In August of 2013 Elon Musk published his paper ’Hyperloop Alpha’, in which he describes an alternative transportation system for the to be built railway connection between Los Angeles and San Francisco. The Hyperloop system that Musk describes relies on partial vacuum tubes through which vehicles can travel at speeds up to 1000 km/h with great efficiency. An innovative breakthrough in the transportation sector if it can be made into a reality. Therefore his company SpaceX organised a contest to which many teams applied to built a concept vehicle to be used in the tubes. In 2017 a team of students from TU Delft won the overall prize for the best design and afterwards the team leaders founded Hardt to develop their ideas and make Hyperloop into a reality. BAM Infraconsult supports Hardt and together they develop the Hyperloop and its tube infrastructure. Currently the preliminary design for the tubes is made in steel and no alternatives have been considered. This research focusses on an alternative tube design in concrete. The tube has to not only satisfy the strict requirements that apply to the Hyperloop technology in general, but it also has to adhere to the specific design philosophy of the Hardt vehicle concept. A concept in which the vehicle is suspended from tracks on the ceiling of the tube by a series of magnets. The report is based on the following research question: Is a concrete design a feasible alternative for the design of airtight Hyperloop tubes compared to the considered steel tubes? To answer this question two philosophies are considered and researched into depth. Firstly a design in prefabricated normal strength concrete is analysed, making use of prestressing and conventional reinforcement, following the requirements set in the Eurocode. Secondly an innovative ultra high performance steel fibre reinforced concrete (UHPFRC) design is considered. Again prestressing is applied, however conventional reinforcement is not present in this design as it relies on steel fibres and prestressing alone. This design is modelled according to the French UHPFRC guidelines. A requirement for the design is that the inner diameter of the tubes is equal to 3.6 m and that the tubes span 30 m between pylons. The design methodology is based on a variable thickness of the tubes in order to find the optimal concrete structure that satisfies all requirements. Checks are made for multiple failure modes after which the governing minimum thickness is derived. Other than proving to be structurally sound according to the Eurocode, the tube also has to abide to a strict deflection limitation under dynamic loading conditions. In order to research this criterion the tube design is validated using finite element modelling. Here a combination of different parameters related to the concrete material characteristics and the dimensions of the tube is researched by means of a sensitivity analysis. Using the dynamic amplification factor specified by Hardt, the maximum deflections of the tube are checked and the parameters that have the greatest influence on the deflection are discussed. The obtained results are compared to the steel tube. Furthermore the possibilities for the construction of a concrete tube are considered, including a recommendation for the connections between tube sections. Moreover the transportation of the tubes to the building site and final assembly are taken into account. After all factors are considered a cost estimation is made for the design of the concrete tubes and compared to the cost estimation of the initial steel design of the tubes. This cost estimation does not only consider the material and production costs of the tubes, but also takes into account transportation, assembly, maintenance and site costs plus an allowance for risks and profit. It is concluded that a design in normal strength concrete is possible, but not practical. Its dimensions make the production and assembly very difficult. However a design in UHPFRC is feasible, as its required dimensions are considerably better. Furthermore it satisfies all structural requirements without the use of conventional reinforcement and even the strict deflection criterion at dynamic loading conditions can be achieved. Moreover the design in UHPFRC is a competitive alternative to the steel design, as it has a higher score when all criteria are considered.

The transportation industry is constantly developing innovative solutions in order to increase efficiency, sustainability and safety. Truck platooning is one of those emerging technologies with high potential. In one way or another, truck platooning will also have an impact on our current infrastructure and the way in which the motorways are managed and maintained.Trucks have the greatest effect on the occurrence of road surface wear unlike smaller vehicles (Mallick & El-Korchi, 2017). The pavement structure is designed according to the amount of truck axle load repetitions that occurs in the design life of the motorway.The current traffic flow is normally distributed on the traffic lane, which is called lateral wander and has a positive effect on the service life of the road structure. Driving in a platoon will influence the wandering effect of trucks which will have a negative effect on the pavement structure. Lateral wander results in the distribution of pavement damage allowing more load repetitions on the lane.Different professionals from Rijkswaterstaat and TNO (research institute) were approached and search engines like Scopus, Elsevier, ResearchGate, ScienceDirect and the library of Tu-Delft were used to obtain scientific papers on truck platooning, pavement structures and the current maintenance strategies. It can be concluded that little to no research has been done into the impact of truck platooning on the pavement structure. This means that there is a knowledge gap in the scientifically area and in the practical area. This resulted in the following objective of this research, which is to fill the scientific knowledge gap and to contribute to the current practise. The resulting main research question has been developed, based on this objective.What are the potential impacts of Truck Platooning on the road infrastructure and how could this affect the construction and maintenance of asphalt pavements on motorways?Research approachA mix of qualitative methods and quantitative methods were used to find an answer on the main research question regarding truck platooning and the pavement structure. First, a literature study was conducted in order to collect the necessary data to identify the characteristics of truck platooning and to analyse the failure mechanisms of the pavement structure.The literature study identified three failure mechanisms which are effected by lateral wander. The literature study also resulted in three basic models, which are used to analyse the failure mechanisms. During the desk research, the models were adjusted to fit the needed situation of truck platooning on the Dutch motorways. After this, the impact of truck platooning on the pavement structure is determined.Next interviews were conducted with the purpose to obtain and evaluate data regarding the failure mechanisms of the pavement structure in relation to truck platooning and their impact on the maintenance strategy. As such, the obtained data is incorporated into the study.ResultsThree possible platooning scenarios were identified, based on the interviews. The impact of truck platooning will depend on the way on which the platoon will be configurated.• The trucks can be connected to each other only in the longitudinal direction.• The trucks can be connected in both the longitudinal and transverse directions, with an independent leading truck.• The trucks can be coupled in both the longitudinal and transverse directions while the leading truck drives in the exact same track as the previous truck platoons. This scenario applies when the trucks start to drive autonomous.The impact of truck platooning will depend on the way on which the platoon will be configurated. As a result of the interview with the professionals of Rijkswaterstaat, it was concluded that only the third scenario will have an impact on the pavement structure. Today's vehicles are getting smarter and are equipped with a lot of technology. The European Uni encourages the use of Advanced Driver Assistance Systems (ADAS) and even made a number of core systems mandatory for vehicles (Dijsselbloem, Asselt, & Zouridis, 2019).The third scenario represents the most negative setting of truck platooning. The trucks in this setting are coupled in both the longitudinal and transverse directions while the leading truck uses a form of cruise control letting it drive in the exact same track as the previous truck platoon. This situation arises when the trucks start using technology to drive. The strains on the pavement structure can be two times as large in case of fatigue failure. The structural damage on the pavement will increase as a result of rut development and of fatigue.The second part of the literature review resulted in three failure mechanisms and three models were identified.• The first failure mechanism is permanent deformation; using the Rut development model.• The second failure mechanism is raveling; using the Raveling prediction model.• The third failure mechanism is fatigue failure. The Dutch Design Method includes a model in order to predict the acceptable amount of load repetitions on the pavement structure,The following findings have been made with regard to the impact of truck platooning on the failure mechanisms:Permanent deformationA maximum rut depth of 18 mm is commonly used on Dutch motorways. It is generally assumed that this standard will be achieved within 30 years without platooning. In most cases, maintenance is already planned when the rut reaches a depth of 16 to 17 mm. The model used to predict the rut development indicates that the rut depth increases with the amount of platoons on the motorway. This development could impact the current maintenance strategy if more than 50% of the trucks drive in a platoon. The maintenance strategy of Rijkswaterstaat will have to be adjusted, because the critical failure mechanism shifts from raveling to deformations of the road surface. Permanent deformation will have to be maintained in a different way than raveling. The critical point of permanent deformation could be reached within 10 years, if all the trucks that participate in traffic on the highways start to drive in a platoon.RavelingRaveling is the loss of aggregate material from the top layer. Literature research shows that, in case of young asphalt, raveling depends on the asphalt composition and traffic characteristics. However, it was also concluded that the impact of traffic decreases and that the impact of climate increases on older asphalt. It was therefore determined that the characteristics of truck platooning won’t lead to an increase of raveling, which means that the same maintenance intervals as in the current situation can be maintained.Fatigue failureMotorways are designed with a lifespan of 20 years based on a certain number of load repetitions and with fatigue failure as criterium. After this, improvements will be made which will extend the service life by another 20 years and so on. Based on desk research and interviews, it is assumed that, in the current situation without platooning, the pavement fatigue life of motorways approaches 25 year. The results in this research show that the acceptable amount of load repetitions will be exceeded within 20 years if 50% of the trafficking trucks autonomously drive in a platoon and nothing is done. When 100% of thetrucks drive in a platoon the acceptable amount of load repetitions will be exceeded within 10 year.Main findingsOverall, it can be concluded that the scale of damage done to the pavement structure depends on the percentage of platoons on the motorways. The current maintenance strategy will be negatively affected if 50% of all freight transport uses a form of truck platooning. The current maintenance strategy, without platooning, mainly focuses on restoring the top layer of the pavement structure due to the loss of aggregate material or raveling. With truck platooning, the other failure mechanisms like fatigue cracking and permanent deformation will change the current maintenance strategy of motorways. The principal design of a pavement structure is based on the criterium fatigue failure, because this is the most expensive maintenance intervention. Especially because motorways are designed for a lifetime.RecommendationsThe development of truck platooning needs to be dealt with in a timely manner. Data needs to be collected with regard to the failure mechanisms in order to determine the impact and to develop a strategy. This can be done during the first use of the technology and during the regular maintenance intervals used for the current motorways. Rijkswaterstaat lacks the data required for predicting rut development in the current situation, because this failure mechanism has no priority.The impact of truck platooning on fatigue failure will result in maintenance in the form of structural interventions, if no measures are taken. Maintenance interventions in the deeper layers of the pavement structure are the most expensive ones. Applying Smart Lanes could be a solution for simulating lateral wander and organizing maintenance more efficiently.Performing a Cost Benefit Analysis (CBA) to determine whether the required interventions yield more than the costs that must be incurred for upgrading the infrastructure. This not only gives the government a clear overview of future costs as a result of truck platooning, but also a tool to determine whether truck platooning can be permitted on the roads. A positive result of a CBA analysis can therefore be used to get support from various stakeholders, to promote cooperation with different manufacturers and with the Market.DiscussionThree models were used to determine the impact of truck platooning on the pavement structure. The models were obtained through literature research and desk research.The rut development model is based on a number of measuring points generated during the LINTRACK tests on a full scale pavement structures. This tests contains a couple variables like temperature, speed of the tire and wheel load, which differ from practice. A correction has been made for the difference in the variables. The LINTRACK tests produced nine measuring points ,from which a regression line has been developed. More measuring points could be used to increase the accuracy of the regression line.The model which predicts raveling was developed by the New Zealand Transport Agency. As a result, this model does not fit perfectly on Dutch motorways. The model was developed for porous asphalt, but the wheel loads had to be adjusted. This research was conducted for motorways in the Netherlands with limited data.

Crossing waterways is crucial to improve transport connections. In particular, new crossing methods are needed when the distance to be covered increases. Submerged Floating Tunnels (SFT) have been recently emerging as a cost-effective feasible crossing technique to connect fjords in Norway. However, only very little research has addressed the vehicle-structure interaction, with attention to the passengers, so far. In the current thesis, an algorithm was developed to study the Fluid-Structure-Vehicle-Interaction (FSVI), where the tunnel has been modelled as a Euler Bernoulli beam, the train car as a 6DOFs system, the supporting cables as linear springs, and the fluid by the Morison's hydrodynamic force expression. The Sperling ride quality and comfort indices were used to address human comfort while crossing the tunnel. It is found that, due to the low-frequency hydrodynamic environment, the influence of the FSVI on the Sperling's indices is limited, i.e. "just noticeable" from the classification table. Low-frequency flow field may cause motion sickness rather than cause comfort/discomfort during the ride. The illness rating, which is the indicator of the motion sickness, gave positive outcomes due to the small amplitude of the accelerations, and therefore no illness is expected to be felt by passengers. This study shows that displacement and acceleration can be controlled and kept inside the proposed boundaries under storm sea states, and the comfort while crossing can be guaranteed. The approach here used can be applied to other sea states with higher frequency content to address the comfort in a storm with smaller return period, which may also be important to address the fatigue resistance of the structure.

Structures may be subjected to both mechanical loads and imposed deformation. On one hand, the mechanical loads include, for example, the self-weight of the construction work, the action from normal use by person, furniture and movable objects, vehicles, snow, wind, execution, etc. On the other hand, when the deformation of a structure is restrained, imposed deformation occurs. The sources of deformation can be various, not only environmental conditions, such as temperature and humidity changes, but also chemical or physical actions, such as sulphate ingress or creep. If the shortening of a structure is restrained, the structure will be subjected to imposed deformation which results in tensile stress. Since the tensile strength of concrete is relatively low, concrete structures, such as tunnels, bridges and pavement roads, always suffer a high risk of cracking. Even if the concrete structure is prestressed, the tensile stress resulting from imposed deformation would consume the compressive stress in concrete and raise the risk of cracking. If the crack width exceeds the limit, leakage, corrosion and even structural failure may happen. According to the schematized 푁 - 휀 diagram of reinforced concrete, the development of cracking caused by imposed deformation and mechanical load are different. Suppose the cracking is caused by imposed deformation, there is a developing stage for cracking. It means the cracks caused by imposed deformation could be either fully or not fully developed. However, suppose the cracking is caused by mechanical loads, the cracks could only be fully developed. The stiffness of fully or not fully cracked members are different. The stress resulting from imposed deformation in a structure is related to the stiffness of the structure. Therefore, cracking has significant impact on the magnitude of stress resulting from imposed deformation. Therefore, when a structure is subjected to imposed deformation and mechanical load together, it is necessary to take the impact of cracking into account during structure design. The combination of imposed deformation and mechanic loads is referred to as combined actions. It is common to use FEM software to analyze the stress resulting from the combined actions during structure design when cracking has to be taken into account. However, FEM analysis only is not enough. It is also necessary to check the results calculated by FEM software to avoid mistakes, for example a wrong input. There is a project called 'Approach Ring South, Groningen'. In the project, widened deck KW03.01 is subjected to a combination of imposed deformation and prestressing force. FEM software called SCIA is used to calculate the prestress consumption in the widened deck KW03.01. According to the data file of the project, 41% in maximum of the compressive stress resulting from prestressing is consumed when the structure is subjected to combined actions, which is much more than the engineering experience. As a result, a simple approach is required to check whether the prestress consumption in widened deck KW03.01 suits the expectation or not, where the prestress consumption is calculated by FEM software.

The Netherlands is currently in the process of transitioning from a linear economy to a circular economy, in accordance with the ”Nederland Circulair 2050” policy. To increase the circularity of buildings, several approaches can be integrated. In this research, the so-called Design for Deconstruction and Donor Structural Framework concepts are elaborated as possible approaches. The first concept focuses on taking the future de- and remountability of a building into consideration during the design process. This concept allows buildings that approach their end-of-life phase to be (partially) reused as structural components, on a new location. The second concept can be applied during the construction phase of a building, where structural components of an old building are dismantled and reused in the to be constructed building. The difference between the two concepts thus being the life cycle in which they are applied. Therefore, the resulting benefit of using a Donor Framework can be seen immediately, whereas the benefit of applying the Design for Deconstruction concept can only be stated in the future. Unfortunately, the current procedure to measure the sustainability score of a building, the Life Cycle Assessment methodology, does not take these concepts into account. This makes determining their impact on the environment hardly possible. Also, due to the fact that detailed information about a design is required, a Life Cycle Assessment is made only once the design is final. In this order, all design variables are set such that designing towards sustainability is not an option. This research focuses on solving the introductory problems and aims to enable sustainable material choices for a structural design possible in the early design phase. Both the Donor Structural Framework and the Design for Deconstruction concepts were taken into consideration. This main goal has been split into two sub–questions:- How to assess the environmental impact of a steel, concrete and timber load bearing structure in the early design phase? -How to implement the Donor Structural Framework and the Design for Deconstruction concept into the existing Life Cycle Assessment methodology? The research questions have been answered by executing the following approach: 1.A parametric model is used in which not only the geometry and structural calculations are included, but the Environmental Impact Calculation as well. In the event of a design change, the Environmental Impact Calculation is automatically reiterated, which means different designs can be compared quickly based on their environmental impact. The model constructed for this study is suitable for designs in steel, concrete and timber. For each material a reference design is created. The Bill of Materials of these designs serves as input for the Environmental Impact Calculation on which the materials were compared in a later research phase.2.First, an existing end-of-life allocation method has been adjusted to include reuse during both the construction phase (Donor Structural Framework) as the end-of-life phase (Design for Deconstruction). Secondly, the Building Circularity Index, which recognizes a ”circularity score”, has been implemented in this method. In this study the Building Circularity Index is assumed as the ”probability of future reuse of the building”. The modified method was implemented in the parametric model to enable a real-time Environmental Impact Calculation. This approach has been fully implemented into a parametric visual script, executed in the Grasshopper, a parametric environment plugin of Rhino which enables visual scripting. Input parameters are imported from Excel, the Grasshopper script calculates the environmental impact and exports the results to Excel where they are visualized in a dashboard. Ultimately, the developed parametric model has been divided into a part containing the geometry and structural calculations of the reference designs and a part where the newly developed Environmental Impact Calculation method is implemented. Combining the results of both parts in the total model, it becomes possible to assess whether a design is best built in a certain material in the early design phase. The final model can provide results with or without the use of a Donor Structural Framework and with or without application of the Design for Deconstruction concept. For the purpose of demonstrating the functioning of the model, a reference design in steel, concrete and timber was implemented as a basic geometry. This geometry was assumed equal across all designs and for comparability purposes, dimensions were fixed. Consequently, it can be concluded from the results of these reference designs that using a Donor Structural Framework results in a lower environmental impact than applying the Design for Deconstruction concept by maximizing the remountability of a structure. Until a lifespan of 75 years, using a timber donor framework is the most sustainable solution for the reference design. From 75 until 100 years this is the case for steel and from 100 years onward, a concrete design, whether or not using a donor framework, results in the lowest environmental impact. In the current design practice of a building, the default lifespan has been determined by the function of the building (Functional Service Life). By using the model developed here, this lifespan can be determined on the basis of sustainability requirements instead of functional requirements. The differences in environmental impact for different lifespans can easily be compared. Therefore, it is made possible to steer towards a certain lifespan, in order to determine the most sustainable construction based on the clients requirements. This is currently not possible in the Dutch construction industry. However, these results do have their limitations, as they should not be interpreted as general but rather specific conclusions. The following points of attention apply: -Results should not be interpreted as general results, but these results only apply on the three reference designs as elaborated further in the research. These reference designs are not optimized for every material used. -Changing input parameters can have a significant impact on the results. In addition, a number of important parameters (reuse percentage, material lifespan etc.) have been assumed due to insufficient existing research. -The developed allocation equations include the incineration of timber too favorably. This results in a significant deviation in timber environmental impact for lifespans much shorter than 75 years. This flaw can be either due to the model, or the impact parameters as stated in the NIBE EPD app. Lastly, it is recommended to further research the assumed parameters in this research, especially the material lifespan and the incineration impact parameters. As these parameters can have a major impact on the environmental impact of a specific design.

The Netherlands is a densely populated country with a congested road and railway network. Therefore more and more highways are widened and expanded. These wider highways create a demand for bridges which are suited for longer spans. These bridge solutions should constructed with a minimum of hindrance for other traffic. Rijkswaterstaat, also wishes to reduce the number of intermediate supports so the space underneath a viaduct can be used more freely. The currently most used solution to build a highway overpass without disrupting the traffic too much is a concrete viaduct consisting of prefabricated prestressed concrete bridge beams. But for spans longer than 60 meters those beams become too long and too heavy for transport by truck to the building site. Therefore the existing bridge solutions are reaching the maximum distance to which they can be built. The primary goal of this report is to find a concrete bridge solution with which it is possible to construct longer bridge spans in prefabricated concrete up to 100 meters. With such a bridge solution it is also possible to span a waterway or a small river in the Netherlands. A beam bridge in which the beam is composed of three parts is the most suitable solution to build these longer spans in prefabricated concrete. This solution can be constructed with relatively little hindrance for the other traffic. This solution is also relatively flexible in the shapes of bridge decks that can be constructed, skew bridges and wide bridge decks are both possible. The design of this beam bridge is extended and analyzed with a more detailed calculation. A bridge span of 100 meters is possible with a construction height of only 3 meters. This relatively slender design is possible because high strength concrete is used and because the bridge deck is designed to spread the traffic load efficiently over the full width of the bridge deck. The beam parts of this bridge can be transported by truck to its destination. A rough cost estimation shows that the designed solution is expensive compared to existing concrete beam bridges, but it is also possible that the designed solution has a lower cost price compared to existing solutions in steel. It is advised to continue the research to and development of the bridge design because of the possible lower cost price and because with this design, bridges can be constructed which currently cannot easily be constructed with the existing solutions.

This research focuses on the structural behaviour of an elastic supported reinforced concrete slab. Over the years, there is a tendency to realise industrial floors with large joint-spacings. The downside of a slab on grade with a large joint-spacing is that the risk of (uncontrolled) cracking due to a shrinkage load is higher, which often results in durability issues. In practice, the slabs on grade are generally designed and constructed based on experience by specialised floor companies and often with less than the theoretical minimum required reinforcement. This research aims to close the gap between theory and practice and to gain insight into the structural behaviour. Moreover, reducing the number of damages in slabs on grade. In the first part of this thesis, the stress development and crack risk in a restrained concrete slab on grade exposed to shrinkage is analysed. The restrained shrinkage stress in the concrete member is mainly influenced by the time-dependent properties of concrete and the degree of restraint of the slab. The most relevant degree of restraint for a jointless slab is by soil friction and depends on the slab length, soil properties and the vertical load like self-weight. From the sensitivity analysis in this research, it is shown that the middle section is fully restrained for slab lengths or joint spacings of 40 to 80 meters long for practical ranged values. The relaxation effect in concrete, based on the creep behaviour, reduces the restrained shrinkage stress over time. Stress reductions of 40% to 70% were found for practical values in the analysis after one year of shrinkage loading. The crack risk in indoor slabs on grade is the highest between two and twelve months after casting according to the findings in practice and this thesis. The early-age crack risk is relatively low for an indoor slab on grade compared to a concrete pavement because of the significant less influences of the environment. The crack risk can be reduced by composing a concrete mixture with a low relaxation coefficient, low concrete shrinkage, low Young's modulus, a high concrete cracking stress capacity and by reducing the degree of restraint of the slab. Secondly, the cracking behaviour of a fully restrained concrete tensile member with only reinforcement near the surface is analysed with analytical models and a finite element model. For modelling cracking in a restrained member initiated by an imposed deformation in the finite element model, the random field application is required. The random field application generates the spatial variation of the tensile strength of the concrete material. The random field simulates weak zones in the concrete member where crack localisation will be initiated. The downside of the random field application is that the crack pattern in the model is predetermined. The cracking behaviour is analysed for a shrinkage load, a point load and for both loads combined. In all the analyses, it is found that cracking in a slab on grade always results in a not fully developed crack pattern. A not fully developed crack pattern is characterised by the forming of additional cracks instead of widening of the existing cracks when the load increases. When cracking due to a shrinkage load in fully restrained members occurs, the imposed load decreases, which reduces the tensile force in the uncracked zone. Force reductions up to 73% were calculated after cracking in a five-meter long restrained slab. For an eccentrically top reinforced member, the first crack occurs at the bottom fibre and is uncontrolled. The tensile force in the reinforcement, in combination with the eccentrical position, induces a negative bending moment in the uncracked zone of the slab on grade. In combination with the restrained shrinkage load, this results in an axial tensile force and a negative bending moment in the uncracked zone after cracking. Over time, the shrinkage load increases and a flexural crack can be initiated at the slab surface. A point load induces a positive bending moment at the position of the load and a smaller negative bending moment next to the point load. After cracking due to the point load, an axial compressive force and an increased negative bending moment are present in the uncracked zones next to the point load. The sensitivity analysis on the behaviour by the point load showed that the principal stresses in the slab could be reduced by increasing the subgrade modulus, the slab height or by lowering the concrete stiffness of the slab. The load combination analysis showed that an axial tensile force and a negative bending moment are present in the uncracked zones. It is found that a higher point load only increased the slab deflection and the number of flexural surface cracks and not the crack width. However, a higher shrinkage strain load did slightly increased the maximum crack width but mainly increased the number of cracks. Therefore, it is concluded that the slab on grade remains in the cracking phase for the combined loading situation. Both in this research and the literature, it is stated that crack width calculations of a restrained concrete slab imposed by a shrinkage load results only in indicative values. The analysis of the cracking behaviour showed that cracking at the surface is induced by an axial tensile force in combination with a negative bending moment. Therefore, estimation of the crack width can best be performed with the CUR-65 model based on an enhanced cracking bending moment of the slab on grade. Because accurate crack width calculations are not possible, recommendations are made on how to reduce the crack widths in a jointless slab on grade. A slender slab with a low concrete tensile strength is advised to reduce the internal cracking force and bending moment. Also, it is found that a lower shrinkage load leads to a smaller crack width. Therefore, a shrinkage reducing concrete mixture is advised. Moreover, high bonding properties between the reinforcement and concrete reduce the crack width, which can be realised with reinforcement with a small diameter and mesh-size. Finally, reinforcement is the most effective in controlling surface cracks when placed in the top fibre of the slab. It is concluded that for a slab on grade, replacing the conventional reinforcement with steel fibre reinforcement does not reduce the required amount of reinforcement for controlling surface cracks.

Old bridges in the Netherlands are reassessed to prove their structural safety because of the increased traffic loads. The Eurocode model for the shear capacity of prestressed concrete beams with sufficient shear reinforcement was found to be very conservative for small amounts of transverse reinforcement, which is typical for old bridges. Code provisions based on the modified compression field theory appear to be much more accurate (Bentz, Vecchio, & Collins,2006). On the other hand, these models make no distinction between flexural shear and shear tension failure, while 25% of the bridges consists of T-, I-, or box beams which are sensitive to shear tension failure. The aim of this thesis is to present a more accurate prediction for shear tension failure based on the modified compression field theory (MCFT). The report focuses on both the CSA-model and Response-2000. The CSA-model is a simplification of the MCFT for beams under the assumption that σ_z=0. The CSA-model shear resistance consists of a concrete and steel part. Response-2000 is a cross-sectional analysis program that works as a non-linear finite element analysis and not only takes into account bending but also shear.Response analysis of 32 beams (experiments of Xie (Xie, 2009), Choulli (Choulli, 2005), Hanson (Hanson & Hulbos, 1965) and Leonhardt (Leonhardt, Koch, & Rostasy, 1973)) have been made and compared with the experimental observations. The failure load is predicted with a mean ratio of 1.38 and a COV of 19% compared to the experiments. It was found that for small a/d-ratios predictions are more conservative. Failure mechanisms: rupture of the stirrups, crushing of the web concrete and slipping/major crack opening are found in Response. 87% of the failure mechanisms was predicted correctly compared to the experiments. The critical cross-section compared with the experimentally observed failure zone showed that 60% of the beams was predicted in the failure zone. The shear force in the cross section is resisted by reinforcement steel, aggregate interlock and the uncracked concrete, which were found to take up respectively 1/2, 1/6 and 1/3 of the shear force. The steel part is predicted accurately while the aggregate interlock part is underpredicted due to an over prediction of the crack spacing. The uncracked part is overpredicted for small amounts of reinforcement and underpredicted for larger amounts of reinforcement. The data of the Response analysis have been used to modify the CSA-model to a model solely describing shear tension failure. The comparison showed that the CSA-model underestimates the steel part, overestimates the concrete part, takes a to large cracked height and doesn't take into account the contribution of the uncracked part. From this comparison, modifications for β,θ,V_max,h_crack and ϵ_x are proposed using Response data and proposals from Esfandiari (Esfandiari & Adebar, 2009). The flanges are taken as uncracked and the contribution of the uncracked part is described with a linear elastic shear stress distribution. This has led to a proposal for a model that solely describes shear tension failure, where the most important addition is the contribution of the uncracked height. Calculations show that the model gives conservative predictions compared to the experiments (mean ratio of 1.36 and a COV 22%) and the predictions are almost the same as for Response. The parameters are predicted conservative compared to the Response-2000 predictions.

Vanuit Rijkswaterstaat is de wens om een snelle, verifieerbare methode te ontwikkelen voor het controleren van de veiligheid voor meerdere T-ligger constructies volgens huidige normen en inzichten. Hierbij dient rekening gehouden te worden met eventuele wijzigingen in de toekomst, welke door de huidige ontwikkelingen op het gebied van dwarskrachtonderzoek te verwachten zijn. Het is de verwachting dat op basis van verfijnde beoordelingen en verder fundamenteel onderzoek de ‘reserves’ middels een quickscan-aanpassing inzichtelijk gemaakt kunnen worden. Hierdoor zou een deel van de onderzochte kunstwerken mogelijk alsnog voldoen aan de veiligheidsnormen. Door diverse berekeningsmethoden met elkaar te vergelijken is getracht een methode te vinden welke simpel toepasbaar is, realistische resultaten voor dwarskracht en moment geeft ten gevolge van de verkeersbelasting en tevens conservatief is. Door deze te vergelijken met diverse Scia-berekeningen is een methode gekozen die het best aan de eerdergenoemde punten voldoet. Tevens zijn de invloeden van meerdere uitgangspunten met elkaar vergeleken. Nadat inzicht is verkregen in de manier waarop de belasting over de liggers is verdeeld, is een generiek systeem gemaakt, een zogenaamde quickscan. De quickscan maakt op een snelle manier duidelijk of de gekozen snede voldoende weerstand kan bieden aan de behorende belastingcombinaties. De quickscan is een generieke, eenvoudig toepasbare, conservatieve methode om ‘het kaf van het koren te scheiden’ voor de dwarskrachttoets, zonder dat daarvoor EEM-software nodig is, welke tevens de Scia-berekeningen zo goed mogelijk benadert. Om deze zo goed mogelijk te ontwikkelen is een beoordelingsprocedure gerealiseerd welke zich vormt tot de quickscan. Om inzicht te verkrijgen in de invloed van de verkeersbelasting op de liggers en om deze conservatief te benaderen, zijn diverse berekeningsmethoden met elkaar vergeleken. Uit deze vergelijking is gebleken dat de beste benadering voor de verkeersbelasting de ‘verspreide methode’ is. Hierbij wordt de belasting gespreid of is deze niet afhankelijk van de locatie van de dwarsdragers. Met deze kennis is de quickscan Boon ontwikkeld. Deze kan worden uitgevoerd door enkele parameters in te vullen, zoals: de lengte van de ligger, het oppervlak van de ligger, het voorspanverloop, de dwarsdragers en door de ‘kritische’ sneden (belangrijke te toetsen sneden) van de ligger te bepalen. Daarna kan snel en slim inzichtelijk worden gemaakt wat de UC op deze sneden van de constructie is, en wat de consequenties van wijziging van uitgangspunten zijn. Uit het onderzoek is gebleken dat het tandemstelsel altijd op een hoek van 30 graden vanaf het gekozen punt tot hart rijstrook moet staan om de maximale dwarskracht in dat punt te vinden. Deze belastingsposities worden automatisch gevonden, waarna direct de dwarskracht en het bijbehorende moment berekend wordt met behulp van de verspreide methode. Hierdoor kan de constructieve beoordeling van de liggers snel inzichtelijk worden gemaakt. De quickscan Boon is een eenvoudig toepasbare, realistische, conservatieve beoordeling voor T-ligger constructies, welke inzicht geeft in de maatgevende belastingcombinatie en gemakkelijk te verifiëren is. De kracht van deze methode is dat door te variëren met diverse parameters (zoals capaciteitsaspecten, te toetsen snede en rijwegindeling) direct de invloed van deze parameters inzichtelijk kan worden gemaakt. Waar de resultaten conservatief en toch reëel zijn.

Auxetic materials are increasingly used in the field of sports, defense, bio-medicine, and acoustic-filtering due to their unconventional behavior of exhibiting a negative Poisson's effect. The prospective use of auxetics to mitigate shock and impact forces have proven the relevance of research on auxetics. It becomes of paramount importance to understand their behavior and mechanics of deformation, especially regarding their response to dynamic loading conditions. Although auxetics have caught attention from several researchers, a detailed overview of computational modeling of auxetics is still missing and the deformation behavior of auxetics subjected to different loading conditions is an unfolded topic in structural mechanics. In this thesis, computational tools are developed and validated to investigate the effect of auxeticity in a linear elastic continuum and a re-entrant honeycomb structure under different static and dynamic loading conditions. The possibility to assess the global behavior of an assembly of re-entrant honeycomb unit cells by the analysis of an equivalent continuum model with the same global dimensions and homogenized mechanical properties has been examined. The dynamic analysis of a continuum model of an isotropic auxetic material presented the influence of auxeticity in increasing the ratio of shear wave velocity to dilatation wave velocity. The finite element analysis of a simply supported auxetic beam subjected to impact at mid-span affirmed the hypothesis that in auxetics, the material flows towards the point of impact, thus increasing the indentation resistance. Computational challenges in analyzing a beam impact problem are discussed through the comparison of results from the standard finite element analysis, modal analysis, and the B-Bar method. It is recommended to further develop the proposed models to have a more robust approach on analyzing the continuum beam impact problem. The assembly of a re-entrant honeycomb structure used in the finite element simulations were modelled with different unit cells by the variation of the two dominant geometrical parameters of the unit cell members. The results highlighted the strong correlation between the effective mechanical properties and the geometrical parameters, therefore indicating the possibility of achieving the desired values of the Poisson's ratio by simply modifying the necessary geometrical parameters. The results also showed that it is possible to obtain a Poisson's ratio more negative than -1 which can be exploited to design a displacement amplifier especially suitable for defense applications. The close comparison of the analytical and the computational results provided a groundwork to extend the numerical study to geometrical nonlinear analysis and other loading conditions like bi-axial loading and bending at the structural level. The comparison of results obtained from the analysis of an assembled cellular structure and an equivalent continuum model subjected to bi-axial loading and bending demonstrated the possibility of assessing the global behavior of cellular structure using the continuum model. Dynamic analyses of a re-entrant honeycomb structure revealed that the wave propagation phenomenon in a re-entrant honeycomb structure is a result of several reflections, transmissions, mode conversions and superposition of waves occurring at the connection of cell members. The proportion of reflection, transmission and mode conversion of incident wave when it passes the connection can be controlled by varying the re-entrant angle between the cell members. For the lower frequency regime, the speed of wave propagation in re-entrant structures can be estimated using the continuum approach. Furthermore, in a secondary study, the influence of the geometrical parameters of a re-entrant honeycomb structure to exhibit the stop-pass band was examined. Recommendations are provided for the further development of computational tools to analyze the three-dimensional and disordered re-entrant structures. In addition, it is also suggested to investigate the beam impact problem in the cellular model, the effect of rigidity of connection of cell members and research the possibility of having an isotropic re-entrant honeycomb structure as the present model is orthotropic in nature.

New and existing bridges in the Netherlands must abide by structural safety codes, such as the Eurocode. In this code, structural safety is expressed through the reliability index 훽. For certain reference periods a threshold value for 훽 exists. When applying prescribed load models given in the Eurocode, the structure is guaranteed to at least fulfil to this threshold value. However, these prescribed load models are deterministic in nature and can be rather conservative for bridges in urban areas. This thesis focusses on creating a probabilistic load model based on actual traffic loading by making use of a camera system that registers license plates to check whether the vehicle is allowed to enter the inner city of Rotterdam due to environmental zones. From this camera system data, technical information such as wheelbase, legally allowed axle loads, gross vehicle weight and such can be extracted since they are coupled to license plates. This technical information is then used to create load models based on actual registered traffic. This load model represents trucks as point loads with interspatial axle distances. In total, one year of collected data by the camera system is stored, called the LP data. This load model is then used in a probabilistic reliability analysis as a load variable input. When comparing the LP data with available weigh-in-motion (WIM) data from two measurement locations in Rotterdam, it turned out that the LP data does not incorporate under- and overloaded axles and was overestimating the accompanying reliability index. Hence to account for this, an axle load factor 휂௜ is introduced to simulate under- and overloaded axles. This factor 휂௜ is based on the WIM data and is different for each vehicle type. With the use of this factor, a second, improved load model is constructed. This is referred to as the modified LP data. A third and final load model was constructed from the available WIM data, called the WIM model. For each of these three load models the load effects were calculated, and distributions were fitted accordingly for simulating several 25 year periods of traffic. The output of these load models is a loadeffect maxima distribution that can serve as a direct input in a probabilistic reliability analysis. With these three load models, a hypothetical slab with a span length of 10 m was probabilistically analysed where the LP model, the modified LP model and the WIM model resulted in reliability indexes of 4.8, 4.1 and 3.7 respectively. When compared to the requirement in the Eurocode, all load models comply. Concluding from this, the modified LP model suggested in this thesis can be used as a load input in a probabilistic verification for this very considered bridge location. For this load model to be applicable to multiple bridges, more research must be done since only one location was considered in this thesis. However, the suggested approach to construct load models based on license plates can be used verify the applicability to multiple bridges.

Compressive membrane action is a phenomenon commonly found in reinforced concrete structures after significant cracking and deformation have taken place. In this thesis report, the potential benefit of CMA in immersed tubes subjected to fires is quantified through a finite element study. Furthermore, sensitivity studies are conducted in order to determine the boundary conditions necessary in immersed tubes to induce CMA.

Several researches have been done in the last decade about the possibility to “give a new life” to the second-hand reinforced concrete elements of a certain building which has been (fully/partly) disassembled. However, not often the actual technical detailing of their reuse practice are addressed. This study is primarily focused on proposing the most suitable solutions to what concerns the reintegration of these structural second-hand parts into a “host” structure, which can contain other reused elements or can be a mixture of new and second-hand parts. The overall approach to the previously mentioned task is structured as follows: -Four structural systems have been considered to formulate the input list of elements for which re-connection approaches need to be formulated; -Connection approaches have been formulated for the elements which have been considered suitable for a potential reuse; -Selected connection methods from the ones formulated above have been studied in detail, assuming to embed them in a hypothetical office building made partially of second-hand elements. From the first part it have been assumed that common columns, shallow beams, load bearing wall panels and one way slabs such as hollow core slabs and plank-floors can be potentially reused. In the second phase several connection approaches have been formulated, highlighting briefly their constructional details and specifying their advantages and drawbacks. Some of these resulted in having different degrees of overall complexity. In any case the proposed designs are requiring more investigation before being actually put in practice, since, for some methods a significantly different design from the one used for traditional connections was used. In the last part, regarding the case study of selected jointing methods, it was chosen to address three approaches: the connection of a second-hand column to the foundation block, a splice joint on a column and a complete study of a columns-to-shallow beams node. In final result it has been deduced that, even if the feasibility regarding the use of second-hand elements requires a careful preliminary assessment and a detailed study about the cost-effectiveness of the details, the proposed connections could be potentially successfully embedded in a new structures. This point has been also confirmed by the positive output results obtained at the end of the analysis of the case-study.

The Strut-and-Tie model (STM) is an efficient technique for the design of concrete structures, but the creation of suitable truss structures gets complicated when these structures become more complex. The topology optimization (TO) is a convenient technique that has been used in recent years for the creation of trusses of complex structures for the STM. This thesis presents a process for the creation of suitable truss structures for the STM using the results obtained with the TO, as well as, an evaluation of them to see which is the most optimal truss structure according to the total amount of tension force present on the full truss, this total amount of tension force is the selected evaluation criterion. Three deep concrete beams were analyzed using two topology optimization (SIMP and BESO approaches) for the generation of stress paths, these approaches are based on the minimization of the strain energy. The procedure starts with the computation of the principal stresses over the results of the topology optimization, then bar elements are placed over the stress paths of these diagrams creating a first (harsh) layout of the trusses. These trusses were not always found stable, but all the trusses were stabilized because, in this way, it is easy to calculate the axial force of in the truss elements, thus satisfy a basic requirement of the STM. To stabilize the truss structures two methods were explored. (i) The addition of new members outside of the stress paths (stabilizers), the essential characteristic of these new elements is that the axial force in them should be zero to not change the stress distribution found during the optimization process. A sensitivity analysis of the stabilizers was performed to track how the axial force changes in these members depending on the position of the nodes connected to them, this process was necessary because when an element outside the stress paths has axial force the stress diagrams have been changed. (ii) The creation of substructures within the stress paths, this process stabilizes the global structure without the addition of members outside the stress paths. Finally, a structural analysis was performed to obtain the axial forces in each member of the truss structure, and through an analysis of these results, the total amount of tension forces in the truss was computed. The truss with the minimum value of total tension force is assumed as the most optimal structure for each case. It is clear through the analysis that the variation of the input parameters does not cause large variations in the results of the topology optimization, but it has an impact in the stabilization process and the performance of the structures according to the evaluation criterion. Furthermore, it has been proved that suitable trusses for the STM can be created using any of the two selected optimization approaches obtaining good results, and a similar performance according to the evaluation criterion.

For calculation of the resistance of a composite slab against the transverse shear force, the Eurocode 4 (composite structures) simply refers to the calculation procedures of the Eurocode 2 (concrete structures). It is assumed that the composite slab consists out of a consecutive range of concrete ribs in its width direction, which are solely responsible for resisting the transverse shear force. To calculate the transverse shear capacity of these concrete ribs, an empirical formula is used that was originally derived for regular reinforced concrete beams (without stirrups). However, the concrete ribs of the composite slab are created by the profile of the steel deck, making that each concrete rib is accompanied by two steel webs on the sides. According to the Eurocode 3 (steel structures), these webs of the steel deck have their own transverse shear capacity, which is neglected by the current design approach defined in the Eurocode 4. Besides, the interaction between the steel deck and the concrete may lead to an even higher transverse shear capacity of the composite slab. In this thesis, the aforementioned two aspects, which are currently overlooked by the design principle of the Eurocode 4, are further studied by means of non-linear finite element modelling. The validation of this empirical formula of the Eurocode 2 for calculating the transverse shear capacity of the concrete ribs is the first point of interest. From the finite element analysis (FEA) of the concrete section of ComFlor 210, it is concluded that the prediction of the transverse shear capacity by the Eurocode 2 is unnecessarily conservative. The study suggests to use the mean width of the concrete rib (b0) in calculation, instead of the minimum width in the tensile area of the concrete rib (bw), as an improvement to the method of the Eurocode 2. In the next stage, the contribution of the steel deck to the transverse shear capacity of the composite slab is studied. The exact bonding properties between the steel deck and the concrete (at the interface) were not clear when the finite element model was developed, so some assumptions had to be made. When assuming that the steel deck can’t separate from the concrete and the relative slip is restrained in longitudinal direction by the embossments, an increase of 131.6% in transverse shear capacity is found. Because of the assumed interface properties, the steel deck contributes to the total transverse shear capacity in the following ways: it resists a part of the transverse shear force in its webs; it acts as reinforcement to the concrete like a longitudinal rebar; it acts as reinforcement to the concrete like stirrups. However, whether this stirrup-functioning of the steel deck’s webs is representative for the actual transverse shear behaviour of deep composite slabs is being questioned, because it relies on the assumption of no separation at the interface. Therefore, a second FEA of ComFlor 210 is executed in which the interaction between the steel deck and the concrete is neglectable. Still, an increase of 51.4% in transverse shear capacity is found, which can be considered as a lower bound value. At last, from the FEA results of this thesis, it can indeed be concluded that the current Eurocode 4 provides a unnecessarily conservative calculation method for the transverse shear capacity of ComFlor 210. However, using a simple engineering model that adds up the partial resistances of the concrete ribs and the steel deck’s webs, gives a better prediction while still being safe. For the partial resistance of the concrete ribs, the empirical formula of the Eurocode 2 is used, but this parameter bw is substituted by b0 as already mentioned in the foregoing. For the partial resistance of the steel deck’s webs, the procedures of the Eurocode 3 are followed.

Numerical modelling of pile foundations can be done in several ways. In commercial finite element packages two main options are available; using volume elements with interface elements between the pile and soil domains and the embedded beam approach. The embedded beam element was first proposed by Sadek and Shahrour (2004) and considers a beam element that can cross a solid element at any arbitrary location with any arbitrary inclination. This has several advantages to the volume pile method, such as the need for fewer elements and the mesh uncoupling of the pile and soil, which make this method much more efficient and leads to a significant reduction in calculation time. However, the embedded beam element also deals with a number of limitations and drawbacks. This research focuses on overcoming the mesh sensitivity, which is caused by the stress singularity that is introduced in the soil by the beam element. Also, the inability to take into account the pile surface will be resolved, aiming to improve the lateral pile-soil interaction. The idea of Turello et al. (2016) of an embedded beam element with explicit interaction surface is extended and generalised leading to a new embedded beam formulation. In the proposed model the beam displacements at the interaction surface are obtained by a mapping scheme that takes into account Timoshenko beam theory and which is generalised to model inclined piles as well. A constitutive equation that describes the relation between the interface stresses and relative displacements between the pile and soil is defined along the shaft and at the foot of the pile. Along the shaft of the pile a shear stress limit is defined based on the Mohr-Coulomb failure criterion in order to incorporate plasticity in lateral direction. Furthermore, a more practical and efficient assembly procedure is proposed. Validation of the proposed method proofs that the proposed model leads to a significant mesh sensitivity reduction in case of axially loaded models compared to the existing implementation. The overall response of laterally loaded piles is improved considerably as well. However, the proposed method is still unable to capture lateral interface behaviour in order to model soil slippage around the pile. Furthermore, it is recommended to formulate a generally applicable foot interface stiffness and to optimise the code in order to reduce the computation time. The description of the interaction surface opens up many new possibilities for future research, such as modelling the true cross-section shape.

The Helperzoom bridge is one of few existing prestressed slab-between-girder bridges that is being managed by Rijkswaterstaat. These bridges are built before 1980 and do not comply with the current standards. To evaluate the structural safety and capacity these bridges are being assessed. A total of four girders were taken from the Helperzoom bridge, named HPZ1 through HPZ4, and have been destructively tested at TU Delft to determine the shear capacity and failure mode. The first two experiments, HPZ1 and HPZ2, have been considered in this research. Shear-tension failure is one of the failure modes that was being looked for and where the experiments were based on. The most important results of HPZ1 and HPZ2 have been combined and summarized in the experimental analysis, such as the failure load, the failure mechanism, the load at which the first inclined crack occurred, the cracking angles of the observed cracks, the calculated inclinations of the compression field from the LVDT measurements, the contribution of the shear reinforcement and the contribution of the prestressing cables to the shear capacity. Remarkably, the outcome of the test resulted in shear-compression/flexure-shear failure instead of the predicted shear-tension failure. The purpose of this thesis is to check whether the observed shear capacity and failure mode from HPZ1 and HPZ2 can be validated with existing models that are currently used by (inter)national standards and numerical programs. The Euler-Bernoulli beam theory and five (inter)national codes: ACI 318-14 (American Concrete Institute), AASHTO 8th Edition (American Association of State Highway and Transportation Officials), NEN-EN 1992-1-1:2011 (Eurocode 2), RBK 1.1:2013 (Richtlijnen Bestaande Kunstwerken) and EC2 draft 2018 (prEN 1992-1-1:2018 D3), have been used to calculate the shear capacity and if possible the failure mode of the Helperzoom girders. Next to the nominal shear resistance, failure of the compression field is considered for three codes: AASHTO, EC2 and EC2 draft 2018. For the two Eurocodes the value of the inclination of the compression field can be chosen by the user: the EC2 has a lower limit of theta = 21.8°, the lower limit of the EC2 draft 2018 (based on state of strains) is reached when theta is chosen such that failure of the compression field occurs simultaneously with yielding of the stirrups. For the EC2 draft 2018 different ways have been used to determine the longitudinal strain: with the expression given in the code, analytically determined with a sectional analysis and with the results of the LVDTs in the two experiments. In addition to the analytical calculations, a non-linear finite element program Response-2010 has been used, with which a cross-sectional analysis was made with two values for the prestressing force. With this program it is easy to determine the maximum shear capacity, the failure mechanism and many other results per loading step, such as the inclination theta, acting and maximum compressive- and tensile stresses, strains, etc. The maximum shear capacity is divided into components: the contribution of the uncracked concrete, cracked concrete, transverse reinforcement and a vertical prestressing force. Four different shear capacities have been calculated: the inclined cracking load, the nominal shear resistance according to the general procedures of the design codes, failure of the compression field and the moment that failure of the compression field occurs simultaneously with yielding of the stirrups. The Euler-Bernoulli beam theory, ACI (flexure-shear) and Response-2010 show that the load for the first inclined crack are close to the results of HPZ1 and HPZ2. For the nominal shear capacity, none of the codes nor Response-2010 are in line with the results of the two tests: all shear capacities are underestimated. The AASHTO overestimates the shear capacity for failure of the compression field, because the inclination theta is not included in the expression. The EC2 overestimates failure of the compression field due to limitation of theta = 21.8°. The EC2 draft 2018 allows for lower values for theta, when the longitudinal strains are based on the state of strains with theta lower than 19.08°. The results for the shear capacity and inclination of the compression field of the latter design code are much more in line with the observed failure loads and inclinations calculated from the LVDTs. The lower limit for the shear capacity is when failure of the compression field occurs simultaneously with yielding of the stirrups. With this limit, the shear capacity is underestimated and the inclination of the compression field is lower than the inclination calculated from the LVDTs. The results between the three analyses have been compared with each other and it was concluded that there are major differences between the analyses for the calculated shear capacities, internal lever arms, critical positions and the inclinations of the compression field. None of the results from the codes match the observed failure load in the experiments. Considering the expressions given for failure of the compression field, the EC draft 2018 based on the state of strains were closest to the test results for both the shear capacity and the calculated inclinations of the compression field from the LVDTs. The moment that yielding of the stirrups occurs simultaneously with failure of the compression field, the EC2 draft 2018 gave too low values for the shear capacity. For the numerical results, Response-2010 gave a representative shear force for the first inclined crack and failure mechanism, but not for the ultimate shear capacity. After the onset of the first inclined crack, the girder did not build up extra capacity as was observed in the experiments. The critical position was also not in line with the results from the test. It can be concluded that the results should always be looked at from a critical point of view and that no clear answer can be given as to which analysis is the "best" to determine the shear capacity of (prestressed) concrete T-girders. For the Helperzoom girders the EC2 draft 2018 based on the state of strains with theta lower than 19.08° gave the best results for the shear capacity.

This master thesis covers the research into cracking behaviour of slender high strength concrete cantilevering balconies. The research emerged from Pieters Bouwtechniek Delft and Hi-Con Denmark. They cooperatively designed very slender balconies in ultra-high performance fibre reinforced concrete. Other engineering firms tend to recreate these balconies in HSC and insecurities emerged around the cracking behaviour and crack width prediction for these slender HSC cantilevering balconies. In addition to this research an informative report, also functioning as a literature study, on the connection of prefabricated concrete balconies is produced. This report is separately attached. The research is step wisely conducted starting with a simple fully clamped cantilevering slab. For this slab the cross sectional height, reinforcement diameter and reinforcement spacing are varied to investigate their influence on analytical crack width predictions. First for all variants an analytical design and analysis process is executed, followed by a numerical analysis with DIANA FEA and a comparison of the results. The most important observation is that for a cross sectional height of 120 mm or smaller reinforcement bars are located outside the effective area, making the analytical method unsuitable. Furthermore, a big discrepancy between the predictions of the different analytical models is observed, indicating an unreliability of these methods. In two steps the fully clamped balcony is transformed into a Hi-con shaped balcony executed in HSC. It appeared that in light of detailing rules from Eurocode 2 an exact reproduction is impossible, but the concept could be reproduced in a less slender way. Furthermore, by comparing analytical and numerical design results for two different balcony designs it is found that the accuracy of the analytical crack width prediction depends on geometric disturbances. In case a geometric disturbance is present in a slender area loaded in tension peak stress concentrations occur, which negatively influence the reliability of the analytical crack width prediction. In case the area is less slender, the effect is less pronounced and the conservative characteristics of the analytical method outweigh the influence of the concentrated peak stresses. When summarizing, it appears that specific care should be taken when analytically predicting crack widths in slender balconies because it might appear that the reinforcement is not located in the effective area. Furthermore, the more slender the structures become, the bigger the influence of a geometric disturbance can be, increasing the risk of an underestimation of the occurring crack widths because peak stress concentrations are analytically not accounted for.

Wood is an important building material that has been used for thousands of years throughout the world. It is the most widely used building material and due to its characteristics suitable for a wide range of applications. Still, for the last century steel and concrete have been the materials of choice for large buildings. Part of the reason for this is the lack of knowledge in the industry regarding timber construction. Now that the environmental problems such as climate change get more and more attention, there is an opportunity for timber as a building material and the manufacturers of timber products to increase its popularity. Cross-Laminated Timber, or CLT, is a relatively new product. First introduced in the early 1990’s in Austria and Germany, now gaining popularity in residential and non-residential applications in several countries around the world. The panels normally have 3 or more layers of side-by-side placed boards, that are stacked crosswise at a 90 degree angle. The boards are glued on their wide faces and may or may not be glued together on their narrow faces. The Derix Group, a company with a vast experience in the timber industry, specializes in laminated timber constructions and are interested in developing a new panel configuration. The idea is that by relocating boards from the middle layer of a CLT element, to a more favourable position, material usage can be optimized. A problem definition is formulated and used to derive the research questions that form the direction of the thesis. The research questions are related to the possible advantages and the consequences of the Hollow Core Cross-Laminated Timber (HCCLT) configuration. The first thing that is done in order to investigate the possibilities, is research into the manufacturing process and the structural design of CLT. As a relatively flexible building material with a low dead weight, the design of CLT is often determined by serviceability criteria, such as deformation and vibration. However, the rolling shear properties of the cross-layers can control the design, it influences the effective bending stiffness and stress distribution. It also causes a larger deformation due to shear than for other wood based products. Since there is not one specific design method, the most common methods are researched and described.  The composite theory  The mechanically jointed beams theory  The shear analogy To determine how the existing methods perform and to investigate the structural behaviour of a HCCLT element compared to a CLT element, the methods are used to calculate different configurations in order to compare the results. The knowledge obtained during the research and calculations is then used to model a HCCLT element. Different models are made in order to investigate the behaviour during manufacturing and for when the element is in use.

Traditionally, steel joints are calculated by the calculation rules described in the Eurocode 3: NEN-EN 1993-1-8. Effective lengths are important parameters to determine the different resistances of the components in the steel joint. Finite Element Analyses (FEA) are becoming increasingly important in engineering, including in construction industry. Specialised software is developed to determine the stresses and corresponding strains in the plate elements of the joints by the Finite Element Method (FEM). This thesis reports on a comparative study of the traditional calculation method and a method which is using partial FEA for determining the resistance of joints. The approach, assumptions and principles used for these calculations are explained in this report. It will be investigated whether the same components of a joint are decisive for each method and if there are differences in joint resistances. If so, the magnitude of the difference will be determined as well. This is done for different simple shear joints (SSJ) and moment resisting joints (MRJ). For the last group, two joint configurations (Flush End Plate Joint and Extended End Plate Joint) are calculated manually, partially modelled with the FEM, and compared with the results of executed experiments.