Fiber Reinforced Polymer (FRP) has increased rapidly in popularity in the past few decades. The material's advantageous properties, such as a high strength-to-weight ratio and low required maintenance, gave rise to its popularity in multiple major engineering branches. Buckling behaviour develops due to the notably low stiffness-to-strength ratio and the usual high slenderness of FRP plates. The occurrence of initial imperfections increases the tendency of the material to buckle. The load-carrying capacity of structures with post-buckling behaviour can be determined with progressive failure analysis, which requires a damage model that characterises the onset and evolution of damage. In Abaqus, the Hashin damage model is implemented by default, which considers the four failure modes of the material. Numerical analysis of strain-softening materials with local damage leads to deformation localisation in a single element: a finer mesh will decrease the amount of energy dissipated. To prevent this localisation into arbitrarily small regions, the stress is related to the deformation of a finite volume. The damage evolution is described with a stress-displacement response instead of a stress-strain response. The energy needed to open a unit area of the crack, the fracture energy, is defined as a material parameter and depends on the mesh size of the model. The assessment of fracture energy properties in composite materials is challenging due to specimen geometry and fibre lay-up, and accurate data of GFRP fracture energy is largely unknown. When no actual post-failure behaviour is acquired, the lower bound fracture energy can be determined from the material properties. Numerical analysis of uni-directional coupon experiments is performed to determine the input values and response of the lower bound fracture energy. The lower bound fracture energy implementation results in an abrupt drop in stress when the material strength is reached. Increasing the lower bound fracture energy by a minimum of 2% prevented numerical inconsistencies. Progressive failure analysis of multi-directional coupon experiments validated an increase of 10% for the lower bound values. The use of lower bound fracture energy for non-linear buckling analysis is verified with progressive failure analysis of the buckling experiments. The lower bound fracture energy, increased by 10%, approximates the ultimate strength of six tests with an average difference of 7.7%. To analyse the non-linear buckling behaviour of a GFRP plate, a buckling curve is created by varying the plate thickness. The influence of geometric imperfections on a plate's buckling strength is studied by applying different initial imperfections. Two types of boundary conditions are used to analyse if they result in a different buckling curve. A difference in the buckling strength reduction factor of 0.1 is found. Initial imperfections reduce the buckling strength of the material, which is most apparent for plate slenderness around 1.0. An initial imperfection of B/125 resulted in a 40% strength reduction compared to the elastic buckling strength. The average difference in reduction factor between an initial imperfection of B/1000 and B/125 was 16%, with a maximum difference of 26%.

Crack growth is an important failure mechanism in many engineering materials. Numerical models for crack growth have been developed within the framework of damage mechanics. All these models aim for the same goal, obtaining accurate results for crack growth under various loading conditions. Many damage models are based upon the cohesive crack approach. However, level set based models provide advantages compared to the cohesive crack models with regard to fatigue analysis. An alternative method to the existing thick level set (TLS) method was proposed, the interfacial thick level set (ITLS) model. The use of interface elements made the model more suitable to simulate several failure processes. In this thesis it is demonstrated that this method suffers from a dependency on the initial interfacial stiffness for the global response of a system by conducting a parameter study under quasi-static loading conditions. This parameter study proves that for a varying value of the initial interfacial stiffness parameter K the global response varies as well. This gives motivation to conduct further research on the removal of the initial interfacial stiffness from the current ITLS model. Two methods are developed to overcome the initial interfacial stiffness dependency. The first method assumes that the initial interfacial stiffness dependency is caused by the current formulation of the constitutive law of the interface. A new expression for the interfacial stiffness is adapted after which all constitutive relations are updated. The new method shows a perfect agreement with the current ITLS model, which validates the method as an accurate alternative. Compared to the current ITLS model, method 1 allows for the control of the initial stiffness of the undamaged part of the interface by changing the lower bound damage without affecting the global response. However, when executing simulations for a varying initial interfacial stiffness K the same problem as for the current ITLS is observed. It can be concluded that in a way this method removes the dependency on the initial interfacial stiffness but the initial interfacial stiffness parameter K should then remain constant. Furthermore, the calibration process is not simplified compared to the current ITLS model. For this reason method 1 is rejected as the final solution to the problem and a second method is proposed. The second method assumes a direct relation between the damage parameter c1 and the initial interfacial stiffness parameter K. This damage parameter is responsible for the steepness of the damage profile. The results from the parameter study showed that an increase of one of these parameters results in opposite behaviour for the initial stiffness of the global response. The leading hypothesis becomes that an increase in the stiffness parameter K can be neutralized by an increase in the damage parameter c1. Proportionality between both parameters is assumed. By trial and error the proportionality is found to be one to one. When using this proportionality condition, simulations with different values for the initial interfacial stiffness showed a perfect agreement for the load-displacement and the crack growth responses. Moreover, the proportionality condition is accurate for both a linear elastic (LE) material and an elastic-plastic (EP) material. The proportionality condition is proven by elaborating the interfacial stiffness over the damaged zone. This elaboration is done both numerically and analytically and proves that there is a one to one proportionality between c1 and K, which validates the replacement of c1 by a constant c multiplied with K. Lastly, the method should be compared to a response obtained through a different type of analysis. The method is compared with the solution of an analytical analysis resulting in a very good agreement for both a LE and an EP material. Therefore, method 2 can be approved as a solution to the initial interfacial stiffness dependency problem.

Fibre reinforced polymers (FRP) can be a solution for future bridge renovation when only the deck of the bridge needs replacement. In these cases the deck is replaced with an FRP sandwich panel deck. The main advantages are a high strength-to-weight ratio which is beneficial for the ever heavier lorries and the fast installation which prevents hindrance. To connect the FRP deck with the steel superstructure, bolted connectors are used. One of the aspects that needs to be investigated before the bolted connectors can be applied are the relevant loads on the bolted connectors. The focus of this thesis will be to investigate the relevant static and fatigue forces on the connectors. 55 existing girder and arch bridges have been selected from a database of Rijkswaterstaat. For each bridge an appropriate FRP deck has been designed with an analytical method. The bridges are modelled in SOFiSTiK to investigate the shear forces in the connectors. The layout of the bolted connectors is kept constant for all bridges, as well as the transverse stiffness of the connector. The shear forces are calculated with a linear analysis. Before the static and fatigue analyses, first the hybrid interaction of the model is investigated. The hybrid interaction is the amount of horizontal forces transferred between the FRP deck and the steel super-structure. Hybrid interaction is beneficial as it increases the strength of the structure. Two models of a generic bridge have been investigated, the first is the standard model which is supposed to use hybrid interaction. The second model is an adjusted version to create a non-hybrid model. Three parameters are investigated: the deflection, the slip and the longitudinal stress over the height of the beam. The results show that hybrid interaction is created with the bolted connectors in the standard model. In the static analyses two loads are investigated: traffic loads and temperature loads. The shear forces in the longitudinal direction are investigated as this is the governing direction. Before the loads are applied on the existing bridges, first a generic bridge has been investigated to gain knowledge over three bridge parameters. First the facing laminate of the FRP deck is changed. Second the direction of the webs of the FRP deck, and this also changes the connector layout due to feasibility. Third the expansion coefficient of the resin is changed. For traffic loads mainly the direction of the webs influences the shear forces in the connectors. For temperature loading the shear forces are largely depending on the expansion coefficient of the laminate, the close the expansion coefficient to the expansion coefficient to the steel superstructure, the lower the shear forces. The existing bridges that have been investigated resulted in a large scatter in results. The layout of the superstructure of the bridge influences the facing laminate and the number of connectors, which influences the maximum shear forces in the connectors. For both traffic and temperature loads, the connectors close to the supports experience the highest shear forces. Besides the static loading, also fatigue is investigated. The shear forces in the connectors are calculated for one bridge, namely the approach bridge Nieuw Vossemeer. This bridge is one of the heaviest loaded bridges in the static analyses and it is according to expect judgement facing deck problems. Two aspects are investigated in the fatigue analysis, first the magnitude and second the type of load cycles. The magnitude is important as this needs to be below the slip resistance of the bolted connectors. The type of load cycles is important as this is related to how damaging the load cycle is. Because there are no S-N curves for bolted connectors between an FRP deck with a steel superstructure, the damage cannot be calculated. The R-ratio is used to investigate the type of load cycles. To calculate the R-ratio of a load cycle, the minimum shear force is divided by the maximum shear force. The resulting number expresses the type of load cycle. For the results, distinction has been made between the connectors close to the supports and connectors in the lengthwise middle of the bridge span. Both the magnitude as the type of loading is different. Finally, it is concluded that the shear forces in the connectors is one of the aspects to be considered when designing a bridge with hybrid interaction between the FRP deck and steel superstructure. A large scatter of shear forces can be expected, depending on the bridge layout. Incorrect deck design can result in unnecessary high shear forces. The connector layout can be optimised to make the design more cost efficient.

This research studies the experimental and numerical behaviour of a simple beam to column joint using a fin-plate welded to an rectangular hollow core section. The following aspects of the joint are investigated: The resistance of the welded connection. Defining the force distribution inside the joint. Improvement of the design method for resistance of the fin plate connection. Four series of controlled experiments are conducted to test the joints until failure. The series combine a S355 plate with S690/S355 column grade and matching and overmatching weld material. With the data from these experiments and coupon tests, a finite element model is created using DSS Abaqus. Results are validated to accurately follow the force-displacements obtained in the experiments. Key findings from the experiment: The resistance of the welds was found to be much greater than predicted using the nominal values from the Eurocode. The utilization of the nominal design resistance compared to the failure load in experiments was 19% following EN1993-1-8:2005 and 25% with EN1993-1-8:2020. The main reason for this was the high penetration depth and increased weld throat when welding a 3mm weld according to standard procedure, accounting for a 100% increase in resistance. The second reason was that the failure stress was 50% higher than nominal for both the matching and overmatching infused weld material. Insights from the finite element models: It was proven that for certain boundary conditions it is possible to only account for shear transfer through the weld. However it was found that when expanding the Abaqus model to a full building size the boundary conditions change such that also a moment needs to be transferred through the weld and the bolts. The ratio between the stiffness of the beam and the column face determines the magnitude of these moments. The addition to the stress in the start and end of the weld can result in a 75% lower design resistance when comparing to the same weld with only a shear load. The bolt group transfers the moment through horizontal forces, again depending on this ratio. The magnitude of this horizontal force component in the outer bolts can be equal to the vertical component. The following calculation methods were proposed: The moment transfer through the weld from bridging the bolts eccentricity can be reduced according to the stiffness ratio R between the beam and the column face. There are four stiffness factors which influence the force distribution; The column stiffness K_c, the column face stiffness K_cf, the plate bearing stiffness K_p and the beam rotation stiffness K_b. It was found that the governing influence comes from the face stiffness and the beam stiffness. The face stiffness can be calculated by integrating the resistance over the effective length of the column h_p. If there is no yielding in the beam cross-section then the problem can be simplified and welds should be calculated with taking into account the shear force V_ed and the bending moment M_ed which follows directly from the stiffness ratio R.

In off-shore structures, the jacket foundations are mainly welded connections in circular hollow sections. These connections exhibit problems in resisting fatigue load. Wrapped composite joints tackle this problem with improved fatigue resistance. However, the material properties are yet unknown. In order to determine the properties on a more fundamental manner chosen than just testing different layups for different scaled experiments. This fundamental manner follows the procedure of identifying the mechanisms and their effect on the composite material. The main effect that will be considered of each mechanism is the stiffness degradation over time in order to determine the fatigue life. For now, the effects of the three (most) significant mechanisms are modelled for a glass fibre reinforced composite layup of a compact tension specimen. These effects are modelled using the plasticity model for inter fibre failure, the virtual crack closure technique for delamination and the ductile damage model for fibre failure.

Fibre reinforced polymers, or FRP, are increasingly used in structural engineering applications. Permeating the construction field from the aerospace industry, FRP are applied in both the rehabilitation of existing degrading structures as well as the conception of new projects such as pedestrian and traffic bridges or building facades. The increase of interest and use in FRP in recent decades is driven by the material’s advantageous properties. Its tailorable mechanical properties, long-term durability, customizable free-form design, and its light-weight feature have engrained FRP as a noteworthy alternative to traditional construction materials such as concrete, steel, or timber. This is of paramount importance in light of the climate change challenge facing structural engineers today. While the material properties have been extensively investigated over the past decades, the structural use in FRP have remained limited to specific applications. As such, FRP, material of the future, has fallen short of its aspirations, disappointing its most ardent proponents. A rift is identified between the academic setting of laboratory testing and the pragmatic essence of the construction industry. This research situates itself as part of the efforts interrogating the industry limits and attempting to bridge these two spheres. It proposes to answer the following research question: What strategies capitalize on FRP’s favorable mechanical properties in order to promote formal exploration with the material in the preliminary phase of a design considering its durable and sustainable potential? This research proposes then a tool that capitalizes on the advantageous mechanical properties of FRP and encourages formal exploration in FRP at the conception phase of a design. Considering the climate change threat, the stakes of such a catalyst framework are high. The Wilhelminaberg Viewpoint, a landmark project in Landgraaf (NL) designed by Ney & Partners, is used as case-study to implement the proposed framework. It also allows to draw a contrast between what is structurally feasible in FRP and what is realistically buildable in FRP. A multi-step single-objective optimization is developed. First, stiffness for a certain design boundary is maximized. Using a brute force algorithm, the first level iterates through all the possible laminate layup combinations to find the combination which generates the stiffest structure. The second level of the optimization finds the lightest geometries using a genetic algorithm. This suggested framework offers an answer to the research question, mentioned hereinabove. Completely integrated in one interface (Grasshopper 3D), the developed tool stimulates formal exploration in FRP structures exhibiting shell-like behavior. The user defines the design boundaries, design constraints, load-cases, and material properties and implements the framework.

This research is about which geometry of FRP slabs is the most optimal, in terms of costs, to use for a given load and boundary conditions taking the occurring uplift bolt forces into account. The first part of the report focuses on the calculation of the uplift forces in the bolted connections caused by the moving loads. For this, first a detailed numerical model is made in Abaqus. Based on this most detailed numerical model, different simplifications are made to make the calculations easier and less time-consuming. Numerical models with linear bolts instead of non-linear bolts and with load superposition using a one-wheel load instead of a complete vehicle are considered. Next to this, equivalent material properties are calculated to make a model with an orthotropic deck plate instead of modeled geometry of skins and webs. For the numerical model with this orthotropic deck, the same simplifications are applied. Next to the numerical models, different analytical beam and plate models are considered. All different numerical and analytical models made, are compared on possibilities, calculation and modeling time and accuracy. Based on the comparison between the models and the capacity of the connections, it is concluded that the uplift design of the bolted connections does not need to be taken into account in the optimization of the slabs. The second part of the graduation work is about the optimization of the FRP slabs considering the global behavior of the deck, for which a genetic algorithm is used to detect the most optimal geometry. The most important parameters for the design are the height of the deck, the spacing of the webs and the layup of the topskin, bottomskin and webs. The layup of the different elements is dependent on the number of plies, the ply orientation and the overlapping length. During the optimization process, design and initial (global) strength, stability and stiffness checks are performed. First, optimization is done for the same deck that is considered in part one of the research. Next to this case, different cases for the distance between the supports are considered for which standardization is done with respect to engineering and production of the slabs. Based on the performed research it is concluded that the uplift bolt forces are in a range of 0.5 to 21.5 kN. Simplifications can be done by the use of an orthotropic deck with equivalent material properties. The maximum difference using this simplification is 2.9 kN, while the calculation time needed is reduced by a factor of 4-5. Other simplifications that can be done are the use of linear bolts and/or load superposition. Using linear bolts gives a maximum difference of 0.5 kN and load superposition a maximum difference of 0.3 kN, both without an improvement of the calculation time. The optimal geometry for different boundary conditions is given as a standard design with a variable number of plies for the topskin and a variable height based on intervals for the distance between the supports.

The growth of world population will be the challenge of the century regarding the carbon footprints. The human activities produce both direct and indirect carbon emission that is contributing to the climate change. The construction industry itself contributes around 30 percent of total carbon emissions in the world. Thus, the challenge is to solve the problem of meeting the increasing needs and expectations of a growing population while at the same time modifying the current production and consumption patterns to achieve a more sustainable development model. Based on this, the need for the sustainable structural element is inevitable. Extending the exploitation life of the structural element is one of the solutions that should be looked. Reusing instead of recycling the structural element is one of the ways to extend the exploitation life which can reduce the carbon emission. Therefore the innovation in the structural design to reduce the carbon emission is important. The purpose of this thesis is to study the feasibility of a conceptual design of demountable structural system. On the first part of the thesis, it investigated the structural behaviour of a composite floor beam that consists of steel beam, prefabricated concrete deck and a single embedded nut bolt shear connector in the SLS condition. To accommodate fabrication tolerance and construction process, the bolt shear connector must have enough clearance. Various bolt-hole gap in bolt shear connector is applied to see the effect on structural performance of composite floor beam in SLS. The study of demountable composite floor beam is performed by mean of analytical calculations and finite element analysis. It is found that the bolt-hole gap clearance influences the deflection of composite floor beam due to partial interaction between prefabricated concrete deck and steel beam which leads to incomplete interaction of composite floor beam. The bigger hole clearance, the higher deflection occurs on composite floor beam. The second part of the thesis explores the conceptual design of plug and play beam-column connection. The purpose of developing a plug and play beam-column connection is to reduce the construction time so that it is easy to be mounted and demounted. Two conceptual designs have been developed and were evaluated through FEA. The resistance of those two conceptual designs is found to be higher than fin-plate connection while the rotational stiffness of this plug-play connection can be classified as a nominally pinned joint. The last part of the thesis aims to see the possibility of having a non-symmetrical column splice connection on the column. This is interesting for the architect as it provides aesthetic benefit for the façade. The non-symmetrical column splice connection located on the corner is evaluated by FEA. The connection is a combination of end-plate and cover plate splice column connection. Due to unsymmetrical nature of the connection, the resistance and failure mode of the connection is different in a different orientation of the loading.

The goal of this research is to optimize the fiber layup of a carbon windsurfing boom for weight and stiffness. A windsurfing boom should be stiff to provide an efficient basis for the energy transfer from the sail through the surfer to the board. The weight of the boom is important as the total weight of the rig influences the performance, especially during movements where the swing weight of the rig is important. To optimize the fiber layup the FEM simulation software of SolidWorks is used. This software allows the user to divide the part in sections and specify the layup per section in terms of orientation, thickness, and material. The output of the FEM simulation is the mass and the displacement under different load cases. The load cases are based on an experiment where the loads during sailing are determined with load cells and strain gauges. The FEM simulation is validated and scaled based on two experimentally determined force-displacement relations. The FEM is scaled with the force-displacement relation of the first loading point by scaling the given material parameters by 0.78. The FEM is then validated with the force-displacement relation of the second loading point. New fiber layups are generated based on stress direction, previous iterations, and engineering intuition. The 50 new generated layups and their respective mass and displacement results are evaluated with a performance equation to determine which layup has the highest performance for the combination of mass and displacement. The coefficients in the performance equation are chosen so that both parameters have equal weight. The chosen layup is further evaluated with a required fiber overlap section. Two booms with the new layup are evaluated with the same experiment that is used to validate and scale the original FEM. At the first loading point, where the main loading during sailing is applied, the new layup is 16 percent stiffer than the original layup, as predicted by the FEM. The experiment results for the second loading point showed that the new layup was 5.5-7.5 percent stiffer than the original layup instead of the predicted 13 percent. This difference is due to the straight tubes that are glued to the end of the optimized boom body which are made by a different manufacturer. Changing the stiffness of these pipes makes the FEM results converge to the experimentally determined values. The experiment results of both layups are evaluated with the performance equation as the stiffness has increased but the mass has increased from 2.19 to 2.25 kg as well. The performance equation showed that the new layup outperforms the original layup for both loading points. The project goal to optimize the layup for mass and stiffness is therefore achieved. For the layup of the boom, a sandwiched layup of unidirectional fibers with biaxial fibers at the in- and outside of the circular cross-section was determined as the best performing layup for the sections loaded under bending. For sections that are loaded under both torsion and bending additional layers of biaxial fibers are added at the inside of the circular cross-section. These biaxial fibers are added at the inside as the unidirectional fibers are used at the outside to create the largest moment of inertia for these fibers as the displacement due to bending is leading in this case. Even the small translation of fibers from the inside to the outside of the layup can make a significant difference.

This master thesis contains a study on the implementation of Fibre Reinforced Polymers (FRP) onto a steel bascule bridge, with the aim of weight reduction. As a case study, the Amalia bridge near Waddinxveen (crossing the Gouwe channel) is used. Two alternative design propositions are presented. The thesis has been subdivided into several parts, which are introduced below. The first part consists of several expositions. It examines the built up of a movable bridge, the material FRP & its properties together with methods of connecting an FRP deck to steel girders and the rules & regulations required for bridge design in the Netherlands. The second part is the design study, which contains an overview of the original Amalia bridge and the designs created based on adaptions of the original. The designs have been made to have a lower total weight than the Amalia bridge. A lower bound approach has been used, not an optimisation. Thus, leaving room for improvement. Two alternatives are discussed: a hybrid and a non-hybrid solution. A hybrid solution is defined as a solution with the full interaction between the FRP-deck and steel girders: allowing for shear transfer between the two and enabling the deck to function as the top flange of the steel girders. A non-hybrid solution only allows for the transfer of vertical forces and limits the transfer of shear, resulting in the structural separation between the deck and the girders. The design study has led to a weight reduction for both the hybrid and non-hybrid solution of 24 and 16% respectively. It can be concluded that both alternatives clearly illustrate the potential of FRP in bridge design, given the objective to reduce weight. It should be noted that in the case of a hybrid solution, the temperature influences become significant. This requires close attention to the details for the connection between the deck and girders.

FRP is increasingly utilised in the built environment, following successful implementations in the aerospace and marine industry. However, it exhibits poor stiffness and stability compared to conventional materials such as steel, making it challenging to satisfy serviceability and comfort requirements. Optimising FRP to address these challenges will allow for lightweight solutions with long service lives which could contribute to a cost-efficient reduction of carbon footprint. To this end, an optimisation tool for the preliminary design of bridges using FRP is presented in this thesis report. The research explores the feasibility of adopting FRP in the main load-carrying system of pedestrian bridges and develops a framework for the concurrent geometry and material architectural optimisation of said structures. The study aims to achieve significant cost- and carbon footprint reductions in monocoque FRP bridges by employing a numerical optimisation approach. The optimisation tool utilizes the computer-aided geometric design (CAGD) software Rhino® and its parametric interface, Grasshopper®, to concurrently optimise the shape and material architecture of the bridges. Through the use of genetic algorithms, the framework overcomes FRP’s poor stiffness and stability, and maximizes its unique advantages, including lightweight and high-strength properties, enabling free-form designs. This feat is achieved by implementing hybrid sandwich panels, comprising glass fibre-reinforced polymer (GFRP) and carbon fibre-reinforced polymer (CFRP) face sheets. Satisfactory stiffness is ensured by defining deflection constraints, whereas constraints on the fundamental frequency and critical buckling load factor ensure adequate stability. The research demonstrates promising results, showing potential cost reductions of up to 17% and carbon footprint reductions of up to 27.4% compared to a real case design carried out by FiReCo. However, certain limitations and areas for improvement are acknowledged, including the required run-time and the complexity of the solution space. Suggestions for enhancing the framework’s efficiency are proposed, including implementing orthotropic failure criteria and reducing the solution space through adjustments to ply thicknesses and foam core configurations. Overall, the developed optimisation tool provides valuable insights and serves as a valuable resource for researchers and practitioners seeking sustainable and economically viable bridge designs. By embracing innovative solutions and eco-friendly materials, this study contributes to global efforts towards carbon neutrality and sustainable infrastructure development in the built environment.

This research investigates the feasibility and potential of utilizing BFRP floors in modular buildings as a low environmental impact and cost-effective alternative to conventional floors. A modular building is introduced as a case study, the Natural Pavilion in Almere, to bring focus to the research and set a baseline for the requirements of the BFRP floor. A second case study, the bio-composite bridge in Ritsumasyl, is introduced to utilize its comprehensive dataset of material properties representing the state-of-the-art BFRP. Using the two case studies, two design solutions, a one-way and two-way floor, are developed. Comparing the designed BFRP floor to conventional floors such as cross-laminated timber, concrete hollow core slab, and concrete flat slab, several conclusions can be drawn: (1) The construction height of BFRP floors is similar to that of conventional floors. The weight of the floor is similar to a CLT floor, while a concrete floor is 6-8 times heavier. Design optimization is possible, and the amount of BFRP material utilized can be reduced by up to 21% for the one-way floor and 19% for the two-way floor. Additionally, the floor design proposed in this thesis is intended for buildings with a design life of 15 years and no specific fire resistance requirements. For structures with a design life of 50 years, it is imperative to increase the floor height to meet deflection criteria. Further research on fire resistance and additional measures is necessary to extend applicability beyond single-compartment buildings and terrace housing. (2) The environmental impact of a BFRP floor, assessed in terms of Global Warming Potential through a Life Cycle Analysis encompassing stages A1-A5, is found to be twice that of a concrete floor. Through optimization of the floor design and reduction of BFRP material usage, it is possible to achieve a reduction in CO2 emissions of approximately 10%. Nevertheless, in the current state-of-the-art, BFRP floors exhibit a higher environmental impact than conventional flooring systems. The use of resin and the production process are the primary contributors to CO2 emissions. The contribution from the production process requires nuance, as results heavily depend on the data source. Factors such as manufacturing techniques and production scale significantly affect this impact. By reducing the impact of the resin and production techniques while also exploring end-of-life possibilities for 100% bio-based BFRP, the environmental impact of BFRP floors holds potential for the future. (3) The floor cost is nearly twice as high as a comparable CLT floor. This can be attributed to introducing new design solutions with a sustainability focus, often resulting in increased costs due to lower demand, higher material and design expenses, and limited production scale. Even though current costs are much higher for BFRP floors than for conventional floors, there is potential for BFRP floors to become more cost-effective and competitive in the future, especially when the environmental impact is reduced. It is difficult to estimate how the price of BFRP floors would change over time, and therefore, it has not been taken into account in the results.

Hybrid concrete-SHCC beams are a new development in construction techniques. SHCC stands for Strain Hardening Cementitious Composite. In such beams, the tension zone could for example consist, next to the traditional reinforcement, of a material that shows strain hardening behaviour. That helps with controlling the crack width. In traditional (non-hybrid) beams, the steel reinforcement would have to control the crack width on its own. This means that there are situations that the steel reinforcement fulfills the strength requirements, but additional steel reinforcement is needed to limit the crack width. Therefore, a certain amount of steel reinforcement is needed for meeting the SLS (Serviceability Limit State) requirements, while it is not used for the ULS (Ultimate Limit State) requirements. The use of hybrid beams consisting of an SHCC layer applied in the tension zone in which the reinforcement is embedded, solves this problem. This was shown in previous MSc studies by Huang and Singh. In this study, the concept of the hybrid beam is extended. A design was made of a reinforced U-shaped SHCC mould, to be used for casting a hybrid beam. In that way, a reinforced hybrid concrete beam is created, in which the webs of the U-shape prevent the need of temporary moulds at the side of the beam, which reduces costs. A complete design is presented which is ready for further research. Next to that, it is investigated how the bending behaviour of beams, that are made using this concept, can be modelled. This was done by extending the multi-layer model, that was first proposed by Hordijk in 1991. Different from the previous built models, the model proposed in this thesis includes additional aspects, such as imposed deformations caused by drying shrinkage, and the possibility to model hybrid beams (with a U-shape). After this model was extended using VBA in Microsoft Excel, it was successfully verified by comparing its results with experimental and analytical results from previous research. Comparing the force-to-displacement curves showed that the end-resistance of the beams is predicted well by the extended multi-layer model, and that generally the same trend of the curve is followed by the model. The bending resistance of the proposed experimental setup of a hybrid beam containing a U-shape was also modelled. However, as this experiment has not been performed before, there were no experimental results to compare with. Therefore, the results for this setup are to be compared with the results that follow after experimenting with the presented design of the beam.

The development towards a circular economy has many hurdles to overcome. For the construction sector an important step in this process is the transition towards reusing structural elements. Prefabrication of elements is a significant step towards achieving this concept. However, a case where both prefabrication and reuse are limited is the replacement of bridge decks. Headed bolts are welded to the steel supporting elements and encased in grout to connect them to the concrete deck elements. This method prevents reuse of the deck elements and hinders reuse of the steel supporting elements. Research and literature exists on a number of alternative shear connectors that increase the modularity of these elements. The best alternatives have a single limitation in common: the allowed deviation for the placement of the shear connectors and bolt holes is smaller than is feasibly possible. The variances of element placement during construction add up to make it incredibly hard for these low tolerance connections to be made. The bolt hole diameter can be increased to increase the deviation tolerances. The large nominal hole clearance this results in needs to be considered. This can be done by using either resin injected bolts or High Strength Friction Grip (HSFG) bolted connections. Using HSFG bolted connections is preferred due to the shorter time spent on site and minimal waste, but research on the subject is sparse. A proposed HSFG bolted connection that implements significantly oversized holes, defined as bolt holes with a nominal hole clearance roughly equal to the bolt diameter, and cover plates was designed together with both a control and regular connection to compare its behaviour with. The control connection is identical to the proposed connection with the exception of its holes which are normal sized. The regular connection has normal holes and does not include cover plates. Finite Element Models (FEM) were made of these connections that were subjected to static loading in a Finite Element Analysis (FEA). Test specimens of these connections were made and subjected to fatigue loading. The numerical results of the static FEA showed that the use of cover plates reduced the stiffness and slip load of the connection. The second observation was the small impact that the hole size had on the slip load when using cover plates. This small impact becomes negligible at design preload. The experimental results showed that the impact of larger bolt holes increased the loss of preload by roughly 1% during both short term relaxation and fatigue loading. The effect of the bolt hole size on the slip after fatigue loading was also concluded to be negligible, but the effect of the cover plates was concluded to be detrimental. It was overall concluded that the use of significantly oversized holes in HSFG bolted connections with cover plates is viable. The negative effects caused by the cover plates and required longer bolt make it preferrable for large disc springs to be used instead of thick cover plates. The viability of the concept allows for further research on the subject.

Many movable bridges, built in the 1950’s and 1960’s, reach their end of service life or do not meet future traffic demands. Renovation of those bridge, if possible, is preferred over newly built from an economical point of view. Fibre-reinforced polymer (FRP) decks prove to be excellent for retrofitting bridge decks compared to traditional decks, mainly due to its high strength-to-weight ratio. Lightweight bridge decks are advantageous in movable bridges considering the savings on foundation, counter- weights and mechanical equipment, not to mention, reduced transportation costs, installation time and traffic hindrance during execution. Connecting FRP decks to the steel girders can either be done mechanically (bolts), chemically (bonded) or in a hybrid fashion. Adhesively bonded connections do not require drilling in the FRP deck, thereby increasing its durability, have a more uniform stress distribution and fabrication costs are lower compared to bolted connections. Complex stress states and strength prediction of a bonded joints are yet not fully understood, therefore rarely being applied in primary load bearing structures like bridges. This thesis focuses on the stress analysis and strength prediction of adhesively bonded connection between FRP decks and steel girders. An existing bridge, representative for renovation projects, is considered as case study. Its former bridge deck is replaced by a FRP deck and adhesively bonded to the steel girders. Structural analysis of the bridge deck performed with a global and local numerical model, focuses on the stress states in the bonded deck-to-girder connections. Traffic and thermal loads are the governing load cases, which show the largest stress concentrations. Peak stress levels are obtained along the edges and ends of the bonded connection between the FRP deck and secondary girders. Comparison of results from the global and local model showed significant difference in stress levels and was further investigated. Stress concentration factors are determined to relate the (peak) stresses from the global and local model for different adhesive thickness and elastic modulus. Stress results from the global model are tweaked with the stress concentration factors and compared with strength values from literature. It can be concluded that bonded FRP/steel deck-to-girder connections are critical details in movable bridges.

Fibre reinforced polymer (FRP) is a new construction material that often is used for pedestrian bridges. It offers a good strength-weight relation, a long-term durability and slender bridge shapes. Slenderness has effect on dynamic behaviour of the construction and vibrations are common for these bridges. Hand calculations are commonly used for the forecast of the dynamic behaviour, but this approach is not very accurate. Royal Haskoning DHV felt the need for a numerical model to be able to forecast the dynamic behaviour of pedestrian bridges of which accelerations, natural frequency and damping ratio are the most important. This thesis aims to fulfil this need. During a literature study relevant calculation methods were found and offered a better insight in the behaviour of bridges and the properties of FRP. FiberCore, manufacturer of FRP bridges, provided information of 15 different bridges all over the Netherlands. These bridges were all examined and vibrations were measured in the field. It was possible to bring 7 of these bridges in vibration using two test methods. To be able to measure accelerations and natural frequency mobile applications were validated in a case study in Puurs Belgium with the University of Leuven. A numerical model has been built for one specific bridge with a finite element method in SOFiSTiK and validated with the information provided by FiberCore. Furthermore, a dynamic load simulating a person walking over the bridge was designed. After having validated the model calculations were made to determine the natural frequency and the accelerations of this bridge as well without as with handrails. The results were compared with hand calculation according to the calculation method of the Joint Research Centre (JRC). Significant differences between the results of the model calculation and the JRC method were found and analysed. The main conclusions of the thesis are regarding the damping factor and the results from the numerical model. The damping factor of 1.4% to 5.4% is measured for 8 FRP bridges spanning 10-25m. The assumption of 1% damping, which is often used in design verifications in engineering practice is conservative. The maximum acceleration from the numerical model, 1.22 m/s2, is higher than the 0.43 m/s2 calculated from the SDOF method from the JRC, which is used in design verifications in engineering practice. The psi factor is a very dominant reduction in the latter calculation. The author concludes with some recommendations for further research.