Limit analysis is a very powerful tool to find accurate solutions of several geotechnical stability problems. This analysis is based on the theory of the plasticity and it provides two limiting solutions within lower and upper bounds. With the advancement of the finite elements and different robust optimization techniques, the numerical limit analysis approach in association with finite elements is becoming quite popular to assess the stability of various complicated structures. The present thesis deals with the formulations and the implementation of the finite element limit analysis to obtain the solutions of different geotechnical axisymmetric stability problems. The objectives of the present thesis are twofold: (a) developing limit analysis formulations in conjunction with linear and nonlinear optimizations for solving axisymmetric stability problems related with soil and rock mechanics, and then (b) implementing these axisymmetric formulations for solving various important axisymmetric stability problems in geomechanics. Three noded linear triangular elements have been used throughout the thesis. In order to solve the different problems, the associated computer programs have been written in MATLAB. With reference to the first objective of the thesis, the existing finite element lower bound axisymmetric formulation with linear programming has been presented. A new technique has also been proposed for solving an axisymmetric geomechanics stability problem by employing an upper bound limit analysis in combination with finite elements and linear programming. The method is based on the application of the von-Karman hypothesis to fix the constraints associated with the magnitude of the circumferential stress (), and finally the method involves only the nodal velocities as the basic unknown variables. The required computational effort becomes only marginally greater than that needed for an equivalent plane strain problem. The proposed methodology has been found to be computationally quite efficient. A new lower bound axisymmetric limit analysis formulation, by using two dimensional finite elements, the three dimensional Mohr-Coulomb (MC) yield criterion, and nonlinear optimization has also been presented for solving different axisymmetric stability problems in geomechanics. The nonlinear optimization was carried out by employing an interior point method based on the logarithmic barrier function. The yield surface was smoothened (i) by removing the tip singularity at the apex of the pyramid in the meridian plane, and (ii) by eliminating the stress discontinuities at the corners of the yield hexagon in the plane. No inherent assumption concerning with the hoop stress needs to be made in this formulation. The Drucker-Prager (DP) yield criterion was also used for computing the lower bound axisymmetric collapse load. The advantage of using the DP yield criterion is that it does not exhibit any singularity in the plane. A new proposal has also been given to simulate the DP yield cone with the MC hexagonal yield pyramid. The generalized Hoek-Brown (HB) yield criterion has also been used. This criterion has been smoothened both in the meridian and  planes and a new formulation is prescribed for obtaining the lower bound axisymmetric problems in rock media in combination with finite elements and nonlinear optimization. With reference to the second objective, a few important axisymmetric stability problems in soil mechanics associated with footings and excavations have been solved in the present thesis. In all these problems, except that of a flat circular footing lying over either homogeneous soil or rock media, it is assumed that the medium is governed by the MC failure criterion and it follows an associated flow rule. For determining the collapse loads for a circular footing over homogenous soil and rock media, the problem has been solved with the usage of Drucker-Prager, Mohr-Coulomb and Hoek-Brown criteria. The bearing capacity of a circular footing lying over fully cohesive strata, with an inclusion of a sand layer is evaluated. The effects of the thickness and internal friction angle of the sand layer () on the bearing capacity have been examined for different combinations of cu/(b) and q; where (i) cu defines the undrained shear strength, (ii)  is the unit weight of sand, (iii) b corresponds to the footing radius, and (iv) q is the surcharge pressure. The results have been presented in the form of a ratio () of the bearing capacities with an insertion of the sand layer to that for a footing lying directly over clayey strata. It is noted that an introduction of a layer of medium dense to dense sand over soft clay improves considerably the bearing capacity of the foundation. The improvement in the bearing capacity increases continuously (i) with decreases in cu/(b), and (ii) increases in  and q/(b). The bearing capacity factors, Nc, Nq and N, for a conical footing are obtained in a bound form for a wide range of the values of cone apex angle () and with  = 0, 0.5 and . The bearing capacity factors for a perfectly rough ( = conical footing generally increase with a decrease in . On contrary for  = 0, the factors Nc and Nq reduce gradually with a decrease in . For  = 0, the factor N for  ≥ 35o becomes minimum for  approximately equal to 90o. For  = 0, the factor N for  ≤ 30o, like in the case of  = , generally reduces with an increase in . It has also been intended to compute the bearing capacity factors Nc, Nq and N, for smooth and rough ring footing for different combinations of ri/ro and ; where ri and ro refer to inner and outer radii of the ring, respectively. It is observed that for a smooth footing, with a given value of ro, the magnitude of the collapse load decreases continuously with an increase in ri. On the other hand, for a rough base, for a given value of ro, hardly any reduction occurs in the magnitude of collapse load up to ri/ro ≈ 0.2, whereas beyond this ri/ro, the magnitude of the collapse load, similar to that of a smooth footing, decreases continuously with an increase in ri/ro. An attempt has also been made to determine the ultimate bearing capacity of a circular footing, placed over a soil mass which is reinforced with horizontal layers of circular reinforcement sheets. For performing the analysis, three different soil media have been separately considered, namely, (i) fully granular, (ii) cohesive frictional, and (iii) fully cohesive with an additional provision to account for an increase of cohesion with depth. The reinforcement sheets are assumed to be structurally strong to resist axial tension but without having any resistance to bending; such an approximation usually holds good for geogrid sheets. The shear failure between the reinforcement sheet and adjoining soil mass has been considered. The increase in the magnitudes of the bearing capacity factors (Nc and N) with an inclusion of the reinforcement has been computed in terms of the efficiency factors c and . The critical positions and corresponding optimum diameter of the reinforcement sheets, for achieving the maximum bearing capacity, have also been established. The increase in the bearing capacity with an employment of the reinforcement increases continuously with an increase in . The improvement in the bearing capacity becomes quite extensive for two layers of the reinforcements as compared to the single layer of the reinforcement. The stability of an unsupported vertical cylindrical excavation has been assessed. For the purpose of design, stability numbers (Sn) have been generated for both (i) cohesive frictional soils, and (ii) pure cohesive soils with an additional provision to account for linearly increasing cohesion with depth by using a non-dimensional factor m. The variation of Sn with H/b has been established for different values of m and ; where H and b refer to height and radius of the cylindrical excavation. A number of useful observations have been drawn about the variation of the stability number and nodal velocity patterns with changes in H/b,  and m. In the last, by using the smoothened generalized HB yield criterion, the ultimate bearing capacity of a circular footing placed over a rock mass is evaluated in a non-dimensional form for different values of GSI, mi, ci/(b) and q/ci. For validating the results, computations were exclusively performed for a strip footing as well. For the various problems selected in the present thesis, the failure and nodal velocity patterns have been examined. The results obtained from the analysis have been thoroughly compared with that reported from literature. It is expected that the various design charts presented here will be useful for the practicing engineers. The formulations given in the thesis can also be further used for solving various axisymmetric stability problems in geomechanics.

The purpose of this thesis is to design bridge over the valley on D1 highway. Length of the structure is 170 meters. Main structure is four spans prestressed beam. The length of fields is 36+48+48+36 meters. The structure is examined in all phases of construction, including the operating phase according to valid standards.

Master's thesis „Study of joints of frame steel structures“ examine certain analysis types of frame steal joints, which are analysed both by component method and by specialized software IDEA RS. Obtained results are compared by both methods, in terms of load-bearing capacity and in terms of stiffness. Theoretical joints stiffness calculation according to standard ČSN EN 1993-1-8 is included in the introductory part of the thesis. In the second part, joints are designed to bear inner forces and moments, which were created by load combination effects and then analysed.

Geokunststoffe sind beständige Produkte aus Polymeren, die in Boden eingelegt werden um geotechnische Probleme zu lösen. Eine Kategorie der Geokunststoffe sind Geogitter, bei denen die Längs- und Querelemente eine offene, gitterförmige Struktur bilden und die meist zur Bodenbewehrung eingesetzt werden. Ihre Verwendung zur Bewehrung von gering tragfähigen Böden für kunststoffbewehrte Erd- und Stützbauwerke kann enorme ökologische und ökonomische Vorteile bieten. Trotz der Tatsache, dass die Verwendung von Geogittern in den letzten Jahren stark zugenommen hat, sind die Grundlagen zum Bau und zur Bemessung limitiert. Besonders die Schlüsselfrage, wie Geogitter und verschiedene Lockergesteine in unterschiedlichen Belastungssituationen interagieren, ist ingenieursmäßig nur lückenhaft untersucht worden. Im Rahmen dieser Dissertation wurde deshalb in über 250 großmaßstäblichen Scher-, Herauszieh- und Reibungsversuchen das Verbundverhalten Geokunststoff/Locker¬gestein eingehend untersucht. Dazu wurden 14 handelsübliche Geogitter, die teilweise auch modifiziert wurden, in dem Interaktionsprüfgerät des Institutes für Geotechnik der TU Bergakademie Freiberg mit verschiedenen Böden systematisch getestet. Die vielen Versuchsanordnungen und die aus ihnen abgeleiteten Überlegungen und gewonnenen Erkenntnisse belegten, dass die wichtigsten Parameter interagieren, und zwar in verschiedenen Abhängigkeiten wie weitere Variationen der Bodenparameter (Kornverteilung, Wassergehalte, Verdichtung, Bindemittelzusatz etc.), der unterschiedlichen Geogitterparameter (Oberflächenbeschaffenheit, Struktur, etc.) und der Belastung gezeigt haben. Darüber hinaus wurde das Interaktionsprüfgerät für zukünftige Versuche weiterentwickelt (Entkopplung des Versuchseinbaus vom Versuchsgerät usw.). Der Fokus der Forschungsarbeit lag dabei in der Schaffung von Grundlagenkenntnissen für den gemeinsamen Einsatz von bindigen Lockergesteinen und Geokunststoffen. Bei rolligen Böden zeigte sich, dass die Rautiefe sich stärker (positiv) auf die Widerstände auswirkt als bei den bindigen Böden. Hingegen waren bei bindigen Böden die Auswirkungen durch eine Erhöhung der Querelemente deutlicher. Darüber hinaus konnte gezeigt werden, dass dreidimensionale Querelemente das Verbundverhalten verbessern und Tests an Geogittern mit einem größeren Verhältnis von Öffnungsweite zu Maschenweite zeigten höhere Adhäsionswerte. Die Reibungsversuche hatten einen gleichmäßigeren Verlauf und geringere Streuungen zwischen den unterschiedlichen Geogittern, weshalb aufgrund der deutlicheren Unterschiede zwischen den Produkten bei den Herausziehversuchen detaillierte Schlussfolgerungen gezogen werden konnten. Die vorliegende Arbeit leistet einen Beitrag zur Verbesserung der Bemessungsgrundlagen und ermöglicht ein detaillierteres Verständnis des Verbundverhaltens. Des Weiteren werden Vorschläge ausgearbeitet die im Labor erzielten Ergebnisse auf die Baupraxis zu übertragen, wie zum Beispiel durch das Vermeiden von Trennflächen zwischen Geogitter und Boden bei der Verdichtung. / Geosynthetics are durable polymeric products placed in soil to help solve civil engi-neering problems; one category of these is geogrids. Geogrids are polymers formed into an open, grid-like configuration and function primarily as soil reinforcement. Their use to reinforce soil with weak bearing capacity could have big ecological and economical advantages. Although geogrid use has grown in recent years, there is still limited design information available due to the wide variety of design configurations and soil variability. One of the key factors lacking for more widespread engineering implementation is a greater understanding of the interaction between various geogrids and soil combinations when exposed to different load effects. In more than 250 shear, pull-out, and friction tests, this interaction behavior was examined in detail. Fourteen general geogrids (sometimes additionally modified) using dif-ferent soil types were systematically tested in the Interaction Testing Device at the Geotechnical Institute of the TU Bergakademie Freiberg. Combining the huge quantity of test results with a theoretical analysis, the main parameters which affect soil behavior could be defined. Furthermore the Interaction Testing Device could be improved for test in future. Our analysis showed us that the roughness of the geogrid has more of a beneficial impact on the strength of frictional soils than it does for silty soils. Silty soils however, were more affected by the height of cross elements in the geogrid than other types. It was also observed that 3D elements in the cross machine direction improve the interaction behavior. Tests with geogrids which have a bigger ratio of opening size to mesh size showed higher adhesion values. The friction test results were more regular, had a uniform progress and had smaller differences between geogrid configurations. Therefore, conclusions with higher certainty could be drawn from the pull-out tests with the differential results. The present research contributes to the limited design information to help provide a better understanding of the interaction behavior. Furthermore, suggestions are given to use the laboratory detected results in real-world applications, one of which is the way of compaction to minimize the potential for creating a slip-surface between the geogrid and soil.

Das Trag- und Verbundverhalten textiler Bewehrungen wurde in den vergangen Jahren umfassend experimentell untersucht. Die dabei gewonnenen Erkenntnisse stützen sich jedoch fast ausschließlich auf einaxiale Beanspruchungszustände. Grundsätzlich können aus dem Vergleich von Versuchen an Rovings und an textilen Bewehrungsstrukturen Rückschlüsse auf den Einfluss der Quer- und Stützfäden und der verschiedenen Bindungstechniken auf das einaxiale Tragverhalten von Textilbeton getroffen werden. Offen bleibt jedoch, inwieweit sich die gefundenen Gesetzmäßigkeiten auf mehraxiale Beanspruchungssituationen übertragen lassen. Dadurch werden Fragen bezüglich des Tragverhaltens textiler Bewehrungen unter mehraxialen Zugbeanspruchungen aufgeworfen, welche die Motivation für die vorliegende Arbeit liefern. Die hierzu durchgeführten experimentellen Untersuchungen umfassen 84 Einzelversuche und wurden in einem speziell für zweiaxiale Zugbeanspruchungen entwickelten Versuchsaufbau durchgeführt. Als textile Bewehrungen kamen zwei verschiedene Gelegearten aus AR-Glas und Carbon zum Einsatz. Die Ergebnisse konnten die bisher ausschließlich an einaxialen Dehnkörpern gewonnenen Erkenntnisse über das Tragverhalten textiler Bewehrungen grundsätzlich bestätigen. Für den Übergang von Zustand I zum Zustand II konnte eine Abhängigkeit der Erstrissspannung vom Spannungsverhältnis nachgewiesen werden. Die Merkmale der Zustände IIa und IIb zeigen hingegen keine signifikante Abhängigkeit vom Verhältnis aus Längs- und Querzugspannung. Darüber hinaus haben offenbar durch Querzug induzierte bewehrungsparallele Risse keine maßgeblichen Auswirkungen auf das Verbundverhalten der Rovings in Längsrichtung. Eine wesentliche Erkenntnis aus den biaxialen Zugversuchen mit Carbon betrifft den Einfluss der Welligkeit. Es wurde deutlich, dass der Abbau der Welligkeit in beschichteten textilen Bewehrungen hochgradig lastabhängig ist. In zahlreichen Versuchen mit Carbon kam es innerhalb des Zustands IIb zu Delamination, einem bisher in diesem Umfang nicht beobachteten Effekt. Die Erkenntnisse hinsichtlich des Abbaus der Welligkeit wurden im Anschluss auf das Tragverhalten von AR-Glas übertragen und führten zu einer Neubewertung des bei AR-Glas beobachteten Steifigkeitsdefizits im Zustand IIb. Weiterhin wurde der Einfluss der Orientierung der Bewehrung unter einaxialer Beanspruchung an scheibenartigen Probekörpern untersucht. Es zeigte sich, dass die untersuchten Bewehrungen aus AR-Glas hinsichtlich der Tragfähigkeit bei schiefwinkliger Beanspruchung deutlich unempfindlicher reagieren als Bewehrungen aus Carbon. Für die Reduktion der effektiven Faserbruchspannungen wurde ein mathematisches Modell vorgestellt, welches eine getrennte Beschreibung der geometrischen Einflüsse sowie alle sonstigen, die Faserbruchspannung reduzierenden Effekte erlaubt. / The load bearing and bond behaviour of textile reinforcements has been comprehensively studied experimental in recent years. The findings are based almost exclusively on uniaxial loading. Generally, from the comparison of tests on rovings and fabrics conclusions can be drawn about the influence of transverse and supporting threads and different binding patterns on the uniaxial load-bearing behaviour. However, it remains open, to what extend the found principles are applicable to multi-axial loading situations. This raises questions about the load bearing behaviour under multi-axial tension loading, which provide motivation for this work. For the experimental studies on 84 specimens a specially developed test setup for biaxial tensile loading was used. Two different types of textile reinforcements made from AR-glass and carbon fibres were examined. The results generally approve the findings on the structural behaviour of textile reinforcements exclusively derived from uniaxial tests. A relationship between first cracking stress level and biaxial stress ratio has been found. The characteristics of the cracking phases and during stabilized cracking, however, show no significant dependencies on the ratio of longitudinal and transverse tensile stresses. Furthermore, parallel cracks induced by transverse tensile stresses have no significant impact on the bond behaviour of longitudinal rovings. An essential result from biaxial tensile tests with carbon is the strong influence of waviness. It became clear that the reduction of waviness in coated textile reinforcement is highly load-dependent. In numerous experiments with carbon reinforcement delamination occurred during stabilized cracking – an effect, that has been observed in this large scale for the first time. The findings regarding the reduction of the waviness were subsequently applied to AR-glass and led to a revaluation of the known stiffness deficit in the phase IIb. Furthermore, the influence of reinforcement orientation has been studied on discoidal specimens under uni-axial loading. It was found that the load bearing capacity of carbon reinforcement is much more sensible to load orientation than AR-glass. A mathematical model was presented, which allows the separate description of geometric factors and as well as all other effects that reduce the fibre tensile strength.

La utilización de ceniza de cáscara de arroz (CCA) puede reducir el gran problema ambiental asociado a su inadecuada disposición. Una forma, es su adición en suelos arcillosos, lo que puede brindar soluciones a los problemas de estabilización, aumentando así su capacidad de soporte del suelo. El presente proyecto de investigación tiene como finalidad la estabilización de suelos arcillosos aplicando ceniza de cáscara de arroz para el mejoramiento de subrasante en la localidad de Moyobamba- departamento de San Martín; donde se obtuvo un suelo de arcilla inorgánica de alta plasticidad siendo su clasificación SUCS “CH” y AASHTO “A-7-6 (20)”. Se realizó ensayos estandarizados de mecánica de suelos, tales como Análisis Granulométrico, Límites de Atterberg, Proctor Modificado y California Bearing Ratio (CBR) con combinaciones de ceniza de cáscara de arroz (CCA) de 5%, 10% y 15%. En el ensayo de CBR la resistencia obtenida al 95% de la Máxima Densidad Seca del suelo natural es de 3,96%, añadiendo el 5% de CCA la resistencia es de 6,90%, con 10% de CCA es de 9,60% y para el 15% de CCA es de 10,5 %, por lo que la investigación concluye que el uso de ceniza de cáscara de arroz (CCA) como material estabilizante de suelos arcillosos brinda buenos resultados. / The use of rice husk ash (RHA) can reduce the big environmental problem associated with its inadequate disposal. One way is its addition to clay soils, which can provide solutions to stabilization problems, causing the increasing its soil bearing capacity. The present research project has as purpose to stabilize clay soils by applying rice husk ash (RHA) to improve the subgrade in the town of Moyobamba - department of San Martín; where a high plasticity inorganic clay soil was obtained, its classification being SUCS "CH" and AASHTO "A-7-6 (20)". Standardized soil mechanics tests were made, such as Granulometric Analysis, Atterberg Limits, Modified Proctor and California Bearing Ratio (CBR) with combinations of rice husk ash (CCA) of 5%, 10% and 15%. In the CBR test the resistance obtained at 95% of the Maximum Dry Density of the natural soil is 3.96%, adding 5% of RHA the resistance is 6.90%, with 10% of RHA it is 9, 60% and for 15% of RHA it is 10.5%, so the research concludes that the use of rice husk ash (RHA) as a stabilizing material for clay soils provides good results. / Tesis

The subject of master’s thesis is determination of bridge load-bearing capacity and fully probabilistic approach to reliability assessment. It includes a nonlinear analysis of the specific bridge load-bearing capacity in compliance with co-existing Standards and its stochastic and sensitivity analysis. In connection with durability limit states of reinforced concrete structures, the influence of carbonation and the corrosion of reinforcement on the structure’s reliability is also mentioned.

Modern-day terrorist attacks present a considerable danger for commercial aircrafts. This thesis analyzes potential methods of such attacks with a critical analysis of the most dangerous type: an attack from the outside of the aircraft via a fragmentation missile warhead. Such missiles cause damage to the airframe of the aircraft through fragments created by the explosion. In this thesis, analytical geometry is used to determine the area of the aircraft affected by the fragmentation. The aircraft’s geometry and the fragments’ dispersion are calculated by analytical functions, and the effect of the damage is analyzed. A shooting experiment was also carried out, in which fragments were shot at a reinforced skin panel that was manufactured according to the real design of commercial aircraft. The results of the experiment revealed that only directly hit sections of the structure are damaged. Data obtained by the experiment was then used for the creation and improvement of the model used in the simulation by means of the finite element method. This model is used for the numerical calculation of the damage sustained. Further included in the thesis is an analysis of the change in the load-bearing capacity after such an attack. The relationship between the size of the damage and its effect on the load-bearing capacity of the component as well as the entire structure is defined. First, the effect of component damage is analyzed via the FMEA/FMECA methods. This analysis is then extended using fuzzy logic. Fuzzy logic analysis is based on the determination of the size of the damaged component area and the component’s importance on the structure’s carry loads. Application of the defined approach is described for several parts of an aircraft’s life cycle, including development, operation after the terrorist attack, and assessment of causes after a crash caused by a fragmentation missile warhead.

The contemporary imperative of sustainable development has established an unprecedented degree of urgency, in view of the intransigent challenges posed by the persistent and ever-increasing energy and climate crises. In 2019, the Swedish building industry accounted for 21% of the nation’s total greenhouse gas emissions, with the structural framework of a building contributing to 34% of its overall emissions. In response to climate change and the housing demand caused by a growing population, sustainable construction solutions are needed. By substituting steel beams with timber beams, the carbon emissions caused by the building industry can be reduced significantly. This study investigates whether timber based, or steel-reinforced timber beams can provide comparable load-bearing capacity to steel beams while reducing carbon. How this impacts the cross-sectional height of the beams is also taken into consideration. Different load-bearing properties were calculated according to Eurocode using Excel for all the surveyed beams. The carbon emissions were calculated based on the weight of each beam combined with climate data obtained from the Swedish National Board of Housing, Building and Planning. Findings suggest that timber-based beams made from glulam or laminated veneer lumber exhibit moment capacity and bending stiffness on par with those of steel beams while reducing the carbon emissions drastically, but at the cost of increased cross-section height. Steel beams were identified as the main source of carbon emissions. Consequently, also making steelreinforced timber beams only marginally successful in reducing carbon emissions if at all.

Während die Zugfestigkeit im Fokus der Forschung am Werkstoff Carbonbeton steht, wurde die Tragfähigkeit des Materials unter Druck bisher kaum untersucht. Aufbauend auf ersten Erkenntnissen zur einaxialen Druckfestigkeit von Carbonbeton werden im Rahmen dieses Projekts scheibenförmige Prüfkörper aus Carbonbeton mit einer kombinierten Einwirkung aus Druck und zusätzlich wirkenden Querdruck- und Querzugbelastungen betrachtet. Dieser Beitrag stellt die ersten Ergebnisse der zweiaxialen Druckbelastungen vor und gibt einen Ausblick auf weiterführende Untersuchungen im Projekt.