (IRTI) are introduced, described and implemented. First, a review of the mechanisms of these technologies is presented. Due to the specific engineering utilization and recent technological development, there is a need to validate effectiveness of HRDI and IRTI for their practical use for engineering purpose. For this reason, a pilot project using these technologies was conducted at an in-service bridge and a parking structure with the support of Florida Department of Transportation District 5 and the results are presented in this thesis. Secondly, in order to explore and enhance the usability of infrared thermography technology (IRTI), experiments on campus and on another bridge were conducted to determine the best time to test bridges and the sensitivity of IRTI to delamination volume. Since the accuracy of damage detection using infrared thermography technology is greatly affected by daily temperature variation, it is quite important to estimate an appropriate duration for infrared thermography inspection prior to the inspection. However, in current practice, the way to estimate the duration is to monitor the temperature of the concrete surface. Since the temperature varies depending on the area or region, there is a need to visit the bridge before the actual test and monitor the temperature variation. This requires additional visits to the bridge site and also access to the bridge for measuring concrete temperature. Sometimes, this can be a practical issue. In this research, in order to estimate an appropriate duration without visiting bridges, a practical method is explored by monitoring and analyzing variation of concrete surface temperature at one location and projected to another location by also incorporating other factors that affect the concrete temperature, such as air temperature and humidity. For this analysis, specially-designed concrete plates of a few types of thickness and shapes are used and the regression analysis is employed to establish a relationship between environmental effects and temperature variation between two different sites. The results have been promising for this research study and it is shown that HRDI and IRTI are excellent technologies for assessing concrete structures in a very practical manner.M.S.
Masters
Civil, Environmental, and Construction Engineering
Engineering and Computer Science
Civil Engineering; Structures and Geotechical Engineering
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Dalcin, Jarbas Bressa. "Avaliação do potencial do uso da sílica de casca de arroz obtida através da queima controlada como substituição parcial ao cimento Portland na produção de concretos autoadensáveis." Universidade Federal do Pampa, 2016. http://dspace.unipampa.edu.br:8080/xmlui/handle/riu/787.
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Avaliação do potencial do uso da sílica de casca de arroz obtida através da queima controlada como substituição parcial ao cimento Portland na produção de concretos au.pdf: 5610666 bytes, checksum: 59bf1f9b8c485e95150b2a114381adde (MD5)Approved for entry into archive by Cátia Araújo (catia.araujo@unipampa.edu.br) on 2017-01-26T11:47:27Z (GMT) No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Avaliação do potencial do uso da sílica de casca de arroz obtida através da queima controlada como substituição parcial ao cimento Portland na produção de concretos au.pdf: 5610666 bytes, checksum: 59bf1f9b8c485e95150b2a114381adde (MD5)
Made available in DSpace on 2017-01-26T11:47:27Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Avaliação do potencial do uso da sílica de casca de arroz obtida através da queima controlada como substituição parcial ao cimento Portland na produção de concretos au.pdf: 5610666 bytes, checksum: 59bf1f9b8c485e95150b2a114381adde (MD5) Previous issue date: 2016-09-01
O presente estudo tem como objetivo avaliar o potencial uso da Sílica de Casca de Arroz (SCA), obtida de queima controlada, como material de substituição parcial em massa ao Cimento Portland (CP) na produção de concretos autoadensáveis (CAA). A SCA empregada neste trabalho foi produzida em condições controladas em um sistema de combustão com leito fluidizado, tendo como resultado uma sílica altamente amorfa e de boa qualidade. Foram avaliados os resultados do comportamento reológico do CAA no estado fresco e a resistência mecânica no estado endurecido de um concreto de referência, sem o uso de SCA, e de cinco concretos produzidos a partir de substituições parciais de 5%, 10%, 15%, 20% e 25% de SCA em relação à quantidade de massa do cimento. Em todos os traços foram utilizado 15% de cinza volante (CV) adicionada à massa do material aglomerante, a fim de auxiliar na diminuição do atrito entre as partículas dos agregados com o cimento. O traço do concreto de referência foi obtido utilizando o procedimento de caráter experimental proposto pelo Método de Gomes. Este traço foi analisado também pelo Método do Empacotamento Compressível, sendo assim, definidos os outros traços com substituições. As amostras foram caracterizadas no estado fresco de acordo com a norma brasileira ABNT NBR 15823/2010, através de: ensaios de espalhamento no cone de Abrans e Anel “J”, de fluidez no funil “V” e habilidade passante na caixa “L” e caixa “U”. Os resultados mostram que os concretos produzidos com SCA possuem boa capacidade de fluidez. No estado endurecido foram verificadas as resistências mecânicas de compressão axial e tração por compressão diametral dos CAAs nas idades de 7, 28, 56 e 91 dias. Os resultados dos ensaios indicam que é possível substituir CP por SCA sem que haja prejuízo às características mecânicas dos CAAs e ainda obter ganhos técnicos e econômicos. O melhor concreto, levando em conta todos os aspectos estudados, foi com 15% de substituição de CP por SCA.
This study aims to evaluate the potential use of rice husk silica (RHS), obtained under controlled burning conditions, such as partial replacement material to the Portland Cement (PC) in the production of self-compacting concrete (SCC). The RHS employed in this study was produced under controlled conditions in a fluidized bed combustion system, resulting in highly amorphous silica and of good quality. We evaluated the results of the rheological behavior of SCC in the fresh state and strength in the hardened state of a reference concrete without the use of RHS and five concrete made from partial substitution 5%, 10%, 15%, 20% and 25% in RHS relative to the amount of concrete mass. In all traces were used 15% of Fly Ash (FA) is added to the mass of the binder material to assist in reducing friction between particles of the aggregates with cement. The trace of the reference concrete was obtained using the experimental procedure proposed by Gomes method. This trait was also analyzed by the method of packaging compressible and based on this method are defined partial strokes with other PC for RHS substitutions. After obtaining the characteristics of the materials and dosages of SCCs, these were featured in the fresh according to the Brazilian standard NBR 15823/2010, as follows: Spreading tests on cone Abrans and "J-ring", pour in "V-Funnel" and passing ability in the "L-box" and "U-box". The results shows that concrete made with RHS have good flow capacity. In the hardened state the mechanical resistances were checked axial compression and tension by diametrical compression of SCCs at the ages of 7, 28, 56 and 91 days. The test results indicate that it is possible to replace PC with RHS without prejudice to the characteristics of SCCs and still get technical and economic gains. The best concrete, taking into account all the points studied, was the one with replacement of 15% of PC for RHS.
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CAVALCANTI, Alan Barbosa. "SOFTPAVE: estudo e desenvolvimento de uma ferramenta para o auxílio à dosagem de misturas asfálticas pelo método SUPERPAVE." Universidade Federal de Campina Grande, 2013. http://dspace.sti.ufcg.edu.br:8080/jspui/handle/riufcg/1296.
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CNPq
A medida que a Tecnologia da Informação (TI) evolui, as organizações acompanham esse crescimento e fazem uso dessa ferramenta integrando-as aos seus insumos e serviços, a exemplo do uso de softwares que automatizam seus processos. Este trabalho teve como objetivo o desenvolvimento de uma ferramenta computacional (Software) visando possibilitar uma análise sobre técnicas, materiais, critérios, normalizações, procedimentos, e resultados obtidos no projeto de Dosagem de Concretos Asfálticos pelo método SUPERPAVE. Para o desenvolvimento do programa SOFTPAVE foi utilizado o modelo de Prototipação visando fornecer aos usuários um aplicativo e uma interface com representação física dos principais aspectos do sistema de implementação da Dosagem. O SOFTPAVE consegue determinar, dentro dos critérios preconizados pelas as normas brasileiras e americanas, o teor de ligante ideal para as misturas asfálticas projetadas de forma que possam atender as exigências no que se refere às propriedades mecânicas, a serem obtidas em laboratórios, e que tenham um desempenho satisfatório em campo.
As the Technology of Information (TI) develops, the companies follow up the growth and make use of this tool integrating it with their inputs and services, as example, the use of softwares that automate their processes. The following paper had as objective the development of a computational tool (software) order to enable an analysis of techniques, materials, criteria, normalizations, procedures and results obtained with the project of Dosage of Asphaltic Concrete through the method SUPERPAVE. In the development of the software SOFTPAVE the model of Prototipation was used to give the users an application and an interface with physical representation of the major aspects of the implementation system of the Dosage. It is possible to conclude that the SOFTPAVE is able to determinate, within the criteria recommended by Brazilian and American standards, the ideal proportion of binding agent for the asphaltic mixtures, designed to meet the requirements regarding mechanical properties, to be developed in research labs, and that present successful results in field.
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Ismail, Eman. "Distribution of stresses and displacements in skewed concrete slabs." Thesis, Linnéuniversitetet, Institutionen för byggteknik (BY), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-66839.
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A 3D nonlinear finite element analysis was developed for simulating the behavior of skewed concrete slabs and to identify the response of the slab with different angles and element sizes. The purpose of this research is helping the engineering and construction industry to utilize the FEM study and results more in different structural applications.Simulations performed in ABAQUS for skewed slabs are also compared to straight and skewed slabs according to the analytical formulation by Timoshenko.The result showed that when the distance increases, the load capacity measured by reaction forces decreases for all different skew angles except angle 0° and 15° which show a stable reaction force along the entire path. .The study reveals that depending on the skew angle and the element size, the stress distribution and vertical displacements in the slab vary significantly from those in a straight slab. It is shown that the displacement decreases with the increase of the skew angle while the stresses increase with the decrease of the skew angle.There are small differences in the vertical displacements and stress distribution between the results obtained by this study and the results obtained by Timoshenko regarding the plates with skews of 0°, 30° and 45°.
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Dry, Carolyn Minnetta. "Design of systems for time delayed activated internal release of chemicals in concrete from porous fibers, aggregates of prills, to improve durability." Diss., Virginia Tech, 1991. http://hdl.handle.net/10919/37870.
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Incorporation of chemicals into the internal matrix of cement or concrete, with later release occurring upon stimulation, alters the matrix parameters from those at the initial set. Permeability is reduced, for example, and therefore durability enhanced. The advantages of these designs would be the ability to reduce maintenance and repair costs in the initial building configuration and to delay the time of eventual repair. The components and the structure could take greater environmental abuse also.
Permeability is significantly reduced by release of a polymer from wax-coated porous fibers upon heating to temperature of polymerization. Freeze/thaw damage is somewhat reduced by the timed release of linseed oil or antifreeze from porous aggregates due to the freezing action itself. These example designs using timed release mostly gave improved durability performance when compared to conventional treatments for durability or environmental distress. Concerns that significant strength reduction would occur due to heating or fiber loading were shown to be unfounded by our test results; indeed, heating and fiber inclusion increased strength. An adequate amount of wetting of the samples could be obtained with 2.75% volume of fibers; however, above a 2.75% volume of fibers, fibers do reduce the strength. Results were analyzed by the method of comparing results in the samples with factors varied to results in samples without variable factors, that is, by comparing to the controls.
This research shows that timed internal release of chemicals into cement can be accomplished; it appears feasible and is potentially useful.
Long-term tests need to be performed on such factors as chloride ion intrusion/ corrosion tests. Filled fiber, aggregate or prill manufacture, storage, and placement need to be researched and assessed for cost. Design of components using only targeted areas for release in the component and the use of time released fibers in reinforced cement laminates should be evaluated.Ph. D.
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Awn, Rim Fares, and Jaqueline Corona. "Hur mogen är marknaden för klimatsmart betong och dess aktörer?" Thesis, Högskolan i Gävle, Energisystem och byggnadsteknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-33390.
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Carbon dioxide emissions have long proven to be one of the greenhouse gases that affect our planet's climate and environment. With the upcoming EU targets and Sweden's own net zero targets, the construction and real estate sector is required to work with climate-smart materials to construct the buildings of the future. The net zero target for year 2045 requires a joint pool of power from all companies to find innovative solutions to reduce carbon dioxide emissions. The purpose of this study was to investigate how conscious and active the construction and real estate sector is for climate-smart concrete through a survey and comparison of different typ of concretes EPDs. The work aims to investigate how far the development has taken place and to investigate how the market has adopted the new products that are available. The purpose was also to investigate which alternative additives are most common and the advantages and disadvantages of the climate-smart concrete. Climate smart is a term for concrete that contains a lower percentage of Portland cement clinker than the traditional concrete. A questionnaire was created to answer the purpose of the study. The survey sent out involved questions about how companies view the new environmental target for year 2045. As well as investigating how the construction and real estate sector works together to achieve the goal of reducing carbon dioxide emissions by 85% less than in year 1990. A comparison was made between three different EPDs of climate-smart concrete and two reference concrete with ordinary Portland cement clinker. Reference concrete one is a standard value derived from previous studies made and reference concrete two is an EPD value. This was done to investigate the amount of carbon dioxide they emit at the production stage. A reference building was used to calculate the amount of concrete. The result shows that the comparison between reference concrete one with the standard value and the three climate-smart concrete from Svensk Betong, Betongindustrin and Swerock gives a carbon dioxide reduction of 29.3%. And the comparison with reference concrete two with the associated EPD value received a percent climate reduction of only 2.8%. The future will require the construction and real estate industry to invest time and training to work with climate-smart concrete. More in-depth work could be explored and mapped as to which are the major obstacles in construction projects. How companies can work to get the entire value chain to work together for a climate-smart thinking and primarily to get the developer to invest in improved concrete with less climate impact.
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Simsek, Aslihan. "Tectonic Expression Of Concrete As An Architectural Material." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613805/index.pdf.
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This thesis is an inquiry into the position of concrete as an architectural material in architectural production and expression. With increasing use of concrete in architecture not only technical properties but also aesthetical ones of the material came to foreground. Reconsidering concrete as a building material, the thesis aims to find out tectonic possibilities of concrete as an architectural expression tool. The purpose to search for concrete's tectonic potentials is to rescue it from its bad connotations and reveal it as an architectural tool instead of being mere constructional mean for an end. In order to explore aesthetic qualities of concrete as a part of architectural production, the scrutiny of tectonic theories provide a conceptual framework for a contemporary interpretation of concrete usage in architecture. Kenneth Frampton, Karl Bö
tticher, Gottfried Semper and Martin Heidegger are the key references to understand the tectonic potentials of concrete material in architecture. Within the framework of Semper'
s abstract procedures, manipulation of concrete material is analyzed through the specific examples. Structure and symbol, material and method, clear structure and joint are the consulted binary keywords related to the evaluation of tectonic aspects of concrete in architecture. By the technological developments, concrete material -both as a science and art- has been freed from the constraints of traditional production techniques and generated a field for the imaginative creations of the architect. When considered as a part of architectural design, concrete constitutes not only the "
core-form"
, but with its innate qualities revealed by the designer it transposes the building into an "
art-form"
. Constituting the structure, surface, or detail of building, concrete material has the ability to express architectural meanings behind design concept. This study attempts to identify concrete material as a value indicating to tectonic, craft, "
poiesis"
, technology connotations and emphasizes its architectural expression power.
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Bengtsson, Pär, and Johan Wallin. "Analysis of a Prefabricated Concrete Skew Angle Slab Bridge." Thesis, Linnéuniversitetet, Institutionen för byggteknik (BY), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-81146.
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Prefabricated concrete elements are widely used in the construction industry today. With advantages such as time savings, increased safety at the construction site and minimized material usage, prefab becomes a major challenger to the traditional on-site casting construction method. However, constructing a bridge in concrete still presents challenges when using prefab as a construction method. Hence, more research in the area is needed. This master thesis has been studying the behavior of a prefabricated skew angle slab and the connection between the slab and wall elements of a bridge. The study was conducted using a finite element software, where three 3D-models of skew angle slabs were created. The three models had different skew angles (0, 15 and 30 degrees) and crossed the same path. The models could represent both the slab and the slab-wall connection. The finite element analysis showed that slabs with angles up to 15 degrees could be designed as a straight bridge. However, when the skew angle increases to 30 degrees, the behavior of the slab and connection changes significantly. Furthermore, the results show that a stress concentration occurs in the obtuse corner and that the stress increases when the skew angle increases. Moreover, there is a slight uplift in the acute corner when the skew angle increases to 30 degrees.
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Wingårdh, Ludvig. "Construction of prefabricated concrete buildings : A comparative attributional LCA." Thesis, KTH, Hållbar utveckling, miljövetenskap och teknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-299525.
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This master thesis investigated the influence of prefabrication rate of buildings on the embodied environmental impacts. Through a comparative attributional LCA four different Swedish buildings were investigated to explore the influence of PR on the environmental impacts in the categories Cumulative Energy Demand, Global Warming Potential, Water Consumption, Fossil Resource Scarcity, and Mineral Resource Scarcity. The reference buildings had prefabricated rates of 14, 26, 38 and 91%. The results indicate that a higher prefabricated rate (PR) can lead to a lower impact in these categories to some extent; mainly due to a lower amount of total concrete material per square meter, dependent on the construction method used. The most influential materials in the comparison where cement and steel. An initial improvement of several impacts was seen when the PR of concrete buildings increased from 14% to 38%, with one reason being increased material efficiency of concrete. When further increasing PR, it is not certain that impacts necessarily continue to improve, as no clear difference was shown between the buildings with PR of 91% and 38%. This seems to point towards that any clear relationship between PR and the chosen impact categories breaks down or flattens out for higher prefabricated rates, and that the most beneficial solution often could be a semi-prefabricated construction method. This is concurrent with previous results in the current body of literature on LCA of construction and prefabricated rates. Instead, for additional reduction of environmental impacts after this point, other factors such as material choice and could become increasingly important. Additionally, the question of which impact category to prioritize arises.Denna masteruppsats undersöker betydelsen av andelen prefabricerad betong i byggnader och dess påverkan på den inbyggda miljöpåverkan. En jämförande bokförings-LCA gjordes av fyra svenska referensbyggnader för att undersöka prefabrikationsgradens inverkan i fem kategorier av miljöpåverkan: kumulativ energiförbrukning, global uppvärmning, vattenförbrukning, och förbrukning av minerala och fossila naturresurser. Referensbyggnaderna hade prefabricerade andelar av 14, 26, 38 och 91%. Resultaten indikerar att en högre grad av prefabricering kan leda till en lägre påverkan i de undersökta kategorierna i viss mån, inte minst på grund av en lägre total förbrukning av betong per kvadratmeter BTA, beroende på vilken konstruktionsmetod som används. De mest betydelsefulla råmaterialen fanns vara cement och stål. En initial förbättring i flertalet kategorier syntes när prefabrikationsgraden ökade från 14 till 38%, mycket tack vare den lägre betongförbrukningen. När prefabrikationsgraden steg ytterligare till 91% syntes ingen tydlig förbättring, och det kan inte anses klarlagt att en högre prefabrikationsgrad nödvändigtvis har lägre miljöpåverkan. Detta indikerar att den mest fördelaktiga lösningen ofta kan vara en semi-prefabricerad lösning, vilket överensstämmer med resultaten i tidigare studier på området. För ytterligare reducering av miljöpåverkan efter en viss grad av prefabricering framstår andra faktorer såsom materialval som allt viktigare.
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Liang, Li. "Recycling of concrete waste with wood waste through heating compaction." Thesis, KTH, Betongbyggnad, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-275674.
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Concrete, as primary building material, is widely used in most construction project. For this reason, large amounts of concrete waste were generated from construction and demolition. One way to reuse concrete waste is to use it as backfill material for landfilling and road bases. While the demand for backfill material is decreasing as the basic infrastructure construction gradually completes. Another way to reuse concrete waste is to grind it and use it as aggregate in casting new concrete. However, the reuse as aggregate for casting concrete requires large amount of cement. It is unsustainable because the production of cement causes significant amounts of carbon dioxide emission. How to deal with the concrete waste in a sustainable way is presently an urgent issue. Powder compaction is a new approach to completely recycle concrete waste in an environmentally friendly way. This new method was studied in the Sakai lab of the Institute of Industrial Science, The University of Tokyo. The process consists of crushing and milling concrete waste into a fine powder, filling the powder into moulds and compacting it under high pressure. By this process concrete waste powder can be turned into a solid concrete with mechanical properties so that it has potentials to be used again as a building material. Data from previous studies show that the compacted concrete waste can reach strength for construction but the required compaction pressure is quite high. Wood flour can be added in compaction for improving tensile strength and reducing compaction pressure. Lignin is a wood substance that melts under high temperature, fills gaps and improves bonding between particles. Cellulose from the wood substance functions as fibres which improves tensile strength. Wood waste from production of timber building materials, furniture and other wooden products also forms a larger quantities. Recycling of concrete waste with wooden waste through heating compaction is a potentially sustainable method. This Master thesis presents research on the effect from different production conditions on the bending strength of recycled concrete waste with wood waste through heating compaction. The condition factors studied were compaction duration, compaction pressure, concrete proportion, mixture percentage, temperature and particle size of wood flour. To enhance the water resistance of this recycled product, different water resistance treatments were discussed theoretically. The independence of production condition factors was analysed using a statistic method. Results indicated that within a certain range, an increase in compaction duration, compaction pressure, the percentage of wood waste and temperature improves the bending strength of the recycled products. Using smaller particle size of wood flour cannot improve compaction but contribute to give higher bending strength. The mechanical properties of these recycled products suggest application as non-bearing building material, such as decoration tiles and bricks for partition walls. The application as a structural material is expected in the future as improvement treatments are discovered.
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Alqahtani, Fahad Khshim. "Production of novel manufactured plastic aggregate and its utilisation in concrete." Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7821/.
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Plastic waste and its low recycling rate make a significant contribution towards the pollution of the environment. Therefore , it is essential that plastic waste is utilised in different applications . One of the applications is its use either as an aggregate or to form aggregate for use in the concrete. New aggregates were developed using plastic waste and by-product or low cost granular materials. These aggregates have a relatively low density and water absorption as compared to conventional aggregates , and were successfully used to produce sustainable or green lightweight concrete. The new aggregates were used to replace the conventional coarse fraction of either nonnal weight or lightweight aggregates at full or partial replacements; where both properties of fresh and hardened concrete were investigated. It was found that the effect of the replacement level of the conventional aggregate with the manufactured recycled plastic aggregates was less prominent on density as compared to the other properties. The hardened concrete showed a reduction in mechanical properties , with an increase in the proportions of manufactured recycled plastic aggregates in the mix . The assessment of durability properties, thermal conductivity and curing temperature was also carried out. The concrete ductility, drying shrinkage, creep strain and thennal conductivity increased as the content of manufactured recycled plastic aggregate increased in the mix. Whilst, the chloride penneability was found to decrease with an increase in the percentage of recycled plastic aggregate. Finally, models were proposed to predict the mechanical and durability properties utilising the results of this study.
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Hughes, Peter. "An investigation into marine biofouling and its influence on the durability of concrete sea defences." Thesis, University of Central Lancashire, 2014. http://clok.uclan.ac.uk/10636/.
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This research has investigated marine biofouling and its influence on the durability of concrete sea defences using on-site and laboratory-based studies. The study was divided into three main phases namely: the surface analysis of armour concrete, the study of algal colonisation within the matrix and investigations into the presence of a bacterial biofilm within freshly hardened armour concrete. The effectiveness of photocatalytic coatings as a non-toxic anti-fouling strategy and cell attachment to synthetic fibres was also studied. It was found that algal growth quickly developed at the interface of inclusions within the matrix and that power washing with the use of Dairy Hypochlorite to remove this accelerated wear, leading to significant mass loss. It was also observed that bacterial growth within local beach sand, which was used in the production of the revetment armour units, survived the concrete manufacturing process. Bacteria were cultured from the sand and were found to match the Actinomycete like growth in the freshly hardened matrix of armour concrete. This thesis proposes a holistic model for biofouling of fibre reinforced marine concrete in which algal growth around inclusions facilitates a complex process of biodeterioration. Bacterial filamentous growth around and through synthetic fibres embedded in the new concrete mix, appears to be detrimental to the long term durability of synthetic fibres. Subsequent algal colonisation on the surface of newly placed units appeared to quickly penetrate the surface through exposed fibres and percolated interfaces of inclusions, subsequently weakening their bond. During the manufacture of the armour units, aggregate segregation in the 90° corners in the bottom of the form created a weaker matrix in the surface region most exposed to biodeterioration, the full force of wave action and power washing. The main conclusions from this study are: • Synthetic fibres used at the study site are inappropriate for marine concrete, particularly in algal rich waters, within the inter-tidal zone where beach sand is used in the concrete mix. Amendments to Concrete Society Technical Report No. 65: Guidance on the use of Macro-synthetic-fibre-reinforced concrete have been recommended. • Bacterial loaded beach sand is detrimental to the durability of marine concrete in the inter-tidal zone and amendments are recommended to PD 6682-1:2013 Aggregates for concrete (BSI, 2013a) in order to highlight this concern. This UK guidance suggests limiting values for aggregate properties within the ranges permitted in BS EN 12620 (BSI, 2013) but does not place any limits on microorganisms present in beach sand. Further work is needed into the susceptibility of synthetic fibres to crystal growth. Alterations in the manufacture of armour units have been recommended by this author.
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Kare, Sridhar, and Heera Lomite. "Impact of Construction Material on Environment : (Steel & Concrete)." Thesis, Högskolan i Borås, Institutionen Ingenjörshögskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-19331.
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All around the globe the consumption of raw materials by the construction industries isaccumulating day by day resulting with an depletion of natural resources, increasing the environmental impacts and CO2 emissions all over the surroundings. Today steel and concrete are widely used and are dominating construction materials in construction industry. These two construction materials are different products and have distinct production flow with significantimpact on the environment. The amount of embodied energy and operational energy which is consumed in the process of production, recycling and reuse are becoming increasingly more important in the construction industries due to the potential shortage of natural resources in thenear by future and due to the inflation in the energy prices. This master’s thesis determines some of the problems of antagonistic environmental impacts due to the use of steel and concrete in the construction industries. To mitigatethese environmental impacts there are two technology and policy strategies summarizedin this thesis. i. Reduce consumption; andii. Material selection to reduce impacts.i. Reduce consumption: All around the globe the consumption of materials is growing day by day with an increase in the population resulting with a depletion of virgin materials. This depletion of virgin materials can be reduced with the help ofrecycling and reuse of the structural members. Recycling of structural members isalready practiced widely than reuse; reuse of the structural members additionallyreduces the consumption of virgin materials. High level of reuse of the structuralmaterials can be achieved by establishing design standards and regulations forstructural sections, and developing a market for reusable structural sections.ii. Material selection to reduce impacts: For the selection of constructionmaterials with minimum impact on the environment the designers needs tohave apropos education or tools. The main areas for augmentation areidentified as education of designers, and standardization and simplification ofselection tools like Life Cycle Assessment (LCA). Some of the main recommendations are: LCA tools standardization; reduce the impact sections and make these impact sections comprehendible and integrate uncertainty dataand educating designers about material selection tools with organized programs.
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Šlepikas, Paulius. "Handheld concrete cutter. Market research and concept development." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-217990.
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In this Master’s Degree project the topic of handheld deep cutting is analysed. These days in the construction business workers face the challenge of cutting into concrete, brick and other mineralbased materials deeper than 15 cm. Currently there are a few handheld solutions for deep cutting but they have some major limitations, such as low reliability and safety, high price, maintenance and tiresome usage of these machines. In this paper the project is divided into two components – market research and concept development. To build a knowledge base, firstly, current technical platforms for handheld deep cutting machines are reviewed. Then, theoretical background behind market research and concept development is analysed. Following theoretical framework market research and concept development are implemented and steps taken described. Secondary research, customer interviews and focus groups are the main sources of information for the market research. Morphological and Pugh’s matrices are then used to generate and evaluate possible concepts, while software packages SolidWorks and KeyShot are used as tools for development of design features. Findings from the market research revealed that window, door, ventilation openings, resizing of bricks or concrete elements and fixing mistakes done during moulding are the main applications of deep cutting machines. It was noticed that most of the construction professionals are not aware of these machines, use workarounds or hire subcontractors. Single-phase electric ring saw is the outcome from product concepting stage. Three design features – toothed ring, telescopic blade guard and start switch – are then proposed. Finally, discussion of the whole project and its conclusions are given, recommendations and short overview on future work are provided. Work consists of 7 parts: introduction, frame of reference, implementation, results, discussion and conclusions, recommendations and future work, references. Thesis consists of: 68 pages of text without appendixes, 40 figures, 4 tables, 35 references. 8 appendixes attached.I detta masterprojekt analyseras ämnet handhållen djupskärning. Nuförtiden inom byggbranchen står arbetarna inför utmaningen att skära i betong, tegel och annat mineralbaserat material som är djupare än 15 cm. För närvarande finns det ett antal handhållna lösningar för djupskärning, dock med stora begränsningar så som låg pålitlighet och säkerhet, högt pris och behov av underhåll samt tröttsam användning av dessa maskiner. I detta arbete delas projektet upp i två komponenter – marknadsundersökning och konceptutveckling. För att bygga upp en kunskapsbas granskas först nuvarande tekniska plattformar för handhållna djupskärningsmaskiner. Därefter analyseras teoretisk bakgrund om marknadsundersökning och konceptutveckling. Baserat på det teoretiska ramverket, implementeras marknadsundersökningar och konceptutveckling och genomförandet beskrivs. Sekundär forskning, kundintervjuer och fokusgrupper är de primära informationskällorna för marknadsundersökningen. Morfologiska och Pughs matriser används sedan för att generera och utvärdera möjliga koncept, medan programen SolidWorks och KeyShot används som verktyg för utveckling av designfunktioner. Resultat från marknadsundersökningen visade att fönster, dörrar, ventilationsöppningar, storlekändringar på tegelstenar eller betongelement och korrigering av defekter som uppkommit under gjutning är de huvudsakliga användningsområdena för djupskärningsmaskiner. Det noterades att de flesta byggnadsarbetarna inte är medvetna om dessa maskiner, använder improviserade lösningar eller anlitar underleverantörer. Enfasig elektrisk ringsåg är resultatet av produktkonceptionsstadiet. Tre designdetaljer – tandad ring, teleskopskärmskydd och startbrytare – föreslås därefter. Slutligen presenteras diskussion om projektet och dess slutsatser samt rekommendationer och en kort översikt över framtida arbete. Arbetet består av 7 delar: introduktion, referensram, genomförande, resultat, diskussion och slutsatser, rekommendationer och framtida arbete, referenser. Avhandlingen består av: 68 sidor text utan bilagor, 40 figurer, 4 tabeller, 35 referenser. 8 bilagor bifogade.
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Khouri, Chalouhi Elisa. "Optimal design solutions of concrete bridges considering environmental impact and investment cost." Licentiate thesis, KTH, Skolan för arkitektur och samhällsbyggnad (ABE), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-244866.
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The most used design approach for civil engineering structures is a trial and error procedure; the designer chooses an initial configuration, tests it and changes it until all safety requirements are met with good material utilization. Such a procedure is time consuming and eventually leads to a feasible solution, while several better ones could be found. Indeed, together with safety, environmental impact and investment cost should be decisive factors for the selection of structural solutions. Thus, structural optimization with respect to environmental impact and cost has been the subject of many researches in the last decades. However, design techniques based on optimization haven’t replaced the traditional design procedure yet. One of the reasons might be the constructive feasibility of the optimal solution. Moreover, concerning reinforced concrete beam bridges, to the best of the author knowledge, no study in the literature has been published dealing with the optimization of the entire bridge including both the structural configuration and cross-section dimensions. In this thesis, a two-steps automatic design and optimization procedure for reinforced concrete road beam bridges is presented. The optimization procedure finds the solution that minimizes the investment cost and the environmental impact of the bridge, while fulfilling all requirements of Eurocodes. In the first step, given the soil morphology and the two points to connect, it selects the optimal number of spans, type of piers-deck connections and piers location taking into account any obstacle the bridge has to cross. In the second and final step, it finds the optimal dimensions of the deck cross-section and produces the detailed reinforcement design. Constructability is considered and quantified within the investment cost to avoid a merely theoretical optimization. The wellknown Genetic Algorithm (GA) and Pattern Search optimization algorithms have been used. However, to reduce the computational effort and make the procedure more user-friendly, a memory system has been integrated and a modified version of GA has been developed. Moreover, the design and optimization procedure is used to study the relationship between the optimal solutions concerning investment cost and environmental impact. One case study concerning the re-design of an existing road bridge is presented. Potential savings obtained using the proposed method instead of the classic design procedure are presented. Finally, parametric studies on the total bridge length have been carried out and guidelines for designers have been produced regarding the optimal number of spans.QC 20190304
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Al-Soudani, Maha. "Diagnosis of reinforced concrete structures in civil engineering by GPR technology : development of alternate methods for precise geometric recognition." Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30090.
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La méconnaissance de la géométrie réelle d'une structure mène à une évaluation incorrecte de son état. Par conséquent, une estimation imprécise de sa capacité portante, sa durabilité, sa stabilité et la nécessité de mettre en place une réparation ou un renforcement. En outre, l'optimisation du temps requis pour le processus de réparation a besoin de bien connaître les différentes parties de la structure à évaluer et également pour éviter les zones critiques telles que les aciers, les câbles, etc., lors de la réparation. Par conséquent, il est nécessaire d'utiliser des techniques d'évaluation non destructive (END) afin de connaître la géométrie réelle de la structure, notamment l'emplacement des armatures dans les structures en béton armé. Le GPR est considéré comme une technique non-destructive idéale pour détecter et localiser les renforts. Cependant, sa précision de localisation est limitée. Le but de ce projet de recherche a donc été d'accroître la précision du GPR en matière de reconnaissance géométrique interne de structures en béton armé. L'objectif principal de cette étude est de localiser précisément le positionnement des armatures dans le plan ausculté ainsi qu'en profondeur. Pour atteindre cet objectif, une nouvelle méthodologie de mesures et du traitement des signaux GPR a été proposée dans cette étude. Plusieurs configurations d'acquisition de données en utilisant des signaux simulés sont testées pour proposer et développer un algorithme d'imagerie du milieu de propagation afin de définir sa géométrie interne et de localiser précisément les barres de renforcement. Des traitements supplémentaires sont appliqués pour améliorer la précision de la détection et pour identifier les différentes interfaces dans le milieu testé. L'algorithme et le traitement sont appliqués aux signaux simulés. Des validations expérimentales ont ensuite été appliquées aux signaux réels acquis sur différentes dalles en béton armé. L'objectif est de tester la capacité de l'algorithme d'imagerie proposé pour localiser différents objets enfouis. Les résultats encourageants montrent que cet algorithme est capable d'estimer la position de différents objets enfouis et pas uniquement les armatures avec une erreur d'estimation de (0-1) mm. Les performances de l'algorithme ont été comparées à celles d'une méthode de migration et aux résultats de mesure obtenus avec un pachomètre. Ces comparaisons ont systématiquement révélé une meilleure précision de la localisation avec l'algorithme développé.Une autre étude a été proposée dans ce travail en testant l'algorithme avec des signaux réels modifiés. Ces signaux sont produits en réduisant le gain le moins possible. La conclusion la plus évidente de cette étude est que l'algorithme proposé est capable de localiser les différents objets même si les signaux réfléchis par eux sont de faible amplitudeLack of acquaintance in the real geometry of a structure leads to incorrect evaluation of its state. Consequently, this will lead to inaccurate estimation of bearing capacity, durability, stability and moreover, the need for repair or strengthening. Furthermore, optimization of the required time for repair process needs to well recognize the parts of structure to be assessed and also to avoid the critical zones such as reinforcing bars, cables, etc., during repairing. Therefore; it becomes necessary to use a non-destructive testing (NDT) method in order to know the real geometry of structure in particular, the location of reinforcements in reinforced concrete structures. GPR is considered as an ideal non-invasive technique in detecting and locating these reinforcements. However, its accuracy in localization is limited. The aim of this research project has therefore been to increase the accuracy of GPR in recognizing the internal geometry of reinforced concrete structures. The main objective of this study is to locate accurately the position of reinforcements into three dimensions. To achieve this purpose, a new methodology for GPR measurement and processing is proposed in this study.Several configurations of data acquisition using simulated signals are tested to propose and develop an appropriate imaging algorithm for the propagation medium to imagine its internal geometry and to locate accurately the reinforcing bars. Further processing are applied to improve the accuracy of detection and to identify the different interfaces in the tested medium. Both algorithm and processing are applied on simulated signals. Subsequent experimental validations have been applied using real signals acquired from different real reinforced concrete slabs. The goal is to test the ability of proposed imaging algorithm for the localization of different targets. The encouraging results indicate that this algorithm is able to estimate the position of different buried targets and not only the reinforcing bars with an estimation error of (0-1)mm.The performance of proposed algorithm has compared to those of migration method and to the results obtained from pachometer. These comparisons have systematically revealed a better localization accuracy using the developed algorithm.Another study has been proposed in this work by testing the algorithm using modified real signals. These signals are produced by reducing the gain as less as possible. The most obvious finding to emerge from this study is that the proposed algorithm is able to localize the different goals even if the signals reflected by them are of low amplitude
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Omar, Wahid. "The shear assessment of concrete beams with a honeycombed zone present in the high shear region." Thesis, University of Birmingham, 1998. http://etheses.bham.ac.uk//id/eprint/4551/.
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A honeycombed zone in a concrete structure is among the forms of defects that can be found in concrete structures. In this study, the effects on the shear capacity of a concrete beam are investigated when a honeycombed zone is present in the high shear region. The honeycombed concrete was simulated using an uncompacted no-fines concrete mix. Tests were carried out on rectangular beams with a honeycombed zone introduced at various locations within the high shear region of the beam. The honeycombed zone was square with the size of about a third of the effective depth of the beam. Two strengths of normal concrete were investigated. The study found that, in a beam with a honeycombed zone, a diagonal crack could form early and the shear capacity of a beam could be reduced. The severity of these effects varies with the location of the honeycombed zone. Modifications were proposed to an existing plastic analysis method to take into account the strength of the honeycombed concrete. Condition factors derived from the test data were also proposed to be applied to the plastic analysis in assessing beams with a honeycombed zone. A honeycombed zone simulating a construction joint in a beam was also investigated analytically and compared with the data from 4 tests.
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Enckell, Merit. "Structural health monitoring using modern sensor technology : long-term monitoring of the New Årsta Railway Bridge." Licentiate thesis, KTH, Civil and Architectural Engineering, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4236.
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Structural Health Monitoring (SHM) is a helpful tool for engineers in order to control and verify the structural behaviour. SHM also guides the engineers and owners of structures in decision making concerning the maintenance, economy and safety of structures. Sweden has not a very sever tradition in monitoring, as countries with strong seismic and/or aerodynamic activities. Anyway, several large scale monitoring projects have taken place in recent years and SHM is slowly making entrance as an essential implement in managing structures by engineers as well as owners.
This licentiate thesis presents a state-of-the art-review of health monitoring activities and over sensory technologies for monitoring infrastructure constructions like bridges, dams, off-shore platforms, historical monuments etc. related to civil engineering. The fibre optic equipment is presented with special consideration.
The permanent monitoring system of the New Årsta Bridge consists of 40 fibre optic sensors, 20 strain transducers, 9 thermocouples, 6 accelerometers and one LVDT. The aims of the static study are: to control the maximal strains and stresses; to detect cracking in the structure; to report strain changes under construction, testing period and in the coming 10 years; and to compare conventional system with fibre optic system.
The system installation started in January 2003 and was completed October 2003. The measurements took place from the very beginning and are suppose to continue for at least 10 years of operation. At the construction phase the measurements were performed manually and later on automatically through broad band connection between the office and central data acquisition systems located inside the bridge.
The monitoring project of the New Årsta Railway Bridge is described from the construction phase to the testing phase of the finished bridge. Results of the recorded statistical data, crack detection and loading test are presented and a comparison between traditional techniques like strain transducers and fibre optic sensors is done.
Various subjects around monitoring and sensor technologies that were found under the project are brought up in order to give the reader a good understanding, as well of the topics, techniques and of the bridge. Example of few applications is given with the aim of a deeper insight into monitoring related issues.
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Alnuaimi, Ali Said Mohammed. "Direct design of reinforced and partially prestressed concrete beams for combined torsion, bending and shear." Thesis, Connect to e-thesis, 1999. http://theses.gla.ac.uk/652/.
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Labib, Wafa Abdelmajeed. "An experimental study and finite analysis of punching shear failure in steel fibre-reinforced concrete ground-suspended floor slabs." Thesis, Liverpool John Moores University, 2008. http://researchonline.ljmu.ac.uk/5893/.
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The present research is concerned with investigating the structural effect of using steel fibre-reinforcement on the punching shear behaviour of ground-suspended slabs with internal columns. The main objectives of this research were to develop a constitutive model for steel fibre-reinforcement (SFRC), to study experimentally the punching shear behaviour of SFRC with no longitudinal reinforcement and to develop a finite element model that can accurately predict the behaviour of SFRC slabs subjected to punching shear. In this respect, a literature review of the work undertaken by previous researchers on punching shear behaviour of concrete slabs is presented. After that, a constitutive model for SFRC was developed. This is followed by a preliminary finite element analysis (FEA) and experimental study of SFRC slabs. Finally, a finite element model was developed. The literature review revealed that little work has been carried out to study the effect of fibre-reinforcement on the punching shear capacity of concrete slabs. Furthermore, structures, hence a thorough investigation in this area was mandatory. A constitutive model for SFRC in post-cracking stage was developed. This enables one to estimate the tension stiffening behaviour of SFRC based on a simple beam bending test and a statistical model developed in this research, this constitutive model was used later on in the modelling of the SFRC slabs using FEA. In the preliminary FEA, sufficient information for the size and the design of test specimens that were used in the experimental programme was produced. In the experimental study, eight steel fibre-reinforced concrete slab-column connection specimens were tested. The variables of the test specimens include the concrete compressive strength, fibre dosage and fibre aspect-ration.
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AVENDAÑO, JUAN CAMILO. "Identification and quantification of concrete cracks using image analysis and machine learning." Thesis, KTH, Bro- och stålbyggnad, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-286025.
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Nowadays inspections of civil engineering structures are performed manually at close range to be able to assess damages. This requires specialized equipment that tends to be expensive and to produce closure of the bridge. Furthermore, manual inspections are time-consuming and can often be a source or risk for the inspectors. Moreover, manual inspections are subjective and highly dependent on the state of mind of the inspector which reduces the accuracy of this kind of inspections. Image-based inspections using cameras or unmanned aerial vehicles (UAV) combined with image processing have been used to overcome the challenges of traditional manual inspections. This type of inspection has also been studied with the use of machine learning algorithms to improve the detection of damages, in particular cracks. This master’s thesis presents an approach that combines different aspects of the inspection, from the data acquisition, through the crack detection to the quantification of essential parameters. To do this, both digital cameras and a UAV have been used for data acquisition. A convolutional neural network (CNN) for the identification of cracks is used and subsequently, different quantification methods are explored to determine the width and length of the cracks. The results are compared with control measures to determine the accuracy of the method. The results present low to no false negatives when using the CNN to identify cracks. The quantification of the identified cracks is performed obtaining the highest accuracy estimation for 0.2mm cracks.
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Yen, Chin-lu, and 顏淇祿. "Ready-mix Plant Concrete Quality Control Technology." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/52141310843521452594.
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碩士國立臺灣科技大學
營建工程系
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In view of the good and bad quality of concrete, reinforced concrete structures seriously affect safety, and even endanger the lives of the people, so quality control of concrete work or even important. But the current construction site inspection and quality control practices, mostly depends on field sampling produced cylindrical specimens at 28 days of age compressive strength, as the basis for quality control assessment, can not fully reflect the existing site management of construction projects and the actual situation quality control to meet the timeliness requirements, this study will be the actual case Taipower plant's construction, nuclear power plant for the supply of ready-mixed concrete plant quality control engineering technical capacity for assessment and compare the ratio of ready-mix plant stability. The use of ACI 214 concrete compressive strength evaluation criteria, to be statistical analysis of the stability of compression specimens, except for the on-site pouring concrete mix design strength and intensity differences between the relevant factors to be explored. After collecting data using statistical quality control techniques computational analysis showed that not only the quality of ready-mixed concrete plant material, mixing, pouring procedures to regulate, and to the establishment of various SOP manual. But the most important thing is to change the concrete mix design concepts, such as the South underground station belongs compactness of concrete mix design method to find "the most dense packing the minimum amount of pulp, the maximum unit weight" ratio of ideas to minimize the amount of cement and water, mixed with pozzolanic admixture, so that work to achieve the best performance and reduce the occurrence of cracks in concrete, increased dimensional stability, uniformity and stability of the concrete quality, improve the overall quality of concrete work, and thus make concrete upgraded to green concrete. In this study, then both concrete mix design concept to analyze the differences. Keywords: compressive strength; statistical analysis; pozzolan admixture; green concrete