O presente trabalho foi realizado por meio de uma abordagem tríplice do problema de compressão dinâmica em risers, fundamentado em ensaios em um Calibrador Hidrodinâmico, com posterior confrontação dos resultados com formulações analíticas e o uso de programas comerciais dedicados ao estudo da estática e dinâmica de linhas flexíveis. O principal objetivo foi a determinação acurada, a partir de uma instrumentação pouco invasiva, dos comprimentos das ondas de flexão geradas no TDP, durante a compressão dinâmica. Esse objetivo, de per si, encerra o caráter de ineditismo da presente tese. Os ensaios consistiram na realização de movimentos circulares no topo de um modelo flexível lançado em catenária, sob diversas configurações, totalizando um total de 72 experimentos: foram utilizados três frequências de movimento, três amplitudes, quatro ângulos de topo e dois sentidos de rotação. Um sistema de monitoramento óptico foi utilizado como principal instrumentação. Além desse equipamento, foi utilizada uma célula de carga, posicionada entre o equipamento que prescrevia os movimentos ao modelo flexível e uma rótula, que permitia que a célula de cargas e movimentasse solidariamente ao sistema. Rotinas numérica próprias foram utilizadas para o pós-processamento dos dados obtidos. Os resultados foram, então, comparados com formulações analíticas constantes da literatura, bem como a adaptação da equação para a carga crítica de flambagem de vigas curvas, para as condições de contorno dos ensaios realizados. Como resultado principal, é possível citar a confirmação experimental da suposição corrente com relação ao número de onda associado às ondas de flexão geradas na compressão dinâmica, até então assumida como uma hipótese ad hoc. Além disso, o procedimento adotado, embasado teoricamente, foi utilizado desde o estabelecimento do material com que o modelo foi construído, passando pela elaboração racional da matriz de ensaios e finalizando com as análises realizadas, quando os resultados experimentais foram confrontados com as previsões analíticas. / This work was carried out through a threefold approach to dynamic compression in risers, based on tests in a Hydrodynamic Calibrator, with subsequent comparison of results with analytical formulations and the use of commercial softwares dedicated to the study of static and dynamic flexible lines. The main aim was an accurate determination, from a minimally invasive instrumentation, the lengths of flexural waves generated in the TDP, during dynamic compression. This goal, in itself, is the novelty of this thesis. The tests consisted in performing circular motion on top of a flexible catenary model launched under several conditions, amounting to a total of 72 experiments: three motion frequencies, three imposed amplitudes , four top angles and clockwise and counter-clockwise rotation. A tracking monitoring system was used as main instrumentation. In such equipment, a load cell was used, positioned between rotor used to prescribe top movements at the top of a flexible model, allowing the load cell jointly move around a bar conected to the shaft motor. Numerical routines, made by author, were used for data post-processing. The results were then confronted with analytical formulations from specialized literature, as well as the adaptation of the equation for the buckling critical load for curved beams under the boundary conditions of the tests. As a main result, it is possible to mention the experimental confirmation of the current assumption with respect to the wave number associated with bending waves generated during the dynamic compression, hitherto assumed as an ad hoc hypothesis. In addition, the procedure adopted, based in analytical theories, was used since the establishment of the material with which the model is built, through the rational development of the test matrix and ending with the analyzes carried out when the experimental results were compared with analytical predictions.

This thesis presents the results of a research programme to investigate the behaviour and robustness of reinforced concrete (RC) frames in fire. The research was carried out through numerical simulations using the commercial finite element analysis package TNO DIANA. The main focus of the project is the large deflection behaviour of restrained reinforced concrete beams, in particular the development of catenary action, because this behaviour is the most important factor that influences the frame response under accidental loading. This research includes four main parts as follows: (1) validation of the simulation model; (2) behaviour of axially and rotationally restrained RC beams at elevated temperatures; (3) derivation of an analytical method to estimate the key quantities of restrained RC beam behaviour at elevated temperatures; (4) response and robustness of RC frame structures with different extents of damage at elevated temperatures. The analytical method has been developed to estimate the following three quantities: when the axial compression force in the restrained beam reaches the maximum; when the RC beams reach bending limits (axial force = 0) and when the beams finally fail. To estimate the time to failure, which is initiated by the fracture of reinforcement steel at the catenary action stage, a regression equation is proposed to calculate the maximum deflections of RC beams, based on an analysis of the reinforcement steel strain distributions at failure for a large number of parametric study results. A comparison between the analytical and simulation results indicates that the analytical method gives reasonably good approximations to the numerical simulation results. Based on the frame simulation results, it has been found that if a member is completely removed from the structure, the structure is unlikely to be able to develop an alternative load carrying mechanism to ensure robustness of the structure. This problem is particularly severe when a corner column is removed. However, it is possible for frames with partially damaged columns to achieve the required robustness in fire, provided the columns still have sufficient resistance to allow the beams to develop some catenary action. This may be possible if the columns are designed as simply supported columns, but have some reserves of strength in the frame due to continuity. Merely increasing the reinforcement steel area or ductility (which is difficult to do) would not be sufficient. However, increasing the cover thickness of the reinforcement steel to slow down the temperature increase is necessary.

Joint behaviour in fire is currently one of the most important topics of research in structural fire resistance. The collapse of World Trade Center buildings and the results of the Cardington full-scale eight storey steel framed building fire tests in the UK have demonstrated that steel joints are particularly vulnerable during the heating and cooling phases of fire. The main purpose of this research is to develop robust joints to CFT columns that are capable of providing very high rotational and tying resistances to make it possible for the connected beam to fully develop catenary action during the heating phase of fire attack and to retain integrity during the cooling phase of fire attack. This research employed the general finite element software ABAQUS to numerically model the behaviour of restrained structural subassemblies of steel beam to concrete filled tubular (CFT) columns and their joints in fire. For validation, this research compared the simulation and test results for 10 fire tests previously conducted at the University of Manchester. It was envisaged that catenary action in the connected beams at very large deflections would play an important role in ensuring robustness of steel framed structures in fire. Therefore, it was vital that the numerical simulations could accurately predict the structural behaviour at very large deflections. In particular, the transitional behaviour of the beam from compression to catenary action presented tremendous difficulties in numerical simulations due to the extremely high rate of deflection increase. This thesis will explain the methodology of a suitable simulation method, by introducing a pseudo damping factor. The comparison between the FE and the experimental results demonstrates that the 3-D finite element model is able to successfully simulate the fire tests. The validated ABAQUS model was then applied to conduct a thorough set of numerical studies to investigate methods of improving the survival temperatures under heating in fire of steel beams to concrete filled tubular (CFT) columns using reverse channel connection. This study investigated five different joint types of reverse channel connection: extended endplate, flush endplate, flexible endplate, hybrid flush/flexible endplate and hybrid extended/flexible endplate. The connection details investigated include reverse channel web thickness, bolt diameter and grade, using fire-resistant (FR) steel for different joint components (reverse channel, end plate and bolts) and joint temperature control. The effects of changing the applied beam and column loads were also considered. It is concluded that by adopting some of the joint details to improve the joint tensile strength and deformation capacity, it is possible for the beams to develop substantial catenary action to survive very high temperatures. This thesis also explains the implications on fire resistant design of the connected columns in order to resist the additional catenary force in the beam. The validated numerical model was also used to perform extensive parametric studies on steel framed structures using concrete filled tubular (CFT) columns with flexible reverse channel connection and fin plate connection to find means of reducing the risk of structural failure during cooling. The results lead to the suggestion that in order to avoid connection fracture during cooling, the most effective and simplest method would be to reduce the limiting temperature of the connected beam by less than 50°C from the limiting temperature calculated without considering any axial force in the beam.

In this thesis, commercially available anti-icing fluids were tested. A methodology of assessment was designed for the effect of anti-icing fluids on the rapidity of ice growth and its development over time. These tests were conducted on a device constructed for the purpose of the thesis. The solutions were tested for their effect on the ice adhesion to a contact wire. The effect of the solutions on the tribological behaviour of the collector strip and contact wire was described. The experiments were supplemented by mensuration of the size of the contact angle of the solutions on the copper surface. However, these fluids anti-icing effect is relatively short-term. On the contrary, the thesis shows that even a small amount of anti-icing solution on the surface of the contact wire can help to significantly lower the ice adhesion.

Multi-pantograph operation allows several short electric multiple unit (EMU) trainsets to be coupled or decoupled to adapt to daily or seasonal passenger-flow variation. Although this is a convenient and efficient way to operate rolling stock and use railway infrastructure, pantographs significantly influence each other and even significantly change the dynamic behaviour of the system compared to single-pantograph operation in the same condition. The multi-pantograph system is more sensitive and vulnerable than the single-pantograph system, especially at high operational speeds or with pantographs spaced at short distances. Heavy oscillation in the system can result in low quality of current collection, electromagnetic interference, severe wear on the contact surfaces or even structural damage. The mechanical interaction between the pantograph and the catenary is one of the key issues which limits the maximum operational speed and decides the maintenance cost.     Many researchers have paid a lot of attention to the single-pantograph operation and have made great progress on system modelling, optimizing, parameter studies and active control. However, how the pantographs in a train configuration affect each other in multi-pantograph operation and which factors limit the number of pantographs is not fully investigated. Nowadays, to avoid risking operational safety, there are strict regulations to limit the maximum operational speed, the maximum number of pantographs in use, and the minimum spacing distance between pantographs. With the trend of high-speed railways, there are huge demands on increasing operational speed and shortening spacing distance between pantographs. Furthermore, it is desirable to explore more practical and budget-saving methods to achieve higher speed on existing lines without significant technical modification.     In addition to a literature survey of the dynamics of pantograph-catenary systems, this thesis carries out a numerical study on multi-pantograph operation based on a three-dimensional pantograph-catenary finite element (FE) model. In this study, the relationship between dynamic performance and other parameters, i.e. the number of pantographs in use, running speed and the position of the pantographs, are investigated. The results show that the spacing distance between pantographs is the most critical factor and the trailing pantograph does not always suffer from deterioration of the dynamic performance. By discussing the two-pantograph operation at short spacing distances, it is found that a properly excited catenary caused by the leading pantograph and the wave interference between pantographs can contribute to an improvement on the trailing pantograph performance. To avoid the additional wear caused by poor dynamic performance on the leading pantograph and achieve further improvement at high speeds, it is suggested to use the leading pantograph as an auxiliary pantograph, which does not conduct any electric current and optimize the uplift force on the leading pantograph. After a brief discussion on some system parameter deviations, it is shown that a 30% of speed increase should be possible to achieve while still sustaining a good dynamic performance without large modifications on the existing catenary system. / <p>QC 20150928</p>

When a building is exposed to fire, it is required to remain structurally stable for a period of time. The regulations do however allow some types of localised failures within this time frame. The damage area of these failures must be contained and remain proportional to the initial triggering action and not continue into a widespread collapse, commonly referred to as a progressive collapse. In order to prevent progressive collapses, it is necessary to first identify which types of failures that could result in a progressive collapse. In a recent study (Iqbal N., Ph.D. thesis, Luleå University of Technology, 2016), single-storey steel frame buildings affected by localised fires were analysed. In the study it was identified that an initial failure in the truss’ top chord could potentially result in a progressive collapse. The reason for this is because when the top chord fails, the truss and its roof sheeting deflect and transitions into only handling catenary forces. The catenary forces present in the roof sheeting are then transferred to the adjacent trusses which therefore risks collapsing. The analysis could however not determine the possibility of progressive collapses and how factors such as truss span length affect the possibility of progressive collapses. The purpose of this thesis therefore became to analyse how span length affect the roof sheeting’s catenary forces and try to determine if a failure in the top chord could result in a progressive collapse. To answer this, finite element analyses where conducted on two different truss models with varying span lengths, i.e. 18- and 36-meter. Each model consisted of three trusses along with columns, bracings, and roof sheeting. Additionally, a hand calculation model was adopted to determine the strength of the catenary forces. From the finite element analysis, it could be seen that the adjacent trusses of the 36-meter truss model became grossly deformed. Hence indicating that a longer span length would increase the possibility of a progressive collapse. However, the hand calculation model used to calculate the strength of the catenary forces indicated that catenary forces present in the roof sheeting of the longer truss model, was relatively weak compared to the shorter truss model. The reason for this could not be determined, but some adjustments to the hand calculation model might be necessary to make it compatible with the analysed truss model. Consequently, it was impossible to determine the possibility of a progressive collapse. Additionally, during this work it was identified that other factors, such as truss model, bay length and roof sheeting thickness, could affect the possibility of progressive collapses. Hence, further work is necessary to determine the possibility of a progressive collapse. / När en byggnad utsätts för brandpåverkan ska den förbli strukturellt stabil under en viss tidsperiod. Regelverken tillåter dock att vissa typer av lokala skador inträffar redan under denna tidsperiod. Dessa skador måste begränsas till en viss area och förbli proportionerliga mot den initiala skadan och inte resultera i utbredda kollapser, det vill säga fortskridande ras. För att kunna förhindra fortskridande ras är det nödvändigt att först identifiera vilka typer av skador som skulle kunna resultera i fortskridande ras.  I en relativt ny analys (Iqbal N., Doktorsavhandling, Luleå tekniska universitet, 2016) analyserades den bärande konstruktionen i enplans stålhallar då konstruktionen utsattes för lokala bränder. Där det identifierades att ett brott i balkens överram eventuellt skulle kunna resultera i ett fortskridande ras. Brottet i överramen medförde nämligen att balken och dess takplåt sjönk ihop och övergick till att endast hantera linkrafter. Takplåtens linkrafter fördelades ut till de angränsade balkarna som därmed riskerade att kollapsa. Analysen kunde dock inte verifiera att ett fortskridande ras var möjligt eller avgöra hur faktorer såsom balkspännvidd påverkade sannolikheten för ett fortskridande ras. Syftet med detta arbete blev därför att analysera om balkspännvidd påverkade takplåtens linkrafter samt att försöka avgöra om ett brott i överramen kan resultera i ett fortskridande ras eller inte. För att besvara detta genomfördes finita elementanalyser på en 18- och en 36-meter lång balk. Varje modell bestod av tre balkar med tillhörande pelare och takplåt. För att sedan kunna uppskatta styrkan av linkrafterna i takplåten tillämpades en handberäkningsmodell.  Resultatet från finita elementanalyserna visade att den längre balkmodellen utsattes för högre påkänningar i jämförelse med den kortare balkmodellen. Detta indikerar att en längre spännvidd ökar sannolikheten för fortskridande ras. Handberäkningsmodellen som användes för att beräkna styrkan av linkrafterna gav dock generellt mindre linkrafter för den längre balkmodellen jämfört med den kortare balkmodellen. Anledningen till detta gick inte att fastställa men det skulle kunna vara så att handberäkningsmodellen behöver justeras för att kunna tillämpas på den undersökta balkmodellen. I och med detta var det omöjligt att avgöra sannolikheten för ett fortskridande ras. Under detta arbete identifierades det även att andra faktorer så som balkmodell, centrumavstånd mellan fackverk och plåttakstjocklek skulle kunna påverka linkrafternas styrka. På grund av detta är fortsatt arbete nödvändigt för att kunna avgöra möjligheten och sannolikheten för ett fortskridande ras.

Railway Catenary systems play a crucial role in the safe and reliable transportation of goods and people throughout the world. Monitoring the catenary infrastructure is crucial for safety purposes and therefore requires inspections. However, the current inspection methods are not sufficient for detecting all possible failure modes. The use of lidar has been proposed to augment the current inspection methods. This research proposes two methods for the classification of various overhead catenary components, resulting from lidar data, both solely relying on the coordinates of the captured datapoints. The methods resulted from a literature analysis and the parameters were obtained trough experimentation with a small dataset. The methods were validated using a larger dataset of 22.5 km between Boden and Gällivare and achieved promising outcomes. The first method resulted in an F1 score of 93,37% was obtained with 87,39% accuracy, whereas the second method, using a simple morphological region filtered obtain an F1 score of 95,48% and an accuracy of 91,27%. The novel contributions of the processing of lidar data in railway infrastructure is the use of a simple morphological region filter and the use of surface variation, a geometric feature for the extraction of masts and bridges. Further research is advised into the computational efficiency and further classification of components in the overhead catenary system.

Railway has the potential to become one of the most sustainable mediums for passenger and freight transport. This is possible by continuous updates to the asset management regime supporting Prognostics and Health Management (PHM). Railway tracks and catenaries are linear assets, and their length plays a vital role in maintenance. Railway catenary does not present many failures as compared to the rail track, but the failures that occur do not give enough opportunity for quick recovery. These failures cause extensive time delays disrupting railways operations. Such situations can be handled better by updating the maintenance approach. The domain of maintenance explores possible tools, techniques, and technologies to retain and restore the systems. PHM is dependent on data acquisition and analytics to predict the future state of a system with the least possible divergence. In the case of railway catenary and many other domains, this new technology of data acquisition is Light Detection And Ranging (LiDAR) device-based spatial point cloud collection. Current methods of catenary inspection depend on contact-based methods of inspection of railway catenary and read signals from the pantograph and contact wire while ignoring the rest of the wires and surroundings. Locomotive-mounted LiDAR devices support the collection of spatial data in the form of point-cloud from all the surrounding equipment and environment. This point cloud data holds a large amount of information, waiting for algorithms and technologies to harness it. A Digital Twin (DT) is a virtual representation of a physical system or process, achieved through models and simulations and maintains bidirectional communication for progressive enrichment at both ends. A systems digital twin is exposed to all the same conditions virtually. Such a digital twin can be used to provide prognostics by varying factors such as time, malfunction in components of the system, and conditions in which the system operates. Railways is a multistakeholder domain that depends on many organisations to support smooth function. The development of digital twins depends on the understanding of the system, the availability of sensors to read the state and actuators to affect the system’s state. Enabling a digital twin depends on governance restrictions, business requirements and technological competence. A concrete step towards enablement of the digital twin is designing an architecture to accommodate the technical requirements of content management, processing and infrastructure while addressing railway operations' governance and business aspects.The main objective of this work is to develop and provide architecture and a platform for the enablement of a DT solution based on Artificial Intelligence (AI) and digital technologies aimed at PHM of railway catenary system. The main results of this thesis are i) analysis of content management and processing requirements for railway overhead catenary system ii) methodology for catenary point cloud data processing and information representation iii) architecture and infrastructure requirements for enablement of Digital Twin and iv) roadmap for digital twin enablement for PHM of railway overhead catenary system.

No / This paper presents the results of a simulation study of 10 fire tests on restrained steel beam–column assemblies using five different types of joints: fin plate, flexible endplate, flush endplate, web cleat and extended endplate. This paper will provide details of the simulation methodology for achieving numerical stability and faithful representation of detailed structural behaviour, and compare the simulation and experimental results, including joint failure modes, measured beam axial forces and beam mid-span deflections. Good agreement between ABAQUS simulations and experimental observations confirms that the finite element models developed through the ABAQUS/Standard solver are suitable for predicting the structural fire behaviour of restrained structural assemblies with realistic steel joints undergoing different phases of behaviour in fire, including restrained thermal expansion and catenary action in the beams. The validated model may be used to conduct numerical parametric studies to generate theoretical data to help develop detailed understanding of steel joint behaviour and their effects on robustness of steel framed structures in fire.

A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Engineering. Johannesburg 2017 / The present study investigates the possibility of designing a catenary barrel vault, which can be implemented in regions where extreme tropical storms are frequently experienced. It moreover investigated the effect of non-uniform wind loads on catenary barrel vaults, and how to solve for these load conditions efficiently. The effects of high, non-uniform wind loads were assessed, and possible solutions were explored to determine a structurally efficient solution in resisting the loads applied. Different analysis and design techniques were explored in this research. These techniques included the optimization of the geometry, in resisting the applied loads most efficiently, as well as the structural design of the section in ensuring a durable and safe structure. The study revealed that the geometry of the structure cannot be optimised to resist the applied loads in a catenary fashion without external aid. By draping the vault in a post-tensioned basalt geogrid mesh, axial compression can be increased in the section and geometry optimisation can be achieved in resisting the applied loads in a catenary fashion. Three post-tensioning techniques were investigated and discussed. / MT 2018