This thesis is concerned with the early-life behaviour of concrete industrial ground floors. Advances in construction methods are placing increased demands on the performance of industrial floors and pushing the limits of the current design guidance. Uncertainties about the true behaviour of industrial floors have been addressed by a programme of in-situ monitoring. An in-situ instrumentation methodology has been developed to monitor the slab and the local climate. Vibrating wire strain gauges and demecs were used to collect concrete shrinkage and joint performance data, whilst thermocouple arrays and thermistors in the strain gauges recorded the slab temperature. This allowed the effects of the cement hydration and the impact of ambient conditions on the slab to be assessed. The use of an automated data collection system allowed the timing as well as the magnitude of the movements to be measured helping identify cause and effect. Floor slabs covering long strip and large area pour construction, jointed and jointless detailing and mesh fabric and fibre reinforcement have been investigated. The data has shown the strong thermal influence on the behaviour of the slabs. Initial joint opening was found to be triggered by the cooling of the slab, whilst the effects of seasonal temperature changes in the first couple of months after construction could be as large if not larger than the drying shrinkage. Frictional resistance was found to reduce the measured movement, whilst the restraint arising from adjacent pours was also found to be significant. Finite element models of the temperature development have been produced using material property data found in the literature. Calibration and verification were carried out using the temperature data collected from site with good agreement. Structural models were then developed using the temperature and degree of hydration output from the thermal analysis as input. These models were used to determine the theoretical stress distribution in slabs at early-ages, and to conduct a parametric study. This demonstrated that the warping stresses present in a slab are generally greater than those from frictional restraint. The thesis concludes with recommendations for the design and construction of industrial ground floors.

This investigation involved creep and moisture movement measurements for about six months on 13-course clay (Engineering class B) and calcium silicate brickwork, and 5-course concrete blockwork, consecutively. Four different geometries of masonry were built, namely: single-leaf wall, cavity wall, hollow pier and solid pier, respectively having volume/surface area (V/S) ratios of 44,51,78 and 112 mm. Deformations were also measured on one-brick wide 5 or 6-stack high model brickwalls which were partly sealed to simulate the V/S ratios of the corresponding 13-course brickwork. At the same time, deformations were also measured on individual mortar prisms and brick or block units in order to verify composite model expressions for predicting masonry movements. Simulation of moisture diffusion of the corresponding mortarjoints and embedded bricks or block were made in terms of V/S ratio by partial sealing of the individual mortar prisms and brick or block units. The tests reveal that the modulus of elasticity to be independent of masonry geometry. However, there is a clear influence of geometry on the vertical ultimate creep and moisture movement of all the masonry types i,.e. creep and shrinkage increase with a decrease of V/S ratio. A similar trend occurs for horizontal shrinkage except for the clay brickwork which undergoes moisture expansion. Deformations of the model walls show reasonable agreement with the 13-course brickwork. When results of individual mortar and brick/block specimens are inserted in composite models,the predicted strains show good agreement with the measured strains, particularly in the vertical direction. There is no consistent pattern in the distribution of load and moisture strains for the different masonry geometries, and the measurements reveal that actual strains can be up to 100% higher than the average strains.

Effective determination of long-term prestress losses is important in the design of prestressed concrete bridges. Over-predicting prestress losses results in an overly conservative design for service load stresses, and under-predicting prestress losses, can result in cracking at service loads. Creep and shrinkage produce the most significant time-dependent effect on prestress losses, and research has shown that high performance and high strength concretes (HPC and HSC) exhibit less creep and shrinkage than conventional concrete. For this reason, the majority of traditional creep and shrinkage models and methods for estimating prestress losses, over-predict the prestress losses of HPC and HSC girders. Nine HPC girders, with design compressive strengths ranging from 8,000 psi to 10,000 psi, and three 8,000 psi lightweight HPC (HPLWC) girders were instrumented to determine the changes in strain and prestress losses. Several creep and shrinkage models were used to model the instrumented girders. For the HPLWC, each model over-predicted the long-term strains, and the Shams and Kahn model was the best predictor of the measured strains. For the normal weight HPC, the models under-estimated the measured strains at early ages and over-estimated the measured strains at later ages, and the B3 model was the best-predictor of the measured strains. The PCI-BDM model was the most consistent model across all of the instrumented girders. Several methods for estimating prestress losses were also investigated. The methods correlated to high strength concrete, the PCI-BDM and NCHRP 496 methods, predicted the total losses more accurately than the methods provided in the AASHTO Specifications. The newer methods over-predicted the total losses of the HPLWC girders by no more than 8 ksi, and although they under-predicted the total losses of the normal weight HPC girders, they did so by less than 5 ksi. / Ph. D.

The thesis deals with design and assessment of all supporting parts of cast-in-place reinforced concrete tank. The thesis includes a technical report, static analysis, drawing documentations, construction proces and visualization. The drawing documentation consists of shape and reinforcement drawings of supporting parts.

The master´s thesis deals with the volume changes of concrete during its concrete glow. These volume changes are generally more susceptible to high-strength concretes – HSC, which contain a bigger dose of binder. The theoretical section describes the possible reduction volume change especially in HSC, which are focused on the composition of concrete, especially on the type and particle size distribution of aggregate. Then attention is also paid to the different types of cements and their possible substitution. The part of the theoretical work describes the types of volume changes that may occur. In the experimental part are suggested the HSC by to secure informations. Different kinds of aggregates are used and a continuous or discontinuous grain curve and a different maximum grain size. Part of the sample was made only from CEM I 42,5 R and the second part of the sample from CEM I 42,5 R with the addition of very finely ground limestone. In terms of the part of the work were monitored volume changes of concrete with different composition and also their mechanical properties after 7, 28 and 90 days. Specifically, compressive strength, tensile strength, strength of the surface layers of concrete, water absorption and water-permeability test concrete. In conclusion, are listed all the results of tests.

Baigiamajame magistro darbe išnagrinėti STR ir EC 2 betono fizikinių ir mechaninių rodiklių nustatymo metodai bei šiose normose pateiktų įtempių nuostolių skaičiavimo modeliai. Aprašytas tikimybinis įtempių nuostolių vertinimo modelis. Atlikta atskirųjų ir suminių įtempių nuostolių analizė pagal STR ir EC 2 modelius, aprašyti šių modelių skirtumai. Išnagrinėta atskirų fizikinių faktorių lemiančių įtempių nuostolius įtaka. Atlikta iš anksto įtemptos gelžbetoninės sijos tikimybinė suminių įtempių nuostolių analizė. Darbe pateiktas kiaurymėtųjų perdangos plokščių suminių įtempių nuostolių skaičiavimo rezultatų pagal EC 2 ir STR modelius ir eksperimentinių įtempių nuostolių palyginimas. / Evaluation of different physical and mechanical factors of concrete according to STR and EC 2 models is considered in this master thesis. Probabilistic model for prestress loss determination is presented in this paper. The analysis of separate and total losses according to STR and EC 2 models was carried out. Some differencies of these models were described. The influence of several factors to the value of separate prestress loss has been studied in this thesis. The probabilistic analysis of long-term losses of post-tensioned RC beam has been carried out. The comparison of total prestress loss values of hollow core slabs according to EC 2, STR and experimental results is subjected in this master thesis.

Tiriamajame darbe nagrinėjami tempiamieji plieno plaušu armuoti gelžbetoniniai elementai. Atliekama teorinių skaičiavimo metodų literatūros apžvalga. Darbe gauti nauji eksperimentiniai tempiamųjų plieno plaušu armuotų gelžbetoninių elementų deformacijų duomenys. Iš bandymo rezultatų eliminuojamas betono susitraukimas. Patikslinami Eurokodo 2 ir Model Code tempiamųjų elementų deformacijų skaičiavimo metodai, įvertinant plieno plaušo įtaką. Liekamieji įtempiai apskaičiuojami taikant empirinį metodą. Atliekama teorinių ir eksperimentinių rezultatų palyginamoji analizė. Darbo pabaigoje pateikiami pagrindiniai rezultatai ir išvados. / In this Master Thesis investigation of steel fiber reinforced concrete members subjected to tension is performed. Literature survey on theoretical investigation methods of steel fiber reinforced concrete is done. New experimental data of steel fiber reinforced concrete members subjected to tension is obtained. Concrete shrinkage is eliminated from experimental data.Eurocode 2 and Model Code strain calculation methods of members subjected to tension are adjusted to steel fiber reinforced concrete members. Residual stresses calculated using empirical method. Comperative analysis of experimental and theoretical results is done.

Determination of rheological phenomenon is very difficult, because there are many unknown inputs parameters, e.g. concrete age, the size of elements, relative humidity of the surrounding environment, cement hydration rate, temperature influence, type of strain and treatment. This Ph.D. thesis deals with the effective cross-section thickness and its effect on the behaviour of concrete constructions that is how the rheological phenomena change in time as a result of the application or removal of insulation layer from the concrete surface. Long-term experimental measurements of specimens and real bridge constructions were performed. The data collected from these measurements were described, evaluated and mathematical modifications for the standards Model Code 2010 and Model B4 (B3) have been proposed. Using these new computational formulas is possible to take into consideration the changes in the effective cross-section thickness and therefore make the computational models for concrete structures more accurate.

No description available.

Gegenstand der Arbeit ist die Entwicklung eines numerischen Stoffgesetzes, welches die materialspezifischen Besonderheiten Selbstverdichtender Betone in jungem Alter erfasst. Durch das erhöhte Schwindmaß eines Selbstverdichtenden Betons innerhalb der ersten zwölf Stunden können Dehnungszustände hervorgerufen werden, welche zu Schädigungen führen, die von den einschlägigen Normen bisher noch nicht erfasst wurden. Im Zuge des Forschungsprojektes „Selbstverdichtender Beton im Untertagebau“ konnten Erkenntnisse über das materialspezifische Verhalten bei konstanten Umgebungsbedingungen erlangt werden. Diese Ergebnisse wurden mit übertägig gewonnen Daten verglichen, um eine klare Abgrenzung zu einem normalen Rüttelbeton zu ziehen. Im weiteren Verlauf wurden die Ergebnisse zur Kalibrierung einer numerischen Simulation herangezogen. Damit kann nun, in Abhängigkeit der relativen Luftfeuchtigkeit und der Bauteilgröße, das Dehnungsverhalten eines SVB in jungem Alter realitätsnah beschrieben werden.:Inhaltsverzeichnis Vorwort II Kurzfassung III Abstract IV 1. Einleitung 1 1.1 Problemstellung 1 1.2 Stand der Erkenntnis 4 1.3 Zielsetzung 8 2. Mechanische Eigenschaften Selbstverdichtender Betone 12 2.1 Rheologische Grundlagen 12 2.1.1 Mischungszusammensetzung für den Einsatz Untertage 12 2.1.2 Kinetik des Erstarrens 17 2.1.3 Frisch- und Festbetoneigenschaften 20 2.1.4 Mischungsentwurf 22 2.2 Feuchte- und Wärmetransport 24 2.2.1 Hydratationsverhalten 24 2.2.2 Feuchtetransport und Speicherung 28 2.2.3 Numerische Umsetzung der Feuchte- Wärmekopplung 32 2.2.4 Finite Element Formulierung und Umsetzung mit Abaqus 35 2.3 Mathematische Formulierung 40 2.3.1 Thermische Leitfähigkeit 40 2.3.2 Hygrische Leitfähigkeit 42 2.3.2.1 Hygrische Transportvorgänge bei Änderung der Umgebungsfeuchte 43 2.3.2.2 Hygrische Transportvorgänge anhand von Temperaturveränderungen 46 2.4 Lastunabhängige Verformungen von Beton 47 2.4.1 Temperatureffekte 47 2.4.2 Feuchteffekte 49 3. Experimentelle Untersuchungen 51 3.1 Ergebnisse der Laborversuche 51 3.1.1 Zug- und Druckfestigkeiten 51 3.1.2 Hydratationsverhalten 55 3.1.3 Feuchtemessungen an Schwindrinnen 57 3.1.4 Schwindverhalten aus Laborversuchen 62 3.2 Untersuchungen am Großversuchsstand 65 3.2.1 Einrichtung des Versuchsstandes 65 3.2.2 Fördertechnologie 68 3.2.3 Schalungsdrücke 69 3.2.4 Hydratationsverhalten und Lastunabhängige Verformungen 70 3.3 Versuchsergebnisse am Großversuchsstand 70 3.3.1 Hydratation und Wärmefreisetzung 70 3.3.2 Schalungsdrücke 74 3.3.3 Schwind- und Temperaturdehnungen 76 3.3.3.1 Schwindrinnen 76 3.3.3.2 Tunnelbauwerk 78 3.4 Rissbildung am Bauwerk 80 3.4.1 Übersicht zu gängigen Risskonzepten 80 3.4.2 Methodenvalidierung der Risskriterien 83 4. Numerische Berechnungen 87 4.1 Numerische Grundlagen 87 4.1.1 Zwangsspannungen infolge Hydratation 87 4.1.1.1 Instationäre Wärmeleitungsprobleme 89 4.1.1.2 Berechnung von Verschiebungsfeldern 90 4.1.2 Thermisch-hygrische Dehnungen 92 4.2 Numerische Detailuntersuchungen und Modellparameter 94 4.2.1 Konstruktive Details des Modells 95 4.2.2 Bewehrungselemente 97 4.2.3 Ermittlung der benötigten Parameter 99 4.3 Vergleichsberechnungen 103 4.3.1 Hydratationswärmeentwicklung 103 4.3.2 Thermisch-hygrische Kopplung 106 4.4 Berechnungsergebnisse 109 4.4.1 Schwindrinne 110 4.4.1.1 Temperaturentwicklung und Trocknungsverhalten 110 4.4.1.2 Schwinddehnungen 113 4.4.1.3 Längenänderungen infolge unterschiedlicher Umgebungsfeuchten 117 4.4.2 Untertägiges Tunnelbauwerk 119 4.4.2.1 Temperaturentwicklung und Trocknungsverhalten bei hohen Luftfeuchtigkeiten 119 4.4.2.2 Spannungsentwicklung infolge Zwang 122 4.4.3 Rissbildung in jungem Alter 126 4.4.3.1 Kritischer Hauptspannungsraum und mögliche Rissbreiten 126 4.4.3.2 Beanspruchungen der Bewehrung 131 4.4.4 Abhängigkeiten der Dehnungsverteilung und Rissbreite von Selbstverdichtenden Betonen in jungem Alter 134 5. Zusammenfassung und Ausblick 139 Literaturverzeichnis 143 Abkürzungsverzeichnis 151 Abbildungsverzeichnis 152 Tabellenverzeichnis 156 Anhangsverzeichnis 157