The Oscillating Water Column (OWC) device is one of many available technologies for generating electricity from water waves. It is a caisson-like structure, which houses a water column in an enclosed chamber with an inlet at the bottom. Waves enter the device, exciting the water column. The trapped air above is forced out through a turbine, generating electricity. The technology is relatively young compared to other sources of renewable energy, such as solar or wind energy. This makes the produced energy expensive, expressed in the Levelised Cost of Energy (LCOE). Integrating devices into breakwaters already resulted in a large reduction of the costs, as they now can be shared. During the design of such devices, main attention is given to the geometrical design. This should be based on local wave conditions to ensure the largest energy production. Having the eigenperiod match with the incident wave period enhances the resonance effect in the chamber. This research explores the potential to reduce the costs of OWC devices integrated in breakwaters through means of structural optimisation. The structural are built quite robust, leaving the thought there is room for improvement. The device in Civitavecchia, Italy was used as a case study. A new method was adopted to investigate the potential. A numerical model was constructed in STAR-CCM+, including both a fluid domain and a solid domain. The two are one-way coupled, from water to structure. The exerted wave pressures are mapped on the structure directly, resulting in a stress state in the OWC structure. Due to the transient nature of the simulations, all results are available through time. It was found, the main walls shaping the OWC device could be built with 35% less material. Variants of the original geometry were tested as well to see how these influence the results. Furthermore, the structural behaviour was investigated. Clear trends were found in position and timing of governing load combinations in the different walls. One of the most important findings was that the governing load case always was in the direction of the transverse width. The walls were found to behave more like beams in this direction. The bending moments could therefore easily be calculated using standard beam equations and the net horizontal pressure on the wall as load. This leads to the beginning of a new simplified design method where the full numerical structural analysis is not required anymore.

The main motivation within this thesis is to explore the possibility of increasing the service life of box-beam bridge girders to aid the ambition of the Dutch government to become a circular economy. The construction industry still follows a more or less linear economy system. Many bridges in the Netherlands are approaching the end of their service lives, and efforts are being made to extend the lives of these bridges. This is but a temporary solution, and these bridges will require replacement within 20-30 years. This provides an opportunity to incorporate circularity within new and upcoming structures from the design phase onward rather than only as an end-of-life practice. Therefore this thesis explores the possibilities of incorporating the strategy of lifespan extension, in the form of a cover increase against chloride-induced corrosion. The exact increase was calculated through the use of a relevant service life design model (DuraCrete) and compared with the Eurocodes. The reliability of the model was checked using a Monte Carlo simulation. Subsequently, the circular aspects of future adaptability were also investigated considering a fictitious scenario of increased traffic load. Hence, it was concluded that a marginal increase in concrete volume and prestressing steel per beam would allow for a more durable and adaptable beam for the future.

The main motivation for this research originated from two ambitions, which involve many challenges for which circular solutions have to be developed. First, the ambition of the Dutch government to achieve a circular economy, which also includes a circular construction industry, in the Netherlands by 2050 at the latest. Secondly, in line with the first, the ambition of Rijkswaterstaat to work climate-neutral and circular in 2030. At this moment, the main focus in the Dutch construction industry is on developing circular solutions which can be implemented and applied during the enormous replacement and renovation task of many of the almost 40.000 bridges and (mostly) viaducts in the Netherlands. Therefore, the main focus of this research has been on developing circular solutions for concrete viaducts for (governmental) roads. This has resulted in the development of a concept demountable footing to foundation (F2F) dowel connection which has been based on, and is suitable for application in, the proposed design of a standard (circular concrete) viaduct. Besides, attention has been paid to desired monitoring aspects regarding such a circular viaduct, and to the life-cycle costs of a circular viaduct compared to those of the same viaduct, constructed in a traditional way, characterized by a linear life-cycle model.

Orthotropic bridges can be modelled using a grillage model and an orthotropic plate model. The grillage model has some benefits (i.e.: shorter calculation time and easier to apply pre-stressing) compared to the orthotropic plate model. However, during the Blankenburgverbinding project Ballast Nedam experienced that the transverse load-spread of the grillage model can be lower compared to the orthotropic plate model. This potentially results into a less economical reinforcement design. The aim of this study is to investigate the differences in transverse load-spread of the grillage and orthotropic plate model and to make a judgement on the practical usability of the grillage model based upon the differences in reinforcement design. To test the hypothesis that the grillage model has less transverse load-spread compared to the orthotropic plate model and to quantify the impact on the reinforcement design, a case study on the bridge decks of the Blankenburgverbinding is carried out. The results of a grillage model are compared to an orthotropic plate model. In order to be able to judge whether to orthotropic plate model describes the correct behaviour of the bridge, this model is verified using a 3D plate model. In total, 3 different single-span, simply supported bridge deck layouts were modelled (straight, curved and curved with a skew angle). The results of the 3D plate model are almost equal to the results of the orthotropic plate model. Both these models show the same transverse load-spread. The grillage model shows less transverse load-spread compared to the orthotropic plate model and the 3D plate model. This difference in load-spread increases with increasing eccentricity of the applied load. The torsional and transverse shear stiffness has the biggest impact on the transverse-load spread. When these stiffnesses are higher, the transverse load-spread increases. Lowering the stiffnesses results into less load-spread. In case of the curved bridge deck, the grillage model results in about 7.3% more reinforcement compared to the orthotropic plate model. For the curved and skewed deck the grillage model results into up to 4.7% more reinforcement compared to the orthotropic plate model. The differences in design bending moments (Wood-Armer moments) are relatively small. Although the theoretical difference in amount of reinforcement is significant, the practical difference in reinforcement design between both models can be small. For example, the structural engineer is limited by the available space, detailing requirements and the available bar diameters. These limitations and rounding differences make that for some bridges it is possible to reduce for example 5% reinforcement and for some bridges such a reduction can be very hard to realise. In that case, the theoretical difference between the amount of reinforcement becomes very small or completely vanishes in practice. Eventually, it depends on the situation whether the benefits of the grillage model outweigh the theoretically less economical reinforcement design. When there are a lot of repetitive bridge decks it can be beneficial to use an orthotropic plate model. In that case, the orthotropic plate model has to be created only once and a small reduction in the amount of reinforcement of one deck can add-up to a significant reduction for the whole project. When there is only one bridge deck to model, or all spans are unique, the benefits of the grillage model most likely outweigh the practical difference in the amount of reinforcement.

An experimental research into the use of basalt as reinforcement in concrete to reduce the ECI value of a concrete quay wall apron. In this research experiments with basalt minibars and basalt reinforced polymer rebars are performed to compare directly to steel fibres and steel rebars. With the test results 4 designs are produced resulting in material requirements per type of reinforcement. By using these amounts of material an ECI value is determined showing that in this research basalt is an option to reduce the environmental impact. The ECI value presented in this research are in euros/year lifespan, meaning that for a different lifespan the material shows different values. Here the pros of basalt come out as the material is resistant to corrosion as it is a stone like material. Therefore in this research with a product that is placed in water, the lifespan of a steel reinforced apron could only reach 50 years where the apron with basalt reinforcement reached 100 years.

Nowadays, most of the historical bridges (Amsterdam, 2019) of Amsterdam do not meet the load-bearing criteria of the current design code (Eurocode: 2012). This has several reasons. It comes partly because of the overdue of the maintenance (Amsterdam, 2019) but also because the traffic load for which the bridge has been designed, is lower than the present traffic load (Amsterdam, 2019). The current Eurocode 4 does not guarantee the safety of this type of bridge decks. To guarantee the safety and the remaining service life of the historical bridges in Amsterdam, the municipality has started an investigation on historical steel-concrete-composite-bridge-decks. The focus in this thesis is on historical steel-concrete-composite-bridge-decks (a.k.a. Verbundträger brücken in German) because this type of bridges does not contain shear connectors in their configuration. This leads to the fact that the capacity of the bridge deck is almost not determined in the longitudinal and completely not determined in the transversal direction. The bridge deck in the longitudinal direction satisfies the unity check based on the protocol of the municipality of Amsterdam to check this type of bridges on safety, where they only consider the steel profile to define the capacity of the bridge in this direction. This is very conservative because the concrete is not taken into account during the calculation of the cross-section. In the transverse direction, the bridge deck does not fulfil the necessary unit check limit, because the municipality takes only the shrinkage reinforcement into consideration during their calculations. In addition to this, the state of the bridge decks and relevant research about how the bridge deck is build-up, is investigated. The main conclusion that can be taken from the cross-section of these type of bridge decks is that there is a lot of variation in all the components of the bridge decks. Furthermore, during the investigation of the bridge decks it is decided to choose three typical bridge decks (A, B, C), which will be simulated to gain more insights about the cross-section of these historical bridge decks. The current Eurocode 4, which is implemented to guarantee the safety of the type of cross-section containing steel and concrete, does not provide an answer to calculate the load-bearing capacity of historical steel-concrete-composite-bridge-decks, because of a significant difference between the designed current Eurocode 4 model and the designed cross section of the historical model. The behaviour of the bridge is studied in two directions based on the available literature. In the longitudinal direction, the focus is on the interaction between steel and concrete and how this interaction can be described. In the transverse direction, the aim is to find the relevant failure mechanism and corresponding modelling approach to define the behaviour of the bridge deck in the transverse direction of these bridge decks. The failure mechanisms that were evaluated are: Punching shear failure, compressive membrane action, and failure of concrete strut. The assessment of the aforementioned failure mechanisms is carried out and the most logical model which can be used to validate during the FEA-simulation is the failure of concrete strut which can be modelled by strut and tie model. This model will also be carried out on the other two chosen bridges, next to bridge A on which the in-situ-load-test is done, to validate this model on more than one bridge deck. There was made use of an analytical model based on Eurocode 2, which has been compared the values of the numerical simulations…

The World Heritage Site Kinderdijk consists of a landscape of preserved 18th-century windmills and is a popular touristic location. The number of visitors is continuously growing for the World Heritage Site at Kinderdijk. Visitors arriving via the water network have to cross a busy road to reach the heritage site. This is an unsafe and unfavourable situation. A new water entrance at Kinderdijk is the solution to this problem. The plan is to add the function of a pedestrian passage to the existing discharge sluice at Kinderdijk named the Elshoutsluice. The discharge sluice is part of a flood defence and must keep its original function. The objective of this thesis is to provide a conceptual structural design for the multi-functional use of the discharge sluice at Kinderdijk including the functions for water discharge, flood defence, passage for (motorised) vehicles and pedestrians, which fulfils standards for flood safety and buildings in the Netherlands. This thesis shows how to approach a design case for adjustments of an existing hydraulic structure as a part of a flood defence. A conceptual design was made for the adaptation of the Elshoutsluice. For this study a design method according to Roozenburg and Eekels (1995) and Voorendt (2020) was used. The Elshoutsluice was divided into different subsystems and elements. The concepts for the location of the new pedestrian tunnel, the floor configuration, the roof and gates were developed. After the functional verification and evaluation, a selection was made from the best remaining alternatives for the elements and subsystems. The selected alternative is a pedestrian tunnel above culvert number 2. As a result, the existing gates of culvert 2 will be replaced with new gates to provide flood protection in case of high water. A flap gate and a vertical unfolding gate are selected. The existing technical area expands above culvert number 3. A multi-functional space is included above culvert number 3. Culverts 1 and 4 remain unchanged. Additional soil will be placed on top of the structure to provide a slope for the connection of the heightened road on top of the sluice to the road at the adjacent levee. The conceptual design and construction phase was checked for the flood safety based on the WBI 2017 and OI 2014 and fulfils the requirements. Stability checks were performed for governing load situations of the Elshoutsluice for the construction phase and use phase. The difference in loading on the structure for the initial design and the new situation was analysed. Additional checks are needed for the lateral walls in all the culverts and the top slab of culvert 1 and 4 due to the increase in shear force and bending moments. The conclusion is the resulting conceptual design.

In recent years, the area of structural engineering has found new interesting prospects in the theory of waves. The acoustoelastic properties of materials are utilized in a new promising structural health monitoring (SHM) technique. The propagation of ultrasonic waves through stressed elements gives the ability to find invaluable information on the stress-state of the concerned element. This information is then analyzed with the use of Coda Wave Interferometry (CWI). This technique explores the late arrivals of the wave field, which is referred to as the coda. Due to scattering of the waves through heterogeneous elements, this part of the wave field holds additional information compared to the early arrivals, which makes it very suitable for application on concrete elements. The use of ultrasonic waves with CWI in concrete elements has been studied enthusiastically by engineers due to its promising prospects. Nevertheless, this technique is still developing both in theory and in practice. The majority of previous similar studies have been conducted in laboratory settings, and thus conditions are very controlled. In this study, the monitoring technique is applied in conjunction with Smart Aggregate (SA) to a concrete structure for practical use. The SA sensors are positioned in groups at key location in the first concrete cast of a cast-in-situ prestressed concrete bridge, which entails two bridge spans of approximately 30 meters length. Measurements are done at different phases during the construction of the bridge, when the stress-state at the positions shifts due to change in loading and boundary conditions. The resulting data is analyzed with CWI and subsequently evaluated whether it coincides with expectations. Deviations from these expectations are rationalized or an attempt thereof is made. The results show significant differences between field measurement results and expectations based on laboratory tests. These differences are explained by the presence of a greater amount of parameters, which influence the data gathered from field measurements. With the appropriate measures, the various factors acting on the structure are isolated and subsequently validated with laboratory data. The most prominent factors affecting the acoustoelastic properties of the structure are established to be time related. These factors involve concrete shrinkage, creep deformation and the concrete hydration process. With laboratory testing the effect of these factors on the wave propagation velocity are determined. By taking into account the additional factors, a strong correlation between changes in the stress-state and changes in the wave propagation velocity is observed when the data is read in an adjusted manner. With a proper protocol, the use of smart aggregates in combination with CWI could be very valuable in accessing concrete structures on-site in both its construction stage and service stage. As it stands, prerequisite knowledge of the monitored structure is necessary to make use of the full potential of the SHM involving CWI and SA. The demand for prerequisite knowledge of the structure increases as the monitored structure becomes more complex, because it increases the amount of additional endeavors required to properly asses the acquired data. As such, the discussed monitoring technique in its current stage of development generally has low accessibility for practical use. But with further research and more understanding of monitoring method, the discussed SHM technique might be applicable for general use in the near future.

Global climate change has been a huge matter of concern today. While there are several factors that contribute to greenhouse gases, adversely affecting the planet, CO2 emission is one of them. It is said that 8% of total carbon dioxide emission is caused due to the production of Ordinary portland cement used for concrete in construction. The construction industry highly relies upon concrete as a major and widely used construction material. Solutions to reduce the production of Portland cement without having to entirely remove concrete as a building material has been an important discussion. A possible solution is to replace the Portland cement in concrete with industrial by-products further activating the binder with alkali activators producing a green concrete called ‘Geopolymer concrete’ (GPC) which would reduce CO2 emission.  The biggest challenge yet is that, designing any structure, a standard validated code/regulation is required and GPC doesn’t have a standard code of practice. All the concretecodes till now are formulated taking the parameters for Ordinary Portland cement concrete. This lack of design models specifically formulated for GPC restricts contractorsand engineers to use GPC in structures. This is why GPC has not gained much acceptance in practice.  This research was done in collaboration with Boskalis. A bridge (KW15-N69) has beenconstructed using geopolymer concrete in North Brabant province of the Netherlands.To make the bridge sustainable and circular, the GPC used contained no cement andaggregates were fully replaced by thermally recycled asphalt aggregates. For design ofthe bridge, Eurocode 2 for concrete structures was used and additionally regulations by Dutch ministry of transport and infrastructure was followed.This research will act asone of the pioneer studies to investigate the overall structural behaviour of geopolymerconcrete beams with respect to standard codes which should help design engineers upto some extent to execute and design structures using GPC in future.   

Adopt the concept of demountable and rebuildable brides to an existing idea of an integral bridge. An understanding of the different forces and moments that the bridge will have to take up and how the critical connections (deck-abutment) can be realized. Applying the understanding of how integral and demountable bridges behave and try to integrate the characteristics of both to achieve rebuildable/demountable construction. In this additional thesis, the first steps to make an integral bridge demountable is looked at in detail. The concepts of vertical prestressing with unbonded bars are explored to achieve the demountable abutment, and abutment- deck connection. The different forces that arise due to this method of prestressing have been accounted for to ensure the basic safety of this design is met.

3D concrete printing (3DCP) is a new, innovative construction method in which concrete structures are produced layer-by-layer using a 3D printer. A printed concrete structure, can be self-supporting, which means no formwork is required anymore, increasing the freedom of form, while decreasing construction cost and material use. However, the engineer designing 3DCP structures is challenged, because the construction process is completely different than from designing conventional concrete structures. The fresh concrete structure must be stiff and stable enough to resist the increasing self-weight of the subsequent layers and the material properties can become anisotropic due to a limited bond-strength between two layers. The objective of this research is to integrate the manufacturing process into the structural design of a simply supported 3DCP cyclist bridge, to provide guidelines for designers and for future research. Using a parametric research model, the performance and feasibility of the design can be assessed as a function of 22 parameters describing the bridge geometry, material properties (fresh and hardened) and printing process parameters. The model is built in Grasshopper and Python by using analytical formulations only. The use of FE software is omitted to make the model as fast as possible. Like this, a global sensitivity analysis based on thousands of parameter combinations could be conducted, revealing the most important parameters for determining the design's performance and feasibility, as well as the absolute effect of specific parameters. These results were used in an optimisation run, seeking the most cost-efficient and sustainable design. The research shows that integrating the manufacturing process into the structural design of 3DCP objects yields more optimal designs and the analytical model that has been developed has proven to be a useful tool for research and design.