In the Netherlands, there is a large and widely used railway system that includes numerous railway bridges. This master thesis investigates the problems caused by these railway bridges. Since World War II, continu- ous welded rails have been used extensively throughout the Netherlands. These rails offer several advantages on embankments, such as reduced maintenance due to less vibration, increased passenger comfort, and reduced noise. However, continuous welded rails can cause problems when they run continuously over a bridge, as is the case in the Dutch railway system. Bridges are not continuous structures and have joints between the decks or between the deck and the transition structure. These joints allow the bridge deck to expand and contract due to temperature changes, move due to longitudinal forces from train braking and acceleration, and deflect due to the vertical load of the train, causing rotations at the ends of the bridge decks. This relative displacement between the bridge deck and the continuously welded rails creates addi- tional stresses in the rails. These additional stresses must not exceed the maximum allowable stress of the rail material, as this could cause the rails to buckle or fracture. Fixed points are often used in practice to limit the movement of the bridge deck and keep additional rail stresses within acceptable limits. This investiga- tion, however, focuses on understanding the interaction between the rails and the structure without the use of fixed points. The study assumes a railway bridge in the Netherlands with a ballast bed and uses concrete precast bridge decks.

To gain initial knowledge of the problem and the various railway components and bridges, a literature review was conducted, and two existing railway bridge projects were analysed. It quickly became evident that there are two different bridge types relevant to the study of additional rail stresses: those without embankment influence and those with embankment influence. The study then identified parameters that could influence the magnitude of additional rail stresses to use them as variables in further investigations.

Two longitudinal force models were created in SCIA Engineer: one without embankment influence (Model 1) and one with embankment influence (Model 2). These models are spring models where the stiffness of connections and elements is schematised as springs. The models were validated with hand calculations and used to obtain results for the influence of various parameters such as bridge deck span length, elastomeric bearings, bridge pier length, and foundation stiffness. The results of the two models were compared to understand the influence of the embankment. Additionally, the spring elongations of the non-linear springs between the bridge deck and the rails, representing the ballast bed, were examined to determine if they were in the linear or non-linear part of the spring characteristic to see if the springs slipped enforcing stress redis- tribution. Finally, the models assessed the individual contributions of three load cases (thermal, longitudinal traffic load, and vertical traffic load) to the combined additional rail stress.

The results lead to the following conclusions:
• When a structure is not influenced by the embankment, the magnitude of additional rail stresses depends on the stiffness of the substructure. The stiffness of the weakest component, in this case, the elastomeric bearings, has a significant influence.
• When a structure is influenced by the embankment, the magnitude of additional rail stresses mainly depends on the dominant stiffness of the embankment, with the stiffness of the substructure having little to no influence.
• Structures with embankment influence experience lower additional rail stresses due to the additional stiffness provided by the embankment. Problems with exceeding maximum permissible rail stresses occur mainly in relatively long railway bridge structures without embankment influence.
• The vertical load has the largest contribution to the combined additional rail stresses for both structure types.
• The thermal load has a larger influence on structures with embankment influence because these structures are more constrained by the embankment and thus more vulnerable to thermal deformations.
• Linear summation of individual stress contributions from different load cases generally results in higher or equal stresses compared to non-linear combinations, making linear summation a conservative approach. The stress difference between linear summation and non-linear combination is usually only a few megapascals. If the springs between the bridge deck and the rails slip into the non-linear branch, this difference increases slightly but remains small.


Based on these conclusions, the following recommendations can be made to prevent additional rail stresses from exceeding maximum permissible stresses without the use of fixed points and to streamline the process of longitudinal force analysis for engineers:
• To prevent exceeding the maximum permissible stress in structures without embankment influence, consider using larger elastomeric bearings or less slender bridge decks that are less susceptible to deflection, thereby reducing additional rail stress, especially from vertical loads.
• Since linear summation of individual contributions to additional rail stresses results in conservative and faster calculations, it is recommended to use linear calculations in the initial phase. Then, perform a final design review with non-linear calculations to ensure accuracy. This approach will significantly speed up the design process, as models will not need to run for hours or days each time.

The use of computers in engineering started in 1960. Before 1960, engineers used physical models to check the results of complex structures. Recently, these physical models have been used for education purposes, namely, in the minor Bend and Break. Conversion from small-scale structures to real-sized structures was taught in this minor (P. C. J. Hoogenboom, n.d.). Therefore, This research aims to find a relation between small-scale and real-sized structures. Namely, the conversion of internal forces and displacements from a small-scale structure to a real-sized structure in both linear and non-linear material behaviour. A linear calculation yields a linear relation between the results and the applied force on the structure, unlike a non-linear calculation. The conversion rules apply to linear material behaviour. However, whether they also apply to physical and geometrical non-linear material behaviour is uncertain. This uncertainty yields the following research question: “There are conversion rules for deflection and stresses from small-scale structures to real-sized structures. Do these apply to non-linear behaviour too?” Multiple structures were analysed. A small-scale and real-sized model of these structures was modelled in the finite element program SCIA Engineer (SCIA, 2024). The geometrical properties of the smallscale structures were 10 times smaller than the geometrical properties of the real-sized structures. The type of structures is itemized below: • A steel truss (with and without bending stiffness) • A steel beam (statically determinate and statically indeterminate) • A steel Vierendeel girder • A concrete two-way slab • A concrete shell roof Geometrical and physical non-linear calculations were done. The geometrical non-linearity focused on local and global buckling, which yields large displacements while physical non-linearity focused on the plasticity of hinges and elastoplastic stress-strain diagrams. Relevant forces in the structures’ members and nodes were computed with linear and non-linear calculations. Additionally, displacement and deformations of relevant members or nodes were analysed. Furthermore, the applied loads are point loads, line loads or distributed loads, which had their conversion rules from small-scale to real-sized structures. Namely, the real-sized point load is 100 times larger than the small-scale point load. The real-sized line load is 10 times larger than the small-scale line load and distributed loads are identical in both structures. This yields identical stresses in the small-scale and real-sized structures. Displacements differ by a factor of 10 and internal forces by a factor of 100 or 1000, depending on the type of applied load. The steel trusses, the statically determinate beam, the Vierendeel girder and the concrete shell roof were all analysed with a geometrical non-linear calculation. All linear analyses followed the conversion rules perfectly. The relevant displacements in the small-scale structures differed by a factor of 10 from the displacements in the real-sized structures. The internal forces differed by a factor of 100 or 1000. Similarly, in the geometrical non-linear calculation, the displacements differed by a factor of 10 and the internal forces by a factor of 100 or 1000. However, there were small numerical errors in the nonlinear calculation. This happens when SCIA Engineer makes a non-linear calculation due to its iterative calculation method. The statically indeterminate beam and the concrete two-way slab were analysed with a physical non-linear calculation in addition to geometrical non-linearity. The plasticity of hinges was tested in the statically indeterminate beam and the elastic stress-strain curve of the two-way slab model was changed to an elastoplastic stress-strain curve which yields large displacements. Again, the internal forces differed by a factor of 100 or 1000, depending on the type of applied load. The displacements differed by a factor of 10, which is in line with the existing conversion rules. In conclusion, for the analysed structures, the conversion rules apply to both geometrical and physical non-linear material behaviour.

Selecting the optimal stability framework for high-rise steel buildings is a critical decision that impact both economic efficiency and sustainability. This decision is not easy since there are many stability frameworks to choose from, such as tube, concrete shear-wall, and outrigger system. Designers and clients aspire to compare multiple structural designs, considering both different frameworks and variations in geometry. Unfortunately, the current process of evaluating multiple designs is time-consuming and relies on the designer's experience and rules of thumb, rather than being driven by data. To address this challenge, predictive models can be used to estimate performance in terms of structural and environmental costs based on the given geometry and framework. However, traditional curve fitting methods often fall short in accurately predicting a complex relationship. In response, this study explores the potential of artificial neural networks to accelerate the decision-making process by predicting the most efficient framework during the early design phase while maintaining sufficient accuracy.

To determine this potential, two parametric models were developed using Rhinoceros software to represent buildings with braced framed tubes and outrigger systems. These models automatically optimised beam and column dimensions by FEM of Karamba, aiming to minimise the mass of these structural elements, across a range of building widths (15 to 60 meters) and heights (48 to 300 meters). The resulting data sets of both braced framed tube and outrigger system reflected the structural and environmental costs for the different designs. Separate neural networks were modelled for each framework. These networks were trained on the different data sets. By comparing predicted structural and environmental costs, the models assisted in the selection between braced framed tubes and outrigger systems.

The artificial neural networks accurately approximated structural and environmental costs for both stability frameworks. The Mean Absolute Percentage Error (MAPE) for the braced framed tube was 14%, while the most accurate alternative curve fit, a third-order polynomial, had a MAPE of 25%. For the outrigger system, the neural network achieved an even lower MAPE of 7%, where the most accurate alternative curve fit, also a third-order polynomial, had a significantly higher error with a MAPE of 31%. The neural networks outperformed traditional curve fitting methods. Additionally, the neural network generated instant results, taking only a second compared to the parametric model’s 5 to 30 minutes. However, achieving overall time efficiency with the neural models will require approximately three months when considering both setup time and output generation time. Optimal stability varied based on specific width and height combinations: when looking at environmental costs, the braced framed tube excelled for lower (50-80m) and higher heights (200-300m), while the outrigger system was more efficient for middle heights (80-200m). As the structure’s slenderness increased, the braced framed tube regained efficiency for the middle heights.

Impact of the stability framework is defined as the relative contribution of embodied carbon of the stability framework to the total embodied carbon of the structure (including superstructure and floors). The impact of the stability framework ranged from 25% to 57% for the braced framed tube and 33% to 66% for the outrigger system, with the impact increasing with the building's height...

The offshore renewable energy market is rapidly growing, particularly in wind and solar sectors. The intermittent nature of these energy sources underscores the necessity for offshore energy storage solutions. Among the techniques being explored, Marine Pumped Hydro-Energy Storage (MPHES) emerges as a promising option. This innovative concept operates similarly to artificial lakes, where water is stored and released to generate electricity. In the MPHES system, a seabed-based reservoir is established, in which water flows, driving turbines to generate electricity. During periods of energy surplus, the system is charged by pumping water out of the reservoir...

Timber as a construction material for high-rise buildings is gradually entering the construction industry. Timber is considered a sustainable option, because it is a natural material that absorbs CO2 rather than producing it.
However, using timber as a building material also introduces new challenges, one of which is the problem with lateral stability, due to the relatively low stiffness of the elements and their connections. This research investigates the value of a timber core in a building that has bracings in the façade. The study examines this value in both normal conditions and the accidental limit state in case of a fire situation. The key question being addressed is:
Can a timber core sustain lateral load as a secondary load path, in case of failure of the tability bracing?
First, a literature review is conducted to understand the material and relevant safety mechanisms. A parametric program is used to explore the core’s parameters, alongside a linear elastic 3D FEM (Finite Element Method) program that utilises members and surfaces to analyze the building structure. The considered building is a 10-story rectangular structure (28.8 x 21.6 meters) with glulam beams, glulam columns, and CLT floors. The building was designed on an infinite stiff foundation by using a timber core and timber bracings in the façade. The core consists of cross-laminated timber (CLT) panels, connected with slotted steel plates and dowels. The bracings are glue laminated timber and are connected with two slotted in steel plates and dowels. The CLT panel connections and the bracing connections were calculated by hand and implemented in the FEM model. Which was validated
by hand calculations. Additionally, wind load, variable load and permanent load were applied on the model.
This model was used to answer the following question. What percentage of the lateral force can the core take?
The model with a timber core in the Urban Woods shows an 18% reduction in global deflection compared to the model without a timber core in the ultimate limit state. The deflection of both models where to be within the prescribed limit. Additionally to the deflection reduction, the forces in the bracing are reduced by 33% in the model with a timber core. The core parameters that influence these reductions are the connections between the core panels and the cut-outs in the timber core. A core parameter study has been carried out to answer the following question:
How do the core parameters influence the global deflection?
For the connections, increased stiffness enhances the contribution of the core to reducing global deflection, with reductions ranging from 0% to 22%. Using longer panels results in fewer connections, which makes up for 7% of the global deflection reduction at any given stiffness of the CLT connections. Regarding the cut-outs, a larger cut-out size results in a lower contribution to deflection reduction. The reduction in global deflection for
different cut-out sizes ranged from 5% to 27%. As the number of floors increases, the value of a timber core diminishes.
In the accidental limit state of fire, strong wind and failure of a facade bracing element, the timber core will serve as a sufficient alternative load path. However due to the wind force reduction in the ALS the remaining bracing is also capable of withstanding the lateral wind force. When two elements are removed than the core will be necessary. The unity checks for the CLT elements and connections did suffice.

This research aims to investigate the influence of Polyisocyanurate (PIR) insulation on small surface load distribution on corrugated steel roofing sheets. PIR foams are used for thermal insulation in industrial buildings. The distribution of surface loads induced by solar panels support structure might be altered by PIR foams. This is completely ignored in the design calculations according to current standard which might results in overconservative designs. In this study, the following main question is going to be investigated using experimental and numerical methods: ‘’What is the influence of PIR insulation on the transverse distribution of small surface loads on corrugated steel roofing sheets?’’.

The methodology involves conducting bending experiments to obtain strains and deflection data, which then are validated using numerical models. The experiments have been conducted on corrugated steel sheets supported by rollers. The PIR insulation is connected to the steel sheet by bolts, and a loading cylinder applies vertical force at the PIR insulation panel side. Two loading configurations are selected to simulate the representative loading conditions in real-life structures. Vertical deflections and strains in the bottom flanges of the corrugated sheet are measured during the experiments. The experimental data are used for the validation of the numerical models that are created by using ABAQUS FEA.

First, a linear F.E Model was developed and validated with experimental results up to the initiation of nonlinearities. The results of the linear models shows clearly that the PIR layer influence considerably the stress distribution in the adjacent ribs to the one of load application. A nonlinear analysis is conducted to determine the maximum load that the roof structure can resist. To capture geometrical nonlinearities more accurately, eigen buckling analysis was conducted to implement initial geometrical imperfections. Considering the imperfect initial geometry of the steel sheet and its plastic properties, maximum strength of the roof system could be estimated. As a note, the damage in the PIR insulation material was not considered as it is beyond the scope of this study, the material was assumed to be linear elastic.

The experiments demonstrate that the behaviour of the roof structure is primarily governed by the rupture of the PIR insulation, occurring prior to any yielding in the steel sheet. The linear numerical model predicts the behaviour of the roof structure within the elastic phase. The linear model can be used to study the influence of the several influencing parameters such as the dimension, PIR material properties and the loading conditions. Expanding the span from 2 to 6 meters with a single mid-span surface load increases the adjacent rib contribution by 20%, meaning that their normalized strain values relative to the load location's maximum strain grow by 20% in the elastic phase. The nonlinear model is employed to establish the force vs. displacement curve and identify the strength of the roof. The non-linear numerical models show that the ultimate load is found to be 8000 N when a single surface load is applied directly on the steel sheet. The experiments show yielding of the steel at 7300 N after the loading jack ruptures both the PIR surface and layer, then the jack reaches the profiled steel sheeting. For design purposes, it is recommended to exclude the influence of the PIR insulation beyond its elastic phase. Compression tests conducted on the specimen revealed damage within the PIR material at a load of 6250 N, which is considered the upper limit for the PIR's elastic phase.

This thesis comprises of vertical deformation differences in high-rise structures where a concrete stability core is combined with a timber frame. The timber frame consists out of prefab timber modules which derive all lateral stability from the concrete core. Due to contrasting elastic, hygroexpansion and viscoelastic properties there is a notable difference in the vertical deformation of the concrete core and the timber units. The impact of these deformations have been outlined and possibilities to minimize the impact have been explored in this thesis.

A structural firm will not invest a large sum of money in early design fase on a wind tunnel aeroelastic model to determine the displacements, forces, and moments when the dimensions of a building have only been estimated because the outcomes are only valid for that specific model. It is well-known that the outcomes are hard to determine precisely in early design fase.

This study aims to make a modelling tool in Matlab to predict the bending and torsional oscillations of a high-rise building due to wind load fluctuations in time and space.

To test the research question, which is, does the designed Juffertoren building in Rotterdam and the structurally strengthened student building Voorhof in Delft comply in the serviceability limit state when looking at bending and torsion accelerations in the along wind direction.

After strengthening the occupants of the student building Voorhof still complained about motion sickness during storms.

The results show that the Juffertoren and the student building Voorhof do not meet the serviceability limit state requirement.

These results suggest that more research should be done when looking at serviceability limit state requirements by light weight and thin buildings.

A steel frame is designed which is expandable and reducible at any time. In order to reduce the assembly and disassembly time of the frame a new type of beam-to-column connection is proposed, a so-called plug & play connection.The design codes cannot be used for the estimation of the structural performance of this connection. Therefor the following objective is defined:What is the structural performance of the plug & play connection and how can the connection be reusable?In the state of art the benefits and problems plug & play connections offer over traditional steel connections is given. A case study of a steel frame, which consists of stacked units with fixed dimensions, is described. For this case study a global analysis is performed to investigate the possible internal forces on the plug & play connection.With the results obtained from the state of art and the global analysis an initial design is made. This initial design assumes a perfect fitted connection.Both the stiffness of a column major and minor axis joint is investigated for a hogging, sagging and out-of-plane bending moment. For all cases the joint is classified as semi-rigid. The inclined parts of both socket and plug will yield for all cases and the highest plastic strain will occur in the inclined parts of the connection. The thin base plate of the socket causes that the socket shows a bending deformation for all displacement cases, this bending deformation makes that the plug will be easier to pull the plug out of the socket, which reduces the stiffness. So an optimized design is checked for the minor axis case. For this optimized design the base plate thickness of the socket is increased in order to prevent the bending deformation of the socket. This optimized design also includes tolerances. The optimized design has removed the bending deformation of the socket. For a downwards displacement slip will occur, as a consequence of the tolerances, before contact between plug and socket is initiated. No slip will occur for an upwards or out-of-plane displacement as the bolt will be immediately in tension. So for the downwards case the initial stiffness is depending on the contact between plug and socket, while for the upwards and out-of-planed is placement the initial stiffness is provided by only the bolts. For all cases the stiffness is increased compared to the initial design.The final step is to evaluate the re-usability of the connection. The plastic de-formation has to be limited in order to be able to reuse the connection. For the upwards and out-of-plane case, in the optimized design, no plastic strainoccurs in the inclined parts of the connection when the moment is below the elastic moment resistance. This is because the elastic moment resistance is only provided by the bolts. For the downwards case there is plastic deformation in the inclined parts. However, increasing the thickness of the plug has reduced the maximum plastic strain compared to the initial design. So when the moments on the connection are below the elastic moment resistance the connection should be reusable. A visual inspection should prove whether the plug still fits in the socket.A real test should prove whether the plug & play connection reduces the assembly and disassembly time. If this is the case, then the moments on the joint should below the elastic moment resistance, so the connection could be reused. The joints will not be classified as rigid, so their semi-rigid behaviour should be taken into account in the global analysis.

In the presented work, we have developed a method to analyse the interaction between the wind and membrane structures. The complex behaviour of light weighted membrane structures can induce dynamic and wind effects, so this requires an appropriate method to analyse the structure. When the deformation of membrane structures is large, it becomes necessary to consider the interaction between wind flow and membrane. This interaction leads to aeroelastic problems.
The necessary properties to be considered for the aeroelastic coupled problem are considered and presented. The major focus of the thesis is to simulate the geometric non-linear behaviour of the membrane structures when subjected to wind loading. To derive the initial equilibrium shape, the method of form finding is applied. To properly simulate the wind flow around the structure, existing research regarding wind tunnel testing of a hemispherical air dome model is used. First, hemispherical model similar to existing research was made to verify the boundary conditions. The results are compared to the wind-tunnel testing results to get proper boundary conditions in Computational Fluid Dynamics models. In order to keep the simulation simple, the wind velocity is considered constant with height and constant wind flow with respect to time.
Partitioned analysis is used to simulate the physics behind the wind-membrane interaction simulation. By using this method, the multi-physics problem is separated into individual fields. Considering the wind-membrane interaction, the problem is separated into fluid domain and structural domain.
The structural and fluid domain mechanics are discussed in detail. For the single field solvers, methods are introduced based on the fundamentals. Finite Element method is used for the form-finding as well as numerical simulation of the structural field and SOFiSTiK software is used. For the fluid simulation, ANSYS CFX is used.
The strong physical coupling is done between the fluid and the structural domain. For this, the partitioned coupling simulation is used. The requirements and methods for the partitioned analysis are presented as well. For the coupling of separate solvers, a central coupling tool is made using Grasshopper. The transfer of coupling data such as displacement and wind pressure on the membrane structure is done using the developed coupling tool. In the development of this coupling method using Grasshopper, Python programming language is used. The developed method was used in iterations to analyse the effect of geometric non-linearity.
In order to make the developed method reusable for the air-supported membrane structures, the whole process is made parametric using grasshopper. This enables us to analyse the membrane structures with known base shape, internal air pressure. Ultimately this method can be used to analyse the effect of geometric non-linearity on membrane structures when subjected to wind loading. To show the use case of developed method, two different models are developed to analyse the fluid structure interaction. First model has been considered with a circular base shape and the second one has been considered with a square base shape. In order to analyse the effect of geometric non-linearity on these structures, the results such as maximum wind pressure on the membrane structure and maximum structural displacement are compared to the results without considering the geometric non-linearity.
Moreover, wind variation analysis is done to analyse the extent to which geometric non-linearity is dependent on the wind speed. Similarly, size variation analysis is also done to analyse the extent to which geometric non-linearity is dependent on the structure size, keeping the wind velocity constant.

Torsional moments and shear stresses are not calculated correctly in the framework analysis software SCIA Engineer for cross-sections with a shear centre eccentricity. The aim of this research is to analyze and solve this problem.

A new approach to applying the finite difference method for solving the shell model problem. By solving the general shell differential equations (Sanders-Koiter equations) with first-order finite-difference approximation only, a finite difference algorithm called shell code has been developed.

To this end, a 1200-line Python program has been built. In the process many versions of shell code were considered, including
1) Two programming languages (Python and R)
2) Three interpolations for approximating gradients (three-point and five-point with two end slopes)
3) Determined and over-determined systems of equations (square and rectangular matrices)
4) Four solvers for the systems of equations

The final version of shell code has the following features; five-point interpolation with zero end slope, rectangular matrix, solver lm.fit.sparse (R). Approximately 80% of the shell code results match the finite element results with a deviation less than 5%. It has been proved that the selected version of shell code can solve shell model problems by solving Sanders-Koiter equations with finite difference method. Many previously assumed important factor for affecting shell code results, like number of nodes and interpolation methods, were actually less significant. However, the most vital difference in results occurred under different computation methods. Maybe under further research of developing mathematic tools, finite difference method could be a more promising and practical method for solving model problems.

Practical combinations of floor configurations and support conditions are studied for the development of a lightweight timber building method that is suitable for multi-family residential buildings. Classical vibration theory forms the base for a methodology that is developed to assess transmittance of vibrations to adjoining floor fields. Especially when the source is out of sight, humans humans are tend to classify vibrations as annoying for low vibration levels. With the introduction of new engineered timber products made wood a more suitable and used material for residential buildings. Strength- and stiffness variation is reduced by homogenizing the material and regarding soundproofing innovative concepts have been improved, such as floating screeds and resilient materials. Based on these products and acoustic concepts, 32 design combinations are studied. A distinction between forced- and free vibrations is made and related to low- and high-frequency floors. Forced vibrations are in structural dynamics described by the particular solution, and free vibrations by the homogeneous solution of the equation of motion. This solution is found through the method of separation of variables, which multiplies the space- and time-related parts. Mode shapes are studied regarding transmittance and effective measures for prevention. Fundamental frequencies of floors supported either rigid and flexible are determined with one-dimensional undamped continuous systems where supported beams are represented by equivalent springs. All floors are transformed into Single Degree of Freedom systems to include damping. These systems are assessed making use of modal superposition, for steady-state- and transient response. The behaviour of floors under walking load harmonics provides the resonant response, and free vibration of the system due to initial conditions the transient response. Since the perception of vibrations by humans is frequency-dependent, vibrations are weighted accordingly. Eurocodes currently available are found to provide guidance regarding human-induced vibrations of lightweight structures marginally. Non-timber Eurocodes do not provide an assessment method, EN1990 only provides requirements when no assessment has to be done, and current code for timber structures prescribe criteria that are not sufficient as found in the literature. The future revision of Eurocode 5 holds several methods for assessment of vibrations but is generally focussed on rigidly supported floors. In extending to this code methods are developed to acquire fundamental frequencies of flexible, supported floors, and by transformation into SDOF systems an equation is developed for the appropriate determination of modal mass for two-span or beam supported floors using a simple formula. 32 combinations of floor configurations and support conditions are assessed at the excited field and at adjoining floor fields, where both steady-state and transient response are combined. Based on this assessment, transient responses are found to contribute significantly for low-frequency floors, where generally is assumed that the mass is sufficient to neglect this response.

A new approach to applying the finite difference method for solving the plate model problem. By decomposing higher-order differential equations in plate theory into several first-order differential equations, a python program was built in an attempt to solve those equations with first-order finite difference approximation. After testing several square plate models with various boundary and load conditions, this program has been proved to work. The major results (displacement, bending moment, and shear force) are generally 10 to 20% smaller than the analytical solutions. The difference can be caused by the grid size but also by a programming error. Compared to the finite element method, this python program has a smaller code size but with less accuracy and more computational time.

As timber is being used for several millennia as construction material, glued laminated timber (glulam), a highly engineered timber product, exists for about hundred and fifty years. In Europe, it is nowadays common practise to make glulam from softwood species, though in the last few decades glulam made from different kinds of hardwoods emerged. Iroko glulam is part of this development, as iroko is a hardwood species from the African tropical regions. The aim of this thesis is to investigate the bending strength of iroko glulam, as well as strength influencing features. From literature it is expected that the following features are of influence: density, modulus of elasticity, tension strength of the lamellas, finger joint strength and size. Several researches conducted in the past experiments to determine these mechanical and physical properties, focusing mainly on iroko sawn timber. Only few investigated iroko glulam, and none of those focused on finger jointed iroko glulam. In this lies the originality of this work: determining bending strength values of finger jointed iroko glulam, as well as density, modulus of elasticity and investigating mechanical and physical properties of the base material: iroko sawn timber and iroko finger joints. The laboratory experiments included the following: tension tests on 38 unjointed and 38 finger jointed lamellas, and four point bending tests on 12 glulam beams. Also density, modulus of elasticity and moisture content were determined. The experimental results yield the following characteristic values: a lamella tension strength of 17 N/mm2, a finger joint tension strength of 29 N/mm2, and a glulam bending strength of 42 N/mm2 (including size effect according to NEN-EN 1995, 2011). The experimentally determined characteristic lamella tension strength is a little lower than values found in literature. This is due to a large scatter in the test results: a coefficient of variance equal to 0.37 was found. However, if the grain angle is equal or smaller than 5°, a higher lamella tension strength of 27 N/mm2 is feasible. Grain angle is as expected a significant strength influencing parameter for iroko sawn timber. And it would suggest that the strength class is as expected D40 if the lamella bending strength equals 0.6 divided by the lamella tension strength. The ratio of finger joint bending strength (30 N/mm2) and tension strength (29 N/mm2) on the characteristic level was found to be equal to 1.06. This is smaller than expected from theory: apparently the 1.4 ratio commonly assumed for softwood finger joint strength values does not hold for iroko finger joint strength values. The investigated iroko glulam beams with depth 108 mm yielded a mean bending strength of 66 N/mm2 and a characteristic bending strength of 42 N/mm2. Due to the size effect and quasi-brittle failure this figures lie lower for full scale glulam beams, however, strength class GL24h is indeed a safe assumption for iroko glulam beams. These aspects explain the higher mean glulam bending strength compared to the mean finger joint tension strength of 40 N/mm2. A strong mathematical relationship between characteristic glulam bending strength and both lamella tension strength and finger joint strength was not found; however lamella and finger joint tension strength do influence the glulam bending strength. Furthermore, density does not influence any strength or stiffness property for both iroko sawn timber, finger joints, and glulam beams. Although there is a slight positive correlation with both dynamic and local modulus of elasticity of lamellas and its tension strength.

Construction and demolition waste form a significant problem in terms of environmental pollution and material depletion. Concrete, as part of construction and demolition waste, is already responsible for 9% of the total anthropogenic carbon dioxide emissions. Consequently, it is important to alleviate the environmental stress of concrete by replacing virgin aggregates and cement by recycled aggregates and liberated cement. This study determines how the properties of recycled aggregates and virgin (new) aggregates compare for using recycled aggregates in a new concrete mixture.
Recycled aggregate properties are examined by performing a variety of experiments, namely
water absorption and specific gravity, Los Angeles abrasion, flakiness and shape index and
compressive strength. Each experiment describes a different characteristic of the aggregates
creating a clear picture of their properties. The properties of virgin aggregates have been
obtained from literature.
In addition, a milling method has been examined as a possible new step in the recycling chain
for liberating cement paste from the fine recycled aggregates.
Water absorption and interfacial transition zone formed problems for the recycled aggregates,
but they show excellent properties in terms of compressive strength, resistance to abrasion,
grain interlocking and shape characteristics.
While very different from each other, recycled aggregates show very good properties when
compared to virgin aggregates giving them potential to be used in new concrete mixtures.

The Netherlands has always been in close proximity to water, whether its rivers or the sea. This proximity to water and the need for land to settle and farm, led to vast amounts of land reclamation by constructing dykes along the water features to prevent flooding of the new earned land. This newly reclaimed land started to subside over the years, increasing the difference between the high water in the rivers and the low-lying land even more. With an expanding population, rising water levels and increasingly severe storms, the consequences of a future flood due to a riverine dyke breach are ever rising.
The aim of this thesis follows from these increasing consequences and is to determine the potential structural damage to a masonry house due to a dyke breach leading to a riverine flood.

Most bridges in the Western European road networks are ageing. The vast majority of about 90% of these bridges have reinforced concrete as a building material. The traffic intensity, as well as the axle, and the average vehicle weight have increased since these structures were opened to traffic. Furthermore, the structural (design) codes have changed over the years. Therefore, there is a need to investigate if existing structures meet the safety/reliability level described by the current codes. However, a frequently faced problem in practice is that the original design calculations and technical drawings of a large percentage of the existing bridges are unknown or lost. Especially for bridges in the lower road network, often designed for the lower load classes B/45 and maintained by a local government, the documentation is missing. The national road network, designed for load classes A/60 is maintained by the national government and faces the same problem but to a lesser extent. Bridges within this scope have different detailing rules and execution practices than used nowadays. Plain reinforcement was in general used which is bend-up at a support. Therefore, the study is twofold: first, Reverse Engineering is applied to determine the reinforcement of existing reinforced concrete slab bridges, second the capacity margin of RE bridges are examined with the current assessment codes. A Reverse Engineering-tool is developed to automate the dimensioning of the required reinforcement according to the former design codes. This tool uses the year of design, load class and the geometric dimensions of the bridge as input parameters. A parametric study is performed to examine bridges from different design periods. Consequently, the Reverse Engineering-tool is used to assess the Reverse Engineered bridge according to the current assessment codes. The validation of the model shows for the majority of the Reverse Engineered bridges that the Reverse Engineered reinforcement is slightly less than the reinforcement amounts from the technical drawings. This proves a conservative approach where the actual structural capacity is underestimated. Consequently, an assessment of the Reverse Engineered bridge can be performed with sufficient robustness.The computer code ran with the input parameters having a normal distribution, showed the largest effect for the uncertainty in the design year and load class especially around 1940 and 1962. Therefore, the design year and load class are crucial in Reverse Engineering and assessment of an existing bridge. The capacity margin of the Reverse Engineered bridges is assessed according to the current Eurocode based design codes. The traffic- and permanent load including load factors according to the general assessment codes from the NEN8700/NEN8701 and the RBK-1-1, and the decentralised load model from TNO are applied. The assessment with the Eurocode including the load factors from the NEN8700 showed Unity Checks for bending moment at the mid-supports and mid-spans of larger than 1.0, where the Unity Checks for shear forces resulted below 1.0. The assessment with the Decentralised load model showed Unity Checks for bending moment at the mid-supports and mid-spans and shear force below 1.0. In case the amount of support reinforcement is based on the amount of span reinforcement, the bending capacity margin at the mid-supports is insufficient for large spans. Significant bending capacity margins are obtained in structural design of RC slab bridges in the period 1930-1970. The main contribution of this research is that bridges designed between 1940 and 1962 show the most critical Unity Checks for bending in the assessed period. In this period account the following design methods: The dynamic amplification factor introduced in the GBV1940 for concrete bridges, the traffic load class from the VOSB1933, the N-method to determine the cross-section capacity and the effective width method from the GBV1940 and from the Guyon Massonnet method.The capacity margin for shear is found to be almost independent of the design period. Here can be concluded that the slenderness of the bridge deck is the main contribution in the shear capacity. Bridges designed in the period 1940-1962 with the support reinforcement based on the span reinforcement and with a span length >10m designed for load class B/45 or with a span length of >11m designed for load class A/60, form the group with the most critical bending capacity. However, the size of the group of former bridges designed according to these conditions is unknown.From the results can be concluded that bridges designed between 1940-1962 with RE reinforcement are found to be legally unsafe for bending according to the parametric assessment with the Eurocode.

In this research project, an attempt is made to fuse the fields of structural mechanics and machine learning. The goal is to find out if models can be created that are capable of predicting the outcomes of (nonlinear) finite element analyses. These models are created by means of Artificial Neural Networks, which is a powerful method in the domain of machine learning. The focus will be on stiffened steel plated structures that are part of a sea lock gate. The power of a trained neural network is that it is able to compute the output for a given set of input parameters within a fraction of a second. Running a complete finite element analysis on the other hand can take a significant amount of time, especially in case of geometrically and/or physically nonlinear analyses. When relying on nonlinear finite element analyses for performing a structural design optimization, a trained network can therefore save a huge amount of time. It also allows to evaluate many more design options, possibly finding a more optimal design than what would be possible with a manual design optimization. An automated procedure has been created to generate datasets by running FE analyses in batch mode. Parametric models are set up in ANSYS FE software, for which random sets of input parameters are generated. After running the analyses, the output is collected and organised in datasets that can be used for training. The sizes of the datasets and the dimensionality of the design spaces are varied in order to study the influence of these quantities on the accuracies of the predictions produced by the neural networks. Genetic algorithms, which is another machine learning technique, are deployed for the optimization of the \textit{hyperparameters} of the neural networks, which are basically the \textit{settings} of the network which determine the learning behaviour. Three standard interpolation techniques (Kriging and polynomial interpolation) are also fitted to the same datasets in order to compare the performance of the neural networks to these interpolation techniques. The final result is an overview of the accuracies of the predictions made with the neural networks on validation datasets. It was found that the neural networks produced accurate predictions on the maximum deflection of a simply supported, stiffened steel plate loaded by a uniform pressure. Most of the relative errors were within a range of 5\% error for design problems with 4 dimensions. Predictions of the linear buckling load of stiffened steel plates were found to be mostly within the range of 10\% error for design problems with 4 dimensions. When increasing the number of free design variables from 4 to 8, the errors were found to be mostly within the range of 20\% error. The predictions of maximum equivalent stresses in stiffened steel plated sections obtained by geometrically nonlinear FE analyses were found to be in the range of $\pm$ 20\%. These models had 13 free design variables. Improvements were made on the available options of hyperparameters for neural networks. With these improvements, new predictions were made on the maximum equivalent stresses and the accuracies were found to be slightly better, with errors ranging between $\pm$ 15\%. For implementation of the predictive model in a design optimization algorithm, these errors are considered to be too high. It is expected that the dimensionality of this problem (13 design parameters) combined with very irregular results due to the presence of peak stresses and different buckling shapes, resulted in these deviations. Additional datasets are generated with results of FE analyses of simplified, unstiffened steel plates. Both geometrically and physically nonlinear analyses are performed, with uni-directional compression applied to the plate edge directly as a displacement. The number of free design variables was set equal to either 1 or 4 free variables. It was found that even with small datasets (with 32 training samples), the neural networks produced very accurate results on predicting maximum equivalent stresses, maximum equivalent mechanical strains (in case of physically nonlinear analyses) and total reaction force. A neural network was found to be capable of producing a nonlinear load-displacement curve of a compressed rectangular plate with elastic-plastic material model.

At the Shonai River around Nagoya, Japan, several flood related problems occur. These problems occur at different locations, each with its own problems or limitations. The desired safety level as requested by the government is that the river should be able to have a discharge which has a probability of failure of once in 200 years. At many locations, the current probability of failure is lower than once in 50 years. This has led to the following research question:
How can the discharge capacity of the Shonai River be improved to modern standards?
The report has been divided in four phases. The first phase is used to formulate the final research question. This phase focuses on which part of the Nagoya urban area is most prone to flooding. Three kinds of flooding were examined: by peak river discharge, impact by tsunamis and impact by storm surge. The area is already well protected against tsunamis due to the natural shape of the bay Nagoya is situated to. The coastline is well protected against storm surges in the second half of the 20th century. At the river banks however, flood safety is still below the desired level. In the area, risks are relatively high along the Shonai River. Therefore, it has been decided to focus on the threats around the Shonai River. As already described above, there are several locations along the river with safety risks.

In phase 2, several locations and solutions are described to increase the capacity of the river. One major problem is the bottleneck around the Biwajima bridges, where four bridges are narrowing the river. At this location, the desired safety level of a flood discharge occurring once in 200 years is still far away. After discussion with officials of the Shonai River office, it was found that this problem was most urgent. Therefore, it had been chosen to elaborate further on this option in phase 3 and 4.
In phase 3, several options are described to remove the bottleneck. The first option is to replace the bridges with more clearance and larger spans. The second option is to remove the bridges and replace them for tunnels. The third and last option is to construct a bypass along the river, with flow through a tunnel. The Shonai River office is already working on a plan to raise the bridges, thus the first option has been dropped. The second option required large amounts of space for the tunnels. Therefore, it had been decided to work out the third option of creating a bypass. To minimise the impact of such a bypass and its construction on the surrounding area, the decision is made to construct a bored tunnel.

In the fourth and final phase the solution is verified. This is done concerning structural, hydraulic and construction method aspects. All the aspects are found to be possible. In hydraulic aspect, it is found that the required discharge capacity to reach a once in 200 year safety level equals 4250 m3/s. The current discharge capacity is found to be 2850 m3/s. Therefore, the bypass should have a minimal discharge capacity of 1400 m3/s. When using a bored tunnel, it is found that two tunnels with the maximal internal diameter of 16 m should be applied. On top of that, because the concrete surface is to rough in the best circumstances, it was decided to apply an epoxy layer on the surface. Using such a layer, it is found that the total discharge capacity becomes 1490m3/s.
The construction of the tunnel would take 137 weeks to complete. The total costs are estimated to be in the order of ¥60,000,000,000, or 60 billion yen, equivalent to 463 million euro. In comparison, the plan of the river office to replace the bridges would cost ¥68,400,000,000. It can be concluded that this option is a reasonable alternative for the current plan.