The purpose of this study is to investigate how accurately the distribution factor method estimates the live load deflections under the principles of the 2012 AASHTO LRFD Bridge Design Specifications (AASHTO LRFD specifications) compared to the results of the NISA finite element analysis software. The simple span bridge model analyzed is developed very similarly to the design example of the PCI Bridge Design Manual. The main difference is a shorter span length and smaller AASHTO-PCI bulb tee sections. Three main finite element models are created to estimate the live load deflections under the recommended live load conditions as per AASHTO LRFD specifications. The first model is simulated with simple support conditions. The purpose of this model is two-fold: compare the deflections to the distribution factor method and to the deflections of the second model that is simulated with elastomeric steel reinforced bearing pads. Thus, the stiffnesses of the elastomeric bearing pads of the second model are varied within the AASHTO LRFD specifications acceptable limits and under low temperature conditions the stiffness is increased accordingly for two cases. The purpose is to investigate if the stiffness have any significant affect on the deflections of the girders. Then a third model is created to investigate if the removal of the intermediate diaphragms have any affect on the deflections. The results of the first and second models, including the models with the allowed varied stiffnesses of the bearing pads, found only the interior girders deflecting up to 4% more and the exterior girders were deflecting up to 5.55% less than the estimates of the distribution factor method. In the case when the diaphragms are removed, the deflections of the inner most interior girders are deflecting up to 10.85% more compared to the same girders of the model which includes the intermediate diaphragms and the bearing pads. In the unique case of the second model where the bearing pads may stiffen significantly under low temperatures, the girders are deflecting up to 23% less than when at room temperature conditions. All these findings and other summarized results are discussed in greater detail in this study.

The relatively few available practice-oriented proposals for performance-based seismic design of conventional and isolated bridges, aim primarily at a more consistent description of seismic demand and capacity of structures on the basis of simplified analysis, and to a lesser extent at the direct consideration of multi-level performance criteria using advanced analysis tools. In view of the type/device-specific existing methods, the present study presents a broad-scope methodology for the seismic design of bridges emphasising on (i) displacement-based principles, (ii) use of nonlinear dynamic analysis, and (iii) explicit consideration of multiple performance levels (PLs) and objectives (POs) in a practical design context, suitable for inclusion in design codes. The deformation-based design (Def-BD) procedure, initially developed for seismic design of conventional (non-isolated) buildings, is first tailored to concrete bridges with energy dissipation in the piers. The key issues in this respect are the proper consideration of the intended plastic mechanism under the considered PLs, and the design of the bearings. The efficiency of the proposed design methodology is demonstrated by applying it to an actual bridge selected with a view to enabling comparisons among Def-BD, the modal direct displacement-based design (MDDBD), and a force-based code-type (Code-BD) method. Refined analysis along with the consistent performance-based design format within Def-BD, result in superior seismic performance. Significant cost reductions are achieved compared to MDDBD, whereas potential cost reductions may generally be obtained compared to ‘standard’ code design. Considering the diversity of passive devices and their inherent weakness to optimise the bridge response under multiple PLs, a methodology is developed to enable the identification of the critical performance requirements and the comparative evaluation of different passive schemes at the early stages of design. Originating from an earlier study focusing on bilinear isolators, the method is extended with a view to developing generalised design equations (GDEs) capable of providing reliable estimates of peak response in linear/bilinear isolation systems with/without supplemental linear/nonlinear viscous damping under different PLs associated with code-based target spectra of different intensity. The Def-BD method is finally extended to address passive (isolation and energy dissipation) systems. Novel features are introduced, including (i) the use of GDEs for the preliminary ‘near-optimal’ selection of the basic system properties and the consideration of nonlinearity of viscous dampers, (ii) the enhancement of POs in line with the higher performance expected in the case of isolated bridges, (iii) specific conditions ensuring the effectiveness of the isolation system, and (iv) the proper consideration of the orthogonal component of seismic action under bidirectional excitation. The validity of the procedure is demonstrated by applying it to the bridge previously used to develop the Def-BD method for bridges with ‘ductile-pier’ behaviour. Alternative isolation schemes are investigated and compared with the design resulting from Eurocode 8 (Part 2), offering a useful insight into some pitfalls of modern code-based approaches. Assessment of the Def-BD designs reveals enhanced and controlled performance under multiple PLs, and significant cost reductions in the substructure design compared to the design for ‘ductile-pier’ response. On the other hand, further cost reduction observed in the case of the code-based design, results in reduced efficiency of the isolation system and improper performance of the piers. In view of the previous remarks, Def-BD emerges as a rigorous methodology, applicable to most of the common concrete bridge configurations, albeit at the expense of additional computational effort associated with the use of nonlinear dynamic analysis and the design for multiple PLs. Nevertheless, minimum iterative effort is ensured by providing design ‘routines’ that facilitate the implementation and address implications resulting from the use of nonlinear dynamic analysis. Considering the suitable formulation of Def-BD, a framework of performance-based control principles for the future extension towards the integration of advanced structural control techniques, is finally set forth.

No início do século XIX, com a Revolução Industrial, o aço passou a ser um material competitivo e utilizado na construção de pontes que, até então, eram de pedra ou madeira. Assim, surgiram as primeiras pontes ferroviárias vencendo grandes vãos, ou seja, estruturas metálicas tracionadas submetidas a milhões de ciclos de carga, condições ideais para a fadiga de alto ciclo. Muitas destas estruturas ainda estão em tráfego, com mais de 100 anos de serviço e submetidas a carregamentos crescentes. Dado este cenário, este trabalho objetiva caracterizar as pontes metálicas ferroviárias, determinando os materiais empregados, tipos estruturais adotados e cargas utilizadas. Além disso, através de uma revisão da teoria de fadiga em aços e dos procedimentos recomendados pelas principais normas de estruturas metálicas, realiza-se um estudo de caso real de uma ponte que apresentou falha por fadiga em suas longarinas. Para tal, modela-se numericamente a estrutura e realiza-se análise experimental da mesma, através de medições in situ, para a calibração do modelo. Após, aplica-se as metodologias apresentadas nas normas e na teoria, a fim de efetuar-se a verificação à fadiga desta estrutura determinando a vida residual de seus elementos. / In the beginning of century XIX, with the Industrial Revolution, the steel started to be a competitive and used material in the construction of bridges that, until then, were of rock or wood. Thus, first great railroad bridges being successful vain, or either, tensile steel structures submitted the millions of load cycles had appeared, ideal conditions for the fatigue of high cycle. Many of these structures still are in traffic, with more than 100 years of service and submitted increasing loads. Get this scene, this objective work to characterize the railroad steel bridges, determining the used materials, structural types adopted and used loads. Moreover, through a revision of the theory of fatigue in steel and of the procedures recommended for the main codes of steel structures, is become a study of real case of a bridge that presented damage for fatigue in its stringers. For such, becomes a numerical model of the structure and experimental analysis of the same one, through measurements in situ, for the calibration of the model. After, one applies the methodologies presented in the codes and the theory, in order to effect it verification to the fatigue of this structure determining the residual life of its elements.

abstract: Most engineers may agree that an optimum design of a particular structure is a proposal that minimizes costs without compromising resistance, serviceability and aesthetics. Additionally to these conditions, the theory and application of the method that produces such an efficient design must be easy and fast to apply at the structural engineering offices. A considerable amount of studies have been conducted for the past four decades. Most researchers have used constraints and tried to minimize the cost of the structure by reducing the weight of it [8]. Although this approach may be true for steel structures, it is not accurate for composite structures such as reinforced and prestressed concrete. Maximizing the amount of reinforcing steel to minimize the weight of the overall structure can produce an increase of the cost if the price of steel is too high compared to concrete [8]. A better approach is to reduce the total cost of the structure instead of weight. However, some structures such as Prestressed Concrete AASHTO Girders have been standardized with the purpose of simplifying production, design and construction. Optimizing a bridge girder requires good judgment at an early stage of the design and some studies have provided guides for preliminary design that will generate a final economical solution [17] [18]. Therefore, no calculations or optimization procedure is required to select the appropriate Standard AASHTO Girder. This simplifies the optimization problem of a bridge girder to reducing the amount of prestressing and mild steel only. This study will address the problem of optimizing the prestressing force of a PC AASHTO girder by using linear programming and feasibility domain of working stresses. A computer program will be presented to apply the optimization technique effectively. / Dissertation/Thesis / Masters Thesis Civil Engineering 2016

A possibilidade de redução ou até mesmo da eliminação do uso de formas e escoramento, diminuição do tempo e melhoria da qualidade da obra, são alguns aspectos que têm levado à adoção da pré-moldagem em superestruturas de pontes. Recentes estudos relatam que as chamadas pontes integrais - pontes sem juntas - estão tornando-se cada vez mais utilizadas nos Estados Unidos e Canadá, pois minimizam os custos com manutenção e prolongam a vida útil da obra. Procurando associar os benefícios conseguidos com a utilização dos elementos pré-moldados aos da ausência de juntas, apresenta-se neste trabalho um tipo construtivo para pontes de pequenos vãos em pórtico, com utilização de elementos pré-moldados na superestrutura ligados rigidamente à infraestrutura. Um processo aproximado de cálculo é apresentado e, a partir de um exemplo desenvolvido, compara-se esta alternativa com uma construção similar em viga, verificando-se que os custos diretos são basicamente iguais. Através da avaliação dos esforços provenientes do carregamento móvel com a técnica dos elementos finitos, chega-se a momentos fletores até 50% menores que os obtidos pelo método aproximado, resultando assim numa considerável redução dos custos diretos quando se utiliza o sistema estrutural em pórtico. / The possibility of reduction or even the elimination of the use of forms and bearings, reducing the time and improving the qualitity of the work, are some aspects which have led to the use of precasting in bridges superstructure. Recent studies report that the so-called integral bridges, jointless bridges, are becoming more used in the United States of America and in Canada because they reduce the costs of maintenance and prolonge the useful life of the constructions. Trying to associate the benefits which have resulted from the utilization of precast elements to the ones from the absence of joints, it is present in this work a constructive proposal to small span frame bridges using the precast elements in the superstructure strictly connected to the infrastructure. A design process for bending moments is presented. The comparation between the construtive proposal and similar with joint between the superestructure and infrastructure, by using this design process, shows that the direct cost is basically the same. Through the evaluation of the efforts that come from the mobile carrying with the technique of finite elements, it can reach bending moments that are even 50% lower than those gotten from the presented method. In this case, a significative direct cost reduction can gotten with frame structure system.

Este trabalho apresenta o estudo teórico e experimental do comportamento de placas ortótropas treliçadas protendidas transversalmente, sendo as ligações das barras das treliças com conector de chapas com dentes estampados (CDE), para aplicação em pontes de madeira observando as principais características do sistema como: avaliação do elemento estrutural e do modelo estrutural para verificação dos deslocamentos da placa. Para esta finalidade foram determinadas as propriedades dos materiais, elementos estruturais e níveis de protensão da placa. A avaliação das propriedades elásticas da placa foi realizada utilizando dois modelos numéricos, sendo um baseado no método dos elementos finitos e o segundo em séries de Levy-Nadai. A aferição do modelo proposto foi realizado com o ensaio de um protótipo em escala real. Os resultados indicaram que a placa tem um ótimo comportamento para a utilização em pontes apresentando elevada rigidez e baixo consumo de madeira, e que os modelos propostos apresentaram-se consistentes para aplicação nos sistemas de placas ortótropas treliçadas com ligações de chapas com dentes estampados / This work aim to the theoretical and experimental study of the behaviour of orthotropic stress-laminated truss plate for timber bridges construction. To this purpose the material properties, structural elements, conections and prestress level were analysed. Two numeric models were used in order to avaliate the plate elastic properties, based on the finite elements analysis method and in Levy-Nadai series. The theorical model calibration was made with the results obtained in a full-scale prototype. The results indicated that the plate behavior was efficiency for the use in bridges with high stiffness and wood low consumption, and that the proposed numeric models was consistent for application in ortrotropic stress-laminated truss plate systems with metal-plate-connected

No início do século XIX, com a Revolução Industrial, o aço passou a ser um material competitivo e utilizado na construção de pontes que, até então, eram de pedra ou madeira. Assim, surgiram as primeiras pontes ferroviárias vencendo grandes vãos, ou seja, estruturas metálicas tracionadas submetidas a milhões de ciclos de carga, condições ideais para a fadiga de alto ciclo. Muitas destas estruturas ainda estão em tráfego, com mais de 100 anos de serviço e submetidas a carregamentos crescentes. Dado este cenário, este trabalho objetiva caracterizar as pontes metálicas ferroviárias, determinando os materiais empregados, tipos estruturais adotados e cargas utilizadas. Além disso, através de uma revisão da teoria de fadiga em aços e dos procedimentos recomendados pelas principais normas de estruturas metálicas, realiza-se um estudo de caso real de uma ponte que apresentou falha por fadiga em suas longarinas. Para tal, modela-se numericamente a estrutura e realiza-se análise experimental da mesma, através de medições in situ, para a calibração do modelo. Após, aplica-se as metodologias apresentadas nas normas e na teoria, a fim de efetuar-se a verificação à fadiga desta estrutura determinando a vida residual de seus elementos. / In the beginning of century XIX, with the Industrial Revolution, the steel started to be a competitive and used material in the construction of bridges that, until then, were of rock or wood. Thus, first great railroad bridges being successful vain, or either, tensile steel structures submitted the millions of load cycles had appeared, ideal conditions for the fatigue of high cycle. Many of these structures still are in traffic, with more than 100 years of service and submitted increasing loads. Get this scene, this objective work to characterize the railroad steel bridges, determining the used materials, structural types adopted and used loads. Moreover, through a revision of the theory of fatigue in steel and of the procedures recommended for the main codes of steel structures, is become a study of real case of a bridge that presented damage for fatigue in its stringers. For such, becomes a numerical model of the structure and experimental analysis of the same one, through measurements in situ, for the calibration of the model. After, one applies the methodologies presented in the codes and the theory, in order to effect it verification to the fatigue of this structure determining the residual life of its elements.

O presente trabalho visa estabelecer uma metodologia alternativa para o levantamento dos principais transitórios elétricos sofridos por excitatrizes brushless, decorrentes de transitórios ocorridos na armadura do gerador principal. O método consiste no cálculo, a partir de dados de projeto, dos parâmetros que compõem os circuitos equivalentes do gerador principal e da excitatriz, seguido de simulações, em ambiente PSIM®, dos piores casos de transitórios de tensão e corrente sofridos pela armadura do gerador principal, como curtos-circuitos monofásicos, bifásicos e trifásicos, operação assíncrona do gerador principal e sincronização com defasagem entre as tensões do gerador e da rede. Em cada caso, monitoram-se as tensões e correntes resultantes nos diodos da ponte retificadora rotativa. Resultados simulados e experimentais são comparados. / This study aims to establish an alternative methodology for determining the main transients on brushless exciters due to transients in the main generator armature. The method consists in calculating, from design data, the parameters of the equivalent circuits of the main generator and the exciter, followed by simulations, with the software PSIM®, of the worst voltage and current transient cases in the main generator armature, like single-phase, dual-phase and three-phase short circuits, asynchronous running of the main generator and out of phase synchronization. In each case the currents and voltages of the rotative bridge diodes were monitored. Simulation and experimental results are compared.

When different type of programs are developed one wants to make these adjustable to future changes and requirements. It must be done a good design of the program from the beginning to make it possible to continue development of it without having to redo big parts of it to high costs. In the area of object orientation there are design pattern, which can be used to design systems that can be adjusted to new changes in an easier way. I have in this thesis chosen to take a closer look at how to design a program that sends SMS to cell phones through a system of an operator. One requirement on the program is that it has to be possible to change what operator to send though in an easy way. I have chosen a design pattern named Bridge and investigate if a use of it makes a program operator independent. This thesis is for system developers who have basic knowledge of object orientation and have programmed in Java. The hypothesis that is tested is: "If the design pattern Bridge is used to construct a program that sends SMS, then it will be a program where an operator's API easily can be replaced by another operator's API. The investigation was done by collecting a number of API's from different companies who offer the possibility to send SMS through themselves. Code was created for the classes that are part of the design pattern Bridge and specific code for every tested API were done and compiled and run. After that the possibility to switch between API's in an easy way was investigated. The result of the investigation was that it is possible to integrate some of the API's with Bridge and that the switching between API's is working. But to find out if Bridge can be used in a real program demands further investigations.

Bridge load rating is a procedure to determine the live load carrying capacity of a bridge. This rating is generally given out on a two-year period, which leaves the structural capacity unknown for this time interval. Conventional bridge load rating is obtained according to the bridge inspection results and commercial bridge rating software. However, this approach cannot effectively reflect actual live load carrying performance of the bridge, due to intrinsic limitation of visual inspection. Structural sensing has been utilized for measuring realistic structural behaviors to reflect the live load carrying capacity. However, this expensive and time-consuming process requires a known-weight vehicle and a substantial number of sensors under controlled full-scale field test conditions. In this research, a continuous live load performance index (LLPI) is proposed to monitor the live load capacity that the bridge can withstand without knowing the vehicle weight while also using a limited number of sensors. The LLPI uses existing bridge load rating methodology, in conjunction with experimental data and numerical simulations, to generate a value that describes the performance of the bridge due directly to the live load applied. Furthermore, the LLPI procedure utilizes an advanced state estimation algorithm, known as the Kalman Filter, to estimate the strain responses of the bridge at various locations while using a limited number of sensors. This procedure allows for an efficient structural health monitoring approach to determine the live load carrying capacity that the bridge can withstand. This research uses a lab-scaled truss structure with known properties for numerical and experimental validation. Because of this, this paper proposes a framework as to which the live load carrying performance can be monitored in real time. Future updates include testing on a real-life bridge structure while also determining optimal sensor placement for obtaining the LLPI. This research looks to develop a new live load performance index (LPPI) by considering: (1) the benefits and limitations of conventional bridge load rating approach, (2) the system identification and multi-metric data acquisition for the bridge structure, (3) numerical modeling and updating to best reflect the current dynamic properties of the bridge, (4) augmented Kalman Filter to estimate structural responses at various unknown locations, (5) LLPI formulation using experimental data, current bridge load rating methodology, and model-response estimations. The results obtained from this research provide a progressive live load capacity performance template to promote the advancement in civil infrastructure smart monitoring.