Large-diameter monopiles serve as foundations for offshore wind turbines (OWT), and the diameters are now up to 10 meters. These monopiles exhibit lower embedded length-to-diameter (L/D) ratios compared to the conventional monopile that is widely employed in offshore oil and gas platforms. They undergo rotation when subjected to lateral loading like rigid or semi-rigid bodies. This distinct geometry necessitates a different approach to describe the soil reaction that is induced when a lateral load is applied. Previous research introduced a 1D model incorporating four soil spring components to represent four aspects of soil reaction namely lateral soil reaction, distributed moment, base shear force, and base moment. However, questions have arisen regarding the contributions of base components, specifically the base shear force and base moment, to maintaining monopile stability. In response, a series of monotonic loading tests on monopiles in dry sand is conducted to assess the contributions of base shear force and base moment to monopile stability. Following this assessment of base components, parametric analyses are carried out to investigate the effect of pile diameter (D), the L/D ratio, load eccentricity (e), and sand relative density on monopile responses under cyclic and monotonic lateral loading. In this study, the SANISAND-MS material model is employed within 3D Finite Element (FE) software to model ratcheting during cyclic lateral loading. Finally, an investigation is conducted with the aim of constructing a 0D model to represent base shear force and base displacement responses under both monotonic and cyclic lateral loading.

In the years to come, the Netherlands will face a substantial challenge as over 1,500 kilometers of aging quay walls and sheet pile walls approach the end of their technical lifespan. Infrastructure managers anticipate that the necessary replacements will necessitate investments amounting to billions of euros. Moreover, this task carries a significant environmental footprint, notably in terms of CO2 emissions. The construction work required for these replacements will also result in disruptions and reduced accessibility, inconveniencing users. This study addresses two pivotal aspects. Firstly, it focuses on enhancing the design aspects of new structures and optimizing costs, with a specific focus exploring how these enhancements can ease the financial challenges faced by infrastructure managers. Secondly, it investigates the safety of existing structures and explores ways to maximize their loadbearing capacity while maintaining safety standards. The expected outcomes of this study promise improved design aspects, cost-efficiency, and enhanced safety measures. Quay walls can fail due to various mechanisms. This research investigates three primary causes: yielding of soil, yielding of quay wall and anchor yielding. Quay walls illustrate the complexities of soil-structure interaction. To address this, models were developed in both Plaxis and D-Sheet Piling. D-Sheet Piling was the preferred choice due to its computational speed. The reliability analysis was conducted with Probabilistic Toolkit. Considering the calculation methods, First Order Reliability Method (FORM) was employed, emphasizing in efficient computational results in contrast to the Monte-Carlo approach. In the first aspect, the partial factors were recalculated and compared them with the existing EC partial factor approach. To optimize the current design methodology, the retaining height of the structure was adjusted based on its reliability index. Additionally, the maximum anchor force required was re-evaluated for the structure. This procedure has been conducted for two scenarios, considering and not considering model uncertainty. Furthermore, an analysis was conducted to understand how altering the retaining height can lead to reduced steel usage, subsequently impacting costs and CO2 emissions. In the second aspect, it was pursued to enhance the structure’s performance by introducing a factor "n" across four distinct scenarios: 1. Simultaneously increasing all loads. 2. Increasing the surcharge loads on the terrain. 3. Increasing the bollard load. 4. Raising the final excavation level in front of the quay wall. While this study aligns with the extensive body of research in the field of civil engineering, It seeks to offer a new and sustainable approach on understanding quay wall design, focusing specifically on the designers’ viewpoint. Through the exploration of innovative design frameworks and approaches, this research seeks to make a valuable contribution to the long-term sustainability of quay wall structures. It aims to redefine our approach to accessibility and safety in these crucial structures. The comprehensive investigations conducted throughout this study provide an enhanced comprehension of quay wall design, reliability, and the optimization of performance.

The rapid growth of Floating Offshore Wind (FOW) has spurred intensive research across various aspects of the floating system. A standard practice in mooring system design within the industry is that anchors remain fixed on the seabed. In contrast, plate-type anchors exhibit mobility under loading, a crucial factor considering the thousands of loading cycles experienced by FOW turbines during operation. Understanding the strain accumulation mechanism during cyclic loading has substantial implications for design. This thesis delves into the behavior of Drag Embedded Anchors (DEAs) subjected to static monotonic and cyclic loading, utilizing 3-dimensional Finite Element simulations. The installation trajectory of DEAs is initially defined through established analytical methodologies. Subsequently, the movement of the anchor and soil response under monotonic and cyclic loads is elucidated. Analytical expressions for monotonic force-displacement curves are examined, identifying optimal models and offering relevant parameter values for different anchor trajectory points. Under cyclic loading, the influence of average load and cyclic load amplitude is studied, along with exploring the feasibility of applying an existing 1-dimensional model for predicting anchor response.