The Netherlands aims to have a fully circular economy by 2050. The construction sector in the Netherlands is only 8% circular (Circularity Gap Report Bouw, 2022). Reuse within construction projects presents various challenges, which will be discussed in this thesis. In the current market, there is more supply than demand (BAMB, 2020). One possibility to stimulate demand is the use of digital marketplaces. This study investigates how a digital marketplace can support the demand side in the design process, leading to the following research question:

How should a secondary ‘digital’ product marketplace function within the construction industry?

Before addressing this question, a literature review is conducted on various aspects. These include the concepts within digital marketplaces and platforms, as well as those within reuse projects, focusing on specific information about materials and products in the context of reuse. Additionally, the current state of the industry has been examined in terms of challenges, opportunities in general, and those related to digitalization. This is done to get a better understanding of the surroundings in which the marketplace must operate.

The literature research concludes that the core interaction is the most important form of activity on a platform – the value that attracts the most users to the platform in the first place (Parker et al., 2016). It consists of three parts: Participants + Value Unit + Filter. Fundamentally there are two participants on the platform, namely producers and consumers. In this case, producers are building/construction elements and their owners/sellers. Consumers are the ones that are willing to buy them (potentially; architects, engineers, contractors, or suppliers). Where the value unit starts with the exchange of information that has value to the participants. This information delivery to consumers depends on filters. A filter enables the transfer of appropriate value units between users. A well-designed filter ensures that platform users see only information units that are relevant and valuable to them. No filters or a poorly designed filter overwhelms users with units they find valueless and irrelevant, which causes them to abandon the platform. No research has been done to the specific design of the core interaction of a secondary product marketplace within the construction industry.

In addition, few scientific articles investigate software interfaces, ease of use and the user's role and experience within the construction industry. An action- and design-oriented research method is a new approach to this problem/goal. The information system framework is chosen to combine rigor research and the application domain within a design practices.

To structure this research the research question is divided into three steps (based on the core interaction). In step 1, the input for the design is investigated, which includes determining the participants who should use the marketplace (champions), how they should search for products, and what improvements can be made in the design process to promote reuse. In step 2, the filters and interfaces of the marketplace are designed. Within step 2, solutions for situations with limited data or, conversely, when there is sufficient data in the future are also explored. In step 3, the chosen champion validates if they can use the designed solution and whether it provides value.

To define the main users/champions (step 1), potential users-(roles) are interviewed about their needs for such a marketplace, assuming reuse becomes the norm. The literature review covers all aspects of digital (construction) applications and reuse in the construction industry. This is supplemented with expert interviews in IFC (an open data standard), user interface/user experience (UI/UX), current construction marketplaces, and material passports. In addition, various roles from several reuse projects are interviewed, including designers, project developers, purchasers, demolition specialists, and engineers, in line with the information system framework and action design. This is done to get an complete overview of all the stakeholders involved within the process of selecting/buying reused products.

The information of the literature research and the first interview phase is used in the design process to create ‘search and facet’ filters. Therefor a division based on the Brand/shearing layers (site, structure, services, skin/facade, space, and stuff) is made to improve the design the facet filters. The engineer and the architect is chosen as the primary user but in consultation with the design team. For all the engineers responsible or related to the a Brand layer a recommendation is made for a first set a (search) parameters.

Concerning the information need (step 2) of the structural engineer, the primary focus is on the elements' functional and physical properties (moment-of-inertia, material type, strength, and dimensions). Thereby the core interaction disregards environmental or economic properties. These are of secondary interest for the core interaction. The three main materials, wood, steel and concrete, require all different ways of working for reuse but share common properties which makes the design of filters less complex. Capacity, dimension, grid size, floor height and more properties could influence the structural design decision, increasing the demand for reusable structural products. However, more traditional engineers prefer to filter within one type of material. Even more in-depth material and product knowledge for reuse could is a next step for the core interaction, thereby evolving into a knowledge marketplace.

The other Brand layers (skin, services and space) information need should also focus on their functional and physical reusability properties, which are covered and designed in this thesis but not validated with real users. The skin and the space layer are more visually oriented; images support the architect's and engineer's decision-making. Aesthetic filters to filter on certain styles, colours, types and tags will support the architect where functional filters relating to dimension are of first need for the façade engineer. Secondly the physical filters benefit the search tremendously, such as; U-value, fire resistance, Rc-value, sound resistance, waterproofness etc. The service/building engineer wants to filter into three categories. Namely the machine, the distribution point (ventilation grille, water tap, heating element) and the transport (cable tray, pipe and wires). The machine (e.g., heating, cooling and air filters) has a more dynamical environment with a high change in regulation, expecting a low reuse pattern. The other two categories, distribution and transport are more suitable for reuse; these filters contain service type (energy, water, air, data and heating), minimum length and the capacity of distribution and transportation.

After step 2 (design) various structural engineers are interviewed using a working digital prototype to examine whether the search filters are effective for their reuse process (step 3). Besides various side notes on the design culture, system changes and the willingness of a client to reuse products. The interviewed users made recommendations which should be taken into account for a next design iteration. The proposed design is usable and could meet its goal/value proposition when reusing products becomes the norm.

This research is a small link in the bigger picture of a ‘circular’ construction industry. Still, many challenges remain that a digital marketplace could not solve. When interpreting the results, the following points should be considered as well. The interviewees in this research are involved or interested in reusing products. When less interested engineers/users must use this marketplace, other items could be of more importance or totally different obstacles could arise.

Further research should examine the other Brand layers and their primary users. Additionally, to succeed as a marketplace, choices need to be made. Which users and product categories will be supported in first place. What is the business plan and initial investment? Building and rolling out a marketplace requires entrepreneurial skills and courage. This research hopes to provide the readers with a holistic view of all the challenges related to a digital market platform that address the construction market for secondary materials. Together with a set of validated user interfaces of such marketplace.

The aim of this thesis is to investigate and quantify the efficiency of high capacity self-stabilising modules in mid-rise residential buildings. These modules have a higher stabilising capacity than modules that are currently being used in the Netherlands and other countries and can therefore be used for more storeys without requiring an additional stabilising structure such as a concrete core.
In the first part, reference projects and case studies are looked at to get a good understanding of the current applications in The Netherlands and the United Kingdom. After analysing four case studies, an assessment is done on the functional efficiency, structural capacity and environmental impact of these modules. By doing so, the load-bearing structure of self-stabilising modules that can be used at a greater height can be identified. Design variants can now be drafted with different bracing configurations, which are later verified on strength and stability requirements. To effectively design a suitable braced frame, it has been researched what the displacement components for braced frames are. This has been done for simple frames without eccentricity as well as frames including eccentricity. Apart from single-cross frames with a relatively large span, double-cross frames are also looked into due to their increased stiffness.
As part of the total structure of the building, a design for the foundation as well as the inter-module joint, which is required to be demountable, has been made. These parts of the design are required to calculate the horizontal displacement during lateral loads.
A structural assessment is done on the stabilising capacity of each variant at 8 storeys. The design adjustments that are required to further increase the number of storeys up to 10 are looked into as to see whether or not an efficient structure can be maintained. It turns out that each design variant requires adjustments that reduces the efficiency. These changes are the result of a large increase of braced span, resulting in either inefficient use of beam profiles or a too large length when there is more than one braced span along the length.
Apart from a structural assessment, the functionality and environmental impact of the design variants has been analysed as part of the overall efficiency of the modules. The functional assessment includes several criteria such as wall-to-floor area and space efficiency factor. Using the required material use in partition structures and load bearing elements, the environmental impact is calculated, resulting in values for the embodied energy and embodied carbon per square meter in each design variant. Since the differences between the design variants are relatively small, they are also compared to four case studies that were done before.
On the basis of the results of this research, it can be concluded that self-stabilising modules can be constructed with different possible bracing layouts and an efficient load-bearing structure up to 8 storeys.

The orthotropic steel deck (OSD) is a deck system applied regularly in steel bridges all around the world. It consists of a steel deck plate which is stiffened by structural elements placed in two orthogonal directions. The deck plate can be used as an integral part of the structure, causing OSDs to achieve a high material efficiency and therefore low self-weight. However, this structural integration requires a large number of welded connections between the deck plate and stiffening members, which also make the system susceptible to fatigue. The fatigue evaluation of these connections is complex and time-consuming, hindering the manual optimization of orthotropic deck designs.

The use of structural optimization could be a solution for this. With parametric optimization, the best possible ratio between structural dimensions may be searched for automatically, while topology optimization could assist in finding new design concepts that could form alternatives to the traditional deck layout. This thesis investigates how these techniques could reduce the self-weight of the design of a case study (the renovated Van Brienenoord bridge) without reducing its fatigue service life. The two methods are treated in separate parts.

In the first part, considering parametric optimization, the traditional OSD concept is maintained and the values of seven selected dimensions are adjusted to obtain a design with a minimized weight. A workflow is developed in which an existing mathematical optimization solver (the artificial bee colony algorithm, a metaheuristic) is coupled to a parametric model, finite element program, and fatigue damage calculator. This enables an iterative process in which designs are generated by the solver and then evaluated in the remainder of the workflow. The information gained from the evaluation is returned to the solver and used to search for lighter designs.

In the second part, the deck remains a stiffened steel plate, but the location and orientation of stiffeners may be changed. Two possible leads for finding new structural concepts are explored. The first considers a topology optimization using the ground structure method, which can find the optimal orientation and size of stiffeners in a plate. This thesis evaluates the method’s current applicability on steel bridge decks. The second lead interprets the results of a topology optimization from existing literature. This gives a new design concept in which the crossbeams curve directly towards the supports instead of being indirectly connected by main girders. A weight minimization using the workflow of the first part and a study of the force transfer in the deck are performed to assess the new concept’s potential.

The first part showed that a 17,4 percent lighter deck structure (280 kg/m2 instead of 339 kg/m2 ) could be obtained for the case study by breaking with the general trend for designing orthotropic steel decks. The optimized design uses smaller and more rectangular troughs than commonly applied, but the largest differences are found in the deck plate thickness and stiffener spacing. For the latter, a value of 300 mm has been in use since the introduction of OSDs in the 1950’s and is present in almost any bridge using an orthotropic steel deck. When fatigue issues started to appear from the 1970’s onward, it was generally decided to increase the deck plate thickness. The results in this thesis strongly suggest that decreasing the stiffener spacing and trough top width is the preferred option when material efficiency is considered. A cost estimation further showed that the price of the optimized design would be comparable to that of the preliminary design that was suggested for the case study.

The topology optimization using the ground structure method showed that the optimal placement of stiffeners for a plate-like bridge deck contains two distinctive zones. Between the supports, the traditional longitudinal-transverse orientation is preferred, while the optimal direction of stiffeners in the middle of the bridge segments is arbitrary. The conventional OSD concept could be seen as optimal based on this result, but for definitive conclusions more research is needed towards a non-linear relation between cross-sectional area and resistance in the applied method. The similar support conditions of decks in other bridges make it likely that these conclusions will apply to those cases as well.

The optimization of the curved crossbeam concept showed the versatility of the workflow developed in the first part of this thesis, as only minor adaptations in the parametric model were needed for the application on a significantly different design. Despite the successful optimization, the potential of the new design to replace the traditional OSD concept is considered low. In its optimized form, the concept was 9,8 percent heavier and less than half as stiff as the best found result in this thesis’ first part. The comparable support conditions for plate girder bridges in general again suggest similar outcomes for other cases, while a different setup of the optimization would not tackle the fundamental stiffness problem of the design. Further research towards the curved crossbeam concept should therefore stick to the original application of box girder decks.

Among the current targets of the building sector, one major goal is to maximize the resource efficiency (in terms of material use and in terms of energy used to produce the buildings); furthermore, the circular economy model aims for maximizing the reuse of the structural elements; thus, minimizing the material waste and avoiding a second production of elements. The high-rise building sector faces the challenge of considering a design that is flexible and adaptable to meet the functional requirements along its life span; and additionally, to consider a design for deconstruction, where the benefits and challenges that arise form reusing and recycling the material can be considered and addressed from early design stages.
This research addresses these trends and challenges by evaluating and comparing the environmental impact of different structural systems for a high-rise building in the Netherlands (151m). The comparison of four different structural systems with two core variations provides eight different stability systems. The scope of the stability systems considers foundations, core, columns, beams, bracings and floor slabs. The design of the structural systems was performed by the elaboration of 3D FEM models with parametrical tools to ensure the structural safety and serviceability of the building. Furthermore, the assessment of the environmental impact (global warming potential) was performed by means of a Life-Cycle Aseessment comparing three scenarios of the structure: cradle to gate, cradle to cradle, and cradle to cradle with 100% reuse of the structural elements; with data from the Nationale Milieu Database and with information from a technical report from the Joint Research Center.
The analysis of the results demonstrated that the environmental impact of the structural systems with steel core is 21% higher than the one that corresponds to the structures with concrete core, However, this variation is only 4% for the two variants of the diagrid structure. Furthermore, by including the average recycle and reuse rates form the market and current construction practices, the benefits at the end-of-life stage of the building can represent up to 17% of the impacts from the production phase. Moreover, when the reuse rate is considered as 100% the benefits increase up to 42% of the impacts from the production phase.
The results indicate that the improvement of the environmental impact of high-rise buildings can be achieved by means of sustainable structural design from the early phases of the design; where the choice of materials and of the structural system play and important role on the outcome of the total environmental impact of the building, which is becoming an important driver for the decision-making of new projects.

The innovative shear strengthening method using externally bonded CFRP reinforcement to strengthen prestressed concrete I-girders has been investigated in this thesis. These girders potentially have insufficient shear capacity because of the combination of thin webs and insufficient shear reinforcement. Shear failure of these girders should be prevented because they do not warn before the element fails in shear. Shear strengthening using externally bonded CFRP reinforcement seems promising because of low installation costs, negligible increase in weight, no decrease of clear height underneath the bridge and minimising the hinderance. The aim of this thesis is to investigate the feasibility of shear strengthening prestressed concrete I-girders using externally bonded CFRP reinforcement. The shear behaviour of prestressed concrete I-girders strengthened using externally bonded CFRP reinforcement has been investigated with the nonlinear finite element analysis (NLFEA) software DIANA. A three-dimensional finite element model of a 1.0 m high prestressed concrete I-girder with a kinked tendon profile and no shear reinforcement has been made to investigate several parameters and aspects of the CFRP reinforcement. Shear strengthening of prestressed concrete I-girders with vertical CFRP sheets and CFRP anchors is a feasible strengthening method because of the demonstrated potential increase in shear capacity. The externally bonded CFRP reinforcement was especially effective to increase the flexural shear capacity of prestressed concrete I-girders. The numerical analysis showed a promising increase in flexural shear capacity between 40-55% and an increase in ductility of more than 80% compared to the I-girder without CFRP reinforcement

A study on the fire safety concepts used in car parks. To asses the possible damage as a result of a fire, case studies were performed and changes in the car industry were analysed. The new type of fuel systems have resulted in new risks, which are not yet covered in the current design methodology. To understand the probability of a car park fire an analysis was done on occurred fires in car parks. The changes in the car industry had resulted in larger fires and bigger fires will likely occur in the near future.

The standard NEN 3215 contains a certain rain intensity for the rainwater drainage from roofs. By making use of the rainfall predictions for 2050, the consequences of this new intensity for the standard are analysed. Based on this analysis, a change of this rain intensity in NEN 3215 is recommended.