Mid-20th-century slender orthotropic steel highway bridges exhibit a significant vulnerability to high-cycle fatigue accumulation induced by modern heavy goods vehicles. As complete bridge replacements impose severe economic and environmental burdens, alongside significant traffic disruptions, the civil engineering sector urgently requires sustainable, low-intervention solutions. As an alternative to traditional stiffening, which adds mass statically, this research evaluates the efficacy of implementing passive vibration-control devices, specifically tuned mass dampers, as a dynamic retrofitting strategy to extend the fatigue life of critical welded details within these structures.

A multi-scale numerical investigation was conducted utilising a finite element model based on the steel arch Bridge Roosteren as a reference structure. The transient structural dynamic response was simulated for a single passage of a moving load, corresponding to the Eurocode 1 lorry silhouette A, along the most critical path. From this passage, the fatigue damage was systematically quantified at three primary connections (Rib-to-Deck, Rib-to-Crossbeam, and Deck-to-Crossbeam) using the hot spot stress method, rainflow-counting algorithms, Miner's linear cumulative damage rule, and Eurocode 3 S-N curves.

The integration of parametrically tested passive tuned mass dampers did not result in an overall extension of the structure's global fatigue life. Whilst secondary connections, such as the Deck-to-Crossbeam detail, demonstrated a localised fatigue life extension, the governing Rib-to-Deck connection experienced a fatigue damage increase across all evaluated configurations. A unique geometric alignment was induced by the relationship between the reference structure and the considered vehicle. Specifically, the relation of the 4.5 m longitudinal vehicle axle spacing to the 2.424 m transverse crossbeam spacing induced substantial secondary bending moments. This alignment, coupled with the inherent stiffness of the finite element model, limited the dynamic mitigation potential of the tuned mass dampers. Furthermore, the spatial arrangement of the tuned mass dampers, which primarily targeted global dynamic behaviour, was deemed ineffective because the governing fatigue-critical details are mostly driven by high-frequency excitations rather than low-frequency global bending. Consequently, the tuned mass dampers did not induce a significant reduction in the stress ranges at all details, thereby failing to yield a notable improvement in the overall fatigue life.
Although the study did not yield an overall extension of the fatigue life, the findings indicate the potential viability of dynamic retrofitting strategies. To further define this potential, future research should explore the application of semi-active vibration-control devices to capture a broader bandwidth of traffic-induced vibrations. Alternatively, investigations should target localised high-frequency responses by attaching smaller tuned mass dampers directly to the stiffening ribs rather than the crossbeams. These studies should include influential dynamic factors such as stochastic traffic modelling and vehicle-bridge interaction, explicitly accounting for vehicle inertia, suspension mechanics, and road surface roughness. Until effective dynamic retrofitting strategies are fully validated, static stiffening should continue to be prioritised.
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Many historic inner-city quay walls in Amsterdam require renewal, while current renewal methods often rely on materials with high environmental impact, such as steel foundation piles. This thesis develops and evaluates lower-impact design alternatives for timber-pile founded quay wall renewal.

The Kloveniersburgwal was used as a representative case location. Based on a system and function analysis, functional and structural requirements were defined. Nine functional variants were developed and evaluated using a Multi-Criteria Analysis and indicative cost comparison. Three variants were then selected for structural verification using Plaxis 2D, including checks for stability, strength and stiffness.

The preferred variant consists of vertical timber piles with steel pile extensions installed through the existing quay wall, combined with two rows of batter piles in the waterway. A soil-retaining screen is placed between the vertical pile extensions, and a prefabricated concrete L-element forms the new quay wall front. During construction, the existing quay wall is temporarily supported by the vertical pile and a collapsible steel support structure.

The preferred variant has a calculated MKI value of approximately €4,190 per 20 m of quay wall, which is considerably lower than the estimated €12,800-€30,700 per 20 m for current renewal methods. Although further development is required, particularly for pile installation, temporary support and connection detailing, the results show that timber-pile based quay wall renewal is a conceptually feasible and promising lower-impact design direction for Amsterdam.
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Ensuring the long-term reliability of ageing concrete infrastructure has increased the demand for effective Structural Health Monitoring methods capable of detecting internal damage at early stages. One promising technique involves the use of Smart Aggregates (SA) to monitor changes within the structure non-destructively. This study focuses on their application in composite precast concrete beams made continuous, particularly at the concrete-to-concrete interface between the precast inverted T-beam and the cast-in-situ topping layer. This interface is vulnerable to degradation due to shear forces and stress concentrations, which can result in internal defects such as microcracking or interface separation—forms of damage that are important to monitor, yet difficult to assess in practical in-situ conditions.

The aim of this study is to evaluate how SA-based ultrasonic monitoring can be effectively utilised to detect, localise, and characterise interface delamination in composite precast concrete beams made continuous. Focus is placed on assessing the complementary capabilities of Ultrasonic Pulse Velocity (UPV), in terms of spatial localisation, and Coda Wave Interferometry (CWI)-derived indicators, in terms of sensitivity to early-stage damage. Additionally, the study evaluates how ray-path and tomographic visualisation approaches support the interpretation of these ultrasonic techniques.

UPV is applied by analysing changes in wave arrival time to determine variations in propagation velocity, enabling detection of discontinuities along defined transmission paths. In contrast, CWI utilises the sensitivity of microcracking and stress redistribution to detect incremental changes within the material. From these methods, three ultrasonic indicators are derived: relative velocity from UPV, and the correlation coefficient (CC) and relative velocity change (ε) from CWI. These indicators are analysed through ray-path representations, which preserve path-based physical meaning. Additionally, UPV results are reconstructed into a tomographic visualisation to provide a spatial representation of internal structural changes, from which the interface time interference indicator is derived to assess interface delamination.

The experimental program consists of large-scale precast girders made continuous, embedded with SA and subjected to staged loading. The experimental work was conducted as part of a broader research campaign at TU Delft, in which the physical experiments were carried out by M. Ibrahim. Ultrasonic measurements are collected and processed using the described methods, and the resulting indicators are compared with Digital Image Correlation measurements for validation. This approach enables assessment of the capability of ultrasonic indicators to detect, localise, and quantify damage progression at the interface.

The results show that the ultrasonic indicators provide distinct yet complementary insight into structural behaviour. CWI-based indicators demonstrate high sensitivity to early-stage changes: ε responds to early disturbances prior to visible damage, while CC provides a clearer and more consistent indication of crack initiation. In contrast, UPV-derived relative velocity correlates strongly with developed cracking and provides reliable localisation along transmission paths, particularly for sensor pairs oriented to capture flexural and shear cracks. However, sensor pairs crossing the interface show reduced capability in distinguishing specific crack types, indicating limitations in isolating interface delamination independently.

Ray-path results show strong agreement with DIC observations in terms of crack initiation, localisation, enabling direct interpretation along propagation paths. Tomographic results provide a spatial overview of damage distribution and indicate potential for identifying interface disturbances through the dt indicator at early load stages; however, reconstruction limitations and numerical sensitivities reduce reliability in consistently representing damage magnitude and progression.
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This research explores the optimization of modular ribbed concrete floor systems as a strategy for circular construction. Ribbed floors can reduce material use and embodied carbon compared to flat slabs, but conventional customized solutions lack scalability while standardized waffle slabs are less efficient. To address this trade-off, a modular design approach is combined with a Deep Generative Design workflow using a Variational Autoencoder (VAE) and Gradient Descent (GD).

The discrete modular configurations are represented as bitmaps, decoupling geometry from structural performance and enabling efficient training of a simple VAE model. Trained on datasets generated in Grasshopper with Karamba3D, the VAE can predict and generate new designs while scaling to larger problem sizes. Optimization is performed by sampling in latent space and refining results with GD.

The workflow flexibly integrates new objectives and constraints without retraining, such as stock availability or embodied carbon. In benchmark tests, the VAE-based optimization outperformed a generic evolutionary solver, achieving lower elastic energy and better stock compliance. The approach demonstrates the potential of deep generative methods for scalable, constraint-aware optimization of modular ribbed floor systems, while challenges remain for extending to more complex structural models. ... Read more

This thesis investigates the application of Bayesian Optimization (BO) for the weight minimization of macrostructural systems, focusing on a cantilever beam, a truss, and two gridshells as case studies. Traditional structural optimization methods often struggle with high-dimensional, non-convex design spaces while being constrained by expensive function evaluations due to repeated finite element analyses.
BO addresses these challenges through surrogate modelling with Gaussian Processes (GPs) and probabilistic acquisition functions that balance exploration and exploitation. The study integrates BO with the finite element package RFEM6, enabling automated optimization workflows subject to Eurocode-based strength, stiffness, and stability constraints.

Four case studies of increasing complexity are implemented:
(i) 1D cantilever beam with a varying size variable
(ii) 2D cantilever truss with varying shape and size variables
(iii) 3D 4×4 gridshell with varying size variables
(iv) 3D 9×9 gridshell with varying size variables
The achieved results via the constrained BO algorithm for the 4x4 gridshell show a 1.67× lighter structure than the reference design and 2.54 × lighter structure than the reference design for the 9x9 gridshell confirming that BO can converge towards feasible and lightweight structural designs. The efficiency of the algorithm is further demonstrated by its ability to converge 18 times faster to a design that is only 0.5% heavier than the reference design for the cantilever truss case study.

Furthermore, the 1D case demonstrated robustness and integration feasibility between the Python implementation and the RFEM6 software. The 2D truss highlighted the benefits of embedding structural knowledge in the sampling strategy and showed that using multiple GPs per member improved reliability compared to aggregated models. For high-dimensional 3D gridshells, the optimizer maintained feasibility but faced some scalability issues. Principal Component Analysis (PCA) is introduced to mitigate the “curse of dimensionality” by exploiting the underlying pattern of the cross-sections that depends on the internal forces while reducing computational cost. However, it is found that excessive dimensionality reduction degrade the solution quality, indicating a trade-off between efficiency and accuracy. Therefore, it has to be applied carefully to retain enough structural variance.

Two other key findings can be emphasized. First, increasing the number of surrogate models to approximate the structural constraints for each element in the system improves accuracy but increases the computational cost. Second, informative initialization and structural-domain knowledge can enhance the convergence rate.

The thesis concludes that Bayesian optimization either with or without applying the PCA, is a viable and sample-efficient strategy for structural weight minimization under realistic structural constraints, capable of being integrated with industry-standard FEM software. Future work should explore the scalability of the BO framework in higher dimensional feature space, the implementation of multi-objective BO and apply it to case studies with broader structural typologies such as moment frames composed of different cross- section types.
Finally, a basic version of an interactive tool is developed that integrates the knowledge discussed in this thesis and that can be used by the structural engineers to explore various design options in the early design phase of a project. ... Read more

Many Dutch bridges were constructed in the decades following World War II and are now reaching the end of their service life. While their overall functionality may be declining, individual components still retain significant structural value. In light of increasing circularity ambitions, reusing these components presents an opportunity to reduce emissions and maximize this residual value. However, steel bridge component reuse remains uncommon in the Netherlands. This thesis investigates why that is the case and what is needed to stimulate broader adoption. The main research question is: “What is needed to stimulate the adoption of steel bridge component reuse among stakeholders in the Dutch construction industry?”

A mixed-method approach was applied, combining literature research, a technical case study, and sixteen interviews with actors from across the construction supply chain. The literature review identified five key obstacles to reuse, difficulty in sourcing of the steel, lack of design guidelines, missing EU regulations, cost uncertainty, and behavioral resistance.

To address the technical gap, a design guideline was developed based on the case study of the Freebrug in Oude Pekela. The focus was placed on Orthotropic Steel Decks (OSDs), where fatigue, corrosion, and their combination were modeled as key damage mechanisms. A finite element model incorporating past loading scenarios and critical weld zones showed that technical reuse is possible, even when damage is present. The resulting design guideline consists of three structured steps: (1) documenting initial data, (2) assessing condition during service life, (3) choosing feasible reuse applications.

Besides to that, interview results revealed nineteen obstacles, of which fourteen were not found in literature, suggesting that practice is evolving beyond academic literature. Two obstacles stood out as most frequent: ‘Availability of steel’ and ‘Negative attitudes’, both acting as ‘pillars’ rooted in deeper systemic issues. Some theoretical concerns, such as missing EU regulation or cost uncertainty, were viewed with more nuance or even downplayed by stakeholders.

Fifteen distinct strategies aiming to address these reuse obstacles were identified in interviews, the most common being: making reuse a requirement in tenders, creating supply storage locations, and training the supply chain through partnerships. To interpret the interrelations between these strategies, they were clustered into three systemic themes: (1) Rules and regulations, (2) Collective learning and shared responsibility, and (3) Practical and physical logistics. This interpretive lens revealed a misalignment between ambition and action, willingness and structure, and innovation and conventional routines.

The thesis concludes that stimulating reuse adoption requires both technical verification and systemic realignment. From a Structural Engineering perspective, the design guideline provides a replicable method to assess reuse potential for steel bridge components. From a Construction Management perspective, adoption is hindered by systemic misalignments. These two dimensions are inseparable: technical confidence alone is insufficient without systemic readiness. Reuse must be understood not as an isolated effort, but as a broader system transition requiring coordination, and adaptive capacity across the entire construction chain.

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Given the importance of modularity in structural design, understanding the performance of modular shell structures is essential for improving both circularity and construction efficiency in spatial structures. To enhance sustainability and aesthetics, timber gridshells can be used to integrate sustainable building materials with complex pattern topologies. Modularity not only contributes to circularity of building materials, but also eases assembly, reducing both cost and construction time. By investigating different segmentation strategies, their impact on structural behaviour and buildability can be identified. This knowledge supports the optimisation of modular gridshells, leading to more efficient construction solutions.

This research aims to explore optimal segmentation strategies for timber gridshells, considering structural behaviour, element reusability and the efficiency of production, assembly and transport. A timber geodesic gridshell dome serves as a case study, but the findings contribute to modularity of gridshells in general. The main research question is: How can the modular segmentation of timber gridshells be designed to optimise their structural and construction efficiency?

For this research a method is developed to generate modular gridshells and optimise their design by evaluating both structural performance and construction efficiency. The modular designs consist of pinned splice joints that longitudinally connect two beams of different modules. Various modular designs are created by defining the location of these intermodular joints, thereby determining the overall modular geometry in the structure. A structural analysis gives understanding of the structural behaviour and the required material use. A construction analysis provides insight into reusability and efficiency of production, assembly and transport. A multi-objective comparative analysis is conducted to identify the most favourable designs based on project goals and stakeholder preferences.

Findings show that this modular approach improves assembly efficiency and the reusability of elements. It is particularly advantageous to choose a modular gridshell over a classic one when the primary design objective is reusability. However, the modular segmentation method negatively affects structural performance and increases material usage, primarily due to the use of pinned splice joints, which reduce overall stability. Additionally, applying modularity results in lower production and transport efficiency.

The results further indicate that larger modules improve structural stability and reduce the required material, due to fewer splice joints. Larger modules also result in higher assembly efficiency and reusability. However, increasing module sizes may exceed maximum transport size limits. It could also lead to a higher number of module types, reducing production and assembly efficiency. Furthermore, the module shape significantly influences the number of splice joints, underlining the importance of careful geometric consideration to minimise joint quantity. Additionally, increasing the rotational stiffness of splice joints could improve the structural performance.

In conclusion, it is crucial to consider project objectives and stakeholder interests in the structural design of a gridshell. Moreover, this research concludes that modular gridshell designs perform best when:
• Module sizes are maximised within transport constraints;
• Module shapes are designed to minimise the number of splice joints;
• An increase in module size comes with a minimisation of number of module types. ... Read more

The construction sector, which is generating 36% of the greenhouse gas emissions, is expected to transition to carbon neutrality by 2050 to combat climate change. Achieving this requires the use of green technology and sustainable construction practices. Demountable constructions are one such approach. Reuse of components may be a solution, although it poses challenges in maintaining structural robustness and integrity. Integrating disassembly can compromise structural robustness, reducing stability and collapse resistance. Ensuring structural integrity under adverse conditions is crucial. Although much is studied in the case of individual demountable connections, a complete study of the overall behavior and strength of the building structures is lacking. Addressing this gap is vital to ensure safety, reliability and compliance with building regulations.
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The renewal of quay walls in Amsterdam presents an opportunity to integrate multifunctional features that introduce additional loads to the existing structures. These loads are caused by the self-weight of trees offering climate adaptable cities, energy storage powering the energy transition or steel panels, which allow additional protection against sea level rise by increasing the retaining height of the quay walls. This research investigates the structural performance of two quay wall configurations at the Marnixkade, which is a street along a quay wall that is in the west of Amsterdam, where renewal is to take place. Out of multiple structural quay-wall configurations, a traditional timber-masonry quay wall and a modern steel sheet pile wall are chosen. The traditional quay wall is currently the most occurring quay wall type, whereas the steel sheet pile wall has been selected as it enables rapid design for high strength and is therefore often seen as emergency structure in Amsterdam for deteriorated quays. Although other methods are in development by different companies, little information is known, and they are therefore not considered.

Using Finite Element Analysis (FEA) in Plaxis and DIANA, both models are analysed with different load cases and validated against analytical checks. The base case follows from the TAK (Dutch document, abbreviated as Toetsing Amsterdamse Kademuren (Ingenieursbureau Gemeente Amsterdam, 2023), which is a guide that provides information on how to structurally assess quay walls in FE software), standard, which applies a distributed downward load of 10 kN/m² from 0.5 m up to 8 m from the waterside of the quay. Additional functionalities are then introduced to assess their impact on structural behaviour compared to the base case. This is done through imposing additional distributed loads of a tree, energy storage and steel panels to increase water retaining height or a combination of them on the structure. A simplified two-layered soil model, consisting of a clay layer over sand, is used to simulate ground conditions. Structural forces in terms of cross-sectional normal forces, shear forces and bending moments, as well as horizontal displacements are considered for the failure mechanisms.

Results indicate that the traditional timber-masonry quay wall exhibits higher stress concentrations in the timber piles, while the steel sheet pile wall is more susceptible to excessive horizontal displacements. It should be noted that the results are based on undeteriorated material properties; in reality, timber pile degradation and steel corrosion are common and can significantly reduce the structural performance of quay walls. Without proper in-situ measurements, the uncertainty in model predictions remains high. Adapting quay walls to additional loads from multifunctionalities requires careful reconsideration of material behaviour and structural limits, as strengthening might be required. While the steel sheet pile wall can be modified through stronger sections or higher-grade steel, reinforcement options for the traditional timber-masonry structure are more limited, involving adjustments in pile count, diameter, or masonry thickness. ... Read more

The construction sector faces an urgent need to reduce embodied carbon and close material loops, yet the structural reuse of cast-in-situ concrete elements—particularly floor slabs—remains rare in practice. This thesis investigates how concrete slab reuse can evolve from isolated experiments into an integrated and reliable strategy within the construction industry. The research addresses two interdependent barriers identified in current practice: the absence of standardised technical verification procedures and the fragmentation of communication and responsibilities between demolition (donor) and new construction (target) projects.

A mixed-methods approach combines a systematic literature review, multiple case studies of recent Dutch reuse initiatives, semi-structured expert interviews, and design-science research. The study develops two complementary frameworks: a Verification Framework, which provides a Eurocode-aligned, stepwise method for assessing the geometry, material properties, durability, and structural performance of reclaimed slabs, and a Communication Framework, which defines how verification data is generated, transferred, and safeguarded across project stages to ensure traceability and alignment among stakeholders.

Validation of both frameworks using real project data shows that reclaimed slabs can meet structural and durability requirements—especially in lower-load, repetitive applications—while achieving substantial embodied-carbon reductions of up to 60% relative to new concrete alternatives. The findings demonstrate that technical feasibility alone is insufficient: successful reuse depends equally on well-structured information flows, early role definition, and integrated collaboration between donor and target projects.

By providing practical guidance for engineers, project managers, contractors, and policymakers, this thesis contributes a coherent, ready-to-apply foundation for professionalising structural concrete reuse. The developed frameworks offer a pathway to reduce uncertainty, improve decision-making, and embed reuse within mainstream construction processes—supporting the wider transition toward a circular built environment. ... Read more

This study investigates the seismic performance of the Adıyaman Grand Mosque, a historical masonry mosque in the East Anatolian Fault Zone, with emphasis on its response during the 2023 Kahramanmaraş earthquake sequence. The two main objectives are: (i) to evaluate the mosque’s inherent seismic vulnerability in isolation, and (ii) to assess how the collapse of adjacent buildings may have aggravated damage.
The work combines nonlinear static and dynamic analyses in DIANA within a macro-modelling framework using a Total Strain Fixed Crack model calibrated from literature. Pushover analyses establish direction-dependent capacity, drift limits, and mechanism trends; nonlinear time-history analyses capture transient response under recorded ground motion. Neighbouring building collapse was examined through an exploratory numerical study in which a simplified sustained lateral pressure was applied to the south wall during the strong-motion window. The representation is non-calibrated and used to indicate trend-level shifts in demand rather than predictive values.
In isolation, results indicate moderate lateral capacity with strain localisation at openings and roof–wall/dome–drum junctions. Dynamic peaks remain within the pushover plateaus, and control-point drifts lie in a range consistent with no indications of triggering full collapse scenario, noting that principal-strain maps reflect upper-bound transient demand because cracks open and close cyclically. A simplified interaction case was included only as a sensitivity check; because it neglects contact transients, friction, eccentricity and vertical load transfer, no quantitative findings are reported from it. At most, the check suggests that adding a sustained lateral pressure could redistribute demand toward out-of-plane action on the loaded façade. These indications motivate future, higher-fidelity interaction modelling rather than supporting a firm conclusion here. Taken together with field evidence, this supports the interpretation that neighbouring collapse plausibly acted as a trigger for the most severe local failures, while the mosque alone would likely have sustained repairable damage.
The findings clarify seismic risk for historical masonry located in dense urban settings and motivate interaction-aware assessment, including explicit contact or bounded pulse models, to study cascading failure mechanisms.
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This thesis investigates the impact of confinement on the structural performance of Concrete-Filled Steel Pipe (CFSP) pile to concrete cap connections in the absence of dedicated force transfer provisions such as dowels or shear rings. Current Eurocode guidelines provide no explicit framework for confinement in partially loaded areas, resulting in uncertainties in design. The research combines theoretical modelling, drawing on Mander’s confined concrete model and the Dual–Wedge Stress Field (DWSF) approach of Markič et al., with a finite element case study to evaluate confinement mechanisms. A quasi-non-linear analysis was implemented to approximate peak concrete strength, supported by analytical formulations and parametric scripts. The findings confirm that confinement significantly enhances bearing capacity and stress transfer in CFSP pile–to–cap connections, with the FEA substantiating several features of the DWSF model while also highlighting limitations in reinforcement activation and stress redistribution. Overall, the study demonstrates that confinement effects are decisive for structural performance and should be explicitly considered in design practice to achieve reliable and efficient CFSP connections.
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Urbanization has significantly altered the built environment, leading to increased urban heat and the loss of green spaces, which are being replaced by buildings, which in its turn retain more heat inside the city. Climate change causes extremer weather, resulting in heavier rainfall and urban floodings, for which cities are often unprepared. Incorporation of nature into the vertical buildings surfaces has the potential to address these challenges. A promising solution for creating these vertical green areas are porous concrete façades. Although research into this application has been performed for several years, a widespread implementation remains limited. A demountable, quick-to-install solution could assist the broader implementation of green solutions in urban areas. This research investigates the feasibility of such a demountable system. ... Read more

This thesis investigates the force transfer mechanisms between concrete substructures and steel pipe piles, specifically focusing on connections made using a concrete plug within the steel pipe pile. This thesis explores the mechanisms of force transfer in concrete plug connections within open-ended steel pipe piles, focusing on the viability of frictional (bond) transfer versus mechanical connections. The primary research objective was to determine the extent to which forces—both normal forces and bending moments—can be transferred through a concrete plug without the use of mechanical connections and to compare this with scenarios where mechanical connections, such as shear rings, are employed.

A comprehensive literature review revealed significant gaps in existing design codes and recommendations, which inadequately address concrete plug connections in steel pipe piles. Notably, regulations such as Rijkswaterstaat’s ROK V2.0 restrict the extent of force transfer through friction without clear justification. Existing standards like Eurocode 4 and the British Standard (BSI) offer bond strength values that vary widely and do not consider key parameters such as connection geometry and concrete shrinkage, potentially leading to inaccurate strength estimations. Although some models for grouted sleeve
connections might be applicable, their validation for concrete plug connections remains uncertain.

To address these gaps, a new analytical model was proposed to estimate the bond strength between
concrete and steel in plugged connections. The model incorporates factors including connection geometry, material properties, concrete shrinkage, surface irregularities, and the Coulomb friction coefficient. Push-out test results were used to update and validate the model, resulting in conservative bond strength values. Key parameters identified were the value for the surface and the Coulomb friction coefficient. The model’s predictions showed a Mean Average Error (MAE) of 0.589 MPa, primarily due to high variability in some test sets. However, the error was smaller for less variable data.

The findings indicate that connection geometry, particularly the diameter of the steel pipe pile, significantly affects bond strength. Smaller diameters exhibit higher bond strength due to better confinement and reduced concrete shrinkage effects. For larger diameter piles, where friction is insufficient to transfer normal forces, mechanical connections such as shear rings are recommended. These connections were evaluated using Eurocode 4 and CUR Recommendation 77 and found to provide substantially higher normal force resistance, enabling effective utilization of the geotechnical load-bearing capacity.

Regarding the transfer of bending moments, the study found that the wrenching mechanism between the concrete plug and steel pipe pile can manage the transfer through contact stresses. This stress distribution is linear along the plug height and sinusoidal around its circumference, provided it remains within allowable concrete compressive stress limits. The plug’s length should be designed to ensure these stresses do not exceed permissible values. A model for the interaction between bending moment and normal force was also developed, indicating that additional normal force resistance can be achieved under a certain bending moment, though this requires careful stress distribution verification.

In conclusion, while friction can achieve normal force transfer in concrete plug connections, it is often insufficient for larger piles. Mechanical connections such as shear rings offer a more effective solution, providing significantly higher normal force resistance and enabling efficient design. The wrenching mechanism can be used to transfer bending moments, but the ultimate bending moment resistance is governed by the concrete plug’s cross-sectional resistance. This is because the resistance of the concrete plug’s cross-section is lower than the wrenching resistance. This research provides a comprehensive framework for understanding and optimizing force transfer mechanisms in concrete plug connections within steel pipe piles, highlighting the importance of mechanical connections for effective and practical design. ... Read more

This thesis investigates the optimization of steel weight and the Environmental Cost Indicator (ECI) in steel structures, addressing the significant contribution of materials and construction to global carbon emissions. Focusing on European office structures, which face high vacancy rates and substantial environmental impact, a parametric study is conducted on a 5-story, 30x30m steel office building. The study evaluates design choices, including column, beam, and composite beam spacings, cross-section selection, connection design, and stability systems.
A preliminary building is designed under consistent load conditions, followed by over 50 variants incorporating different stability systems, frame designs, and composite beam spacings. Analysis indicates that smaller column and beam spacings, along with larger composite beam spacings, optimize steel use and ECI costs. HEA sections for columns, IPE sections for beams, and CHS sections for diagrid braces and angled columns are identified as the most efficient.
The study also highlights that material use does not always correlate with ECI costs. Designs incorporating demountability initially increase steel use due to elastic design requirements but result in lower ECI costs over multiple lifecycles by enabling reuse of materials. Several diagrid designs, benefiting from lower ECI costs per kilogram of CHS sections, perform better than conventional and braced structures despite higher initial material use.
Demountability was a key focus, with bolted connections identified as essential for achieving demountability standards. The reuse potential of stability members varies significantly; unlike conventional designs, diagrid structures are tailor-made, making their reuse challenging for subsequent applications.
The findings are consolidated into a final design framework to guide engineers in optimizing steel use and ECI costs, providing a practical tool that reduces the need for extensive modelling. This research fills gaps in the literature by focusing on short structures and offering insights into efficient structural design practices.
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In the Netherlands, there are hundreds of operational locks for both recreational and inland shipping. Due to the growing economy, inland shipping is expected to increase in the future. The growing economy causes an increased likelihood of ship collisions with infrastructure, currently estimated at approximately 50 cases per year in the Netherlands. It is necessary to determine the collision energy of a vessel to account for collisions, because this clarifies the potential load. In the context of determining the collision energy for ship collision, the guidelines of the Eurocode, PIANC, and AASHTO involve uncertainties and exhibit variability among them. Therefore, the thesis was initiated to provide more accuracy in the estimation of collision energy in the event of ship-lock collisions. The main objective of this thesis was to enhance the structural design process of lock gates regarding ship-lock collisions. This was done by improving the understanding of the effect of potential loads occurring at a ship-lock collision, and using basic mechanics to estimate the energy absorption capacity of the lock gate. ... Read more

Due to the transition towards a circular economy, sustainable design strategies are growing in importance. An example of such a strategy is IFD: Industrial, Flexible and Demountable design. This design strategy has been developed recently and focuses on modular designs that can be changed in shape and whose components can be demounted and reused. This thesis aims to investigate how the principles of IFD can be applied in the design of a sustainable superstructure for an overpass. The goal is to assess which structural system is best for use in a sustainable IFD overpass and to determine how the overpass can be converted into a modular overpass by focusing on connections and module dimensions. To demonstrate the potential of the IFD design, the sustainability benefits of the overpass are evaluated.

Through a review of literature on IFD and similar design strategies, guidelines were formulated that are relevant for overpasses. Based on the guidelines, designs for three structural systems were developed using a preliminary design approach. These designs were assessed on their environmental impact and compliance with IFD principles, using an Environmental Cost Indicator and Multi-Criteria Assessment respectively. Due to its good behaviour on both aspects, the Composite alternative was found to be the best.
Then, a literature study on the connections was performed to investigate the different options. The number of relevant shear connectors was reduced to four by considering the tolerances for assembly and the protrusion of connectors from the main elements of the structure. A finite-element model was made to evaluate the effects of the four different shear connectors on the structural behaviour. To be able to use the connectors in the model, an elastic limit was imposed to ensure demountability and reusability; small adjustments were made on the reported behaviour of the connectors using a parametric study. From the four remaining connectors, the Embedded Coupler Device connection without injected resin was found to be the most favourable, due to it requiring the lowest number of connectors in the serviceability limit state. For the steel girder connection, a shear-loaded bolted connection was proposed; shear keys were found to be a good solution for the deck connection. Moreover, module dimensions were determined based on sustainability considerations and IFD principles, leading to the final design.

The proposed design shows that IFD principles can successfully be applied to come to a design for an overpass. The use of a small selection of modular elements and demountable connections creates a flexible design, which complies with all the IFD principles. By application of a structural system with a low environmental impact, sustainability of the design is also accounted for.

The IFD design is competitive in situations where the overpass is extended or when it is disassembled and reassembled, since for these scenarios it ends up with the lowest overall environmental impact. This leads to the recommendation to use IFD design in situations where flexibility and reusability are advantageous.
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This thesis explores the use of Axle Box Accelerations (ABA) in passenger trains as a means to monitor and assess the structural health of railway turnouts, particularly the crossings. The increasing demand for higher capacity, speed, and axle loads, coupled with reduced maintenance time, has put a strain on the reliability of these sensitive components. The study focuses on the fixed crossing, a vulnerable component due to its discontinuity that can cause large impact forces leading to potential failure and disruptions.

The research aims to develop an assessment method to determine crossing health using ABA measurements from two retrofitted intercity trains. The crossing, formed by the wing rails and a crossing nose, presents a discontinuity that disturbs wheel motion and generates impact forces. The study acknowledges the challenges related to data quality, quantity, and processing due to the random nature of measurements and conditions. Despite these challenges, the research leverages the Law of Large Numbers and the Central Limit Theorem to overcome frequency-limited measurements.

The proposed assessment method is validated against geometry metrics derived from train-borne laser measurements. However, the current approach does not establish a reliable relationship between the impact angle and wear levels, making it unsuitable for monitoring wear levels of crossings. Nevertheless, a strong correlation was found between the kinematic wheel dip angle, mean and standard deviation of vertical impact, indicating that a larger mean or standard deviation suggests a more degraded vertical geometry. This finding is in agreement with prior research based on wayside measurements and underscores the potential of in-service passenger train ABA for assessing the structural health of turnout crossings. ... Read more

The presented research aims to design and optimize a timber observation tower, with a primary focus being the influence of topological and curvature parameters on its stability and lateral stiffness in resistance to non-uniform wind load profiles.

Having recognised the environmental benefits and urgency to find other alternatives, there's a clear necessity to incorporate wood as the main construction material into the infrastructure projects, like observational towers. By conducting a study on hyperboloid towers implemented in the last 100 years, this project questions the necessity of in plane stiff platforms, flexurally stiff rings and continuous vertical members as being pivotal to the stability and lateral stiffness of the global structure when subjected to non-uniform wind loads. In addition, the study intends to investigate how the narrowness of the hyperboloid might affect the lateral stiffness of the structure. Thus, by utilizing parametric tools (Grasshopper, Karamba3D and Beaver plug-in), the study aims to design a timber tower structure comprised of fully segmented members as well as incorporation of circular (flexurally stiff) rings, aiming to address the questions raised. In terms of structural member arrangement, the study will investigate two topologies: one featuring a diagrid pattern that emulates a geometrical shape of an antiprism, and a custom pattern inspired by the post and beam approach, which resembles a regular prism shape. The study emphasizes the tower's multi-functionality and adaptability throughout its lifespan. Tower's main structural framework is a pivotal element in providing required stiffness and strength by excluding the need for in-plane reinforcement provided by arbitrarily placed platforms.

The key realisation of this research was the kinematic behaviour exhibited by the segmented, triangular tower, adversely impacting its stability characteristics. The study used a combination of analytical and graphic kinematics techniques, along with a physical mock-up model, to confirm the kinematic behavior of the tower given that even sided polygons for rings are incorporated. This revelation would have an impact on how a structure like that would perform as well the way it would be built. Further research unveils the strong influence of ring type on structural stiffness showing that segmented rings render tower structures less stiff than ones employing curved ring members, regardless of the pattern. In terms of the direct comparison between tower patterns, custom one demonstrated a more consistent and stable performance in general, particularly achieving higher stiffness levels when employing segmented rings. As regards the triangular pattern, the stiffest response against wind loads has been exhibited through the use of curved rings. In addition, the study validates that adopting a hyperboloid shape along with smaller shape factors for the global tower geometry yields more favorable lateral stiffness characteristics. Finally, the study navigates through the exploration of the most optimal connection design, illustrating how considerations related to detailing have necessitated a re-evaluation of the most optimal tower configuration, which initially was chosen to be a triangular one equipped with curved rings. A qualitative assessment of a potential joint within this specific tower variant has confirmed that designing such a connection is significantly more complex. This is due to the necessity of ensuring the continuous flow of the curved ring, emergence of a kink within the insertion of the plate and how that is needed to be addressed.

Alternatively, these considerations have motivated the design process to converge into a new hybrid design, integrating segmented rings with a curved top ring defined by the custom pattern. This choice has been made by conducting a separate parametric study of the new tower design and ensuring that the new connection design fulfills elastic slipping modulus and ultimate strength requirements. The final topology that showed higher stiffness metrics was the custom one. It's also highlighted that maintaining the top of the tower constrained leads to favorable effects on stability and stiffness, irrespective of the chosen topology. The resulting structure is optimized for mass by strategically reducing member cross-sections in accordance with connection scheming while adhering to both SLS and ULS criteria. ... Read more