A Winkler Model for the Seismic Analysis of Monopile Foundations - An Exploratory Study on the Modelling of Soil-Structure Interaction during Earthquakes

The growing interest in the development of offshore wind farms in seismic active areas demands a better insight into the requirements earthquakes impose on the design of wind turbine foundations. The complexity of the Soil-Structure Interaction (SSI) during an earthquake results in large uncertainties in the design process of a monopile foundation. The design codes do not provide a structured framework on how to deal with these uncertainties. On top of this, the design codes are for (offshore) structures in general and do not specify for the large diameter tubulars which are characteristic for the offshore wind energy sector. This thesis presents the investigation into a 1D seismic Winkler foundation that is able to represent the SSI during an earthquake. The model, a Beam on Nonlinear Winkler Foundation (BNWF) coupled with a nonlinear ground response model, is a fast method to determine the structural response for the stochastic seismic and offshore wind load cases. Semi-empirical formulations are used to implement cyclic loading effects into the model. A 3D finite element model of an embedded monopile is developed in parallel with the seismic Winkler foundation for tuning and validation purposes. The resistance of the soil to lateral pile deflections is further investigated to address the uncertainty in the SSI. A 2D horizontal cross-section of the embedded monopile is considered to determine the linear dynamic properties (impedance) of the soil, and a plane strain finite element model is developed to investigate the effect of nonlinear soil behaviour. A combined frequency-time domain method is used as extension for the Winkler foundation to incorporate the obtained frequency-dependent foundation properties into a time-domain analysis. It was found that none of the 2D analyses resulted in SSI representation that could be directly applied in a time-domain analysis. Moreover, the large D/L ratio of a monopile activates a global soil response, making an uncoupled 2D analysis inaccurate for the frequency range of interest

Gendered geography of energy consumption in the Netherlands

Household energy consumption (HEC) significantly impacts global greenhouse gas emissions and can trigger fuel and energy poverty among vulnerable households. Due to environmental policies and geopolitical turmoil limiting the energy supply, HEC needs to be curbed. This urges the identification of most energy-dependent consumers at different locations and the particular life circumstances that trigger such a high level of dependency. A gender perspective can provide insights into the life circumstances of households. Applying a geographically weighted regression model on HEC, including explanatory parameters on gender composition, age, ethnicity, income, home ownership, microclimate, urban morphology and land cover, the results show significant variations in HEC of gender groups in 87% of Dutch residential zones. Women with an immigration background (20%), children younger than 14 years old -presumably single mothers (14%), old buildings in hot climates (10%), or high income (9%) are the most energy-dependent gender groups in a significant portion of residential zones. So are the men in large-size households (18%) and older-than-65-years men in rural areas (8%). The study offers discussions on the results and a series of policy recommendations.</p

Developing an empirically based agent-based model to support local transitions

Sustainable technologies (e.g., hydrogen) have great potential to contribute to achieving sustainability goals. Nevertheless, sustainable technologies are often not readily adopted. Many transitions are currently being explored with agent based models, allowing stakeholders to explore different scenarios to advance local transformations. However, in most cases, agent-based models, mainly built by engineers, still assume the rational actor. Actual decision-making behaviour is, however, hardly rational, lowering model reliability. A theory-based framework describing technology adoption behaviour is needed to represent local systems and actor behaviour in agent-based models accurately. Integrating psychological factors regarding adopting sustainable technologies in agent-based models helps address the complexity of the interrelated technical and social phenomena and the heterogeneous social actors. In the presented research, we, based on the results of a quantitative literature review and an initial study, build a theoretical framework that includes influential psychological factors of technology adoption and distinguishes between individuals, households and organisations. With this distinction, we explore whether similar or different factors are relevant for the various stakeholders. Through our research, we seek to advance the application of behavioural insights in energy system modelling and provide a better understanding of agent-based model potentials, which allow the exploration of outcomes of different scenarios and thereby contribute to successful decision making and intervention design. We discuss implications for transition research and reflect on hurdles and solutions regarding the integration of psychological insights into an agent-based model

Insights from early COVID-19 responses about promoting sustainable action

Early in 2020, the coronavirus disease (COVID-19) spread around the world, disrupting lives and societies. In some places, public responses to COVID-19 were remarkably rapid and forceful, particularly in comparison to global environmental crises. What can we learn from these responses to promote mitigation of global environmental crises? We hypothesize that supportive public responses to COVID-19 were partly promoted by strong personal norms: feeling morally compelled and responsible to act. We discuss what aspects of COVID-19 may have engaged antecedents of personal norms, and how these dynamics could be enhanced in global environmental crises to promote their mitigation