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

Between the 1950’s and 1970s, a large increase in bridge construction was realized accompanying a large increase in infrastructure. The increase in traffic intensity and weight results in that many of these bridges are now in need of reevaluation, possibly resulting in renovation or renewal. Meanwhile human-caused adverse environmental effects are increasingly impacting the world, of which the infrastructure sector is a large contributor.
This thesis provides a study into more sustainable renewal projects. The objective of this study is to provide a design which will increase the sustainability of renewing bascule bridges. The approach for this study is to:
• Literature review to set a scientific basis for this thesis project.
• Design study to explore the possibilities for bridge leaf design.
• Summary, conclusions, and recommendations to conclude the research project.
To design a more sustainable alternative the “Design for sustainable infrastructure” is followed. The ambitions identified following the “Ambition web” methodology highlights a great influence of a structural engineer in environmental sustainability. Key opportunities to increase environmental sustainability include reusing structural elements, maintaining or reducing the mass of the bridge leaf and designing the structure to fit inside the footprint of the current bridge.
The design process starts by applying “Circular design principles” to design a variant which reuses most of the available elements. Following variants increasingly differ from the current structure by removing elements, changing the materials from of the elements, or using free forming opportunities of FRP to come to new designs.
The sustainability performance is strongly dependent on the current state of the structure. Reusing the main structure and renewing only the deck can reduce the environmental impact of the bridge leaf by up to 53%, while not increasing the mass or requiring more space. Redesigning the entire structure with a full FRP structure can reduce the environmental impact by up to 48% and could reduce the mass of the bridge leaf by up to 33%. For both scenarios, the use of FRP, with a balsa core and partly recycled resins, was thus beneficial for the sustainability of a bascule bridge renewal project.

The use of Glass Fibre-Reinforced Polymer as a building material in structures or structural components is on the rise. Standards such as CUR96, DNV and JRC provide a basis of design with the material. However, there is a lack of confidence in the design phase with structures made of Glass Fibre-Reinforced Polymer, resulting in the use of large safety factors causing the components to be bloated in size. At the time of writing this report, the technical committee, CEN/TC 250 (responsible for developing structural Eurocodes), establishes a technical design specification for Fibre-Reinforced Polymer (FRP) structures. This technical specification describes a simplified and linear criterion to determine the capacity of a GFPR Laminate, in addition to being open for the use of Progressive Failure Analysis (PFA). However, the simplified and linear criterion is overly conservative, whereas there is a lack of faith in the use of the PFA considering the failure theories and degradation models that are currently in use. This report discusses the PFA, a non-linear, 5-step, advanced 2D analysis model, that can predict the static strength of in-plane stress dominated Glass Fibre-Reinforced Polymer laminate, with an arbitrary lay-up composition, based on existing knowledge and experiments, including the damage development under multi-axial stress states and stress redistribution. The research is limited to in-plane behavior, under tensile and compressive stresses. The static material response is characterized on a unidirectional ply level based on principal directions and based on experimental results obtained from the OptiDat program. The response predicted by the PFA for both tension and compression was in reasonable agreement with the experimental results. However, depending on the failure theory and degradation model used, there is potential for optimistic predictions of the laminate stress capacity. For future work, it is recommended to continue the research on a larger variety of laminate lay-ups and include more failure theories and degradation models.

The increase in road traffic intensity and loading capacity of a truck over the last decades causes fatigue problems in existing bridges built in the 1960s and 1970s. For steel bridges, this means that the deck structure does not meet the current demands. A solution would be to replace these existing deck structures with Glas Fibre-Reinforced Polymer (GFRP) sandwich webcore deck panels. However, the ministry of infrastructure in the Netherlands has voiced its concern about the fatigue performance and displacements of these deck panels under the high traffic load and intensity. Furthermore, the knowledge about the fatigue performance of GFRP deck panels, applied in the main road network, is still limited. At the time of writing this report, the technical committee, CEN/TC 250 (responsible for developing structural eurocodes), establishes a technical design specification for Fibre-Reinforced Polymer (FRP) structures. This technical specification requires full-scale fatigue testing due to the complex failure modes that can occur. General fatigue damage summation methods like Palmgren-
Miner [30, 41] are not allowed by this technical specification. This report discusses the development of Virtual Fatigue Stiffness Simulation (ViFaSS), a numerical non-linear fatigue stiffness reduction model that can predict the fatigue performance of in-plane stress dominated Glass Fibre-Reinforced Polymer components, with a wide range of lay-up compositions, based on existing knowledge and experiments, including the damage development under multi-axial stress states and stress redistribution. The damage development includes damage accumulation dependency on damage history and damage development dependency on the load type, e.g. Tension-Tension (T-T) or Compression-Compression (C-C). With the low utilisation of the material strength in civil engineering applications, the research is limited to the stiffness degradation of the material. The numerical model is coupled with the Finite Element (FE) software SOFiSTiK where the component is modelled with shell finite elements. The fatigue material response is characterised on a unidirectional ply level based on principal ply directions and based on experimental results from the Optidat program [36]. The coupon response predicted by ViFaSS for constant amplitude T-T and bending fatigue loading was in reasonable agreement with experimental results. For future work it is recommended to extended the model with the ability to use non-linear material behaviour and to include the strength degradation caused by fatigue.