Ultraviolet corona detection sensor study

The feasibility of detecting electrical corona discharge phenomena in a space simulation chamber via emission of ultraviolet light was evaluated. A corona simulator, with a hemispherically capped point to plane electrode geometry, was used to generate corona glows over a wide range of pressure, voltage, current, electrode gap length and electrode point radius. Several ultraviolet detectors, including a copper cathode gas discharge tube and a UV enhanced silicon photodiode detector, were evaluated in the course of the spectral intensity measurements. The performance of both silicon target vidicons and silicon intensified target vidicons was evaluated analytically using the data generated by the spectroradiometer scans and the performance data supplied by the manufacturers

Addressing the complexity of sustainability-driven structural design: Computational design, optimization, and decision making

Being one of the sectors with the largest environmental burden and high socio-economic impacts sets high requirements on the construction industry. At the same time, this provides the sector with great opportunities to contribute to the globally pursued sustainability transition. To cope with the increasing need for infrastructure and, at the same time, limit their sustainability impacts, changes and innovation in the construction sector are required. The greatest possibility to limit the sustainability impact of construction works is at the early design phase of construction projects, as many of the choices influencing sustainability are made at that point. Traditionally, an early choice of a preferred design is often made based on limited knowledge and past experience, considering only a handful of options. This preferred design is then taken on to the successive stages in the stepwise design process, leading to suboptimization.Alternatively, many different design choices could be considered and evaluated in a more holistic approach in order to find the most sustainable design for a particular application. However, finding design solutions that offer the best sustainability performance and fulfil all structural, performance and buildability requirements, require methods that allow considering different design options, analysing them, and assessing their sustainability. The aim of this thesis is to explore and develop methods enabling structural engineers to take sustainability objectives into account in the design of structures. Throughout this thesis, a number of methods have been explored to take sustainability aspects into account in the structural design process. As a first step, highly parameterized computer codes for sustainability-driven design have been developed. These codes interoperate with FE analysis software to automatically model and analyse design concepts over the whole design space and verify compliance with structural design standards. The codes were complemented with a harmonized method for life cycle sustainability performance assessment, in line with the state-of-the-art standards. Here, sustainability criteria were defined covering environmental, social, economic, buildability and structural performance for multi-criteria assessment of design concepts. To identify the most sustainable designs within the set, multi-objective optimization algorithms were used. Algorithms that address the high expense of constraint function evaluations of structural design problems were developed and integrated in the parameterized computer codes for sustainability-driven design. To ensure the applicability and validity of these methods, case studies based on real-world projects and common structural engineering problems were used in this thesis. Case studies for bridges and wind turbine foundations as well as a benchmark case of a reinforced concrete beam were investigated.The case studies highlight the potential of the methods explored to support the design of more sustainable structures, as well as the applicability of the methods in structural engineering practice. It is concluded that it is possible and beneficial to combine computational design, life cycle sustainability assessment, and multi-objective design optimization as a basis for decision making in the design phase of civil engineering projects. A wide adoption of such a sustainability-driven design optimization approach in structural engineering practice can directly improve the sustainability of the construction sector

Two-scale modelling of reinforced concrete deep beams: Choice of unit cell and comparison with single-scale modelling

Two-scale and single-scale models are used to analyse the response of reinforced concrete deep beams with different reinforcement layouts. To this end, a novel approach of modelling non-uniformly reinforced structures in a multiscale manner is developed. Parameterised generation of suitable unit cells is described, and the subdivision of problem domain into regions with different substructures is presented. Three different reinforced concrete deep beams with available experimental data are analysed. Mid-span deflections are slightly underestimated by both models, while the maximum load is captured reasonably well

A practical finite element modeling strategy to capture cracking and crushing behavior of reinforced concrete structures

Nonlinear finite element (FE) analysis of reinforced concrete (RC) structures is characterized by numerous modeling options and input parameters. To accurately model the nonlinear RC behavior involving concrete cracking in tension and crushing in compression, practitioners make different choices regarding the critical modeling issues, e.g., defining the concrete constitutive relations, assigning the bond between the concrete and the steel reinforcement, and solving problems related to convergence difficulties and mesh sensitivities. Thus, it is imperative to review the common modeling choices critically and develop a robust modeling strategy with consistency, reliability, and comparability. This paper proposes a modeling strategy and practical recommendations for the nonlinear FE analysis of RC structures based on parametric studies of critical modeling choices. The proposed modeling strategy aims at providing reliable predictions of flexural responses of RC members with a focus on concrete cracking behavior and crushing failure, which serve as the foundation for more complex modeling cases, e.g., RC beams bonded with fiber reinforced polymer (FRP) laminates. Additionally, herein, the implementation procedure for the proposed modeling strategy is comprehensively described with a focus on the critical modeling issues for RC structures. The proposed strategy is demonstrated through FE analyses of RC beams tested in four-point bending—one RC beam as reference and one beam externally bonded with a carbon-FRP (CFRP) laminate in its soffit. The simulated results agree well with experimental measurements regarding load-deformation relationship, cracking, flexural failure due to concrete crushing, and CFRP debonding initiated by intermediate cracks. The modeling strategy and recommendations presented herein are applicable to the nonlinear FE analysis of RC structures in general

Sustainability-driven structural design using artificial intelligence

The construction industry is responsible for a large share of the global environmental impact. The need for addressing sustainability and increased competition calls for the development of innovative design methods that include sustainability in a transparent way. The aim of this work is to propose a framework to use machine learning and artificial intelligence (AI) for structural design optimization based on sustainability and buildability criteria. AI opens up new possibilities to optimize and assess structures early in the planning and design stages. In that way, it is possible to decrease the negative and enhance the positive environmental, economic and social impacts and create a more time‐ and cost‐effective design process. The work is meant to serve as a first step toward the development of AI‐based methods in the construction industry, which can bring digitalization in the construction industry to a new level and create new services and business models

Recent and future trends of onshore wind turbine foundations

The decarbonization of the economy and the growing need for electricity are two trends that call for greener energy sources. Wind is a growing renewable energy source, which is expected to become the first source of power in the European Union in the next decade. In particular, onshore wind energy is expected to double by then. Fundamental structural components of wind turbines are their foundations, which are large structures associated with important material consumption and many construction challenges. The dimensions of these foundations are continuously increasing as turbines with taller towers and larger rotor diameters are being built. Designing cost- and material-efficient foundations is crucial to reduce the economic and environmental impact of wind energy. An important factor to successfully address these evolving requirements in the planning and design process is to build on the experience from previous projects. The aim of this work is to investigate the evolution of onshore wind turbines and its consequences on the design and climate impact of gravity foundations by analysing data from Swedish wind farms set in operation between 2013 and 2022. The evolution of turbine size, and foundation dimensions, reinforcement layout, material types and quantities, and embodied carbon are analysed in this paper

A review of online sources of open-access life cycle assessment data for the construction sector

The importance of life cycle sustainability in the construction sector is increasing in the light of rising awareness on sustainability issues in society. A means to identify more sustainable options is to assess and compare their sustainability performance. The standards ISO 21931-2 and EN 15643-1 to 5 establish the framework and requirements for sustainability assessment of buildings and civil engineering works. The standards require life cycle assessment (LCA) to be the basis for the environmental part of the sustainability assessment. LCA is a powerful evidence-based method but it requires extensive data. Access to free, easily available and preferably machine-readable LCA data is essential to increase the use of LCA in the construction sector and to make competition fair for all tenderers. This paper aims to compile existing online sources for open-access LCA data of interest for the construction sector. The purpose is to provide a reference document that facilitates the use of LCA in construction. An in-depth search of publications and internet resources was performed, focusing on European sources of Environmental Product Declarations (EPD) and process-based LCA datasets. A comprehensive overview of the European data sources available online and relevant to the construction sector is presented. This research work reveals the existence of numerous sources, often difficult and time-consuming to find. The overview in the paper facilitates finding online data needed for LCA, in many cases in a machine-readable format. This can contribute to increasing the use of LCA in the construction sector, which is important when developing buildings or civil engineering works that are more sustainable over their whole life cycle. A greater use and better integration of LCA in the design process contributes to evidence-based life cycle sustainability of our built environment

Potential improvements in the life-cycle performance of support structures for onshore wind turbines – an interview study in Sweden

Wind energy is one of the fastest growing renewable energy sources thanks to its cost-effectivity and sustainability. This paper investigates how construction and maintenance of support structures for onshore wind turbines can be improved. Interviews were performed to identify potential areas for improvement in design, construction, operation, maintenance, and end-of-life. Defects due to poor detailing in design and construction have been recurring and may have important consequences. More structured data collection during the construction stages and more robust inspection protocols can help to ensure adequate life-cycle performance of the support structures. Possibilities to reuse and recycle foundations by the end of the turbine’s operational lifetime, which remain unexploited and unresearched, are also discussed

Concrete Support Structures for Offshore Wind Turbines: Current Status, Challenges, and Future Trends

Today’s offshore wind turbine support structures market is largely dominated by steel structures, since steel monopiles account for the vast majority of installations in the last decade and new types of multi-leg steel structures have been developed in recent years. However, as wind turbines become bigger, and potential sites for offshore wind farms are located in ever deeper waters and ever further from the shore, the conditions for the design, transport, and installation of support structures are changing. In light of these facts, this paper identifies and categorizes the challenges and future trends related to the use of concrete for support structures of future offshore wind projects. To do so, recent advances and technologies still under development for both bottom-fixed and floating concrete support structures have been reviewed. It was found that these new developments meet the challenges associated with the use of concrete support structures, as they will allow the production costs to be lowered and transport and installation to be facilitated. New technologies for concrete support structures used at medium and great water depths are also being developed and are expected to become more common in future offshore wind installations. Therefore, the new developments identified in this paper show the likelihood of an increase in the use of concrete support structures in future offshore wind farms. These developments also indicate that the complexity of future support structures will increase due to the development of hybrid structures combining steel and concrete. These evolutions call for new knowledge and technical know-how in order to allow reliable structures to be built and risk-free offshore installation to be executed