In the Netherlands, there is an increasing need to create residential spaces in its already crowded cities to accommodate the growing population. Constructing high-rise buildings is one way to try to solve the issue. However, high-rise buildings are sensitive to wind-induced vibrations. The accurate prediction of the dynamic response is important in high-rise building design. In building design practice, calculating the dynamic response of high-rise buildings under wind loading typically involves simplifying the structure as a single degree of freedom system, characterised by the first eigenmode properties and subjected to a white noise spectrum. The damping and natural frequency of the building substantially impact its dynamic response. These parameters are challenging to predict with accuracy. Additionally, in the presence of soft soils, soil-structure interaction can play an important role in energy dissipation and influence the structure's natural frequency. In practice, soil-structure interaction is either disregarded or simplified. In order to assess the effect of soil-structure interaction on the dynamic response of the building, this study models in a robust manner: the foundation, the tower structure, and the wind load. This newly developed model is addressed as the HF model. The investigation consists of a case study and a parametric study. Additionally, this study compares the predictions by the newly developed model with those obtained with a model as specified in the Eurocode. The case study provides a comparison between the models and the measured dynamic response of the New Orleans Tower. The parametric study looks into the influence of soil stiffness and material damping on the dynamic response of high-rise buildings. Furthermore, it investigates how these parameters affect the dynamic response of structures with various slenderness ratios. The case study was used to demonstrate that the developed model accurately predicts the measured dynamic response of the New Orleans Tower in the along-wind direction. For all the examined dynamic properties, the error compared with the measurements was lower than 7%. In the case of the Eurocode model, the results demonstrate that, when using the natural frequency estimation recommended by the Eurocode, it provides a 30%–35% underestimation of the peak acceleration compared to measurements. This Eurocode model overestimates the natural frequency and overall damping, which causes it to underestimate peak acceleration. However, the natural frequency determined in the design phase of the New Orleans Tower was significantly lower than the value obtained with the recommended estimation method in the Eurocode. With this lower natural frequency, the peak acceleration is overestimated by around 50%. This underestimation of the natural frequency and overestimation of the damping provided acceptable conservative results. Although this showcases the importance of accurate predictions of both natural frequency and damping, having poor predictions that cancel out each other’s effects is not desirable. The results from the parametric study support the findings from the case study. This shows that the case study’s findings apply to the more extensive range of building configurations investigated in the parametric study. In general, the Eurocode model, for slender structures on soft soil, overestimates the natural frequency and overall damping, which causes it to underestimate peak acceleration. The parametric study revealed that the building's first natural frequency and global damping ratio are significantly influenced by the soil stiffness and soil material damping, which can result in various effects on the peak acceleration. In the case of soil material damping, not considering it at all or considering a higher value could lead to 20% overestimation and 40% underestimation of peak acceleration, respectively. Soil stiffness had more intricate effects since it affected the natural frequency and the amount of energy dissipated by the soil radiation damping, the soil material damping and the structure material damping. For particular combinations of parameters, soil stiffness had up to a 40% increase in the peak accelerations compared to the fixed foundation. The results of this research show that the soil stiffness and soil material damping, for the ranges of properties relevant to the Netherlands, significantly influence the accurate predictions of the wind-induced dynamic response of high-rise buildings. Especially, there was found a higher influence on the dynamic response for the extreme cases of high slenderness ratio structures on very soft soils.

An analytical study of an energy-based approach to damping of a clamped timber column in free vibration under axial, lateral and torsional loading conditions was conducted. Backed by experiments it was confirmed that an energy-based approach, as proposed by Sánchez Gómez (2018), could describe the energy dissipation in a laterally vibrating timber column. With the help of an energy balance equation, the energy flow in a timber column was formulated including any energy dissipated during vibration. It was found that the energy in the system could be approximated by an exponential function for which a new dissipation constant ED (s-1) was introduced. For lateral vibrating columns of Norway spruce, typical values of ED were 0.4 - 0.6 s-1. Furthermore, a case study on a timber high-rise building demonstrated that damping has a significant influence on reducing peak accelerations which, in turn, could potentially lead to lowered costs. This largely untapped design lever warrants significant research and design improvement for these timber high-rise structures and, hence, several recommendations for follow-up research are offered.

Energy transfer between guides and bumpers duet to impulse loads During reverse installation for executing platform decommissioning and removal projects, heavy modules such as the topside of an offshore platform are cut off their substructures and lifted back on the deck of crane vessels or onto cargo barges. To assure that the modules are placed on the intended location and to prevent the modules from moving during transportation, a guide and bumper system is used. During set-down, it is possible that the module bumps into one of the guides. The relative motions between the vessel and the barge can cause significant impulse loads when the module and guide make contact. To prevent the module from being damaged, bumpers are welded onto the module to protect the module during the contact phase. Both the guide and bumpers are designed to only deform elastically and to cope with the expected impulse loads. the designs are based on internal standard criteria that state that the guide and bumper system will be designed for a maximum horizontal load that is 10% of the designed weight of the lifted module. During the design state, this load is statically applied on the weakest spot of the guide and bumper system. In reality, the loads are not applied statically but dynamically and it is still unknown how to correctly estimate the magnitude of the impact. The estimated loads might differ from the actual loads due to unaccounted forms of energy transfer that occur during the impact, such as the rotation of the module, motions of the bumper and guides or deformations in the guides and bumpers. To analyse the energy transfer during impact and to say something about the magnitude of the impact an experiment was conducted with a scaled model. The scaled model exists of two standard steel guides clamped to steel plates and a squared module with a bumper that with the motions of a pendulum. The module is pulled back to a magnet, from where it is let go to hit both the guides once, after which the module is pulled back again. The impact location on the guides and bumpers is enclosed with sensors that measure the potential energy in the form of strain and the kinetic energy in the form of accelerations. The sensors are situated so that they enclose the energy flow in every possible direction. For each of the enclosed segments, an energy balance was set-up. The guides were tested as a guide with an inclined brace and as a simple cantilever beam. A number of case studies were tested to analyse the energy transfer as a result of impulse loads and to estimate the magnitude of the loads; impact location on the guides, bumper height of the module (at the CoG of the module, above and below), weight of the module, deviation of the module and different damping materials around the guides. The energy balance consists of the external energy that enters the segment, which should be equal to the energy flux, the energy that exits or enters the segment through the cross-section of its boundaries, the energy rate of the segment and the energy that is dissipated. Both the externally applied load which was needed to calculate the external energy that enters the system, as well as the rotational velocity that was needed to determine the energy flux, are computed with an analytical model. This model compares the response of a unit load of 1 to the responses of the experiment. The difference between the two is computed as the applied load on the system. The computed energy balance shows the energy flow through the structure as a result of the impulse load. From the results, it is possible to conclude that the impulse loads in this experiment can be assumed to be linear elastic. Based on these experiments a more accurately description of impulse loads can be used as an input for models, for both duration and shape. The second one is that based on these experiments, at least 97% of the energy is transferred back into motions of the module, the effect of energy transfer in a linear elastic response has little to no effect on the magnitude of the loads.

The demand for wind energy has led to the need for larger offshore wind turbines, which require larger monopiles for support. Vibratory pile driving is a common technique for installing these monopiles, but current engineering models are designed for smaller diameter monopiles and may not be applicable to larger ones. Additionally, the vibratory action produced by counter-rotating eccentric masses in the hammer can cause unintended bending motions in the pile if there is a slight misalignment. This study aimed to investigate the effects of gear misalignment on the response of monopiles under vibratory action, including these imperfections. To achieve this, a hammer model was created and coupled with a pile model and a simplified soil reaction. A parametric study was conducted to evaluate the pile response to the modeled vibratory hammer with imperfections over a range of specified variables. The transfer of force from the hammer to the pile and the range of driving frequencies that activate the isolation springs in the vibratory hammer were examined, as well as the effect of misalignments on the power consumption of the vibratory hammer and the bending displacements caused by these misalignments. The study found that there was no significant impact on axial vibrations as a result of misalignment of rotating masses. The force transfer ratio from hammer to pile is 0.5 to 0.7 for smaller diameter piles, and it is important to include force transfer ratios in simple engineering models during the initial design phase of pile drivability prediction models when the decision is made not to model the hammer. The study also showed that modeling the hammer-pile-soil system with shell elements instead of 1D rod elements yields similar trends in the responses, but the absolute response values of large diameter piles with simple 1D rod elements leads to an underestimation of the response in the lower driving frequency range and an overestimation in the higher driving frequency range. Even if as much as 50% of the eccentric masses are misaligned, the impact of bending vibrations on the power consumption of the vibratory hammer is insignificant. However, bending displacement can become substantial when 6% of the eccentric masses are misaligned. Smaller diameter piles are more susceptible to vibrations at lower frequency ranges, while larger diameters are impacted in higher frequency ranges. Only large diameter monopiles are susceptible to axial vibrations near their natural frequencies, while all diameter piles are affected by bending vibrations near their natural frequencies. Isolator springs are effectively activated in the region of higher driving frequencies (> 28 Hz) for large diameter monopiles. In the case of small diameter piles (< 3 m), the relative motion between suppressor housing and pile head remained above unity for all driving frequencies, meaning poor activation of the isolator springs.

As buildings get taller and lighter, structural engineers are increasingly faced with the consequences of the dynamic response of high-rise buildings to wind. Damping is an important property for the dynamic response of high-rise structures, but is a combination of many mechanisms, which makes it a complex phenomenon to account for in the structural design. Empirical damping predictors currently exist, but a large scatter is found among predictors, as well as between predictors and identified damping from measurements. Damping values are prescribed in codes, but are not consistently conservative. Therefore, there is a strong desire from both structural engineers and researchers to obtain further understanding of damping behaviour in high-rise structures. Damping identification techniques, such as the Half-power Bandwidth method and the Random Decrement technique are commonly used. However, these are not applicable to buildings with closely spaced modes, and require extensive measurements. Besides, they only provide a damping value, and cannot find damping of separate components of a system. A novel technique, the Energy Flux Analysis, approaches damping from an energy point of view, making it more widely applicable, and allowing for damping identification in components of a structure. The Energy Flux Analysis has been verified to lab structures, but its performance when applied to a high-rise structures using in situ measurements is still unknown. The aim of this research is to investigate the sensitivities of and prerequisites for the application of the Energy Flux Analysis to high-rise buildings excited by wind using spatially limited measurements. The sensitivities were sought for in the uncertainty of required input for the Energy Flux Analysis: structure motion, which includes internal forces, wind load, data acquisition, and structural properties. The research was performed through application of the Energy Flux Analysis to the New Orleans tower in Rotterdam. While the sensitivity to structural properties and the magnitude of measurements is limited, the Energy Flux Analysis demonstrated to be highly sensitive to the phase of structural motion, internal forces, and wind load. The first two points are relevant for computing the energy flux at the boundary of a system, when one is interested in damping in the superstructure and due to soil-structure interaction separately. The last point is relevant when one is interested in the total or superstructure damping. The phase differences occurring between structure motion and internal forces are a direct result of damping. Material damping resulted in a phase difference between stress and strain in the numerical model, while a local damper resulted in a phase difference between structure motion at different locations. The many damping mechanisms occurring in a high-rise structure may each affect the phase of structure motion and internal forces differently. When these phase differences are not taken into account in the Energy Flux Analysis, for instance due to extrapolation of measurements, an erroneous result will be obtained. A brief investigation was performed as to whether these effects can be expected in true structures, but additional research is required. The fluctuating wind load at the natural frequency of the structure is dominant for the flux of energy from wind to the structure, which is obtained by multiplication of the wind load with the structure velocity. Again, the phase of this wind load is highly important. When measured at one location, little is known about the phase of the wind load at other heights. Different approaches of extrapolating the measured wind load demonstrated a large scatter in the Energy Flux Analysis results. In this research, the Energy Flux Analysis found not to be repeatable, which was proven to be a direct result of the phase difference between the measured wind load and structure velocity. Possible causes for this varying phase difference were formulated. It is essential, but due to the major advantages of the Energy Flux Analysis also profitable, to perform further research into its application to high-rise structures. Therefore, this study provides extensive recommendations mostly focused on simple numerical and lab experiments.

The trend of the slender and high-rise building has made the structure prone to dynamic loading. This thesis is focused on the dynamic behavior of the high-rise building subjected to wind action. The acceleration becomes a limiting criterion in designing such structure which can be categorized as the comfort criteria of the building. Nausea and motion sickness from the acceleration of the building has been studied by human experience, and numerous building code has included this in the design criteria [6]. The tuned mass damper (TMD) comes from the basic vibration absorber theory by Frahm in 1909; then the studied continued and applied in a building. At present, the TMD is a well-known technology to mitigate vibration, but it is not always applicable in every building case. Therefore a study of the interaction between the building properties also the soil structure interaction (SSI) is made in the application of the TMD.This thesis aims to study the dynamic behavior of a high rise building with the implementation of TMD and to take into account the SSI, also to indicate which type of building is preferable to apply a TMD. The model for the high-rise building is an analytical one-dimensional model which is validated by the finite element program (FEP). The analytical model can give a good fit for the building response but due to the model of the wind load is a random load, it is challenging to match precisely the TMD performance due to the comparison of different load phase. The physical characteristic and tendency of the TMD performance to different building parameter still can be studied in this analytical model. It is shown in this study that the damping plays an important role not only to reduce the acceleration of the building but also influence the effectiveness of TMD. The acceleration is drastically reduced in the lower damping ratio area, which makes theTMD more effective if the building has lower damping ratio contributed from the material, structural joints, and SSI. The reducement of the acceleration by increasing stiffness and mass is very limited compared to the application of TMD. There are two building data for the base of the analysis; the first is the European Patent Office EPO building which is designed by Zonneveld Ingenieurs and the new proposal of slender high rise building in Rotterdam. The EPO building has a unique geometry which the contribution of torsional vibration is high. The slender high rise building shows that the TMD is more effective in reducing the acceleration in this case. The reason is the slender high rise has higher acceleration compare to EPO building when the required building stiffness for the deformation limit is applied.

During the last decades, the development of high-rise increased quickly. The Eurocode is frequently used to make wind calculations for high-rise structures. To make those calculations, the dynamic wind load is simplified to a conservative equivalent static load. An alternative to calculate wind loads is a physical wind tunnel test. Wind tunnel tests are expensive. An alternative for these methods is the use of Computational Fluid Dynamics(CFD). CFD makes it possible to simulate the wind. At this time, CFD is still very user-dependent and therefore it is stated in the Eurocode that CFD simulations cannot be used as a design tool. This research aims to examine the impact of different parameters in evaluating the dynamic loading on a high-rise structure by the use of CFD. The results of the CFD simulations are compared with a spectral approach. The Navier Stokes (NS) equations are the basics for CFD. Different models are used to solve the NS equations. The costs of CFD increase exponentially with demanding more accuracy. An extension of the RANS model is used in this research: the Unsteady-RANS(U-RANS) model. Where the RANS model only computes the steady-state solution in a simulation, the U-RANS captures the slow turbulences as well. For the objective of a dynamic wind load on a high-rise structure the slow turbulences are of more importance than the faster turbulences. Especially the frequencies close to the natural frequencies of the structure are important. The CFD simulations are performed using Star CCM+ by Engineering Company ABT BV. A reference structure is used to validate the CFD simulation procedure with existing available wind tunnel data of the Tokyo Polytechnic University. The wind tunnel data contains dimensionless pressure coefficients on several locations on the model. The results show a lot of noise, which is visible when the time domain's pressure coefficients are translated into the frequency domain. A dominant peak is observed at a frequency of 10 Hz, but other frequencies are triggered as well. The CFD simulation for the same reference block show less fluctuating results than the wind tunnel data: the results are only fluctuating on one frequency of 12 Hz. Afterwards, a case study is used to compare CFD results with a spectral approach. A high-rise structure of 40 x 40 x 200 meters is used for this study. The results of the spectral approach are compared with existing literature using the structural factor cscd. The results coincide. Several CFD simulations are performed on the same model. The absolute values of the peak velocity pressure are of the same order of magnitude, with a difference of 10 to 25 percent. However, the values of the standard deviation differ more substantially. The CFD simulation stores the average pressure over an area of 10 x 10 meters, which balances out some fluctuations. Furthermore, it can be concluded that the CFD simulations underpredict the absolute values of the pressure consistently compared to the spectral approach. It can be concluded that the CFD simulations require exact defined input values.

A research into the influence of the main parameters in the preliminary structural design on the wind-induced dynamic behaviour, including soil-structure interaction effects, of high-rise buildings in the Netherlands. The dynamic behaviour becomes more and more important for higher and more slender structure. The dynamic response is controlled by the maximum acceleration at the top of the structure. The maximum acceleration is determined with a spectral analysis for a large amount of building variants, ranging from a 100 meters to 300 meters high. The influence of each parameter can be obtained from the generated data in this research within the considered domain. Having insight into the influence of design decisions on the dynamic response already in the preliminary design, can be beneficial for the whole design process and can result in a higher comfort level our high-rise buildings.

The slip joint connection is a relatively new alternative method for connecting offshore wind turbine towers to prior installed monopiles. It consists of two overlapping conical sections that together form a connection. There are several challenges left to be solved before the slip joint can be applied on a commercial scale. One of those challenges lies in the decommissioning process of the slip joint connection. It is proven that build-up settlement can increase the friction force within the joint over its lifetime and complicate its disconnection. One potential method for reducing the friction force in the slip joint is the excitation of one of the structures shell modes localized around the slip joint. Good estimations of the shell modes of the structure are therefore essential. Models for precise estimation of the shell modes of a wind turbine with a slip joint are difficult and expensive to develop due to the complexity of the joint. This thesis is a study into the possibility of using simplified finite element models to estimate the shell modes of a wind turbine connected with a slip joint. This is done by estimating the shell modes of the structure using a reference model and seven simplified models in a modal analysis. The estimated shell modes are compared based on their eigenfrequency and mode shape. Based on this comparison, conclusions about the applicability of simplified models are drawn. The first 300 eigenmodes of the structure are estimated with both the reference model and simplified models. Of these eigenmodes, ten shell modes of interest are selected based on their eigenfrequency and location at which the modes are localized. The modes of interest are than compared for their eigenfrequency and mode shape. The mode shapes are compared based on the Modal Assurance Criterion (MAC), which is calculated at a specific location of interest. In addition to this, the angle in which the modes are orientated is measured and compared, as this can be useful information for the decommissioning process. Results showed that three out of seven simplified models studied resulted in a estimation of the shell modes which was sufficiently accurate. The simplifications used for these models consist of the averaging of wall thickness for the upper and lower slip joint and a simple model for the upper slip joint. From these results it can be concluded that some of the simplifications can be applied when estimating shell modes of a wind turbine tower connected with a slip joint, as they lead to only a small decrease in accuracy of the shell mode estimation. However, using these results to make predictions about other potential simplifications is challenging as each different simplification has a unique influence on the estimation of the shell modes.

The offshore monopile decommissioning demand will become definite in the coming years. Our responsibility is to ensure the rights and duties of other legitimate uses by completely removing the ageing monopile from the seabed to continuously redeveloping offshore wind farms within the same location. The growing number of past, present, and future monopile installations opens up the challenges and opportunities to be responsible and lead the decommissioning market. With the goal of complete removal, a novel GDP technique can be the win-win solution for offshore wind operators and contractors to extract the monopiles completely from the seabed using torsional and axial vibration This thesis seeks to understand the torque and normal force to safely clamp a monopile during a torsional vibration so that the monopile continuously slips over the soil. Gradual soil failure along the pile-soil interface's full depth due to the monopile's torsional motion is a possible theory to explain the failure mechanism. When an upper part of the pile successfully moves relative to the soil, kinetic friction occurs until the soil resistance is larger than the shearing at one point. If more shearing is added by adding more torque, more layers below will be broken while the upper part keeps sliding due to lower friction than static friction. While the linear elastic theory of solid and thin shell bodies is used within a 3D FE modelling in Ansys to couple the soil and pile, the clamping force due to the GDP shaker is decoupled from the analysis. Failure criterion is defined outside the simulation so that the gradual soil failure is done through several simulations assuming discrete soil layers. The FE model is constructed and verified by analytical calculation through the semi-infinite cavity-pile-soil, wave reflection, and finite cavity-pile-soil-spring-dashpot problems. Several cases of gradual soil failure are simulated and show that the torque amplitudes form a distribution. Firstly, a probabilistic sense is proposed to interpret the torque amplitude and search for the optimum depth of the soil failure. Secondly, a convergence check is made with the help of an analytical shell-spring by considering more soil elements by virtue of good correlation of the shear stress between the analytical and FE model. It eventually suggests that a convergence of the torque amplitude can be achieved, which reinforces the theory of gradual soil failure. The interpretation suggests that the current GDP shaker is one step closer for a monopile extraction test with typical monopile dimensions that correspond to a typical 1 m diameter. A first approximation of the required torque and clamping force is then proposed to benefit the analytical model for larger diameters up to 6 m.

The world faces an increasing energy problem, forcing people to search for sustainable energy sources. Offshore wind energy has shown great potential to financially compete with traditional energy sources. Recent developments like the slip-joint connection increase this potential. However, for further optimization of the design of a slip-joint, the location of the contact areas between the two cones must be known. Previous attempts to detect these contact areas based on techniques such as heat transfer or ultrasonic measurements have proven insufficient. A possible new way of detecting contact areas, is through the behaviour of Energy Flux. Energy Flux methods have shown great potential as a damping identification tool in other applications. Therefore, in this study the relation between Energy Flux behaviour and the presence of a contact point in the time-, frequency- and time-frequency-domain is studied. To this end, a numerical analysis of a vibrating simply supported Euler Bernoulli beam is conducted, simulating a contact area with a point load. The analysis in the frequency-domain showed the most promising results. Presence of a contact point (i) introduces peaks at twice the first and twice the second eigenfrequencies, and (ii) increases peak height at the location of the contact point. The pressure of the simulated contact point increased these effects. In the time-domain the presence of a contact point increased the amplitude of the cumulative energy flux. This change was most significant at the antinode of the first eigenmode. The location of the contact point was of little influence on this effect. These results show that the presence of a contact area influences the behaviour of the energy flux. The results are encouraging for a later implementation of the energy flux method for the detection of contact areas in a slip-joint. As a validation of these results, an experiment has been proposed. After execution of this experiment, further research is needed in (i) the behaviour of Energy Flux in a conical shape, and (ii) Energy Flux measurements of higher frequencies.