The work presented in this thesis studies the load and loadeffects of traffic loads on railway bridges. The increasedknowledge of the traffic loads, simulated using fieldmeasurements of actual trains, are employed in a reliabilityanalysis in an attempt at upgrading existing railwaybridges. The study utilises data from a weigh-in-motion site whichrecords, for each train, the train speed, the loads from eachaxle and the axle spacings. This data of actual trainconfigurations and axle loads are portrayed as moving forcesand then used in computer simulations of trains crossing twodimensional simply supported bridges at constant speed. Onlysingle track short to medium span bridges are considered in thethesis. The studied load effect is the moment at mid-span. Fromthe computer simulations the moment history at mid-span isobtained. The load effects are analysed by two methods, the first isthe classical extreme value theory where the load effect ismodelled by the family of distributions called the generalisedextreme value distribution (GEV). The other method adopts thepeaks-over-threshold method (POT) where the limiting family ofdistributions for the heights to peaks-over-threshold is theGeneralised Pareto Distribution (GPD). The two models aregenerally found to be a good representation of the data. The load effects modelled by either the GEV or the GPD arethen incorporated into a reliability analysis in order to studythe possibility of raising allowable axle loads on existingSwedish railway bridges. The results of the reliabilityanalysis show that they are sensitive to the estimation of theshape parameter of the GEV or the GPD. While the study is limited to the case of the ultimate limitstate where the effects of fatigue are not accounted for, thefindings show that for the studied cases an increase inallowable axle load to 25 tonnes would be acceptable even forbridges built to the standards of 1940 and designed to LoadModel A of that standard. Even an increase to both 27.5 and 30tonnes appears to be possible for certain cases. It is alsoobserved that the short span bridges ofapproximately fourmetres are the most susceptible to a proposed increase inpermissible axle load. <b>Keywords:</b>bridge, rail, traffic load, load effect,dynamic amplification factor, extreme value theory,peaks-over-threshold, reliability theory, axle loads, fielddata.

<p>The work presented in this thesis studies the load and loadeffects of traffic loads on railway bridges. The increasedknowledge of the traffic loads, simulated using fieldmeasurements of actual trains, are employed in a reliabilityanalysis in an attempt at upgrading existing railwaybridges.</p><p>The study utilises data from a weigh-in-motion site whichrecords, for each train, the train speed, the loads from eachaxle and the axle spacings. This data of actual trainconfigurations and axle loads are portrayed as moving forcesand then used in computer simulations of trains crossing twodimensional simply supported bridges at constant speed. Onlysingle track short to medium span bridges are considered in thethesis. The studied load effect is the moment at mid-span. Fromthe computer simulations the moment history at mid-span isobtained.</p><p>The load effects are analysed by two methods, the first isthe classical extreme value theory where the load effect ismodelled by the family of distributions called the generalisedextreme value distribution (GEV). The other method adopts thepeaks-over-threshold method (POT) where the limiting family ofdistributions for the heights to peaks-over-threshold is theGeneralised Pareto Distribution (GPD). The two models aregenerally found to be a good representation of the data.</p><p>The load effects modelled by either the GEV or the GPD arethen incorporated into a reliability analysis in order to studythe possibility of raising allowable axle loads on existingSwedish railway bridges. The results of the reliabilityanalysis show that they are sensitive to the estimation of theshape parameter of the GEV or the GPD.</p><p>While the study is limited to the case of the ultimate limitstate where the effects of fatigue are not accounted for, thefindings show that for the studied cases an increase inallowable axle load to 25 tonnes would be acceptable even forbridges built to the standards of 1940 and designed to LoadModel A of that standard. Even an increase to both 27.5 and 30tonnes appears to be possible for certain cases. It is alsoobserved that the short span bridges ofapproximately fourmetres are the most susceptible to a proposed increase inpermissible axle load.</p><p><b>Keywords:</b>bridge, rail, traffic load, load effect,dynamic amplification factor, extreme value theory,peaks-over-threshold, reliability theory, axle loads, fielddata.</p>

No description available.

In this dissertation, we present analytical and experimental investigations of the electrically actuated micro resonators, when using multi-frequency and/or multi-mode excitation, combined with partial electrodes. We aim to understand their interesting frequency performance and use it to improve the sensing and actuation in microelectromechanical systems (MEMS) and explore their potential applications, such as amplification, gas sensing, magnetometer, multi-physical sensors, and digital-to-analog converters. In the first part, we propose a method of the multi-mode excitation (MME). The concept of the multi-mode excitation is demonstrated by utilizing the superposition principle of two vibration modes in the same phase. To fully understand the difference between the single source excitation (SSE) and multi-mode excitation, we derive the dynamic equations of motions of the electrically-actuated micro cantilever beam and clamped-clamped beam actuated by single/multi-mode excitation. Then, we analytically solve the equations based on the procedure of the Galerkin method with five modes. The simulated results indicate that the MME is clearly superior to that of the SSE, as it can amplify the amplitude performance and signal-to-noise ratio of micro resonators. In the second part, we aim to experimentally prove the concept of the multi-mode excitation and explore its use for gas sensing applications. First, we experimentally investigate the performance of MEMS resonators by single source excitation and multi-mode excitation. We prove the feasibility of the MME approach in enhancing the higher-order mode response for both cantilever and clamped-clamped beams, respectively. We prove that the multi-mode excitation approach provides a better way to activate the higher-order modes with an improved amplitude under a small actuation compared to using a single-source excitation. We then show an improved performance for gas detection. In the third and fourth parts, we propose a technique based on multi-mode excitation for simultaneous sensing for two physical parameters: magnetic field and gas concentration. We respectively investigate a single out-of-plane/in-plane device for in-plane/out-of-plane magnetic field and gas concentration sensing based on tracking the first two vibration modes of a heated buckled micro-beam. We found that operating the resonator at the post-buckling regime, the magnetometer is gas-independent since the first antisymmetric mode (f2) is unaffected by the thermal axial load. Based on it, we utilized the first resonance frequency f1 to detect the gas based on the cooling/heating effects while the second resonance frequency f2 to sense the in-plane/out-of-plane magnetic field. The obtained results demonstrated the sensor acts as a magnetometer and gas sensor, showing good sensitivity, linearity and repeatability. Thus, this technique provides a good candidate for multi-environment monitoring applications. In the last part, we aim to investigate the effects of partial electrodes actuation on the micro resonator and explore its application on the digital-to-analog converter. We analytically and experimentally present modeling, investigation, validation, and optimization of the MEMS resonator-based 3-bit digital to analog converter (DAC) consisting of an in-plane clamped-clamped beam actuated by partial electrodes with different air gaps. The results suggest that the proposed modeling, simulations, and optimization analysis could be successfully implemented in the design of the DAC under various digital combinations. The rich nonlinear behavior with low energy consumption could provide some high potential applications in IoT, such as logic, computation, sensing, and actuation.

No description available.

La plupart des bâtiments de moyenne et grande hauteur en béton armé sont munis de murs de refend ductiles afin résister aux charges latérales dues au vent et aux séismes. Les murs de refend ductiles sont conçus selon des règles conception stricts. Ces murs sont généralement conçus de façon à forcer la formation d’une rotule plastique à leur base dans l’éventualité d’un séismemajeur. Lors de la conception d’un mur, l’enveloppe des moments fléchissants ainsi que l’enveloppe des efforts tranchants dans la portion du mur situé au-dessus de la rotule plastique sont basés sur la résistance probable en flexion du mur dans la région de la rotule plastique. Plusieurs études sur les murs de refend conçus selon cette philosophie de conception on fait le constat que l’effort tranchant maximum dans un mur peut être sous-estimé lors d’un séisme, et que des rotules plastiques peuvent également se former à d’autres endroits qu’à la base du mur, ce qui constitue un mécanisme de ruine indésirable. Ces effets sont principalement attribuables à la contribution des modes supérieures à la réponse dynamique globale des bâtiments lors d’un séisme. L’effet des modes supérieurs est particulièrement important dans les bâtiments élancés de grande hauteur ayant une période propre de vibration longue. L’essai pseudo-dynamique avec sous-structure est uneméthode efficace et économique d’évaluer expérimentalement l’effet des modes supérieurs sur le comportement sismique des murs de refend dans les bâtiments. Lors de tels essais, comme la masse du bâtiment est modélisée numériquement, ceci permet de tester des structures à de relativement grandes échelles sans avoir à combattremécaniquement les forces d’inerties générées lors d’un séisme. Dans le cadre de la présente étude, la portion constituant la base d’un mur de refend correspondant à la zone de rotule plastique faisant partie d’un bâtiment de huit étages à l’échelle 1/2,75 a été testé. Les dimensions générales de la portion de mur testée étaient de 1800 mm de longueur, par 2200 mm de hauteur par 160 mm d’épaisseur. Le mur étudié a été conçu selon l’édition 2015 du Code National du Bâtiment du Canada (CNBC 2015) ainsi que selon la norme CSA A23.3-14 (Calcul des ouvrages en béton), où le facteur d’amplification de l’effort tranchant causé par l’effet des modes supérieurs n’a pas été pris en compte. Lors des essais pseudo-dynamiques avec sous-structure, une nouvelle méthode de contrôle à trois degrés de liberté convenant à des spécimens d’essai très rigides axialement a été développée et validée. Une procédure novatrice de redémarrage d’un essai interrompu en cours de route a également été développée et validée. Lors des essais, le bâtiment de huit étages incluant la portion de mur dans le laboratoire a été soumis à trois séismes. Le premier séisme était de très faible intensité, l’intensité du deuxième séisme correspondait au séisme de conception, et le troisième séisme correspondait au séisme de conception dont l’intensité a été doublé. Durant les deux séismes de forte intensité, le mur testé s’est comporté de manière ductile et des fissures de cisaillement et de flexion importantes ont été observées. Même si l’effort tranchant maximum mesuré durant le séisme de conception a atteint 2,16 fois la valeur de conception du mur, et 3,01 fois la valeur de conception du mur dans le cas du séisme amplifié, aucun mécanisme de ruine n’a été observé. Suite aux essais pseudo-dynamiques avec sous-structure, un essai par poussée progressive a également été effectué. Les résultats des essais pseudo-dynamiques avec sous-structure portent à croire que la valeur de l’effort tranchant de conception d’un mur selon la norme CSA A23.3-14 est sous-estimé. De plus, l’essai poussée progressive a permis de démontrer que lemur était beaucoup plus résistant qu’anticipé, puisque l’effort tranchant avait été sous-estimé lors de la conception. L’essai par poussée progressive a également permis de démontrer que le mur peut atteindre des niveaux de ductilité en déplacement supérieur à celui prévu par la norme CSA A23.3-14. / Abstract: Most mid- and high-rise reinforced concrete (RC) buildings rely on RC structural walls as their seismic force resisting system. Ductile RC structural walls (commonly called shear walls) designed according to modern building codes are typically detailed to undergo plastic hinging at their base. Both the design moment envelope for the remaining portion of the wall and the design shear forces are evaluated based on the probable flexural resistance of the wall in the plastic hinge region. Several analytical studies have shown that so-designed structural walls can be subjected to shear forces in excess of the design values. Plastic hinging can also develop in the upper portion of the walls. These effects are mainly attributed to higher mode response and, hence, are more severe in taller or slender walls with long fundamental periods. Considering the literature, there is a significant uncertainty regarding the behavior of the structural walls under the higher mode of vibrations excited under earthquake excitations. Hybrid testing is an effective experimentalmethod to study the natural behaviour of structures such as shear walls. The hybrid testing method enables the simulation of the seismic response of large structural elements like RC shear walls without the need to include large masses typically encountered in multi-storey buildings. In this study a barbell shaped RC shear wall specimen of 1800mm in length including a 300mm × 300mm boundary element at each end that is 2200mm in height, and 160mm thick was investigated. A test specimen corresponding to the base plastic hinge zone of an 8-storey shear wall was tested in a laboratory evolvement whilst the reminder of the building structure was modeled numerically. The reference wall was scaled down by a factor of 1/2.75 to obtain dimensions of the test specimen. The RC wall was designed in accordance with the 2015 edition of the National Building Code of Canada (NBCC 2015) and the Canadian Standard Association A23.3-14 code. The amplification of the base design shear force accounting for the inelastic effects of higher modes specified by the CSAA23.3-14 standard was not taken into account in order to evaluate the amplification experimentally. In order to investigate the response of ductile RC walls under earthquake ground motions and track the effect of the higher vibration modes on the shear force demand, three earthquakes with different intensities were applied on the hybrid model successively. The RC wall exhibited a ductile behaviour under the ground motions and flexural and shear cracks developed all over the height of the wall. In spite of amplifying the shear force demand by a factor of 2.16 under the design level earthquake and 3.01 under a high intensity earthquake, no shear failure was observed. The test results indicated that the amplification of the design shear forces at the base of ductile RC shear walls are underestimated by the CSAA23.3-14 standard. A new method for controlling three degrees of freedomin hybrid simulation of the earthquake response of stiff specimens was developed and verified in this study. Also, an innovative procedure to restore an interrupted hybrid test was programmed and verified. The hybrid tests were followed by a push-over test under a lateral force distribution equal to the square root of sum of the squares of the first five modes in order to evaluate the displacement ductility of the RC wall. Findings of the final push-over test showed that the tested ductile RC wall can withstand higher displacement ductilities than the presented levels in the NBCC 2015.

An increase in the demand for the freight shipping in the United States has been predicted for the near future and Longer Combination Vehicles (LCVs), which can carry more loads in each trip, seem like a good solution for the problem. Currently, utilizing LCVs is not permitted in most states of the US and little research has been conducted on the effects of these heavy vehicles on the roads and bridges. In this research, efforts are made to study these effects by comparing the dynamic and fatigue effects of LCVs with more common trucks. Ten Steel and prestressed concrete bridges with span lengths ranging from 30’ to 140’ are designed and modeled using the grid system in MATLAB. Additionally, three more real bridges including two single span simply supported steel bridges and a three span continuous steel bridge are modeled using the same MATLAB code. The equations of motion of three LCVs as well as eight other trucks are derived and these vehicles are subjected to different road surface conditions and bumps on the roads and the designed and real bridges. By forming the bridge equations of motion using the mass, stiffness and damping matrices and considering the interaction between the truck and the bridge, the differential equations are solved using the ODE solver in MATLAB and the results of the forces in tires as well as the deflections and moments in the bridge members are obtained. The results of this study show that for most of the bridges, LCVs result in the smallest values of Dynamic Amplification Factor (DAF) whereas the Single Unit Trucks cause the highest values of DAF when traveling on the bridges. Also in most cases, the values of DAF are observed to be smaller than the 33% threshold suggested by the design code. Additionally, fatigue analysis of the bridges in this study confirms that by replacing the current truck traffic with higher capacity LCVs, in most cases, the remaining fatigue life of the bridge is only slightly decreased which means that taking advantage of these larger vehicles can be a viable option for decision makers.

No description available.

Due to the emergence of new materials and advanced engineering technology, slender footbridges are increasingly becoming popular to satisfy the modern transportation needs and the aesthetical requirements of society. These structures however are always &quotlively" with low stiffness, low mass, low damping and low natural frequencies. As a consequence, they are prone to vibration induced by human activities and can suffer severe vibration serviceability problems, particularly in the lateral direction. This phenomenon has been evidenced by the excessive lateral vibration of many footbridges worldwide such as the Millennium Bridge in London and the T-Bridge in Japan. Unfortunately, present bridge design codes worldwide do not provide sufficient guidelines and information to address such vibrations problems and to ensure safety and serviceability due to the lack of knowledge on the dynamic performance of such slender vibration sensitive bridge structures. A conceptual study has been carried out to comprehensively investigate the dynamic characteristics of slender suspension footbridges under human-induced dynamic loads and a footbridge model in full size with pre-tensioned reverse profiled cables in the vertical and horizontal planes has been proposed for this purpose. A similar physical suspension bridge model was designed and constructed in the laboratory, and experimental testings have been carried out to calibrate the computer simulations. The synchronous excitation induced by walking has been modelled as crowd walking dynamic loads which consist of dynamic vertical force, dynamic lateral force and static vertical force. The dynamic behaviour under synchronous excitation is simulated by resonant vibration at the pacing rate which coincides with a natural frequency of the footbridge structure. Two structural analysis software packages, Microstran and SAP2000 have been employed in the extensive numerical analysis. Research results show that the structural stiffness and vibration properties of suspension footbridges with pre-tensioned reverse profiled cables can be adjusted by choosing different structural parameters such as cable sag, cable section and pretensions in the reverse profiled cables. Slender suspension footbridges always have four main kinds of vibration modes: lateral, torsional, vertical and longitudinal modes. The lateral and torsional modes are often combined together and become two kinds of coupled modes: coupled lateral-torsional modes and coupled torsionallateral modes. Such kind of slender footbridges also have different dynamic performance in the lateral and vertical directions, and damping has only a small effect on the lateral vibration but significant effect on the vertical one. The fundamental coupled lateral-torsional mode and vertical mode are easily excited when crowd walking dynamic loads are distributed on full bridge deck. When the crowd walking dynamic loads are distributed eccentrically on half width of the deck, the fundamental coupled torsional-lateral mode can be excited and large lateral deflection can be induced. Higher order vertical modes and coupled lateral-torsional modes can also be excited by groups of walking pedestrians under certain conditions. It is found that the coupling coefficient introduced in this thesis to describe the coupling of a coupled mode, is an important factor which has significant effect on the lateral dynamic performance of slender suspension footbridges. The coupling coefficient, however, is influenced by many structural parameters such as cable configuration, cable section, cable sag, bridge span and pre-tensions, etc. In general, a large dynamic amplification factor is expected when the fundamental mode of a footbridge structure is the coupled lateral-torsional mode with a small coupling coefficient. The research findings of this thesis are useful in understanding the complex dynamic behaviour of slender and vibration sensitive suspension footbridges under humaninduced dynamic loads. They are also helpful in developing design guidance and techniques to improve the dynamic performance of such slender vibration sensitive footbridges and similar structures and hence to ensure their safety and serviceability.

Comme dans d'autres pays européens, en France, les lignes classiques constituent la plupart du réseau ferroviaire (94%) et elles sont généralement âgées de plus d'un siècle. Aujourd'hui, on est demandé d’améliorer les réseaux pour faire face à une augmentation de la charge du trafic et de la vitesse de service. Dans ce contexte, ce travail de thèse vise à étudier expérimentalement l'influence de la vitesse et de la charge sur le comportement dynamique des matériaux constituant les voies classiques, à travers à la fois le suivi «in-situ» et des essais en laboratoire. Pour les études «in-situ», une section de ligne représentative du réseau classique a été sélectionnée dans le réseau français. Le site choisi a fait l’objet d’une prospection géophysique et géotechnique, ce qui a permis de définir les propriétés géotechniques des différents sols constituant la plateforme. L’impact de la vitesse du train et la charge à l'essieu sur la contrainte verticale, déflection/déformation, et en particulier leurs amplifications ont été évalués avec l’augmentation de la vitesse d’un train d'essai Intercités roulant à des vitesses différentes de 60 km/h à 200 km/h et les différentes charges à l'essieu appliquées par des voitures de passagers et la locomotive. Une analyse statistique est aussi réalisée afin d'évaluer la variabilité de la réponse de la voie et leur amplification dynamique avec la vitesse, en se basant sur les données enregistrées lors des passages de trains commerciaux. On observe que l’'amplification dynamique de la réponse de la voie due à la vitesse des trains est directement liée au rapport entre la vitesse des trains et la vitesse des ondes de surface du site. Un matériau représentative du sol intermédiaire des voies classiques a été préparé et testé dans une cellule triaxiale cyclique pour étudier son comportement mécanique. Deux types de charges, de forme sinusoïdale et de forme M, ont été appliqués et, en outre, deux teneurs en eau ont été examinés. Des variations des paramètres dynamiques des sols tels que le module élastique et le rapport d’amortissement avec le nombre de cycles ont été évalués, et les effets des paramètres de chargement tels que la forme de la charge, l'amplitude de la charge et la fréquence de charge ont été étudiés. L'effet de la teneur en eau a été étudié également. Il a été observé que la réponse de l'énergie développée pendant le chargement cyclique est un paramètre qui gouverne le comportement mécanique des sols à petit et grand nombre de cycles. En outre, la charge en forme sinusoïdale a été trouvée plus agressive que celle en forme de M parce que ce chargement sinusoïdal développe plus d'énergie, engendrant ainsi plus de déformations permanentes du sol à grand nombre de cycles, particulièrement le cas lorsque le sol est saturé. A partir des résultats obtenus sur le terrain et en laboratoire, deux modèles analytiques en 2-D ont été développés permettant de décrire la distribution de contrainte verticale et la propagation des déflections verticales. Certains paramètres mécaniques tels que les modules élastiques des couches de la voie, leurs rapports d'amortissement, leurs épaisseurs, ainsi que la vitesse moyenne des ondes de surface dans la section de voie considérée se sont révélés être les principaux paramètres contrôlant le comportement dynamique de la voie. Une comparaison entre les mesures effectuées sur le terrain et les résultats des essais en laboratoire a été également réalisée. La réponse de la voie sous différents types de trains, TER et TGV avec des charges équivalentes mais avec différentes configurations spatiales des essieux, est présentée. On observe que la réponse en énergie est plus élevée pour TGV que pour TER. Cette plus grande énergie développée suggère une plus grande agressivité vis-à-vis de la structure de la voie. Ainsi, la réponse en énergie est un indicateur important à prendre en compte lors d’un suivi du comportement mécanique d’une voie / As in other European countries, in France the conventional lines constitute the main part of the whole railway network (94%) and they are generally over a century old. Nowadays, facing the demand of upgrading both the traffic load and speed, it is of paramount importance to acquire good knowledge on the corresponding impact on the mechanical behaviour of tracks, at both short and long terms. In this context, this PhD work aims at investigating the influence of train speed and axle load on the dynamic behaviour of materials constituting the conventional track-beds, through both ‘in-situ’ monitoring and laboratory testing. For the field monitoring, a representative track was selected from the French conventional network following well-defined criteria. The selected site underwent a geophysical and geotechnical prospection, allowing the site critical speed and the geotechnical properties of different soils constituting the track-bed to be determined. The first data allowed assessing the influence of the track state conditions and the traffic loading on the measurements of each sensor. The train speed and axle load impacts on the vertical stress, deflection/strain, in particular their amplifications with speed increase were evaluated based on the data with an Intercity test train running at different speeds from 60 km/h to 200 km/h and the different axle loads applied by Coaches (105 kN/axle) and Locomotive (225 kN/axle). A statistical analysis was made to assess the variability of track response and their dynamic amplification with speed based on the data with passages of commercial trains. The dynamic amplification of track response due to train speed was found to be directly related to the ratio of train speed to the surface wave velocity. The laboratory test conditions were defined based on the field measurements. A material representative of an interlayer soil was prepared and tested in a large-scale cyclic triaxial cell to investigate its mechanical behaviour. Both Sine-shaped and M-shaped loads were applied and in addition, two water contents were considered. The variations of dynamic parameters such as resilient modulus and damping ratio with number of cycles were assessed, and the effects of loading parameters such as consolidation pressure, load shape, load amplitude and load frequency were investigated. The effect of water content was studied as well. It was observed that the response of energy developed during cyclic loading is an important parameter controlling the soil mechanical behaviour at both small and large numbers of cycles. Also, the Sine-shaped loading was found more aggressive than M-shaped loading since the former results in higher energy and therefore larger soil deformation. This is particularly the case when the soil is saturated. Based on the results obtained in the field and laboratory, two 2-D analytical models were developed allowing the description of vertical stress and vertical deflection transmissions in track-beds. Some mechanical parameters such as the moduli of track-bed layers, their damping ratios, thicknesses as well as the average track surface wave velocity were found to be the key parameters governing the track dynamic behaviour. A comparison between field and laboratory results was also made. The track response to the loading by different train types, considering equivalent loads but different spatial loading configurations from TER and TGV train axles is presented. It was found that for each monitored position in the track, the response energy was higher for TGV than for TER. This larger developed energy suggests a higher aggressiveness to the track structure. Thus, the energy response is a key indicator to be taken into account when performing a track mechanical behaviour monitoring