Dissertations / Theses on the topic 'Concrete arches'

CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Arco segmentado é uma estrutura composta de vários segmentos retilíneos,emendados em pontos pertencentes a uma curva em forma de arco que circunscreve a estrutura. A coincidência dos pontos das emendas (nós) com essa curva permite a redução dos momentos fletores nesses pontos. O arco segmentado assim idealizado apresenta algumas vantagens para a indústria de pré-moldados, quais sejam: permite a utilização das fôrmas empregadas na moldagem de outros tipos de peças retilíneas como pilares e vigas; permite a construção de arcos com qualquer relação entre a flecha e o vão, empregando-se as mesmas fôrmas, bastando para isso variar os ângulos entre os segmentos emendados. Neste trabalho é feito um estudo teórico sobre a estabilidade dos arcos segmentados,utilizando para isto o modelo computacional baseado no método nos elementos finitos. Dentro deste estudo são realizadas análises sobre a influência da relação altura/vão, da variação do número de segmentos, da presença de imperfeições iniciais e da ação do vento no comportamento global destes arcos. Também é desenvolvido um procedimento para o cálculo da carga crítica dos arcos segmentados bi e tri-articulados e que leva em consideração tanto as cargas caracterizadas por pontos limite como as por pontos de bifurcação. São apresentados os detalhes e resultados de um ensaio experimental de um arco segmentado de concreto armado, que teve como objetivo principal a verificação do comportamento global deste tipo de estrutura e da eficiência do modelo computacional aqui utilizado.
Segmental arch is a structure made of several straight segments of precast concrete connected at points belonging to a curve in the form of an arch which circumscribes the structure. This type of arch has some advantages for the precasting industry: a) it allows the use of the same forms used to cast other types of straight pieces such as beams and columns; b) it allows the construction of arches with any height/span ratio, using the same forms, which is achieved just by varying the angle between the connected segments. In this work, a study of the stability of this type of arch is developed, with the use of a computer model based on the finite elements method. In side of this study, the effects of height/span ratio variation, segment number variation, initial imperfections presence and the wind action are investigated. In addition, a calculus procedure of the critical load to the segmental arches is developed. This procedure takes in consideration the loads characterized by limit points as much as that by bifurcation points. Is also presented an experimental test, of a segmental arch made of reinforced concrete, that was conducted with the purpose of studying the global behavior of this type of structure, and verify the efficiency of the computer model used.
El arco segmentado es una extructura compuesta de varios segmentos rectilíneos,enmendados en puntos que pertenecen a una curva en forma de arco que circunscribe la extructura. La intercepción de los puntos de las enmiendas (nodos) con esa curva permite la reducción de los momentos flectores en esos puntos. El arco segmentado presenta algunas ventajas para la industria de premoldados como son: permite la reutilización de las formas para el moldeado de otros tipos de piezas rectilíneas como pilares y vigas; permite la construcción de arcos con cualquier relación entre la flecha y el vano, utilizando las mismas formas, tan solo variando los ángulos entre los segmentos enmendados. En este trabajo, se desarrolla un estudio teórico sobre la estabilidad de los arcos segmentados,utilizando el modelo computacional basado en el método en los elementos finitos. Dentro de este estudio se analiza la influencia de: la relación altura/vano, la variación del número de segmentos, la presencia de imperfecciones iniciales y la acción del viento en el comportamiento global de estes arcos. También se desarrolla un procedimiento para el cálculo de la carga crítica de los arcos segmentados bi y triarticulados que lleva en consideración tanto las cargas caracterizadas por puntos límites como por puntos de bifurcación. Se presentan detalles y resultados de un ensayo experimental de un arco segmentado de concreto armado, cuyo objetivo principal es verificar el comportamiento global de este tipo de extructura y la eficiencia del modelo computacional aqui utilizado.

A rigorous structural analysis is fundamental in the safety assessment of the built heritage and in its efficient conservation and rehabilitation. In line with the necessity of refined techniques, the objective of the present thesis is to develop and validate, in a displacement-based finite element framework, a nonlinear model apt for the study of masonry and concrete structures under monotonic and cyclic loading. The proposed constitutive law adopts two independent scalar damage variables, d+ and d−, in combination with the spectral decomposition of the elastic strain tensor, to simulate the pronounced dissimilar response under tension and compression, typical of these materials. The assumption of energy-equivalence between the damaged solid and the effective (undamaged) one is considered for representing the orthotropy induced in the material by the degradation process, with the consequence that a thermodynamically consistent constitutive operator, positive definite, symmetric and strain-driven, is derived. The formulation is integrated with a multidirectional damage procedure, addressed to extend the microcrack closure-reopening (MCR) capabilities to generic cyclic conditions, especially shear cyclic conditions, making the model suitable for dealing with seismic actions. Maintaining unaltered the dependence of the constitutive law from d+ and d−, this approach activates or deactivates a tensile (compressive) damage value on the base of the current maximum (minimum) principal strain direction. In correspondence with damage activation (crack opening) or deactivation (crack closure), a smooth transition is introduced, in order to avoid abrupt changes in stiffness and enhance the numerical performance and robustness of the multidirectional procedure. Moreover, the mesh-objectivity of the numerical solutions is ensured by resorting to a nonlocal regularization technique, based on the adoption of damage variables driven by an averaged elastic strain tensor. To perform the averaging of the strain tensor, an internal length lRG is considered in the continuum. The strategy chosen to define the parameters affecting the softening behaviour consists in the modification of the local softening law on the base of the internal length, with the intent of ensuring the proper evaluation of the correct fracture energy Gf. The adequacy of the proposed constitutive model in reproducing experimental results is proven for both monotonic and cyclic loading conditions. Under monotonic loads, unreinforced concrete notched elements subjected to pure tension, pure bending and mixed-mode bending are studied. The two examples of application involving cyclic loads, a masonry and a reinforced concrete wall under in-plane cyclic shear, constitute a validation of the multidirectional damage approach, showing how the suitable representation of unilateral effects and permanent deformations is essential to model the observed structural response in terms of maximum resistance and dissipation capacity. The effectiveness of the regularized damage formulation is proven by successfully studying a masonry arch and reinforced and unreinforced concrete elements. Besides the validation of the numerical results with experimental or analytical data, each application is exploited to highlight one or more features of the formulation: the mesh-size and mesh-bias independence of the results, the effect of the choice of the variable to be averaged, the possibility to reproduce structural size effects, the influence of the internal length lRG. On this latter aspect, the almost null dependence of the regularized solutions on the internal length in terms of force-displacement curves, achieved thanks to the calibration strategy adopted to define the energy dissipation, suggests the interpretation of the internal length as a regularization parameter. On the one hand, this implies an analogy between the role played by the nonlocal internal length in a nonlocal model and the one’s of the mesh size in the crack band approach (Bažant and Oh, 1983). On the other hand, this translates in the versatility of the regularized damage model, which requires only the identification of the standard material properties (elastic constants, fracture energies and strengths). Finally, the d+/d− damage model is successfully applied to the study of a three-span masonry arch bridge subjected to a concentrated vertical load, in order to evaluate its carrying capacity and its failure mechanism. Numerical issues, usually neglected in large-scale applications, are also addressed proving the reliability of the regularized approach to provide mesh-independent results and its applicability.

The aim of this master´s thesis is design and statically examine a bearing structure of ice hockey stadium in Jihlava with axial ground area measuring 43x85 m. Design od structure was prepared in three variants. The core bearing structure composed of three-joint arched roof beam create timber and steel lower beam, or solid wood of glulam timber. The third variant was work out in detail. Scia Engineer 2013 software has been used to create a three-dimensional model for the purpose of dimensioning each member and global analysis. Results obtained from the computer analysis were taken and double-chcecked with a hand assessment of the structure elements.

The aim of diploma thesis is a design of project for realization of a building of kindergarden construction. Also there are solved suitable disposition for this purpose and design of a bearing structure with a respect to static and thermal part of documentation. Part of kindergarden is designed as day nursery. That means the building is used for care for children in age of 6 months up to 6 years. The kindergarden has three classes with overall capacity of 60 children. The day nursery part of the building has capacity of 12 kids. The building has two floors without basement, groundplan has irregular arched shape with structurally divided parts. A shape and altitude of the building is adapted to vertical alignment of a ground. The main entrances into the building are situated from two height levels of a slope. A residential rooms are situated from southeast to southwest. Part of the building is protected from north by adjacent soil. The structural system of kindergarden is timber. Structurally divided part of day nursery is a combination of hidden reinforce concrete skeleton and lime-sandstone masonry system. A ceiling structure is made of glue laminated timber system. Roofing of the building is solved as vegetational roof with a smooth connection to slope terrain by arched structure. A facade is made as breathable system of timber plates.

The diploma thesis deals with the design of a bridge in Most. It bridges the railway line and the river Bílina. Three possible variants have been proposed. One of the variants has been selected and further elaborated. The solved variant was an arc with a suspended pre-stressed bridge beam. The supporting element is a reinforced concrete backbone. The construction is built on a ring. Static analysis partly includes the effect of phased construction. The design was assessed according to EN.

Master's thesis addresses the design and assessment of the load bearing structure of the shopping gallery. The building is designed as a three-storey rectangular plan with a flat roof. The structure is composed of steel frames and composite steel and concrete slabs. There are proposed two possible solutions - variant with a flat roof and direct central gallery, a reinforced rigid steel frames and a variant with a cupola roofed circular inner atrium, solidified with rods.

This master‘s thesis deals with the design documentation Fit4You sports center. The new building is located in the district of the City of Brno in the cadastral Brno – Líšeň. The building is designed as a reinforced concrete skeleton system with ceramic masonry infill with two floors. Part of the building with the sports hall is roofed with arched trusses made of laminated wood. The second part of the building with facilities for the hall is roofed with a flat floor.

The content of the thesis is a proposal of steel load-bearing structure (carrying structure of a steel) bridge of the span of 31+74+31m with the bottom bridge deck taking over the second-class road in the territory of Olomouc city. The bridge deck is created by composite steel-concrete slab with crossbars. The solution was focused on using arched construction in the middle of the bridge with different tilt of arches to the horizontal central axis of the bridge. Under the term of the solution four alternatives have been calculated. The most optimal solution was selected and processed in detail. The calculations were made in compliance with the Czech technical norms ČSN EN.

Newly built Wellness hotel. The building is partially basement. The building has three parts. The central part is made of reinforced concrete skeleton and has five aboveground floors. This part serves as the main entrance hall and staircase. The side tracts have four aboveground floors and their support system is a transverse wall, brick, from the system Porotherm. In the basement there is a swimming pool and hotel facilities. There is located a restaurant too. On the second floor there are rooms, a gym and services. On the top floor there are only hotel rooms. The building is based on thecontinous footings. Roofing is made arched trusses.

The diploma thesis deals with the design and assessment of the steel construction of the car showroom in Jihlava. The ground dimensions of the structure are 40,0 x 52,0 m and the height at the highest point is 13,14 m. The supporting structure consists of a truss girder consisting of a set of arches, outer columns and an inner column with a strut. This is a freebase system, the distance of the bindings is 4.0 m. In the framework of the work is elaborated the comparison of two variants, more suitable includes the static calculation of the main supporting parts, including the joints and details. The main construction material is steel, grade S 355.

Sport Airport complex Brno-Medlánky is nestled in the undulating hilly terrain in fields just beyond populated areas in Brno-Medlánky. The history of the airport dates back to 1924 when it was built the first wooden hangar for training purposes glider flights. Current state urban of airport is orderless. The aim is to streamline the complex and give it the order, allowing easy and efficient orientation in the space. The main intervention was the creation of a new central building - Aviation Museum. The concept of the design is based on the division of the whole area into two branches - communication axes, based on the mass preserved historic wooden hangars. Between the two communication arms is inserted a central axis on which is located the heart of the complex - Aviation Museum. It is a building organic form, inspiring axially symmetric wingspan (bird, airplane, beetle). It is this symmetry axis of the building creates a view towards building on the runway. Mass of the building used by the sloping terrain and is partially sunk under the ground. Building volume follows an upward slope from the outside and blends with the surrounding terrain. The internal layout consists of three floors, one of them is completely sunk below ground level and second half. The main entrance to the gallery is located in the uppermost floors, the direction of the exhibition is therefore directed downwards into the basement. The exposition is divided into six parts: RC models exposure, gliders exposure, powered aircraft exposure, screening room, children's exposure and air trainers. Other areas consist of building technical facilities. In the basement there is a workshop with aircraft lift, with the possibility of placement unexposed aircrafts. The supporting system of the building consists of two parts: reinforced concrete tubs and arched steel structure with a span of 50m.

The stability of arches is a classical mechanics and pragmatic engineering problem that has been extensively studied by many researchers over the years. Despite the comprehensive construction and research of arches throughout history, their complex behaviour still presents a challenge to engineers and ensures they are the subject of continual investigation. The problem of arch stability is of contemporary relevance due to the surging popularity of concrete-filled steel tubular (CFST) arch bridges. Hence, due to the inherent complex structural function of arches when coupled with the increasing construction of CFST arches, research into the response and stability of CFST arches under all possible environmental conditions is necessitated. However, investigations into the effects of extreme temperatures on concrete and CFST arches have not been conducted. This thesis presents a comprehensive analytical and numerical investigation into the stability of circular concrete and CFST arches subjected to combined mechanical and thermal loading. Original models are derived for the non-linear prebuckling and buckling analysis including closed-form solutions for the in-plane elastic buckling loads of concrete and CFST arches, and non-discretisation mechanically-based numerical models for their elastic and inelastic analysis prebuckling analysis. Additionally, a numerical methodology to determine the elastic flexural-torsional buckling loads of CFST arches is proposed. Furthermore, a novel fractional viscoelastic creep law is developed for concrete at elevated temperatures in order to analyse the significance of basic creep strain on thermal response and stability boundaries. The fractional-derivative creep law proves to be a robust and compact method of modelling basic creep strain under stress and temperature varying conditions. Finite difference schemes are employed to numerically approximate the fractional derivative and incorporate basic creep into the prebuckling and stability analyses. Finite Element (FE) models are developed to verify the derived models and to also investigate the inelastic buckling strength and fire performance of concrete and CFST arches. The findings of this study provide a detailed understanding of the fundamental thermomechanical behaviour and failure modes of concrete and CFST arches. Consequently, engineers may utilise the results detailed herein to assess and improve the fire resistance of concrete and CFST arch structures. Additionally, the developed creep law has widespread application in the analysis of concrete structures under elevated temperatures. The proposed inelastic numerical models also provide efficient tools for the analysis of other structures such as steel arches and beams.

This thesis investigates the effects of elastic restraint at the supports on the behaviour of shallow concrete arches, and the time-dependent effects of shrinkage and creep of concrete on the nonlinear behaviour of shallow arches. The nonlinear behaviour of shallow circular arches with elastic rotational restraints at each support and subjected to a uniformly distributed radial load is firstly investigated. A virtual work formulation is used to establish both the nonlinear equilibrium equations and the buckling equilibrium equation for shallow arches. The analytical results show that the effects of the stiffness of the rotational restraints on the prebuckling and buckling response are significant. An analytical model is developed for the in-plane elastic stability analysis of shallow parabolic arches with horizontal spring supports subjected to a uniformly distributed vertical load. A parametric study is undertaken using the proposed analytical model. It is found that the effects of the stiffness of the horizontal springs on the prebuckling response, buckling load and buckling behaviour of arches are significant. An analytical model is developed to simulate the time-dependent behaviour of shallow concrete parabolic arches with horizontal spring supports subjected to a sustained loading, and in particular to investigate creep buckling. The time-dependent buckling load and the critical time (or age) of the arches are calculated by using an iterative process based on the proposed model. A systematic parametric study is undertaken, and the results show that the various parameters have a profound effect on the time-dependent buckling load and the prebuckling life of arches. Both short-term and long-term experimental investigations of shallow parabolic tied concrete arches are described and used to validate the analytical models. For the short-term tests, three concrete arches were subjected to a uniformly distributed vertical load and were loaded to failure. For the long-term tests, seven concrete arches were subjected to sustained service loads. The instantaneous and time-dependent deflections were recorded throughout the period of loading, together with the distribution of the horizontal thrust at the supports. Comparisons between the experimental results and the analytical predictions using the analytical models are made to verify the accuracy of the theoretical models.

Due to their structural efficiency and architectural elegance, concrete arches have long been used in bridge applications. However, the construction of concrete arches requires significant temporary supporting structures, which prevent their widespread use in modern bridges. A relatively new form of arch bridges is the network arch, in which a dense arrangement of inclined hangers is used. Network arches are subjected to considerably smaller bending moments and deflections than traditional arches and are therefore suitable for modern, accelerated construction methods in which the arches are fabricated off-site and then transported to the bridge location. However, service-level stresses, which play a critical role in the performance of the structure, are relatively unknown for concrete network arches and have not been sufficiently investigated in the previous research on concrete arches. The primary objective of this dissertation is to improve the understanding of short-term and time-dependent stresses in concrete arches, and more specifically, concrete network arches. The research presented herein includes extensive field monitoring of the West 7th Street Bridge in Fort Worth, Texas, which is the first precast network arch bridge and probably the first concrete network arch bridge in the world. The bridge consists of twelve identically designed concrete network arches that were precast and post-tensioned before they were transported to the bridge site and erected. A series of vibrating wire gages were embedded in the arches and were monitored throughout the construction and for a few months after the bridge was opened to traffic. The obtained data were processed, and structural response parameters were evaluated to support the safe construction of the innovative arches, identify their short-term and time-dependent structural behavior, and verify the modeling assumptions. The variability of stresses among the arches was also used to assess the reliability of stress calculations. The results of this study provide valuable insight into the elastic, thermal, and time-dependent behavior of concrete arches in general and concrete network arches in particular. The knowledge gained in this investigation also has broader applications towards understanding the behavior of indeterminate prestressed concrete structures that are subjected to variable boundary conditions and thermal and time-dependent effects.

The Texas Department of Transportation (TxDOT) has completed the design of a signature bridge in Fort Worth, TX. The proposed structure is comprised of precast, post-tensioned concrete network arches. The arches will be cast on their sides and then rotated into the vertical orientation. Concerns exist about the durability and stability of the arches during stressing, handling, and transportation. The rotation process in particular represents a critical period in the life of the arches. A monitoring system was proposed to track stresses in the arches throughout the construction operations. The primary goals of the project are to install vibrating wire gages (VWGs) in the arches prior to casting to monitor the performance of the arches until the bridge is completed. The instrumentation will be used to provide real-time feedback to TxDOT and the contractor during stressing, handling, and bridge construction. This thesis focuses on the results of a preliminary laboratory study conducted in support of the instrumentation initiative. The purpose of the study was two-fold: to establish the capabilities and limitations of the VWGs and to study the buckling behavior of slender concrete elements with unbonded post-tensioning. More than sixty axial load tests were performed on two slender concrete specimens instrumented with VWGs. Observations are made on the accuracy and reliability of the VWGs. In general, the VWGs were found to be both accurate and reliable in measuring structural parameters and reporting trends in behavior, even at low loads. Some apparent errors were identified, but these were attributed to testing inconsistencies and scale factors rather than to gage error. Observations were also made on the buckling behavior of the elements under a variety of axial loading configurations. The effects of the engagement of the tensioned strand with the duct had a significant impact on the behavior. Strand engagement was shown to increase the buckling capacity of the members through stiffening action, but did not necessarily eliminate the risk of instability. Both the gage resolution study and the stability tests are expected to significantly enhance the ability of the research team to support the arch construction operations.
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In this thesis, new design concepts for arch bridges using ultra high-performance fibre-reinforced concrete are developed for spans of 50 to 400 m. These concepts are light-weight and efficient, and thus have the potential to significantly reduce the cost of construction. Lightness is achieved by the thinning of structural components and the efficient use of precompression in the arch, rather than by the decrease of bending stiffness. Using the advanced properties of the material, the design concepts were shown to reduce the consumption of concrete in arch bridges by more than 50% relative to arches built using conventional concrete technology. In addition to span length, other design parameters including span-to-rise ratio and deck-stiffening were considered, resulting in a total of seventy-two design concepts. Other important contributions made in this thesis include: (1) the development of a simple analytical model that describes the transition of shallow arches between pure arch behaviour and pure beam behaviour, (2) a comprehensive comparative study of 58 existing concrete arch bridges that characterizes the current state-of-the-art and serves as a valuable reference design tool, and (3) the development and experimental validation of general and simplified methods for calculating the capacity of slender ultra high-performance fibre-reinforced concrete members under compression and bending. The research presented in this thesis provides a means for designers to take full advantage of the high compressive and tensile strengths of the concrete and hence to exploit the economic potential offered by the material.

Current design of cemented paste backfill (CPB) barricades tends to be of unknown conservativeness due to limited understanding of their behaviour. Previous work done to characterize barricade response has not accounted for the effects of the surrounding rock stiffness, which can have significant impact on the development of axial forces which enhance capacity via compressive membrane action. Parametric analyses were performed with the finite element analysis program Augustus-2 to determine the effects of various material and geometric properties on barricade capacity. Equations based on Timoshenko and Boussinesq solutions were developed to model rock stiffness effects based on boundary material properties. An iterative simulation process was used to account for secondary moment effects as a proof of concept. It was found that, for a range of typical rock types, barricade capacity varied significantly. The commonly made design assumption of a fully rigid boundary resulted in unconservative overpredictions of strength.