In light of the growing impact of the production of construction materials, the imperative for sustainable design is considered a necessity. Newly developed design strategies and design for deconstruction offer great potential and perspective to achieve the sustainability goals that are set in the European Commission’s ”Green Deal” towards net zero greenhouse gas emissions by 2050. Demountable and reusable steel-concrete composite structures allow for the opportunity to contribute to these sustainability goals. Demountability in steel-concrete composites is generally offered through the application of demountable shear connectors. Multiple studies have investigated the performance of various shear bolt connectors. Shear connectors generally showed inferior structural performance compared to that of conventional welded shear studs. Throughout the years, there has been significant advancement in the practice of reusing structural steel elements in the construction industry. Conversely, the exploration of re-purposing concrete from existing structures for structural use has not been extensively investigated. In response to this growing emphasis, reusing concrete slabs appears to be a sophisticated and innovative strategy. To enable deconstruction and reuse practices in such steel-concrete composite structures, bolted connections are considered a key characteristic in establishing the incentive. To maintain the strength characteristics of conventional shear studs in composite beams, demountability of a steel-concrete floor system can be offered through a concrete deck-to-deck connection between the composite beam and concrete slab. However, there exists a scarcity of solutions for connecting concrete slabs through demountable shear connectors, limiting comprehension on the structural behaviour and performance on true floor level. This thesis presents two numerical finite element models, the first of which is a simplified deck-to-deck connection subjected to tensile loading conditions to determine basic characteristics and behaviour. The knowledge gained from the first model is implemented in the secondary finite element model, comprising a demountable floor system which is compared with a traditional conventional floor system. A subsequent parametric study focused on altering bolt spacing, edge distance and span width to allow for a broader perspective on the performance of the proposed demountable floor system. The numerical results showed that the demountable beam model is able to replicate the behaviour of the conventional beam system, where local plastic deformation of the connecting elements was hardly observed. The numerical results demonstrated that the serviceability loading capacity of the demountable floor system was 3% lower, and the discrepancy in ultimate loading resistance was magnified further. The parametric study indicated that modifications to the distance of the bolts from the edge of the slab and bolt spacing did not show a shift in the ultimate loading resistance and ductility. Increasing the span width of the demountable slab model indicated a gradual reduction of approximately 24% in load carrying capacity, where the ductility was not affected. While future research into the reliability and validity of the numerical results is considered necessary, the proposed solution for connecting concrete slabs has shown significant potential in terms of replicating the structural behaviour of conventional floor systems, without compromising the structural integrity. The solution demonstrated the ability to develop a demountable and reusable floor system, thus contributing to an enhanced sustainable and circular built environment.

Studies have shown that urban areas globally grapple with high energy and material demands for new constructions while existing buildings often remain underutilized. This issue can be mitigated by designing buildings to be adaptable to future changes. Despite its clear advantages, adaptability as a circular strategy is notably absent from widely used circularity assessments like the Building Circularity Index (BCI) Tool. This research aims to develop a more advanced and holistic tool that integrates the Design for Adaptability as an Adaptability Index (AI) within the BCI assessment model. This innovative tool, known as the A-BCI Tool, incentivizes structures where designing for adaptability is crucial, even if other key performance indicators (demountability and smart material selection) are less emphasized. With this enhancement, the beneficial impact of adaptability in achieving circularity will be quantified, introducing a correction factor or "bonus" to the current method’s score, enabling a more thorough and accurate evaluation process. This research tackles the knowledge gap and problem through a three-stage methodology. The first stage involves a comprehensive theoretical study based on an extensive literature review to gather secondary data on the Circular Economy and circularity and adaptability assessment methods. The second stage uses insights from stage one to enhance the existing BCI, leading to the development of the A-BCI tool. The third stage collects vital primary data through an extensive design study centered on the C-pier project at Schiphol Airport. This study explores eight innovative design alternatives, of which one is conventional, and the rest are adaptable designs, carried out in two phases: an initial design and a compliance review following structural changes. The financial and environmental performance of these designs is evaluated using Life Cycle Assessment (LCA) and cost assessment, validating the A-BCI tool and demonstrating its strong alignment with circular design principles. The research seamlessly integrates an Adaptability Index that underscores the positive impact of designing for adaptability within the existing BCI assessment model. The results demonstrate that this innovative tool provides a bonus for adaptable designs, with the bonus varying based on the significance of incorporating adaptability and the building’s utility. Highly significant adaptability requires a higher level of adaptable design strategies implementation to achieve the same level of circularity as designs with lower significance of adaptability. The multi-objective study demonstrates that designing for adaptability is economically and environmentally advantageous when the likelihood of future changes is high. Adaptable designs, although initially requiring higher investments in both CO2e and costs, show significant reductions when changes occur, compared to the conventional design, as they demand no technical interventions. This data emphasizes that planning for structural changes can lead to substantial reductions in emissions and costs compared to slight initial increases. The remarkable reduction in emissions highlights the alignment of adaptable designs with Circular Economy principles. Keywords: Adaptability, Building Circularity Index (BCI), key performance indicators, Circular Economy, Functional useful life, Adaptable design strategies, Building Utility, Adaptability significance

The construction industry significantly contributes to global greenhouse gas emissions, underscoringthe need for sustainable building practices. Floor systems, which comprise 68% [1] of building materials,are critical in determining environmental performance. Despite their importance, comprehensive Multi-Life Cycle Assessment (MLCA) of floor systems in the Dutch context are scarce. Given the importanceof these considerations, this study addresses the following research question:

”What are the structural and sustainability performance characteristics of different floorsystems used in buildings in the Netherlands when evaluated using a Multi-Life CycleAssessment (MLCA)?”

To address this main research question, a systematic MLCA framework was developed, integratingstructural and environmental performance evaluations. This framework was applied to evaluate threecommonly used floor systems: cast-in-situ concrete slabs, hollow core slabs, and deep deck compos-ite slabs. The methodology included parametrizing the design of these floor systems using Excel andGrasshopper, designing slabs for comparable load-bearing capacities, assessing environmental im-pacts using the Nationale Milieu Database (NMD) and GPR Materiaal, and accounting for degradationfactors such as reinforcement corrosion and concrete strength reduction.By applying the outlined methodology, the key findings of this study were identified and are explainedin this report, including:

• Adopting a circular building economy approach significantly reduces environmental impacts. Forexample, the prefabricated hollow core slab and deep deck composite slab reduced the Environ-mental Cost Indicator (ECI) by 78.06% and 87.10%, respectively, compared to the cast-in-situconcrete slab. These results highlight the advantages of material reuse and improved efficiency.

• The deep deck composite slab consistently achieved the lowest environmental impacts acrosscategories, requiring no additional interventions over three life cycles. In comparison, the hol-low core slab performed well but incurred higher impacts due to the environmental burden ofstrengthening measures.

• When evaluating performance across multiple life cycles, it is essential to consider long-termfactors such as material degradation. This study found that reinforcement corrosion in the hollowcore slab necessitated interventions, demonstrating the impact of degradation mechanisms onstructural integrity and environmental outcomes.

• While reuse feasibility shows promise, its scalability relies on robust inventory management, stan-dardized material passports, and design-for-disassembly practices.

These steps are critical toovercoming current barriers and realizing widespread adoption of circular construction principles.This research provides a robust MLCA framework and highlights the benefits of circular constructionprinciples, offering valuable insights for sustainable floor system design and reuse strategies in theconstruction industry.

As sustainability becomes increasingly essential in construction practices, the incorporation of concepts such as circularity and material efficiency are more required than ever. The present research investigates how these concepts can be effectively applied to Steel-Cross Laminated Timber (CLT) composite floor systems in order to promote more sustainable construction methods, specifically reducing carbon footprint. The findings are intended to benefit practicing engineers and designers, as well as lay the groundwork for future academic research and innovation in sustainable construction.
WSP developed the baseline steel-CLT composite floor system, which bonds composite materials using shear studs and grout . However, this design restricts disassembly at the end of its lifecycle, posing challenges that limit its potential for reuse in subsequent applications. In addition to that limitation, while the system was validated via laboratory push-out tests, using a standardized CLT configuration across varying spans resulted in material inefficiencies, highlighting the need for additional optimization.
To address the aforementioned drawbacks, this study develops an "optimized design" for a Steel-CLT composite floor system that enhances both circularity and material efficiency. The optimized system, which includes demountable shear connectors, allows for easy disassembly and reuse, extending the life of its components. The study also investigates the optimal CLT configuration and lay-up to maximize material efficiency, demonstrating that adapting the CLT design to the unique characteristics of each composite floor structure (e.g., dimensions, spans, and load requirements) is crucial for optimal performance.
Finally, the baseline- and optimized designs were compared in terms of environmental impact, focusing on a Life Cycle Assessment (LCA) of embodied carbon. This evaluation highlights the environmental benefits of the optimized design, offering valuable insights into how circularity and material efficiency can significantly reduce the carbon footprint in constructions.
Overall, this research transforms the baseline steel-CLT composite floor system from a linear to a circular design, thereby highlighting the significant advantages of circular design principles within the construction industry. By advocating for the broader adoption of circular approaches, this research underscores the potential for creating a more environmentally sustainable future in building practices. In addition to achieving circularity, the study focuses on optimizing the CLT design to enhance material efficiency within the floor system. It also identifies key factors to consider when designing CLT for composite applications, ensuring that the material is used most effectively within this innovative context.
The present paper begins with a comprehensive literature review, which provides the foundational background necessary for the research. This is followed by a detailed explanation of the design rules employed in the structural analysis. Next, the application of demountable shear connectors is discussed, highlighting their role and implications for the steel-CLT composite system. A subsequent chapter delves into the design of CLT panels, emphasizing their dual function within composite floor systems. Both the baseline and optimized floor systems are then presented, with an outline of their structural characteristics and geometric configurations, followed by a rigorous structural analysis. The study proceeds with a comparative analysis, evaluating the structural and environmental performance of both designs. This analysis resulted in conclusions that highlight the substantial role of circular design principles and material efficiency in reducing the environmental impact of construction materials and systems, as well as the crucial role that structural designers can play in advancing the decarbonization of the built environment.

This thesis investigates the feasibility of using concrete-filled double skin steel tubes (CFDST) as an innovative design for wind turbine towers, addressing the need for lighter, stronger, and more sustainable structures in the wind energy sector. The research is motivated by the challenges faced by the industry, including the limitations of traditional tubular steel towers, the increasing size of wind turbines, and the demand for cost-effective and environmentally friendly solutions.

The primary objective of this study is to explore whether CFDSTs could reduce steel usage while maintaining or enhancing the structural integrity of wind turbine towers, particularly in resisting local buckling under axial loads. To achieve this, both experimental and numerical investigations were conducted. The experimental phase focused on analyzing the local buckling behavior of S355 steel skins, both in single and double skin configurations, filled with high-strength concrete (C60/67). A finite element model (FEM) was developed to simulate these experiments, validate the results, and provide insights into the performance of CFDSTs under axial loading conditions.

Key findings from the study indicate that the inclusion of concrete infill significantly alters the buckling mode of the steel skins, increasing the resistance, and enhancing the post-buckling capacity. This effect was particularly pronounced in sections with higher cross-section slenderness, suggesting that CFDSTs could allow for the use of thinner steel sections without compromising structural performance, provided that optimal cross-sectional dimensions are selected. The numerical models show comparable resistance to the experimental results, though further fine-tuning of the models is necessary to enhance accuracy and better align the outcomes.

The research concludes that CFDSTs offer a promising alternative for wind turbine tower design, with the potential to achieve significant steel savings. Furthermore, suggestions for future research are presented, focusing on optimizing material selection, investigating the long-term durability of CFDSTs, and enhancing the numerical model.

The characteristics of the joints play a considerable role in the stability of grid shells. Therefore, the connections are usually assumed to be rigid during the design phase. However, considering the semi-rigid behaviour of connections in the design could be beneficial. This leads to two major challenges. (1) The application of semi-rigid joints increases the indeterminacy of the structure. And (2) the current connection design strategy is not well-equipped for the integration of semi-rigid connections in the design. The following research questions is formulated: How can a semi-rigid approach to steel connection design and considering the semi-rigidity of the joints, be combined in a parametric design strategy for grid shells?

To answer this, three objectives have been formulated. Objective 1 focusses on the connection design, creating a design method for connection based on a pre-determined stiffness. Objective 2 focusses on the influence of joint stiffness on the structural behaviour of grid shells. Objective 3 is to design a grid shell, applying the results from objectives 1 and 2. Finally, the method is applied to a case study.

Results from objective 1 show that the load ratio can significantly influence the stiffness of connections. Also, design parameters, such as plate thickness and bolt spacing, can be adjusted to achieve different stiffness values. Combining these findings, a design space is generated to enable stiffness based connection design. Results from objective 2 show that the axial stiffness and the out-of-plane bending stiffness of the joints are relevant for the stability of the shell. Depending on the boundary conditions, shape and size of the shell, also in-plane stiffness parameters are relevant. For objective 3, a design workflow is proposed. A design space for the connections is combined with joint stiffness optimisation, resulting in the design of a grid shell with reversible connections. The application is checked with a case study of the C30 Shell. Complexities with increased size of the shell were managed by segmentation of the shell and clustering of the nodes. Resulting in a structure with 58% reversible joints.

The following conclusion is drawn: A semi-rigid approach to connection design and the inclusion of semi-rigidity of the joints in the structural design of a grid shell can be combined in the design of a grid shell. This can be achieved by defining a relation between the connection design and the joint stiffness design. This way, a design space can be created that links the connection design to pre-determined stiffness requirements and load ratios in the structural design. Which allows for efficient design iterations and eliminates guesswork in the design of both the connection and the joint stiffness distribution of the shell.

For effective application of this method it is important to be aware that the initial design largely determines the efficiency of the end result. The effectiveness of the stiffness optimisation, the segmentation of the shell, and the clustering of the joints all impact the result of the design significantly. Future research could be directed towards a better understanding of these aspects.

Selecting the optimal stability framework for high-rise steel buildings is a critical decision that impact both economic efficiency and sustainability. This decision is not easy since there are many stability frameworks to choose from, such as tube, concrete shear-wall, and outrigger system. Designers and clients aspire to compare multiple structural designs, considering both different frameworks and variations in geometry. Unfortunately, the current process of evaluating multiple designs is time-consuming and relies on the designer's experience and rules of thumb, rather than being driven by data. To address this challenge, predictive models can be used to estimate performance in terms of structural and environmental costs based on the given geometry and framework. However, traditional curve fitting methods often fall short in accurately predicting a complex relationship. In response, this study explores the potential of artificial neural networks to accelerate the decision-making process by predicting the most efficient framework during the early design phase while maintaining sufficient accuracy.

To determine this potential, two parametric models were developed using Rhinoceros software to represent buildings with braced framed tubes and outrigger systems. These models automatically optimised beam and column dimensions by FEM of Karamba, aiming to minimise the mass of these structural elements, across a range of building widths (15 to 60 meters) and heights (48 to 300 meters). The resulting data sets of both braced framed tube and outrigger system reflected the structural and environmental costs for the different designs. Separate neural networks were modelled for each framework. These networks were trained on the different data sets. By comparing predicted structural and environmental costs, the models assisted in the selection between braced framed tubes and outrigger systems.

The artificial neural networks accurately approximated structural and environmental costs for both stability frameworks. The Mean Absolute Percentage Error (MAPE) for the braced framed tube was 14%, while the most accurate alternative curve fit, a third-order polynomial, had a MAPE of 25%. For the outrigger system, the neural network achieved an even lower MAPE of 7%, where the most accurate alternative curve fit, also a third-order polynomial, had a significantly higher error with a MAPE of 31%. The neural networks outperformed traditional curve fitting methods. Additionally, the neural network generated instant results, taking only a second compared to the parametric model’s 5 to 30 minutes. However, achieving overall time efficiency with the neural models will require approximately three months when considering both setup time and output generation time. Optimal stability varied based on specific width and height combinations: when looking at environmental costs, the braced framed tube excelled for lower (50-80m) and higher heights (200-300m), while the outrigger system was more efficient for middle heights (80-200m). As the structure’s slenderness increased, the braced framed tube regained efficiency for the middle heights.

Impact of the stability framework is defined as the relative contribution of embodied carbon of the stability framework to the total embodied carbon of the structure (including superstructure and floors). The impact of the stability framework ranged from 25% to 57% for the braced framed tube and 33% to 66% for the outrigger system, with the impact increasing with the building's height...

The objective of the European Green Deal is to reduce net greenhouse gas emissions by at least 55% by 2030 and to achieve climate neutrality by 2050 [1]. Due to a growing global population and increased needs for travelling on the one hand, and progressive bans of short-haul flights by the governments on the other, the need for a more sustainable and fast means of transportation comes in high demand.

The Hyperloop transportation system has emerged as the fifth mode of transportation, offering an energy-efficient, fast alternative for freight and passenger transportation. However, to successfully establish the Hyperloop network, an extensive tube infrastructure would need to be constructed with requirements of being safe, sustainable, and cost-effective. At the time of this project, various tube designs and materials have already been examined and evaluated; given its preliminary stage of development, new design ideas are rapidly emerging. Engineers are faced with two fundamental challenges: firstly, defining safety limits, and secondly, establishing the balance between the safety, environmental footprint, and operational efficiency of hyperloop infrastructure.

The Hyperloop Skeleton tube design is the latest addition to the integral designs that holds great potential in terms of weight efficiency. The aim of this research is to determine the applicability and efficiency of the newly proposed tube design and to evaluate structural performance to imposed loads.
For the design evaluation, the study uses a numerical approach. Skeleton tube design is initially disassembled into individual components, which are analysed separately to identify potential weaknesses of the design as well as to predict their behaviour within the assembly. After that, the study conducts the analysis of the assembly. The initial design lacked rail support design; thus, a design is proposed and implemented in the model for the global analysis. Within the assembly, the research identifies critical sections and design weaknesses. In accordance with this, it proposes and analyses a new ring-to-stringer connection design. Additionally, a comparison study has been conducted with the conventional (plain) tube design, currently used at the European Hyperloop Centre (EHC) [2].

Based on numerical results, the skeleton tube design is conditionally satisfactory in terms of ultimate and serviceability limit states. The design can resist the main load case – vacuum pressure. Nevertheless, the slender components and thin plates make the tube susceptible to plate rupture or penetration if exposed to environmental actions; thus, making the hyperloop system vulnerable to accidental and impact loads. Moreover, the elastic strength capacity of rings, which are primarily in compression and are therefore critical components, is nearly reached. An initiation of local plastic response is observed, yet due to integral design, the stresses distribute among components; thus, it does not progress into a fully plastic response. Based on these findings and considering that dynamic loads are yet to be assessed, it can be projected that a strength capacity will be exceeded in further research.

The proposed steel bracket design for ring-to-stringer connection provides an alternative to welded connections. It improves stress concentrations within the ring, and considering that it is a bolted connection, further contributes to the ease of assembly, maintenance and the demountability aspect. However, the requirement for 288 such connections per 16-meter-long tube section might significantly increase the total cost of skeleton tube design.

Based on the comparison study, it is proven that the conventional tube design performs better in terms of structural performance under the considered loading conditions. However, in a controlled environment with the absence of external actions, the skeleton tube design could efficiently operate. In this case, a material efficiency of 28% can be achieved if the structure supports the rails and the pod, and up to 37.8% if the tube is solely used for vacuum pressure retention.

Emerging technologies, currently in the process of development and yet to demonstrate their contribution to a more sustainable future significantly depend on the performance and success of their initial prototypes and real-world applications. Skeleton design offers a cutting-edge design, which is on the safety – sustainability spectrum drastically leaning to the latter. A secondary protective structure is required for consideration of the skeleton design in the hyperloop application. The design can nonetheless be viable for other applications, which operate in a safe and controlled environment, with the absence of external loads. This research lays a foundation for any further research on the skeleton tube design.

To align with the objective of the European Green Deal [46] policy of achieving net-zero greenhouse gas emissions by 2050, the construction sector must transition to a circular built environment. Most of the waste in the Netherlands is related to construction and demolition waste, with the industry accounting for approximately 35% of CO₂ emissions [89]. The goal of the circular built environment is to minimise waste by reducing, reusing, recycling, and recovering materials throughout the life cycle of a product [66]. Therefore, making an impact in the construction industry can lead to a significant reduction in CO₂ emissions and contribute to the achievement of the European Green Deal [46].

This research contributes to the "reuse" component of the aforementioned circular built environment goals. Specifically, the focus is on developing a reusable connection between hollow core slabs and steel frames by implementing increased execution tolerances. Increased tolerances are necessary to allow reuse, as alignment-related problems often occur. The research consists of several parts: the design process, structural verification, experimental research on demountability, and environmental impact assessment. The design process comprises a tolerance analysis supported by a Monte Carlo simulation, variant studies, and a comprehensive qualitative trade-off analysis. After the best scoring alternative is determined, the verification part assesses the structural behaviour of the connection in terms of strength and stiffness. This is done using a combination of analytical and numerical calculations. The purpose of the experimental research is to investigate the demountability potential of the reusable connection. The final part of the research investigates the impact of the reusable connection compared to conventional connections for different lifecycle scenarios.

The research demonstrated that incorporating additional tolerances in the connection between the hollow core slab and steel frame is crucial to achieve a reusable construction. Three connection alternatives were generated that can incorporate these tolerances based on a literature review and meetings with experts in the field of building construction. The alternatives were weighted on tolerance inclusion, ease of installation, demountability potential, and costs. The best option was identified as a connection consisting of a square hollow section and a bolted shear stud encased in mortar. This alternative outperformed competitors in terms of tolerances, installation, and costs. However, the demountability potential was identified as a critical part of the connection and, therefore, was further investigated experimentally. The experiments showed an increased demountability potential in situations that include pre-treatment. Vaseline-treated specimens showed no signs of chemical bonding and better lubrication compared to oil-treated specimens, resulting in the lowest resistance and, therefore, the best demountability. The last step of the research investigated the environmental impact of the reusable connection and compared it with the conventional construction technique. Results showed that a marginal addition of 1.3% to the initial environmental impact of the superstructure results in a significant reduction over the full lifespan of the structural elements. This was attributed to the reusability of the connection and the ability to reuse structural elements in another building in a second life cycle.

From the results, it is concluded that a reusable and structurally feasible connection between hollow core slabs and integrated steel beams can be created with a small additional investment upfront, resulting in a substantially reduced environmental impact. The purpose of this study is to provide guidance and persuade decision makers, such as project developers, building owners, and government organisations, to consider implementing reusable construction methods in their real estate projects. By doing so, they can contribute to the objective of the European Green Deal [46] policies and the goal of achieving net-zero greenhouse gas emissions by 2050.

This research explores the integration of machine learning to support sustainable design in data centres by incorporating reclaimed steel elements into automated structural design workflows. The study begins with a literature review addressing the impact of steel reuse, the availability of reclaimed sections, strategies for automated, stock-constrained design and the applications of machine learning within the structural design process. Three reclaimed steel element databases are considered and three cross-section selection methods are evaluated and validated, establishing the optimal basis for a machine learning application within the design process. The cross-section selection method is used to gather data on generated
design configurations for braced structures and moment-tight frame structures. Per element, the element location, length, type and profile are recorded for four separate design choice configurations. The data collected acts as a basis for a machine learning application for cross-section prediction.

Central to this research is the development and training of a Recurrent Neural Network (RNN) for sequential classification, aimed at predicting cross-sections based on design parameters. Four models were trained, each tailored to different combinations of design choices and reclaimed steel profiles. The second step in this workflow is the reclaimed steel integration which is an optimization model that integrates the RNN’s predictions to refine grid-spaces in response to available reclaimed steel databases. Finally, the models and the resulting designs were validated to assess performance and applicability.

The trained RNN models reached a test accuracy ranging between 82% to 93% and the optimized steel integration resulted in design configurations which are slightly over-dimensioned, but all have an overall steel utilisation between 0.2 and 0.8. These findings underscore the feasibility of applying machine learning within the structural design domain to promote reclaimed steel integration at the early stages of the design process. A practical workflow is established that creates the possibility for adaptation to other building design typologies, making reuse-oriented design more accessible and efficient.

In many structures, space frames are used as the main load-bearing system. Especially for structures that are designed to have large spans or free-form in design. The reason is that space frames have a very high structural performance. Besides, they are also material and cost-efficient. Challenges for space frames are that they often require complex designs and the elements used are unique. Joint design is also difficult for these irregular constructions. This thesis explores the possibility of structurally optimising space frame design by using topologically reconfigurable modules, taking into account circularity. The focus lies on planar, square on square double-layered grids. The research question to be answered is the following:

”What kind of topologically reconfigurable modular system enables the generation of efficient space frames that are suitable for circular construction?”

The first design step is the initial topological design of steel cubic modules. This forms the basis of the catalog. With Grasshopper and Karamba3D (parametric FEM software) single-span trusses are then designed to determine the required cross-sections of the elements. The beams and columns are given SHS cross-sections for different spans and the diagonals are given various CHS cross-sections. With the software IDEA StatiCa various intra- and intermodular joints are designed and the rotational and translational stifffnesses analysed for
the different modules.

The former Grasshopper model is extended with a GA called Galapagos which is a plugin just like Karamba3D. This is used for topological optimisation of a given space frame structure. A GA is an evolutionary algorithm that is inspired by the natural selection process that Darwin described. The fittest genes in every population of solutions are used in further iterations. This process continues until the total number of iterations is reached or a threshold is met [1]. The algorithm reconfigures the different modules and minimises the weight of the structure
while staying within the constraints of maximum deflection, maximum material utilisation, and avoiding buckling. Logarithmic barrier functions are used for these constraints and together with the minimisation of the weight a fitness function is made. The lower the value of the fitness function, the better the solution is. The joint stiffness for each of the joint types for different |M|/N ratios is known. In the model, an initial stiffness is assigned to the joints. Then, depending on the moments and forces found in the joints, a new stiffness is assigned corresponding with the relations found in the stiffness analysis. The resulting stiffness loop describes non-linear behavior.

A verification is performed for the joints in the model. It was observed that the model was sensitive to small differences in stiffness within the joints of a standard truss. There were torsional moments observed that also resulted in an uneven distribution of the forces in the truss. To overcome this problem the stiffness of all joint groups is changed at once instead of individually. This resulted in more logical results where the support reactions were symmetric again. The model is then verified with a simple structure to see if the performance of the algorithm matches the expectations. A simple 2 x 2 grid is constructed and the model is tested. The simulation could not be performed until 50 generations because the stiffness loop led to a large accumulation of memory on the computer. It was concluded that the loop was not needed and therefore omitted because mostly only 1 iteration was needed. The model then was tested again on the small-scale model and compared to a couple of intuitively good-performing structures. This resulted in the conclusion that the model performed well and converged towards a final solution. However, since there were 106 different configurations possible the best solution was not reached in the end. It is recommended to always perform a couple of simulations to get a good solution.

After verification, the model is validated with a different FEM software called RFEM 5. Single grasshopper modules are structurally analysed in Karamba3D and imported in RFEM as well. The results show similarity in the order of magnitude of the stresses and the way the stresses are distributed. Furthermore, the reaction forces are also similar. The percentual differences between both models for the minimum and maximum stress are all below 5% except for module type 4. The absolute differences are in the order of 0.01 kN/cm2. Besides, a small frame is analysed in Karamba3D and RFEM as well to check if the deflection is in the right order of magnitude which is also the case. The percentual differences for the maximum and minimum stress are 6.40% and 7.85%, and for the deflection 12.15% and thus slightly larger than for the modules. However, for the deflection, the difference is just 1.5 mm for a structure with a span of 16 m which is a small difference. The Karamba3D model is valid and also conservative because the observed stresses are larger than in the RFEM model for the same
load condition.

A literature case study is performed on a space frame located in India. It is compared to the topologically reconfigurable model to check if the order of magnitude of the deflections and stresses is normal for this type of truss. First, a standard Pratt truss is modelled in Grasshopper to see if it is possible to design a feasible structure. This structure stayed within the limits of the constraints for the applied load which meant it worked. The case study truss is of a different size than the small structure used in the verification. With the catalog of 6 different modules and 66 possible locations for the modules as many as 10101 configurations would be possible. For this reason, the simulations are performed with 1 module type first (module type 6) and then with 2 (module types 3 and 4), greatly reducing the amount of possible
configurations. These are respectively 10^71 and 10^19. There are more solutions for the simulation with 1 module type because this module has a larger number of orientations than the other two modules combined. The outcome of the case study was that the algorithm did
not find better or equal solutions than the truss structure. This was because the convergence of the model was very slow, even for a simulation of more than 200 generations (10050 solutions) the best solution had a fitness value much larger than the truss structures. The issue was mainly that the extreme utilisation of some of the members was too large which made them fail. The BLF and displacement were within the boundaries. Comparing it with the case study the maximum stresses were indeed larger but the deflection was in the same
order of magnitude. The Pratt truss with reconfigurable members which resembled a regular truss was in the right order of magnitude for deflection as well. This truss does not have extra parallel beams since not entire cubes are joined together but single beams and columns.

An application is analysed to see how the model acts when the supports are irregular. From this setup, it was unclear what would be an optimal solution. The selected modules for this problem did not give the option to create a regular truss-like structure. The model found a slightly better solution than the one initially found using intuition and expert judgment. The value of the fitness function decreased from 0.84 to 0.80, which is a 5.5% decrease. The conclusion from this case study is that when the optimal solution is unclear and the design
space is large the model can find a relatively good solution. Combining this expert judgment and computational design can improve a model even more.

Overall the model can be used to design planar steel space frames with varying support conditions. These space frames are circular in design because their parts can easily be deconstructed and reused in similar structures. This is a huge advantage because it can save a lot of material and construction time as well. The modules themselves have the extra advantage that they can also easily be changed to a different type by varying the diagonals. This makes the system flexible in design. However, the optimisation efficiency is not very good.
The algorithm does not find optimal solutions that can be used in practice for a large design space. The type of structure is also much heavier in general compared to conventional space frames. This is because joining entire modular cubes together requires more steel. There are numerous parallel members that do not appear in regular space frames where beams, columns, and diagonals are individually placed in the structure. This makes stress on the members relatively high and therefore unfeasible. To use the system is therefore a consideration for the designer. When focussing on modular and circular construction this system is very useful but it is less structurally efficient. The model with ”modular elements” could potentially be used for a more structurally efficient system if the convergence towards a solution can be improved (with a different algorithm) and the speed at which solutions are calculated as well.

In the construction industry, composite structures combining concrete and steel are commonly employed in floor systems due to their exceptional performance in compression and tension. With a growing emphasis on sustainability and Life Cycle Assessment (LCA), this thesis introduces a novel concept: a modularised floor system consisting of reusable concrete deck and composite beam. This research focuses on analysing the behaviour of an innovative demountable "concrete to concrete" by FEA. A connection between the composite beam and concrete deck connected by a shear connector (bolt). The goal is to understand the mechanical behaviour of such connections.
This design differs from cast-in-situ traditional composite floor systems by having a concrete deck divided into three separate parts that are connected by bolted shear connectors. The composite floor consists of composite girders and concrete decks. A key advantage of this system is the ability to extract the concrete deck from existing floor systems, offering economic benefits and reducing carbon emissions over its life cycle. The mechanical performance of the newly designed connection between two concrete segments (a composite beam and a concrete deck) is examined through a shear and bending model using Abaqus Software.
The shear model does not represent a real case loading, and it is introduced to gain confidence in the numerical analysis due to the absence of experimental data in this research. The specimen consists of two concrete blocks being pulled apart. These blocks are connected by a demountable shear connector (bolt) in the middle.
A three-point bending model presents the mechanical behaviour and realistic potential failure modes of the innovative demountable "concrete to concrete" connection. It consists of three connected concrete segments. This model reveals failure modes, including cracking at the “re-entrant corners” of the connection points, crushing of concrete at the mid-plane of the connection and under the bolt nut, and transverse concrete cracking originating from the bolt hole, refer to Figure 6.26.
To enhance the structural behavior of this modularised floor system, several methods are investigated. First, adding steel plates at the connections effectively mitigates concrete crushing at the mid-plane and prevents cracking at the re entrant corners. Second, relocating the connection to zero-bending moment positions results in a notable reduction in the three failure modes, improving loading capacity by about 10%. Furthermore, the environmental impact of this novel design is noteworthy. With the assumption given in this thesis, for an area of 5.67m*8m concrete deck, reusing the newly designed concrete deck can result in a savings of approximately 4.2 tonnes of CO2 emissions per subsequent life cycle. Similarly, reusing concrete decks from existing buildings can lead to a reduction of around 2.33 tonnes of CO2 emissions per life cycle with this size of the floor. Based on the assumptions made in this research, the results suggest that the newly designed concrete deck may have a lower loading capacity than traditional concrete slabs. However, its potential economic and environmental advantages make it a promising topic for future investigations.

With the building and construction sector accounting for a significant portion of final energy use and emissions, and society’s increasing focus on environmental awareness and improvements, the impor- tance of sustainable construction has never been greater. The utilisation of timber in construction offers clear sustainability benefits and has the potential to replace traditional functions of concrete. One notable replacement is the use of Cross-Laminated Timber (CLT) in composite structures with steel, enabling the potential creation of greatly performing floor systems which has seen a limited amount of research. The research explores the application of Steel-CLT Composite floor systems and assesses composite beam performance as well as predictive methods for analysing their behaviour in hopes of advancing the body of knowledge on this method of environmentally friendly construction. The literature study revealed the current knowledge on steel-CLT composite floor systems and connections. Two particular floor systems, with and without the use of grout, are highlighted as well the potential for future exploration. The steel-CLT composite connection utilised in the floor system significantly impacts performance and composite action as the use of grout is concluded to increase initial-, secondary stiffness and load carrying capacity of the connection. However, restricting the use of grout can promote circular con- struction practices. In this research the behaviour of steel-CLT composite beams is predicted by the use of a numerical finite element model with shell elements and an analytical approach based on the simplified analysis of Eurocode 5(EN1995-1-1): Mechanically jointed beams. The analytical method can predict the bending stiffness with a margin of error just slightly above 10%. However, it should be noted that the analytical method incorporates an incomplete representation of the composite connection used in the beam. On the other hand, the finite element model is able to accurately capture the pre-plasticity behaviour of the steel-CLT composite beam. This is achieved by incorporating the complete load-slip behaviour of the shear connection. A parametric study was conducted to assess the importance of closely spacing composite shear connections in a steel-CLT composite beam to achieve a higher level of composite action. The study also demonstrates that by utilising connections with higher initial stiffness, secondary stiffness, and ultimate capacity, this effect can be further strengthened. As a result, the force resisted at the service- ability limit state experiences a notable boost due to the implementation of both a stronger and stiffer connection, as well as their close spacing. Shear connection position optimisation by concentration of connectors near the supports showed to have a small positive effect on beam deflection. After evaluation of steel-CLT floor systems the research concludes that a steel-CLT composite floor system can be successfully constructed, offering environmental benefits and reduced structural weight while achieving the required structural performance for the set design conditions.

This research aims to investigate the influence of Polyisocyanurate (PIR) insulation on small surface load distribution on corrugated steel roofing sheets. PIR foams are used for thermal insulation in industrial buildings. The distribution of surface loads induced by solar panels support structure might be altered by PIR foams. This is completely ignored in the design calculations according to current standard which might results in overconservative designs. In this study, the following main question is going to be investigated using experimental and numerical methods: ‘’What is the influence of PIR insulation on the transverse distribution of small surface loads on corrugated steel roofing sheets?’’.

The methodology involves conducting bending experiments to obtain strains and deflection data, which then are validated using numerical models. The experiments have been conducted on corrugated steel sheets supported by rollers. The PIR insulation is connected to the steel sheet by bolts, and a loading cylinder applies vertical force at the PIR insulation panel side. Two loading configurations are selected to simulate the representative loading conditions in real-life structures. Vertical deflections and strains in the bottom flanges of the corrugated sheet are measured during the experiments. The experimental data are used for the validation of the numerical models that are created by using ABAQUS FEA.

First, a linear F.E Model was developed and validated with experimental results up to the initiation of nonlinearities. The results of the linear models shows clearly that the PIR layer influence considerably the stress distribution in the adjacent ribs to the one of load application. A nonlinear analysis is conducted to determine the maximum load that the roof structure can resist. To capture geometrical nonlinearities more accurately, eigen buckling analysis was conducted to implement initial geometrical imperfections. Considering the imperfect initial geometry of the steel sheet and its plastic properties, maximum strength of the roof system could be estimated. As a note, the damage in the PIR insulation material was not considered as it is beyond the scope of this study, the material was assumed to be linear elastic.

The experiments demonstrate that the behaviour of the roof structure is primarily governed by the rupture of the PIR insulation, occurring prior to any yielding in the steel sheet. The linear numerical model predicts the behaviour of the roof structure within the elastic phase. The linear model can be used to study the influence of the several influencing parameters such as the dimension, PIR material properties and the loading conditions. Expanding the span from 2 to 6 meters with a single mid-span surface load increases the adjacent rib contribution by 20%, meaning that their normalized strain values relative to the load location's maximum strain grow by 20% in the elastic phase. The nonlinear model is employed to establish the force vs. displacement curve and identify the strength of the roof. The non-linear numerical models show that the ultimate load is found to be 8000 N when a single surface load is applied directly on the steel sheet. The experiments show yielding of the steel at 7300 N after the loading jack ruptures both the PIR surface and layer, then the jack reaches the profiled steel sheeting. For design purposes, it is recommended to exclude the influence of the PIR insulation beyond its elastic phase. Compression tests conducted on the specimen revealed damage within the PIR material at a load of 6250 N, which is considered the upper limit for the PIR's elastic phase.

In Amsterdam, more than 30 steel-concrete composite bridges were constructed from 1880-1960 without mechanical connectors and transverse reinforcement. Currently, there are no simplified analytical methods to determine the bearing capacity of these bridges. Thus, the bearing capacity is verified using NLFEM or oversimplified analytical calculations. This research proposes an analytical method to determine the bearing capacity of historic steel-concrete-composite bridges without mechanical connectors to avoid time-consuming FEM calculations and offers reasonable results.

An experimental and numerical study is performed on data from in situ and laboratory testing of samples from two different bridge decks from these Amsterdam bridges. The tests are accompanied by a numerical model that has been studied and adjusted to a more generalized loading case. This study determined that the exterior composite girders are critical due to their lower lateral stiffness.

An analytical model is proposed to examine the behaviour of the exterior composite girder. The model considers a 3-point bending load at midspan between the exterior composite and adjacent girder. The force distribution is described through a compatibility-based strut and tie model (C-STM). The concrete in compression is considered elastic compression struts, only limited by the ultimate load of the model. The concrete in tension is interpreted as a tensile tie, which fails when it exceeds the concrete tensile resistance. Following the failure of the tensile tie, it is assumed that a longitudinal crack propagates between the exterior composite girder and the adjacent girder. Additionally, vertical and lateral stiffness components are included in the model. These account for the flexural stiffness of the exterior and interior composite girder. The vertical stiffness is accounted for as elastic springs, and the lateral stiffness as spring beams. The interior lateral spring beam summarises all the interior composite girders' stiffness, whereas the exterior lateral spring beam only considers the exterior composite girder. Therefore, the configuration assumes that the interior spring beam is significantly stiffer than the exterior. Moreover, the stiffness of the exterior spring beam reduces when the longitudinal cracking occurs, assuming a part of the concrete fails. The C-STM is linked to the cross-section verification of longitudinal shear, biaxial bending and vertical shear resistance in two stages. Stage 1, at the load at longitudinal cracking, determines if the specimen fails at this moment, indicating that there possibly is a brittle failure. Stage 2 is after longitudinal cracking, where the steel-concrete contact perimeters have reduced, and the corresponding resistances accordingly reduce.

The failure modes obtained by the analytical model are comparable to the ones observed during the experimental testing. The analytical model showed that the bridges failed due to biaxial bending limited by partial shear interaction. One of the specimens from the testing yielded due to bending but with limited ductility. The other specimen also yielded due to bending with concrete crushing at the top concrete fibre. Further, the bearing capacities obtained from the analytical model are comparable to the failure loads from the experimental and numerical results.

The model predicts the failure modes and the bearing capacity and can therefore contribute to the assessment of the historic Amsterdam bridges, helping to reduce the assessment time of the bridges and understand their load-bearing behaviour better. Future work should focus on verifying the method by examining more bridges using FEM.

The demand for offshore wind energy has never been higher, yet the number of ideal areas for wind farm installations is decreasing. As a result, larger wind turbines are being placed in deeper waters, which poses opportunities for floating foundations. However, due to the industry's inability to scale up the production of relatively expensive floaters, companies are exploring alternative foundation methods for offshore wind turbine generators in deep water, including the extension of the use of monopiles, which are now being considered for use in water depths up to 60 meters. However, higher loads in deep water require increased stiffness in the monopile structure, which is typically achieved by using larger thicknesses and diameters, resulting in XXL-monopiles. The steel used for these XXL-monopiles increases exponentially for greater water depths, and the designs cross the production limits. This study investigates the use of a guyed monopile as a more favorable alternative to a conventional monopile for deepwater applications with large wind turbine generators in the range of 60-120 meters of water depth and a rated power of 15 MW. The guyed monopile concept involves adding moorings to a conventional monopile to provide additional stiffness at a certain elevation, reducing the required material within the monopile. A numerical model is elaborated where the structure is represented by a one-direction FEM model having two degrees of freedom. The model is supported by springs that represent the soil and mooring system. The soil is modelled by a series of p-y reaction curves. For the mooring stiffness, a nonlinear stiffness approach is used where the axial stiffness and geometry of the mooring are considered. The method is used to determine the maximum stiffness that a mooring system can bring. After that, the mooring system is included in the FEM model. Static and dynamic analyses are performed to determine the response of the structure. The described methodology also implements requirements based on potential resonance (1P and 3P frequencies), ultimate limit state (yield strength, column buckling, and local buckling), and fatigue limit state (fatigue damage due to wind and waves). The static and dynamic responses are validated using Ansys. It is concluded that the moorings can provide enough stiffness to reduce the impact of the acting loads on the structure. A case study is conducted to compare the use of a conventional monopile and a guyed monopile for a foundation based on realistic wind and wave loads. Data of a reference wind turbine and a reference location is taken to find the advantages of a guyed monopile for a realistic case. The study iterates the process for different water depths and varying numbers of moorings. Greater water depths lead to more issues due to resonance and fatigue, which can only be overcome by increasing the diameter and thickness of conventional monopiles. This can also be overcome for guyed monopiles by increasing the mooring stiffness. The results show that the guyed monopile is favored over the conventional monopile in all cases, with up to a 45% reduction in steel required.
The case study's findings are used to identify key parameters in the design of a guyed monopile. The sensitivity of the mooring system stiffness is compared to other key design parameters, including monopile diameter, thickness, and embedded length. The study finds that the moorings have a favourable effect on the system's natural frequency. Also, bending and shear stress may be reduced when moorings are applied.

Tensioned membrane structures are increasingly in demand, because of their ability to cover large spaces with minimum use of material. The material’s mechanical properties play a key role in the design of such structures. The shear behaviour is one of the main influential properties of woven textiles during complex deformations, such as the ones in doubly curved structures where the change in curvature challenges the shear-bearing capacity of the textile during its service life.
This study provides a methodology to characterise a novel uncoated woven solar cell integrated textile for tensile structure application. It consists of investigating the limit angle, that avoids damage to the inserted solar strips, and the determination of the shear stiffness of the material. To evaluate the applicability of the material, different mechanical properties are assessed. Mono-axial, picture frame and bi-axial tests were used to determine the strength, elasticity and shear modulus. All results have been validated by comparison with existing experimental data of similar architectural textiles.
This research introduces a method of investigation of shear properties of uncoated textiles that can be followed to evaluate other uncoated textiles. In addition, it is now possible to start a preliminary design of a tensile structure with the newly developed material. It is the first step in the introduction ofthe new building material.

The Mekong Delta is facing some complicated challenges in the near future. Its geographical location and the fact that it is a delta result in low elevation levels which makes it vulnerable to inundation. This problem will only become bigger in the future due to the effects of climate change. To get funding from organisations like the world bank it is important to propose multiple solutions that are beneficial to multiple parts of society. It is favourable to split
a complex system like the Mekong Delta into subsystems to make it more feasible to build realistic models. The subsystem defined in this report is the Hau River estuary. This area mainly suffers from riverine inundation caused by tidal variation in the South Chinese Sea. The biggest city in the region is Can Tho with 1.3 million inhabitants.

The research question is: Which integrated solutions reduce riverine inundation problems in the Hau River estuary while also considering socio-economical aspects? To answer this research question the following four solutions are proposed and designed.

• Discharge sluice in the mouth of the Hau River to reduce the tidal influence

• Wetland with a double levee system and buffer zones to reduce peak discharge

• Bypass channel to the Gulf of Thailand to reduce discharge during the wet season

• Protection of valuable assets and adaptation of local citizens to the new natural balance

Based on desired discharges and water levels preliminary design parameters of the proposed hydraulic structures were determined. The effectiveness of these solutions was assessed based on their ability to reduce the water level in Can Tho. The reduction that the discharge sluice achieved was determined with a zero-dimensional model, whereas the water level reduction that the wetlands and bypass option achieved were determined by Delft3D models. The discharge sluice performed best in reducing the water level in Can Tho, as it opposes the tidal influence in the Hau River.

To assess the quality of the solutions relative to each other a best-worst multi-criteria analysis is done. In this assessment other factors such as financial aspects, socio-economics and transportation are taken into account. The most important criteria are flood reduction and funding opportunities. According to the assessed criteria, the discharge sluice and the wetland are the best-scoring solutions. These solutions have the most potential in reducing the river inundation problems in the Hau River estuary. This does not mean that the bypass and adaptation solutions should be neglected or are not useful. For a complex problem in a complex system like the Hau River estuary, one solution is not going to solve all the problems. A good balance between different aspects has to be determined by also considering other problems like sand mining, subsidence and salt intrusion.

A series of critical transmission lattice towers failures due to severe ice and wind loads forced German utility companies to reassess the structural stability of their power grid infrastructure. During the structural reassessment process, a problem related to an outdated or even missing documentation of the in-use infrastructure occurred. This issue forced utility companies to gather the data regarding the geometry of the lattice towers on-site, using specialized and labor-intensive geodetic measuring methods. The scale of the required data acquisition endeavor and stability checks to be performed encouraged the use of alternative methods to capture the geometry of the in-situ structures and reconstruct geometric models to be applied during the structural stability checks in a reliable and efficient way.

This work presents an innovative method to generate a geometric CAD model using point cloud data captured by a LiDAR scanner. The CAD model can be later implemented for FEA utilized during structural stability assessments. The modeling process defined in this study is fully automatized, enabling to obtain repeatable results and save the time required for manual data processing. For the input point cloud data, two types: Aerial and Terrestrial LiDAR point clouds have been investigated allowing to identify the applicability of both data sets for the proposed method.

The model generated with the automatic method proposed in this study is compared in terms of geo-metric discrepancies to an idealized model based on design documentation and a LiDAR point cloud based model manually generated with a commercial software. The two models used for comparison depict a traditional structural engineering approach and a state-of-the-art method within the point cloud processing field accordingly. At the final stage of this work, the automatically generated point cloud based model is used for a non-linear FEA and compared to a FEA response of the idealized mod-el.

Results showcase that LiDAR point cloud data is a good source of geometric information to reconstruct a geometric CAD model which can later be implemented in FEA. Obtained results are comparable to the ones of an idealized model based on design documentation in terms of collapse mechanism and ultimate load applied at the failure step. Additionally, the geometrical comparison between the point cloud based models generated with the manual method and the one proposed in this work underline the ad-vantage of the automatic method in terms of permissible level of detail and overall precision of the final geometric model. What is more, the impact of point cloud data usage for FEA modeling is shown. Investigating differences between FEA results of the point cloud based and idealized models allow to showcase the influence of real life imperfections on force redistribution across the analyzed structure and ultimate forces reached by members loaded in compression.

The modeling method and analysis results presented in this work can be applied as a set of guidelines for future applications related to point cloud data processing of steel lattice structures used for FEA modeling purposes.