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.

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.

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.

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.

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.