Reusing construction materials has become increasingly significant in the context of the Netherlands’s goal to achieve a fully circular economy by 2050. This thesis provides a guideline for the reuse of masonry, emphasising the transition from traditional demolition methods into techniques that facilitate the reuse of masonry elements. The research explores the development of masonry, current practices, and future perspectives, highlighting the environmental gain and durability proceedings.

Masonry, a cornerstone of Dutch residential construction, offers significant potential for reuse due to its durability and historical prevalence. Despite innovations like drystacking and prefabrication, traditional masonry remains dominant. This study underlines the urgency of enhancing masonry reuse in light of the projected increase in new housing construction and subsequent demolitions. The research identifies a gap in the reuse methods of masonry, proposing an approach of cutting out panels from exiting walls for incorporation into new projects.

The thesis begins with a historical overview of masonry and its separate elements, mortar and brick. It traces its development from Roman times to the present. Early masonry in the Netherlands saw the use of tuff stone and brick, evolving through various phases influenced by technological advancements and changes in construction methods. The introduction of cavity walls, the development of different brick bonds, and the use of various mortars are detailed, highlighting the transition from masonry as a structural element to its current role as a (decorative) façade.

Innovations in masonry construction are examined, focussing on drystacking, robotics, and prefabrication. Drystacking allows erecting masonry facades without mortar, facilitating easy disassembly and reuse. While promising, Robotics in masonry construction face challenges in widespread adoption due to the complexity and precision required. Prefabrication, though historically significant, remains underutilised in modern construction.

The thesis analyses the current stock of buildings in the Netherlands, emphasising the potential of masonry reuse. It discusses the materials flow, highlighting the substantial use of bricks and concrete in new construction. The research outlines the demolition trends, noting that older buildings, particularly those from the post-war period, are prime candidates for material recovery.

A significant portion of the thesis is dedicated to the practical aspects of masonry reuse. It describes the process of removing masonry elements, including desk research, visual inspection, and destructive tests. Techniques for sawing, hoisting and transporting masonry panels are discussed, providing a step-by-step guide for practitioners. The study also addresses storage and implementation, emphasising the need for proper handling to maintain the integrity of the reused material.

Durability is a critical concern in masonry reuse. The thesis evaluates structural and climate durability, assessing the properties of masonry elements under various conditions. It explores the impact of frost/thaw cycles, improper joint application, and strategies on the longevity of reused masonry. The research employs DIANA modelling to simulate the structural behaviour of masonry panels, providing insight into their performance during non-conventional boundary conditions of lifting the element from the existing structure.

The environmental impact of masonry reuse is quantified through a life cycle assessment (LCA). The study compares the environmental burdens of reused masonry elements with traditional buildings and reusing masonry bricks. It highlights significant reductions in CO2 emissions and total MKI value in both comparisons.

The thesis concludes with practical recommendations in the form of a guideline, encouraging a shift towards more sustainable building practices. The research emphasises the importance of quality control and standardisation in reusing, ensuring that reused material meets current regulations and performance standards.

By addressing the technical, environmental, and practical aspects of masonry reuse, this thesis contributes to the broader discourse on sustainable construction. It provides a valuable framework to enhance masonry reuse, aligning with the Netherlands' ambition for a circular economy. The guideline presented in this thesis research aims to facilitate the adoption of masonry reuse practices, promoting environmental conservation and resource efficiency in the construction sector.

Masonry structures subjected to a lateral load, such as earthquakes and wind, can be prone to out-of-plane failure. It is known that geometrical properties and boundary conditions have a large influence on the out-of-plane bending capacity of walls. In this thesis, a numerical study is performed to evaluate the influence of the bond pattern on the two-way out-of-plane bending capacity of unreinforced brick masonry walls. A nonlinear finite element analysis with a 3D block-based model has been adopted to simulate the texture of the wall in detail. The study builds on the work of Chang et al., which was validated against the experimental benchmarks by Griffith et al. The numerical model can accurately estimate the initial stiffness and out-of-plane bending capacity, but the model is less accurate post-peak.
It is assumed that the material properties of the mortar in the bed joints are the same as the one of the head and collar joints. The masonry wall was first subjected to self-weight and a vertical pre-compression of 0.1 MPa. Afterwards, a monotonic out-of-plane pressure placed on the face of the masonry wall is applied. The numerical model takes both physical and geometrical nonlinearity into account.
In the first phase, different modelling assumptions were checked and a sensitivity study was performed. Prior to the study must the compressive behaviour of the brick be determined, as the bricks are elastic without a limit, thus nonlinear effects like crushing are not modelled. The resulting check determined that the minimum principal stress did not exceed the compressive strength of the brick.
A mesh sensitivity study has also been performed as a change in mesh size was needed. In the model of Chang, the face of the brick was divided over its length into two parts called a halfbrick (Hbrick). The bond patterns require a division of the face into 4 parts, a quarterbrick (Qbrick) or an octogonalbrick (Obrick) which maintains the aspect ratio of the Hbrick. Eventually, the Qbrick mesh is the best option as convergence issues arose for the Obrick.
Additionally, experiments have shown that cracks can propagate through the bricks, while this is not possible with a smeared cracking model. To simulate this effect a discrete cracking model within the brick was introduced. The possible locations of the cracks can easily be assumed in a masonry wall, to be in line with a mortar joint in the course above or below it. The change to the discrete cracking model did not influence the out-of-plane two-way bending capacity, while convergence issues arose, and it was subsequently not used.
Finally, in the experiment by Griffith et al., clamps are installed over the height of the end of the return walls. These clamps prevent any horizontal translations and rotations in the horizontal plane. These clamps are represented by tyings in the numerical model. In this study are these tyings removed and is the length of the return wall parametrised. A masonry wall without any return walls is fully one-way bending and to a length of 360 mm does the masonry wall show a transition between one-way to two-way bending. A return wall of at least 480 mm long is sufficiently long to achieve two-way bending.
A parametric study was performed considering five single wythe and three double wythe bond patterns: stretcher bond, quarter bat bond, lateral bond, half Flemish bond, stack bond, chain bond, English bond and Flemish bond. The double wythe masonry wall has been assembled by adding an outer shell to the single wythe wall and by decreasing the pre-compression to 0.0478 MPa to maintain the same vertical force as the single wythe bonds.
The highest out-of-plane bending capacity for the single wythe bond patterns is the half Flemish bond with 4.9 kPa with a spread of 5.4% and for the double wythe bond patterns it is the Flemish bond with 18.7 kPa with 7.2%. The spread between the highest and lowest out-of-plane bending capacity is small. All the walls, except the one in stacked bonded masonry, show a crack pattern in the form of a cross. The slopes of the diagonal cracks with respect to the horizontal bed joint line have also been studied and relates as follows: a shallow slope in the crack pattern coincides with a higher two-way out-of-plane bending capacity. While a steeper slope or the absence of a cross-shaped pattern coincides with a lower out-of-plane bending capacity. On the contrary, the initial stiffness of the masonry wall does not relate to the out-of-plane bending capacity.
To further confirm these findings, research is needed concerning different masonry types, considering relative properties between bricks and mortar joints, different properties between bed, head and collar joints, and spatial variability of properties.

Urbanisation has increased the worlds' cities populations and influenced the living conditions within these cities. Temperatures rise, the air becomes more polluted and noise levels increase. It has been proven that types of vegetation such as plants and trees can reduce the negative effects of urbanisation by for instance cooling cities, filtering the air or damping out noise. Due to the limited space in urban areas, placing vegetation on building façades and roofs can be a practical solution to gain the benefits of natural elements without the need for large pieces of land. A total of seven benefits provided by greenery systems can be distinguished which were researched intensively, however it is unknown how these benefits compare to the downsides of adding extra loads to a structure, which come in the form of extra material use and lead to an increased environmental impact for the building. In this research these benefits and downsides were compared to determine whether the application of greenery systems actually makes the building more sustainable or not. In this research the effect of six horizontal greenery systems (also known as green roofs) and eight vertical greenery systems (also known as green façades) on the sustainability of the building was assessed.
The effects of the benefits of the greenery systems on the sustainability of the building were determined using three different certification methods: BREEAM, LEED and WELL. In these certification methods credits related to one of the seven benefits can award the building a preset number of points, thereby increasing the overall amount of points awarded to the building. The impact of extra material use was determined using the environmental cost indicator (ECI), after determining the needed element sizes. The percentage increase of the sustainability certification score and the ECI were compared to determine which of the two has a higher percentage increase. When the increase in the sustainability certification score is larger than the increase in ECI, the greenery system receives a 'positive score' meaning the building has become more sustainable. If this is the other way around, the greenery system has a 'negative score' meaning application of the greenery system has made the building less sustainable. When both are equal the system has a 'neutral score'.
This research has shown that it is currently not possible to value all aspects of greenery systems in the certification methods used. Nonetheless, greenery systems lead to an increased sustainability of a building in 52% of the tested cases. The nature roof always receives a positive score and application of a direct green façade can result in a positive or neutral score but never a negative score. These two systems can thus always be applied to a building without having a negative effect on the building's sustainability. There is potential for modification of the existing certification methods so they can score all benefits provided by the greenery systems properly, giving more insight into the impact of these greenery systems on a building's sustainability and potentially affecting the number of cases with a positive score.

Currently, most of the modular building can be fabricated off-site, except for the stability system. Therefore, the question arises: Could modules be designed such that there is no need for an additional stability system? As modules are typically built in a rectangular shape, incorporating stability elements such as bracings along the longer side of the module is not the problem. The main challenge lies in the limited length available for stability elements on the shorter side of the module, combined with the fact that this shorter side is commonly used for windows and openings for door frames. This introduces a conflicting interest between structural capacity and daylight within the module. This conflicting interest becomes more and more prominent as the building height goes up. A possible solution to this problem can be found in the use of a load-bearing window frame with glass infill as a stability element, often referred to in literature as a timber-glass shear wall (TGSW).

Therefore, this thesis will answer the main research question: 'To what extent can the structural performance of a timber-glass shear wall as a stability element in a timber module be used to accommodate for the stability of a mid-rise modular timber building?'

The approach to answering the main research question consists of several steps. First, a literature study was conducted on modular buildings and TGSW's. The outcome of the study has provided insight into how modular buildings are constructed in general and how relevant aspects such as progressive collapse, fire safety design, and foundation design influence structural design. The study also resulted in an analytical prediction model for the load-bearing capacity and stiffness of the TGSW. Through this prediction model, it became clear how the properties of individual components relate to the load-bearing capacity and stiffness of the total TGSW-system.

The second step was to propose a design for a modular timber building composed of timber modules. To save on computational time, the stability elements of the building are modelled using steel diagonals as an equivalent system for the TGSW. The cross-sectional area of the steel diagonals is directly related to the properties of the TGSW. Therefore, the steel diagonals have identical stability properties as the TGSW. In this study, varying the type of adhesive and the spacing of the screws was found to have the most significant impact on the overall structural properties of the TGSW. The horizontal connections are made of steel plates fastened with screws. The vertical connections are realised by shear plate connectors. The entire building was modelled in a 3D FEM programme to assess the structural behaviour of the building and its compliance with building regulations. Several building configurations ranging from 1:1 to 1:3 height-to-width ratio were investigated. For each building configuration, the cross-sectional area of the steel diagonals was adjusted within a specified range. This range corresponds to variations in adhesive type or screw spacing. As a result, design graphs were produced, which present the requirements for the load-bearing capacity and stiffness of the stability system. These can be compared to the load-bearing capacity and stiffness of the TGSW. This comparison can be used as a validation method to determine the viability of the TGSW stability element in a modular building.

The results of this study indicate that a modular building can be stabilised by a TGSW up to six stories within the height-to-width ratio of 1:1 to 1:3. The minimum building configurations per story height are: 3 modules high by 5 modules wide, 4 by 8 modules, 5 by 12 modules, and 6 by 18 modules. These slenderness ratios were governed by the strength of the TGSW. The limiting factor in the load-bearing capacity is the shear strength of the adhesive. These slenderness ratios could only be reached with elastic adhesives such as silicones.

The next step is to create a more extensive FEM model that could predict the load-bearing capacity and stiffness of the TGSW in a more accurate way compared to an analytical model. Furthermore, exploring the performance of the TGSW under different horizontal loads, such as earthquakes, would give valuable insight.

As many bridges in the Netherlands are past their design-life and yet still have well-functioning steel superstructures, their bridge decks are often due to be replaced. FRP panels are promising alternatives to concrete decks for these renovation works due to their low density, fast on-site construction time, and excellent acoustic and thermal properties. Many of these bridges are originally designed with hybrid interactions occurring at the connection level. Multiple connection types exist to ensure hybrid interaction with FRP decks. However, there is a gap in this field concerning a rapidly demountable connection able to transfer shear forces at girders with oversized holes. The injected reinforced resin connector is designed and aimed at achieving hybrid interaction through combined injection and preloading of the connector. The aim of this thesis is to find a viable design for this connection, and to test the connection under local compressive wheel loads. be able to design the connector and test it according to standards as expected to occur in real bridge applications, a FE-model of the bridge Nieuw-Vossemeer is made to assess expected loadlevels in the connection. The result is a combined list of loadlevels and geometrical tolerances that the connection will have to be able to sustain or perform under. Based on the resulting design requirements a main design is proposed. Here a steel bolt is embedded in the bridge deck and held in place by injection with reinforced resin. A steel plate separates the bridge deck from the girder flange, and creates a full steel clamping package. Multiple design alternatives are tested by the use of FE-models, where the variable is the type of steel plate used between the bridge
deck and the girder flange. The most viable design to continue experimental tests with is selected by its stiffness, ultimate resistance, and a qualitative assessment regarding expected cyclic endurance. The best performing concept is a steel plate with a spherical bottom, a diameter of 150mm and maximum thickness of 20mm. Extra FE-analyses are performed on a local scale, and take into account positional deviations from the most ideal situation. In addition a series of two static and two cyclic experiments has been performed. Apart from finding their respective resistances, the failure modes are assessed and compared together with the numerical analysis. The static tests show an ultimate resistance of 501kN, the numerical analysis shows a resistance of 498kN. Both the static tests and the numerical analysis failed ultimately due to delamination in the bottom facing of the FRP, the cyclic tests failed under a similar failure mode in the bottom FRP flange. On loading ranges with R = 0.1 it is found that the primary failure mode is a horizontal crack opening up in the bottom FRP flange, which propagates into the webs. The connection withstood 2 million cycles at 9kN - 90kN without damage. Subsequently, two different loadranges were applied to the two different tests, which failed after 394 thousand cycles at 13.5kN - 135kN and 34 thousand cycles at 18kN - 180kN. It is concluded that the spherical plate is able to function as a coverplate and withstands rotations, displacements and the required loadlevels as expected in bridge applications. The primary recommendation is to continue performing tests with a similar plate with a thickness of 15mm, as the current design overshoots the required resistance significantly.
The results show that the design is well able to sustain the required local compressive wheel loads, both in ultimate and cyclic resistance. With the ability to (de)mount these FRP panels quickly on-site, two main goals have been reached. Firstly, this brings the use of FRP panels in infrastructure closer, leading to reduced loads onto steel superstructures of existing bridges (and hence an extended lifetime). Secondly, a fundamental step has been set towards modular bridge design, where during failure only specific panels of the system have to be replaced. Together these developments can lead to a reduced impact of the construction industry on the environment.

Problem definition: In the car park industry, a new trend has emerged, shifting the demand for parking from permanent one-of-a-kind parking structures towards temporary modular structures (Drenth, 2020). Meanwhile, the building industry faces a transition into a more sustainable industry. This requires rethinking of the design process, taking into account possible reuse of a building or its elements as well as potential use of different materials. Timber is a renewable material and as a result of developments in timber engineering, now allows the construction of taller and larger structures. Given these trends and challenges, the objective of this thesis is to provide a structural system proof of concept for a temporary multi-storey car park, using timber as primary structural material.
Approach: A broad literature study provides background information on the various relevant topics and is followed by a refinement of the objective, substantiated by two sub-studies. This has resulted in two sub-goals: the minimization of total deck height (< 700 mm) and minimization of the structural systems weight (column load < 1,000 kN). A proof of concept is developed through a parametric study with structural validation into four main design variants (consisting of a deck and framing system), for which the effect of altering four geometric parameters (parking deck span, use of struts, distance between columns in transverse direction and minimum distance between joists) on these sub-goals is studied. Furthermore, a sensitivity analysis is performed on the effect of altering the requirements concerning fire-safety, vibrations and deflections on the deck height and weight. Finally, the proof of concept’s performance is compared to five alternative modular and/or timber car park concepts in a case study.
Evaluation: It is concluded, that design variants using long-span deck systems result in a relatively small deck height, but high self-weight. A CLT rib deck should be applied under “standard” assessment criteria, but significant reductions in deck height (31%) and weight (49%) can be achieved by using LVL rib decks when vibrations are not considered and deformation limits are increased. The total deck height of design variants with short-span decks, which use solid LVL panels, highly depends on the supporting framing system, but its self-weight is roughly halve of the long-span design variants. The effect of alternative assessment criteria on design variants with short-span decks is rather limited. It is concluded that the use of struts significantly reduces the total deck height (17-30%) and structures weight (5-11%) and a transverse column distance of a single parking bay width is preferred. The distance between joists is of less relevance, but a bigger parking deck span increases both deck height and total weight.
The resulting proof of concept consists out of a short-span solid LVL deck system, which spans two times 2.5 m (single parking bay width). It is supported by glulam main girders, spanning the entire parking deck, which are simply supported by a set of columns at a transverse distance of 2.5 m and are additionally supported by slanted struts between the columns and main girders.

The results from the case study show, that the total deck height of the proof of concept (666 mm) is smaller that the sub-goal of 700 mm and comparable to alternatives with decks made of steel, concrete and GFRP. Furthermore it is 40% thinner than the alternative in timber as a result of the use of LVL and struts. In terms of weight, the use of timber is much lighter than using concrete decks (<25%) and only 17% heavier than the extremely lightweight GFRP decks. Furthermore, it results in the smallest loads on the foundation (678 kN which is smaller than the sub-goal of 1,000 kN). A first extremely simplified durability analysis on amounts of embodied carbon in the main structural elements indicates timber has significantly lower amounts of embodied carbon in comparison to the alternative concepts.
Implications: Based on the results presented, it is concluded that timber is applicable for almost all main structural elements of a temporary and modular multi-storey car park. The case study has shown that the proof of concept can compete with alternative modular car park concepts in terms of deck height and outperforms most alternatives in terms of the structures weight. It is also indicated, that timber has the potential to significantly improve the performance of a structure in terms of sustainability.
For future research, it is advised to further develop the proof of concept, focussing on the connections and durability risks and study the incorporation of circular design strategies into the design and construction process of the proof of concept. Furthermore, alternative assessment criteria should be validated. Finally, it is advised to study the potential use of other innovative sustainable building materials like BauBuche and make a detailed LCA study assessing the performance on sustainability.

We are currently facing a transition of economy. Previous years were focused on a linear economy, consisting of the make-waste concept. The products that are made with raw materials are thrown away after its use. Unfortunately the Earth does not contain an unlimited source of materials and we need to focus on reusing materials. Concluding to create a circular economy in which waste does not exist at all.

The goal is to start with reusing as of today, instead of in the future. In other words, using the current existing elements. However, to do so it must be known which elements are available. Therefore, a data analysis has been done on the current existing structures as well as the future perspective. These analyses combined concluded in a common scope, visualized as a Lego box. This Lego box does not only consist of all the current existing structures (within the determined scope), but also provides a future perspective on the demolishing plans in the near future. Based on a time-consuming manual research a variety of nearly 70 viaducts have been examined. This lead to the summarization of 5 different girder categories: Box girders, inverted T-girders, Infilled girders, T-girders and remaining.

With the specific girders known, design applications can be created. The focus on these applications is to think outside the box and reusing a girder in a different function than the original purpose. The design applications are created with a brainstorm session. For this session multiple different broad-minded individuals had been invited for an open discussion which concluded in over 20 different design applications. Thereafter, these applications have been examined with the help of an MCDA, based on the three main criteria. This MCDA is executed with the help of multiple different experts with a background regarding one of the three main criteria. With these expert judgements the total amount of design applications have been demarcated to a top 5. Reusing a girder as: Bicycle bridges, (non-)residential buildings, retaining walls, sound barriers and culverts

In conclusion, this thesis provides valuable outputs and the first impressions regarding reuse in another application seem at least interesting. With the different impact factors determined, the possibility looks very promising. It can be stated that reusing in general will be better for the environment, as well as for your own wallet. Reusing a girder as culvert can in theory be seen as a good reuse application, but not higher in a general value than reusing again as a girder. This is based due to the fact that using the girder as a culvert will take more research in practice, especially regarding structural aspects. However, from this thesis it the first impression conclude in the fact that the impact in costs as well as environmental impacts are bigger when reusing the girder in another function

The search for a transparent, reusable, innovative, architecturally aesthetical, structural material that could be used as consolidation system for decayed historic buildings led to the ambition to test a topological interlocking (osteomorphic) design by using numerical calculations. In the last decennia glass has evolved to be a structural material that could be implemented in diverse structural elements. The mechanical properties of glass, in particular the high compressive strength, offer today a competitive solution that can be used for the purpose of restoration, allied to its transparency and aesthetics. The use of glass as a material is also aligned with the recommendations laid down by the international agreements for restoration. Due to its transparency it allows the ruin (Schaesberg Castle) to be perceived in its damaged state keeping the identity and at the same time being distinguishable from the original material in a subtle and immaterial way.
A literature research gave the technical background necessary related to glass, and how by choosing cast glass in the form of topological interlocking (osteomorphic) this would improve its strength and stiffness by introducing a 3d dimension and optimizing the use of compression. The case study’s main purpose was to give a context for the architectural and structural design and evaluate the technical consequences of applying a topological interlocking structural assembly to replace the missing parts of the existing castle. A design was proposed based on the topological interlocking osteomorphic stability system. The design criteria obtained by the literature and case study were then combined to obtain a model to be tested using numerical calculations.
A global model in Finite Element Analysis, with Diana FEA was chosen to test the whole structural integrity and performance by looking at the stresses and the maximum capacity of the system to check if it fulfilled the strength and stability requirements and to test the influence of two types of connections between the materials.
The results suggested that the system performed well and was strong enough but are based on the assumption of a monolithic system which resulted in a less accurate outcome, unable to predict the failure mode by delamination. According to the results, this system can be implemented to replace the missing parts of a monument but a more detailed model is needed to study more accurately the local failure behaviour.
This can serve as a starting point for future research in similar situations. The study of the connections, although conceptual, can support decisions for detailed design proposals.

The purpose of this thesis is to determine the most optimal material use and configuration of structural elements with regard to minimizing shadow costs associated with the main bearing construction of industrial halls. Central themes in thesis are reusability, parametric modelling and generative design.

The construction sector is responsible for a large amount of pollution due to its high energy consumption during extraction and transportation of raw materials. Paradoxically, this offers the construction sector a unique opportunity to notably decrease its negative environmental impact. More and more industrial halls are built due to an increase in online shopping and the subsequent need for the distribution of consumer goods. However, the current inefficiency in shadow cost reductions of main load bearing elements presents a problem for the decrease in harmful emissions as a consequence of construction.

Shadow costs associated with structural elements decrease as a result of reuse. Connection types have been identified as the most influential factor for reusability. Therefore, a connection reusability factor was developed which was given according to four material independent criteria. Subsequently, a corrected shadow cost (CSC) can be calculated by multiplication of this reusability factor with the original ECI. However, this method is experimental and is not sufficiently corroborated by relevant literature yet.

A parametric model of an industrial hall was constructed in Dynamo which could be optimized using a genetic algorithm in Autodesk generative design in order to minimize the shadow costs of the design. No biogenic carbon storage was accounted for during these optimizations and only single span hinged construction elements were assessed. Furthermore, all designs were assumed to be located in a rural part of Dutch wind zone II and no fire protection measures were accounted for in the ECI or price of the designs.

Based on these assumptions, several conclusions could be drawn from the optimization of an arbitrary hall and two case studies. For the boundary conditions that were selected for the arbitrary hall, steel elements performed best with regard to the total ECI value as well as the corrected shadow costs. Contrary to popular belief, timber elements performed best in terms of price. A combination of both materials therefore has a high probability of resulting in the most cost effective ECI optimization. The results from the first case study indicate that the ECI of an existing hall could be reduced by 16 % as a result of the optimization methodology as presented in this thesis. The second case study was not accurately comparable enough to the optimized hall as a result of large differences in the connection types that were used.

The results that are presented in this thesis are based on specific loads, connection types and boundary conditions and configuration of the halls. The conclusions that are drawn in this thesis are therefore only valid in case similar halls with similar boundary and load conditions are assessed.

For centuries timber has been the most commonly used material for constructions. All over the world examples of timber structures that date back from a few centuries are still standing today. The Netherlands feature about 60,000 national monuments with internally timber structures. These timber structures often need strengthening due to increasing loads that are applied. The strengthening techniques are narrowed down to a few options whenever historical ceiling designs, such as ceiling paintings, plaster works or timber beams need to remain intact.

Timber floors encounter two major challenges: low stiffness which leads to limited load-bearing capacity and low surface mass which leads to poor acoustic sound insulation. This research seeks to provide structural engineers to make a factual choice in an early design stage for using a reversible strengthening technique on a monumental timber floor preserving original appearance. This strengthening technique is verified for strength, stiffness and acoustics, both airborne and structure-borne sound transmission. To this end, the following research question was formulated: "What is the influence on the strength, stiffness and acoustic properties of monumental timber floors by strengthening them with multiple layers of plates fastened on top of the existing floor?"

To answer the research question, a case study was performed on two monumental floors of the Prinsenhof Museum in Delft. These floors were investigated for their current strength, stiffness and acoustic properties. Then, equations were derived which considered the separate timber plates in the reinforcement technique as an equivalent layer. This equivalent layer is used to determine the effective stiffness for mechanically connected girders by the gamma-method. These equations were validated using software for 2D frameworks. Subsequently, a parameter study was used to determine the influence of the parameters on the strength, stiffness and acoustic properties. Finally, by applying the reinforcement technique to the case study based on the results of the parameter study, the strengthening technique was assessed more in detail by taking into account the influence of the non-cooperating intermediate layer.

The results of the parameter study and the case study demonstrated that the strengthening technique increase the strength and stiffness of the floor considerably. However, by increasing the stiffness, the connections between the additional timber plates and the reinforced component becomes governing. Furthermore, the increase in stiffness does not significantly improve the acoustic sound insulation, as this is mainly governed by the surface mass of the timber floor.

It is therefore concluded that strengthening of monumental timber floors, by means of several layers of separate timber plates fastened on top of the floor, is an effective way to achieve the desired strength and stiffness. Thick plates, small spacing between fasteners and inclined fasteners are a requirement to achieve higher strength and stiffness. However, additional measures must be taken to meet the sound transmission requirements. For the original perseverance of the monumental timber floor and reversibility, these measures would be dry floating floors. A significant fact is that dry floating floors only add mass and do not increase stiffness, which lowers the maximum allowable load on the floor.

A major limitation of this thesis is the consideration of the non-cooperating intermediate layer between the additional timber layers and the reinforced component. This intermediate layer results in multiple shear planes between the reinforced component and the additional timber plates. This thesis suggested to use a factor, determined from Roensmaens et al. (2020) research, to convert the multiple shear planes into a single shear plane. It is therefore important that further research investigates the influence of these multiple shear planes that do not contribute to the bending stiffness of the reinforced component.

In order to help the building and construction sector move towards a Circular Economy and lower its environmental impact, a better founded choice regarding the design and selection of building materials for a building’s load bearing structure is required. By investigating different design strategies that focus on optimizing various aspects of the Circular Economy, an office building can be designed in such a way that it matches both the initial client’s requirements as well as possibly changing future needs. Different design strategies then lead to varying lay-outs of a building’s load bearing structure and the building material it’s made of.
By ranking ten design perspectives in varying orders, three main design strategies can be formed. The first one maximizes a building's technical service life, thereby limiting the use of new materials and energy during maintenance activities. The second strategy aims for a maximal functional service life, by making the original building fit for possible other functions in the future. The final strategy maximizes a building's residual value, which includes re-use of building elements in new projects.
The next step is to link these design strategies to various criteria that can be included in the Multi Criteria Analysis. This results in a total of nine criteria, some of them being linked to the characteristics of a building material and the type of connections that come with that material. Other criteria depend on the design of a load bearing structure, such as the total weight of a structure, its ECI value and a cost indication. Now, all these MCA criteria can be given different weights, according to their level of importance per design strategy.
Finally, the MCA as explained above, can be tested on a case study from Witteveen+Bos. Based on the Program of Requirements as formulated by the client, both design strategy 2 and 3 could be followed during the design phase. The main difference between these two strategies can clearly be seen in the lay-out of the load bearing structure’s. After completing the MCA for both strategies, it can be concluded that a bolted steel structure is most likely the best option for design strategy 2. On the other hand, a bolted CLT structure seems to be the best solution when designing according to design strategy 3 for this specific case study. Concluding these results, it can be stated that the MCA can indeed help in selecting a design and building material, however in some cases, the differences between some building materials seem limited. Therefore, it can be said that the MCA is more likely to be helpful in eliminating some of the building materials from next design steps, based on their low MCA results.

Over the last few years, the construction sector has experienced increasing demand for raw materials due to the rapid growth of the urban population. At the same time, most of the post-war buildings in Europe have reached the end of their service life. As a consequence, a period of intense demolition activities with
significant waste generation is expected in the upcoming years. Both situations are eventually translated into significant environmental pressure. Concrete is the main component in construction and demolition waste (C&DW). Due to the high environmental footprint of this material, it is crucial to eliminate its consumption
through recycling and re-use. Currently, concrete rubbles are crushed with regular crushers and used mainly for low-grade applications (down-cycling) such as road foundations. Despite the environmental and financial benefits, this practice is still not at a sustainable level since raw materials are still needed for new structures, while the demand for low-quality secondary materials in the construction sector has already declined.

Two innovative recycling technologies called C2CA and Smart crushing (SC) developed recently in the Netherlands, aiming to close the material loop in the construction sector. These technologies recover most of the original concrete materials at high-quality, which can be use in the production of new concrete at
higher rates than traditionally. This research focuses on the environmental and financial implications of the novel C2CA and SC recycling systems as alternative solutions to the Traditional crushing (TC) method. The evaluation was conducted based on an integrated LCA&LCC analysis framework in which the monetised
environmental impacts (shadow costs) were internalised in the actual costs occurred within the supply chain of recycled concrete (production of primary materials, recycling, transports). On this basis, the recycling systems were compared from two different perspectives. First, the recycled materials produced were used for concrete production according to the current European standards. In this case, the traditional recycled coarse aggregates (TRCAs) were used to replace 50% of the primary gravel, while the innovative coarse (IRCAs) and fine (IRFAs) aggregates from the innovative systems replaced 100% of primary gravel and 60% of primary sand respectively. The maximum potentials of the innovative systems were investigated in a second scenario in which IRCAs and IRFAs completely replaced the primary concrete aggregates. In addition to that, the produced recycled concrete powder (RCP) was used as supplementary cementitious material (SCM) to replace 20% of the primary cement. In this study, the innovative recycling systems were considered mobile units located at the demolition site. In contrast, the TC recycling was executed off-site at a stationary plant to secure the sufficient quality of TRCAs.

The results of the integrated LCA&LCC study revealed that both C2CA and SC systems were financially better options than the traditional recycling route. Especially when the SC system was used to replace higher quantities of primary materials, the total cost was reduced by up to 19% relative to the TC method. On the other hand, the C2CA technology showed better performance when following the current standards, where about an 8% cost reduction was achieved. However, environmental improvements were reported only for maximum utilisation of the SC products, resulting in about 17% lower shadow cost than the traditional method. In the case of the C2CA system, the environmental impact was found 5% increase for both scenarios. Both innovative systems displayed overall benefits over the TC method regarding social cost (internalised environmental impacts), with the SC system exhibiting the best overall performance for maximum use of its products. In this case, the overall benefits reached almost 19%, while the rest scenarios were not higher than 5%.

The sensitivity analysis emerged that the innovative recycling systems presented benefits only when they were located close to the demolition site due to increased transportation of EoL concrete. For the same locations and up to 23 km away from the demolition site, only the SC2 scenario (maximum use of SC products) was more efficient than the traditional recycling route. The rest scenarios became more effective as the traditional plant was placed away from the demolition site. On the other hand, changes in the recycling phase, such as energy consumption and equipment operating costs, had a negligible impact on the results. Even if renewable energy sources would power the recycling plants, the environmental and cost benefits throughout the supply chain were not higher than 5% and 2.5%, respectively

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.

Recycling and reuse of structures and elements is important to reduce the carbon footprint of the building industry. Reuse requires much less energy than recycling and therefore has much potential. However, reuse is still rarely put in practice due to the many challenges constructing with reuse involves. One of these challenges is the complex design process. In this research, I have developed a tool able to design with reused elements. Topology optimization is combined with reclaimed elements with the aim to simplify the design process for steel truss structures. The member adding scheme of Linwei He. et al (2019) is used as a basis. Adaptations and additions are made to include geometry information and limited availability of reused elements. In the final tool, capacity utilization of elements is maximized, material volume of the structure minimized and percentage of reused versus new elements maximized. In conclusion, discrete topology optimization proved to be an effective method to simplify the complex design process. The tool can generate multiple different designs for every optimization problem with limited complexity. Volume increase or decrease compared to standard designs depends on availability of elements. In examples in this research volume increase could be limited to 20-30% with limited availability of elements. With large availability, multiple different designs could be obtained with an average unity check close to the maximum unity check. Recommendations are to improve applicability of the tool and to make an estimation of the reduction in carbon emissions and construction costs compared to designs with new elements. These estimations could increase attractiveness of designing with reused elements. Finally, accessibility of designing with reuse should be increased. It should be less difficult to obtain data of existing buildings planned for demolition to experiment with designing with reuse.

During the last decades, the development of high-rise increased quickly. The Eurocode is frequently used to make wind calculations for high-rise structures. To make those calculations, the dynamic wind load is simplified to a conservative equivalent static load. An alternative to calculate wind loads is a physical wind tunnel test. Wind tunnel tests are expensive. An alternative for these methods is the use of Computational Fluid Dynamics(CFD). CFD makes it possible to simulate the wind. At this time, CFD is still very user-dependent and therefore it is stated in the Eurocode that CFD simulations cannot be used as a design tool. This research aims to examine the impact of different parameters in evaluating the dynamic loading on a high-rise structure by the use of CFD. The results of the CFD simulations are compared with a spectral approach. The Navier Stokes (NS) equations are the basics for CFD. Different models are used to solve the NS equations. The costs of CFD increase exponentially with demanding more accuracy. An extension of the RANS model is used in this research: the Unsteady-RANS(U-RANS) model. Where the RANS model only computes the steady-state solution in a simulation, the U-RANS captures the slow turbulences as well. For the objective of a dynamic wind load on a high-rise structure the slow turbulences are of more importance than the faster turbulences. Especially the frequencies close to the natural frequencies of the structure are important. The CFD simulations are performed using Star CCM+ by Engineering Company ABT BV. A reference structure is used to validate the CFD simulation procedure with existing available wind tunnel data of the Tokyo Polytechnic University. The wind tunnel data contains dimensionless pressure coefficients on several locations on the model. The results show a lot of noise, which is visible when the time domain's pressure coefficients are translated into the frequency domain. A dominant peak is observed at a frequency of 10 Hz, but other frequencies are triggered as well. The CFD simulation for the same reference block show less fluctuating results than the wind tunnel data: the results are only fluctuating on one frequency of 12 Hz. Afterwards, a case study is used to compare CFD results with a spectral approach. A high-rise structure of 40 x 40 x 200 meters is used for this study. The results of the spectral approach are compared with existing literature using the structural factor cscd. The results coincide. Several CFD simulations are performed on the same model. The absolute values of the peak velocity pressure are of the same order of magnitude, with a difference of 10 to 25 percent. However, the values of the standard deviation differ more substantially. The CFD simulation stores the average pressure over an area of 10 x 10 meters, which balances out some fluctuations. Furthermore, it can be concluded that the CFD simulations underpredict the absolute values of the pressure consistently compared to the spectral approach. It can be concluded that the CFD simulations require exact defined input values.

A transition towards a circular economy is proposed by initiators like the Ellen MacArthur Foundation and architect Thomas Rau, in order to preserve and enhance natural capital, optimise resource yields, and minimise system risks. A circular economy seeks to ultimately decouple global economic development from the consumption of non-renewable resources, and will eventually result in an economy of services. In this transition, the construction sector plays a major role because it is responsible for 50% of the total resource use, 40% of demolition waste and 35% of CO2 emissions.
The design of the façade system of a building which is offered as a service is essential. Assembly and disassembly of components of such a building occurs more often compared to traditional buildings, so the components and elements have to be designed so that they can facilitate this. This is especially true for the components of the façade which, due to the relatively short lifespan of a façade have to be flexible. To help incorporate circular principles in the design, a new method or tool is needed to help making design decisions and compare different alternatives. The main objective of this master thesis is to investigate the suitability of cold-formed steel components for circular façade design and to develop an assessment method to measure the degree of circularity of façades. Current assessment methods for determining the circularity of products either focus on the environmental impact or the flow of materials and protecting existing value, and not on the degree of circularity related to certain design options. Also, there is no method which focusses specifically on façades.
A circular economy is restorative and regenerative, and aims to keep products, components, and materials at their highest utility and value at all times. This is achieved by controlling finite stocks and balancing renewable resource flows, circulating products, components, and materials, and designing out negative externalities. Circular design criteria are derived from the design strategies Design for Disassembly, Design for Adaptability and Modular Design. Currently used façade systems do have the potential to be used in a circular economy, provided that the design criteria for circular use are met.
During the Case Study two designs are proposed: a traditional façade system which uses sandwich panels, and a façade system which uses façade panels designed based on a concept for roof panels developed by CFP Engineering (two alternatives). The aim of this case study is to investigate the suitability of the newly developed façade element for circular façade design. Additionally, it will serve as input for the assessment method which is illustrated later in this thesis, and set boundary conditions for the comparison of the life cycle costs and level of circularity.
The most important design parameters to determine the circularity of a façade system are: the amount of materials used, the possibility for reassembly, the environmental impact of the system, the amount of reused and renewable materials, the availability of information and the amount of toxic materials. These parameters can be measured by calculating the Façade Circularity Indicator which, as the name suggests, cannot be considered an exact value. The Façade Circularity Indicator originates by combining an existing method (Material Circularity Indicator, developed by the Ellen MacArthur Foundation) with research on Design for Disassembly (Durmisevic, 2016). A prerequisite of this method is a Life Cycle Assessment calculation. The method can be used during the design phase to help making design decisions. Based on the Life Cycle Assessment, the environmental costs of the traditional façade system are 22% higher than the environmental costs of the case study alternatives, which makes the traditional façade system less suitable for use in a circular economy. When the mass of the components is used as a weight variable, the Façade Circularity Indicator of the traditional façade system is 9 to 12% lower than that of the case study alternatives. When environmental costs are used as a weight variable, the Façade Circularity Indicator of the traditional façade system is 54 to 60% lower than that of the case study alternatives. This also indicates that the traditional façade system less suitable for use in a circular economy.
As an overall conclusion, it can be stated that cold-formed components are suitable for use in circular façade design because of their relatively low weight, low life cycle costs and the possibility to (dis)assemble them with relative ease. Furthermore, an indication of level of circularity of façades can be given based on a combination of the Material Circularity Indicator and Design for Disassembly factors.

The work processes of structural engineers have been changing over the last decades. Digitalisation and automation play an important role in this change. One of the major developments in this context has been the introduction of Building Information Modelling (BIM). In a BIM model the geometry of the actual building is represented. To this geometry additional information regarding the design, construction, and maintenance of the building is attached. In current engineering practice, BIM software is only used for drawing purposes. This is unfortunate, as a lot of the information present in the model can be used for calculation purposes as well. At the same time, structural calculations still contain manual and time-consuming tasks. This also holds for the vertical load calculation (Dutch: Gewichtsberekening). An important calculation in the design of a building, as it is used to determine how the loads acting on the building are distributed to and carried by the foundation. The aim of this thesis is therefore to research and develop a method and tool that can be used to automate the manual processes in the vertical load calculation based upon a BIM model. The focus is specifically on multi-storey residential buildings. As a basis for the development of a method, the state-of-the-art in research and practice of the vertical load calculation and its automation has been investigated using interviews and a literature review. A framework is developed in which the different steps of the vertical load calculation are described using a number of flowcharts. Furthermore, responsibilities are assigned to the different persons involved. Adjustment scenarios are developed using which the structural engineer can correct the information that is retrieved from the BIM model. The practical applicability of the developed method is tested using Dynamo, a parametric engineering software connected to Revit. It is concluded that the vertical load calculation can be automated based on a BIM model. It is important to clearly specify the different steps of the process and to provide the structural engineer with the means to interfere with the outcomes of the calculation. The potential of BIM-based automation of structural calculations is demonstrated. Using the developed tool, schematisations could be quickly generated and directly calculated using the connected structural analysis software. By supporting the structural engineer in documenting design choices early, the introduction of errors and misunderstandings is prevented. In the end this results in time-saving, time that can be spend on the more detailed and complex parts of calculation processes.

Shape has long been an important parameter in improving the internal comfort of buildings and reducing energy demand. This can be seen from historical vernacular architectural typologies, like igloos, which have minimal thermal loss surface to provide a comfortable internal climate.  Using a shape factor to reduce the building envelope and to minimise thermal loss is incorporated into the Dutch Building codes for a long time, aimed at a comfortable climate and low energy demand. This research is focussed on optimising building shape to reduce energy demand but combining this with demands for thermal comfort and daylight entrance.  By making use of Grasshopper a parametric design model is created. Using this model, a large variety of building designs was generated which are analysed on their daylight entrance and energy demand using Honeybee and Ladybug. By analysing the outcomes of these performance analyses, the window-to-wall-ratio and shape, quantified by shape factor Lc, of these designs were optimised using the autonomous optimisation algorithm pilOPT in modeFRONTIER. The optimisation objective is to minimise the total energy demand for heating and cooling. This is assessed by calculating the normalised energy demand for heating and cooling for both a summer and winter period. To execute the optimisation, the Erasmus Campus Student Housing project by Mecanoo in Rotterdam was used as a reference project.  The optimisation results show more compact buildings, with low WWRs have lower energy demands. This can also be seen from the Pearson correlation between the Lc [m] and the normalised energy demand [kWh/m2]. Which is found to be -0.624 for the first optimisation and -0.632 for the second optimisation. This confirms current building practice in which the relative building envelope is tried is be reduced.  Low WWRs (< 0.2) can obtain a minimum daylight factor (DF50%) of 2.1%, which is lower than current practice. However, the minimum WWR is largely affected by the presence of neighbouring buildings. For facade orientations with adjacent buildings, minimum WWR is significantly higher (up to 0.8). Since buildings outside the own plot are not considered in the daylight calculation according NEN 2057 and the new NEN-EN 17037 situations may occur where buildings will obtain legal requirements but acquire poor daylight entrance. For future building shape optimisation studies, it is recommended to make use of visible part of the sky analysis (VSF) in the assessment of daylight criteria. Using VSF can save minutes of computation time per building analysis thereby speeding up the optimisation process. Recommendations for further research following this thesis are to: enlarge the number of case studies; focus on more detailed WWRs in a smaller range, by allowing smaller steps for WWR parameters, more detailed optima may be found; include the effect of installation efficiency, as this will affect the primary energy demand; assessing the effect of on-site energy production such as PV-panels on the building shape and WWR, as increasing the building envelope might not increase the net energy demand of buildings if more energy can be produced.    

Drying shrinkage can cause structural damage to concrete industrial floors. Shrinkage is caused by evaporation of moisture from the drying material. In the design- and construction-standards, this complex process is not described on a fundamental level. Using finite element modelling to simulate the flow of Moisture through the concrete, it is possible to simulate drying shrinkage. The research question of this thesis is: ‘How can a parametric FEM model efficiently simulate drying shrinkage in industrial concrete floors?’. Verification of the produced model is performed. The outcome is compared to shrinkage
measurements of concrete prisms. The theoretical framework presented in this thesis is based on the fact that the relative pore humidity is changing during drying. In a finite element model, the changing relative pore humidity (pore-RH) over time is calculated. Drying is caused by internal diffusion of moisture, which is driven by differences in concentration. The moisture flow is modelled using the transient heat equation. The resulting pore-RH values are used to determine the hydrostatic capillary pressure based on the equations of Kelvin and Laplace. The material response of cement paste subjected to the capillary pressure is calculated using Bentz law. At last, the models of Pickett and Neville are used to include the restraining effect of aggregates and determine the absolute deformation of concrete subjected to drying. The initial conditions of the material are determined based on HYMOSTRUC cement simulation and Powers’ volumetric model. The results of the presented theoretical framework are reasonable. Usage of the framework and the heat equation for modelling drying in FEM, proved to be successful. A significant uncertainty is found in the restraining effect of aggregates. The theoretical model is based on material modelling of drying cement paste. However, the deformation of concrete is only
16%~23% of the total deformation of cement paste. Recommended is to further research the (local) effect of aggregates on drying shrinkage. Drying shrinkage has been calculated according to the construction standards and compared to the measured drying shrinkage of the concrete prisms. From this, it can be concluded that calculations by structural engineers on drying shrinkage are preferably done according to the ‘Model code 2010’.

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