The Hyperloop is a high-speed means of transport, consisting of a bullet-shape vehicle travelling in a quasi-vacuum tube, electrically powered and moving through an electromagnetic levitating system. This allows the reduction of air resistance and wheel-rail contact friction, which translates in higher speeds for smaller power inputs. In the Netherlands, the Dutch company Hardt Hyperloop, has developed a new design concept of such technology, by means of electromagnetic suspension systems, unlike the most commonly applied levitating techniques.

The main aim of this project is to investigate the stability of the electromagnetic suspension levitation system, study the effect that the implementation of an error-based closed-loop control system has on the system dynamics and investigate the vehicle-structure interaction once a control system has been applied to the system.

Along these lines, the overall infrastructure-vehicle system is modelled through an equivalent two degrees of freedom system. In this manner, the inherent instability of the electromagnetic system is confirmed and the initial vehicle dynamics are highlighted. Afterwards, an error-based closed-loop PD-control system that applies to the system definition and reacts on the uncontrolled system dynamics is implemented and the effect of the control parameters on the dynamics and the stability of the system is studied. A certain stability region in the parametric space is derived, which ensures the stability of the system for significant perturbations of the vehicle from its equilibrium point. Besides, the existence of a subcritical bifurcation with respect to the parameter combination is demonstrated. The safety margin in the time delay of the controller response is studied, so as to define a slack time that accounts for not only processing and sampling delays, but also unforeseen events. Finally, the vehicle-infrastructure interaction is studied and its stability is ensured, by means of the previously defined control scheme.
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The instability of a moving mass / oscillator due to surpassing the velocity of the minimum group wave velocity (in a continuous homogeneous structure) has been studied extensively and is well understood. In contrary to that, Parametric Instability of a moving mass / oscillator on a continuous periodic structure has been studied less extensive and therefore the mechanism behind the instability is unknown. Literature that is avaiable on this topic mainly focuses on continuous periodic inhomogeneous structures, namely where the foundation is modeled as a continuous periodic inhomogeneous structure. Even less well studied are models where instead of a continuous periodic inhomogeneous foundation discrete periodic supports have been used. So far as known to the author there has also been no studies where the discrete supports are coupled through a medium. In order to solve the transition curves discerning the stable and unstable domains concerning the parametric instability of a moving mass / oscillator the analogy with the Mathieu equation is used, which tells us that the solution on those transition curves will be periodic with once or twice the period of the parametric excitation. In this thesis we have focussed on studying the use of the analogy on continuous structures founded upon periodic supports.

The Mathieu equation describes the motion of a parametric oscillator, for example a pendulum with a length that periodically varies over time. The theory that predicts the solution to the Mathieu equation is called Floquet theory and ascociated with the solution are the Floquet exponents, these exponents dictate whether the solution will be periodic and bounded or unbounded. By solving for the Floquet exponents of the Mathieu one sees that for an increase of the amplitude of the parametric excitation the system will experience a greater exponential growth. For a greater mistuning between the parametric excitation and the natural frequency of the equivalent non-parametrically forced equation we see that the system will experience a smaller exponential growth. Outside the instability domains the solutions will be bounded and periodic and contain a wide variety of frequencies. When damping is introduced, the value of the damping coefficient (if written in the canonical form of a viscously damped single degree of freedom equation) will be subtracted from the value of the undamped Floquet exponents and by that result in an upward shift and narrowing of the transition curves. Furthermore, outside the instability domains we will see two regions: the first lies close the the transition curves and is asymptotically stable with a period equal to that of the transition curve, the second covers the remaining stable region and is asymptotically stable and periodic with a wide variety of frequencies.

Regarding the Parametric Instability of a moving mass / oscillator we have studied three different models: a continuous Euler-Bernoulli beam on periodic spring supports, a continuous Euler-Bernoulli beam on periodic supports that are complex (i.e. modeled as an oscillator between two springs), and a continuous Euler-Bernoulli beam on periodic supports that are founded upon a 2-dimensional lattice. Of these models we have conducted a parametric study as to study what the effects are of the various parameters. We have seen that whenever the ratio between the stiffness of the supports and that of the beam is increased, the instability domains will shift to higher velocities and become wider. For certain combinations also 'islands' of instability may appear, where these 'islands' indicate stable areas between regions of instability. If damping is introduced into the system, this will generally narrow the instability domains and shift them to higher values of the mass and lower values of the velocity. However, for certain parameter combinations adding damping will lead to a widening of the instability domain. In the case of a moving oscillator the instability domains will narrow and be shifted to lower values. If the support is modeled with a mass it will affect the general trend of the transition curves through its own resonance, hence for a complex structure it is advised to model the supports with the correct dynamic equations. Last but not least, if the supports are coupled through a medium (a 2-dimensional lattice in this case) one will generally see a similar effect as adding damping has.

In this thesis we have also studied three real world cases: a regular railway track, a high-speed railway slab-track, and the Hyperloop. In the first case we have seen that Parametric Instability will most likely have no influence. For the slab-track, being much more stiff, Parametric Instability will be important. However, a more extensive study with several cases must confirm this. In the last case, namely the Hyperloop, we have seen that for a moving mass the instability domains are relatively large as compared with the other cases. We have also studied the Parametric Instability of a test-pod, which showed that its instability domains that are negligible. Of course, this was merely a test-pod not capable of transporting people, hence when a larger pod is studied it may be expected that the instability domains may not be neglected. ... Read more

The Submerged Floating Tunnel (SFT) is an innovative type of transport structure, with significant advantages in crossing long, deep and wide water areas, compared to more conventional types of bridges. Recognizing its potential, the Norwegian Public Roads Administration is planning to use such technology, in creating a ferry-free highway that will connect the west coast of Norway. The objective of the present Master thesis report is to develop a model on a tether-stabilized SFT and investigate the static and dynamic load effects acting on such a structure in order to estimate how safe can such a structure be. The modeling of the SFT has been based on prototype designs, specifically developed for Bjornefjord in Norway. Focus has been put on capturing the Vortex-Induced Vibrations generated on the structure, when interacting with a current flow. Matlab has been used to describe the SFT and solve the dynamic problem. Facchinetti's wake oscillator model is applied to couple the tunnel motions with the vortex shedding. In the present report, the tether motions are not taken into account and, conservatively, tethers are modeled as springs. The 100-year current speed was used to excite the structure and it was found that the SFT is not influenced significantly. An SFT configuration with a free-span length of 210m, between two consecutive tethers along the total length, is capable enough to dissolve any VIV effects. Only when a free-span length of 700m is used, vibrations in the cross-flow direction make their presence felt. A simple estimation of the 100-year swell wave force was also performed, showing similar forcing magnitudes as the current force with an excitation frequency much closer to the 1st natural frequency of the structure. This renders the structure a lot more sensitive. Furthermore, the effect of an unexpected tether failure was investigated and showed that the system can safely reach to a new equilibrium position, without any progressive damage. Overall, despite all the hesitation around this concept, it has proven to be quite promising. ... Read more

With increasing demand for renewable energy, the offshore wind industry is ever growing. Wind turbine generators (WTGs) proceed to grow in numbers and in size, wind farms are located further offshore, in deeper waters, poorer soil conditions or in areas prone to earthquakes. These changes make it increasingly difficult to find capable and affordable jack-up vessels for transport and installation of WTGs. Installing with Thialf, one of Heerema’s semi-submersible crane vessels (SSCVs), would mitigate most of the problems jack-ups have today and is thus regarded promising. However, Thialf is expensive and has a low sailing velocity. To optimize its installation up-time it will stay offshore for the project duration. A feeder system is required to supply it with WTG components, which are readily available at the marshalling yard. The objective of this research is to determine the critical activities in a feeder system for installation of WTGs with an SSCV, and to improve them so Heerema can make a competitive entrance to the WTG installation market.
Turbine manufacturers demand that WTG towers are positioned vertically at all times. A qualitative assessment for all components points to transport and offloading of the turbine towers to be critical activities. A comparative motion response analysis between a barge and a heavy transport vessel (HTV) shows that during transport, both solutions perform well in sea states higher than the intended installation sea state, thus making them suitable for the task. As offloading demands stricter limits than transport, vessel motions for that activity are too severe. The natural frequency of the vessel-tower system increases with each removed turbine, moving into governing wave frequency ranges for North Sea conditions. This phenomenon shows for both vessel types, from which it is concluded that a supply vessel will be selected based on project specific parameters, rather than motion response.
During preliminary developments within Heerema, tipping of the tower when its sea fastening is released and large swinging motions of the tower after lift-off were main problems found during offloading, to which improvements are necessary. Three concept solutions are assessed: one an alteration of the existing, single tower lift solution, two others making use of the SSCV’s cranes with high capacity by respectively lifting a frame with 4 towers and two frames with 8 towers. For each concept, response limits are defined at relevant locations in the system. In-house software is used to determine the RAOs, from which the heading with the highest operability is computed. The offloading and installation activity sequence for wind farms of 48 and 96 turbines are defined, followed by a weather downtime assessment.
First simulations show waiting on weather (WoW) is governed by crew transfer from a crew supply vessel to the barge for mooring operations. This can be improved by using a crew basket, motion compensated gangway or HTV. Simulations with revised limits show that using a frame with 4 towers results in significantly lower WoW days and shortest net project times, making it the most promising concept. Shorter lifting exposure and reducing motion amplification by means of a low frequency system are drivers for the decrease in weather downtime. With a lower total project duration, costs are reduced substantially. ... Read more

Researchers of TU Delft have been designing and engineering with columns created out of multiple glass rods that are bundled together to form a single column. These aesthetically attractive and slender columns were tested to ensure safety before implementation in the real structure: the Glass Truss Bridge located at the campus of the university. However, the ultimate capacity and structural behaviour of such columns remained unknown. In this studies the structural behaviour of two designs of such columns is researched. It appeared that, among others, the differences in length between the rods within the columns caused an unequal distribution of stresses. This resulted in a large range of ultimate capacities of bundled glass columns that were designed according to the same design principles. Using a special approach in finite element modelling of the glass until failure, furthermore, resulted in more thorough knowledge regarding the failure behaviour of glass and the best way to model this behaviour. ... Read more

In this research project, an assessment of an abatement measure for mitigating railway induced vibrations is carried out. Ground-borne vibrations, which are primarily generated due to wheel-rail interaction, may also result in ground-borne noise in the buildings located in vicinity of railway tracks. An example of adverse environmental impact caused by ground-borne vibration and noise is the annoyance to people living those buildings. Assessing ground-borne vibration and noise is of crucial importance, especially in soft soils in which Rayleigh wave velocity is low and amplification of vibrations is more likely to occur. For mitigating the ground-borne vibration and noise exceeding the threshold values defined by technical standards in each country, abatement measures are applied. The main objective of this research is assessing the effectiveness of ‘concrete slab beneath ballast bed’ used as the abatement measure for reducing vibrations. For this purpose, Plaxis 3D based on Finite Element Analysis method is employed. Numerical model is created and validated through measurement data available from field tests conducted in the Netherlands. After having numerical model validated, several simulations are performed in order to study the factors influencing ground-borne vibrations.
From the results of this study, one can conclude that ‘concrete slab beneath ballast bed’ is effective in reducing vibration strength at all distances when train speed is considerably lower than Rayleigh wave velocity of the uppermost soil layer. It is notable, however, that the application of this measure may bring about amplification of the vibration strength in the vicinity of the track for trains running at higher speeds. Nevertheless, regardless of the train speed, there is always a reduction in the vibration strength at further distances from the railway track. From practical standpoints, this aspect is of interest for the buildings located in the far field. From the results of a sensitivity analysis on changes to the width and thickness of the concrete slab, it can be concluded that an optimal solution of concrete slab dimensions can be found. It is observed that by changing concrete slab dimensions, the maximum vibration strength is mostly affected in close proximity to the railway track. In addition, the dispersion lines and oscillatory moving load in the Wavenumber-Frequency plane are analyzed. Their intersection indicates that the moving oscillatory load excites a wave of frequency and wavenumber given by the intersection point. If these frequencies are harmful for the environment then concrete slab application can diminish their content from response. Sleeper passing frequency content increases when the concrete slab is applied. The obtained results and recommendations from this study can be used for further studying the other factors influencing the effectiveness of the measure. Examples of these factors include, among others, various ground conditions (e.g., soft soils of different stratification, local changes in soil proper-ties, etc.), and optimization of concrete slab dimensions, material parameters, as well as, cracked and uncracked concrete stage. The numerical model developed during this research study can be further employed to analyze different aspects of railway induced ground-borne vibrations. ... Read more

The prediction of structural vibrations in vibration sensitive laboratory structures is a complex problem involving computationally heavy 3D models with long computational times. However, in the early design phases of a project long computational times are undesirable. Therefore the problem statement of this Master thesis concerns the development of a practical engineering tool which can be used in the early design phase of a vibration sensitive laboratory structure. The resulting tool is called EDDABuSgs (Early Design Dynamic Analysis of Building Structures by Gerwin Schut) and is the final product of the thesis research. The main focus of EDDABuSgs is on structural vibrations induced by heavy traffic at geological locations with soft soils (e.g. Amsterdam, the Netherlands). The thesis research concerns the four interrelating parts: source of vibrations (truck), transmission of vibrations (soil), soil-structure interaction and the structure (receiver of vibrations). The software FEMIX is used for computing the 3D soil response (source and transmission). The soil response is then used as input for EDDABuSGS, which computes the 2D structural vibrations by the aid of a Python script. The global structural response is computed from a rigid 3DoF system which is supported elastically by the soil and a pile foundation. The local structural response (ground floor) is computed from a flexible frame, composed of the analytical solutions of Euler-Bernoulli beam elements. The flexible frame is excited by the global 3DoF structural response by means of the boundary- and interface conditions. The results of FEMIX and EDDABuSgs show good agreement with the used verification projects. Several iterations have been made using EDDABuSgs to see how several parameters change the 2D structural response. The results of these iterations are well in line with general known theory about structural dynamics. From this Master thesis research one can conclude that soft soils excited by heavy traffic have a responsive frequency spectrum generally in-between 3 and 15 Hz. Therefore it generally holds that the eigenfrequencies of the global building response should be made relatively low (< 3 Hz), while the eigenfrequencies of the local structural elements (e.g. floors) should be made relatively high (> 12 Hz). Additionally, the resistance against vibrations (impedances) of the structural elements should to be as large as possible, which might sometimes contradict the preferred shift of the eigenfrequencies. ... Read more