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.

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.

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.

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.

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.

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.

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.

This design report outlines a preliminary masterplan for developing a sustainable village in Patagonia, Argentina, addressing the unique challenges of remote living within a sensitive natural landscape. The project centres on creating a resilient, socially sustainable community that coexists harmoniously with its environment. A key objective is to assess multiple sustainable options for essential infrastructure, encompassing energy supply, accessibility, water and wastewater management, and other critical systems.
The report begins with an exploration of the site’s distinctive environmental conditions, informed by a two-week site visit, as well as an analysis of key stakeholders, including residents, tourists, and potential investors. This groundwork establishes both community needs and environmental constraints, forming the guiding principles for the design. The preliminary masterplan then proposes practical solutions to meet these requirements, including infrastructure development such as jetties for enhanced accessibility, a hybrid renewable energy system to support off-grid living, and water and waste management systems that minimise ecological impact.
The proposed design is evaluated for economic feasibility, ensuring the village can support sustainable eco-tourism and community growth over the long term. This project could be used as an example for future developments in rural areas by prioritising sustainability for all social, environmental and economic aspects. This preliminary masterplan aims to contribute to ongoing research on environmentally conscious and socially inclusive development in challenging environments.

Steel-concrete composite (SCC) slabs are extensively used in construction, particularly in multi-story buildings, due to their efficiency and structural performance. SCC slabs combine the strengths of steel and concrete, where steel provides tensile strength and concrete offers compressive resistance. This integration results in lightweight, robust structures that save costs and allow for taller buildings with larger spans.
New designs of steel-concrete composite slabs have to be extensively tested before the new designs are approved. It is therefore important that information is gathered during testing. Strain measurements are often done on composite slabs, for example, strain gauges have been applied to the steel sheeting and distributed optical fibers (DOFs) have been applied to the reinforcement rebars. However, there have never been distributed strain measurements on the steel sheeting of steel-concrete composite slabs. This research aims to gain new insights into the structural performance and behaviour of deep steel-concrete composite slabs using distributed strain measurements.
SCC slabs often have embossed regions of steel sheeting, these embossments or indentations transfer shear forces between the steel sheeting and the concrete. DOFs were applied on the embossed parts of the steel sheeting in the direction of the span in four composite slabs. The strain data showed oscillations in the strain values, and that the embossed/indented parts of the steel sheeting were in tension, while the flat areas were in compression. Local deformations, due to the geometry of the embossments, caused the oscillations.
The N.A. position was another critical focus of the study, which was determined using fiber data at five locations on the middle rib of three slabs. The N.A. was determined for three loading stages: initial, elastic, and plastic. The fibers captured the upward movement of the N.A. from the steel sheeting into the concrete during the initial and elastic stages, as expected according to theoretical calculations of the N.A. position. However, in the plastic stage, the N.A. shifted downward, back into the steel sheeting, instead of continuing its upward trajectory, as expected. This unexpected shift was attributed to partial shear interaction, where the steel sheeting and concrete began acting separately, leading to separate strain
profiles.
Buckling of the steel sheeting was observed in two slabs, Slabs 10 and 11, with fibers providing critical insights into the timing and extent of buckling. In Slab 11, where four fibers were located in the buckling zone, two fibers showed early signs of buckling in the top flange at 97% and 98.3% of the peak load. The strain patterns indicated buckling before the peak load was reached, offering valuable data on the onset of this failure mode. For Slab 10, buckling was detected after the peak load.
Lastly, the research explored the use of DOFs for crack detection. Fibers were applied to the bottom of the ribs on one slab to identify crack locations based on strain data. While cracks typically cause localized peaks in strain, the results revealed limitations in the accuracy of crack detection using DOFs on steel sheeting.
In conclusion, this research demonstrates the potential of DOFs for strain measurement in steel-concrete composite slabs, offering valuable insights into strain distribution, N.A. position, and buckling behaviour. However, the crack detection capability of DOFs, particularly when applied to steel sheeting, requires further refinement to improve accuracy and reliability.

A large number of offshore wind turbines have been installed in recent years, and even
more are being erected in current and future projects. The majority of these turbines
have been or are being built of monopile foundations. Eventually, both the turbine and
the foundation have to be decommissioned. However, decommissioning options for
monopile foundations are limited, especially for complete removal of the foundation.
This thesis aims to study a new removal method patented by the company Iv-Consult,
which could potentially make entire monopile removal possible. The method uses
deformation of the monopile wall by a clamping tool to generate a vertical force. Since
the thesis served as a preliminary study into the removal method, it was chosen to limit
the scope of this study to the monopiles that are expected to be decommissioned in the
near future. With this information, a single case of monopile with dimensions that are
representative for these monopiles was presented. To analyse the removal method on the
case monopile the finite element method was used. In order to ensure results obtained
using the finite element method are accurate and representative, a convergence study was
carried out. To determine the element type and the mesh size that was the most suitable,
two different models were used: a ring model and a small cylinder model. Each was
studied using different combinations of inputs. After the results from the convergence
were obtained, these results were used on the models with which the removal method
was studied. Different configurations of the removal method were analysed with the
aim of maximizing the force that can be generated by the method to overcome resistance
forces. As a final step, the resistance forces that need to be overcome were calculated
for different soil types and compared to the results obtained from the removal method
models to verify the feasibility of the method.
From the results of the convergence study, it was shown that it is possible to model
the removal method using the finite element method and obtain representative results.
The final results of this thesis showed that clamping the monopile multiple times
does not have a positive influence on the vertical force that can be generated. This is
because clamping the monopile only once caused the highest vertical force. However, the
forces generated using the different setups of the clamping method were not sufficient
to overcome the resistance forces. This shows that the removal method in the current
configurations is not feasible, without applying any soil resistance reducing methods.

To stick to climate change targets and reduce global carbon emissions, the building sector needs to adopt a circular economy. In the steel sector, reuse or elements can reduce carbon emissions which are created in today's steel scrap recycling practices. This thesis contributes to closing the knowledge gap on design, costs, and environmental impact score for working with reclaimed steel elements. The tool Steel-IT is created to research the business-case and environmental impact score of low-rise office buildings. Steel-IT uses a donor element database and new office design, which are specified by the user, and generates new and reclaimed steel design alternatives. Using a weight and activity-based costing method, the costs of these design are estimated. Life-cycle analysis is used to quantify the impact. By generating results and analysing the effect of the input in the tool Steel-IT, the following conclusions can be made regarding the business-case and impact score of reclaimed steel in low rise office buildings. A case study using Steel-IT shows that a 25% impact reduction against minimal cost increase is possible. For this, the match between design and donor elements needs to be good. This match can be searched for using Steel-IT. In terms of design, connection detailing is the most critical factor in the success of a donor steel skeleton. Donor steel elements should be sourced from an existing building to limit storage costs and should not have toxic conservation systems applied to them. Both induce extra costs and make the business case of donor steel less competitive with new steel. In the future, currently suggested emission taxes do not affect the business-case significantly as these taxes are low compared to the total building costs. The most helpful action to increase the business-case is to apply donor steel more often. If the experience with donor steel and its availability grows, reuse will become easier. Steel-IT can contribute to this as it contributes to closing the knowledge gap on costs and impact and can help to match demand and supply.

Structural joints influence the design strength, material requirement of a structure. Structural joints experience damping dissipation due to friction damping or hysteresis damping. Damping is often used for reducing the vibrations in a structure. However, large amount of energy dissipation leads to deterioration of the material used for constructing the joint. Hence it is important to identify the system parameters like stiffness, viscous damping, friction force as well as the hysteretic restoring force that cause the energy dissipation in the structure.
For identifying the uncertain system parameters like stiffness, viscous damping and magnitude of friction force, the SINDy algorithm is extended by using stick and slip temporal constraints. This is done by segregating the data of external forcing and response of SDoF system, applying the existing SINDy algorithm and applying the sticking and slipping conditions in the time domain. The proposed Extended SINDy approach estimates the system parameters more accurately compared to the existing SINDy algorithm.
For studying the hysteresis in the structural joints, a pinned column base-plate was considered in an elastic region. Further, the Dahl model with different slope parameter for each branch of moment-rotation hysteresis is employed. The correct values of parameters are estimated using the Bayesian Optimization technique. This procedure yields a functional form representing a resisting hysteretic moment-rotation behaviour in a structural joint with good accuracy.

The building and construction industry is one of the main polluting sectors contributing to climate change, and is responsible for around 37% of global CO2 emissions. A circular approach is needed to address the global demand for construction materials and resources in a sustainable way. Steel is a commonly used material in construction and fully recyclable. Recycled steel has to be melted in a furnace, which is a polluting process. For reuse of steel only disassembly and transport is necessary. The general shift from recycling to reusing steel can offer environmental benefits.
A number of steel bridges in the Netherlands are being renovated or replaced by Rijkswaterstaat in the coming years. Rijkswaterstaat has been investigating the reuse of its bridges on object level, i.e. reusing the complete structure. This has proven to be difficult. Disassembling the bridge and reusing the structure on an element-level has not been thoroughly investigated. As reuse of construction elements in general is relatively novel practice, not much is known about how to determine the reuse potential of structural bridge elements. This thesis aim to identify current knowledge gaps and provide research results that encourages future reuse of steel bridges. As a case study the eastern Van Brienenoord bride is investigated. This bridge is scheduled to be replaced in 2026-2028 and there currently are no plans for reuse.
The goal of this thesis is to examine the reuse potential of steel bridges on element-level, focusing on two critical factors: fatigue and corrosion. Fatigue and corrosion are two of the most deteriorating processes for steel bridges. The reuse potential can be evaluated using the remaining service life of the elements. The remaining service life based on both fatigue and corrosion can be determined by implementing the corrosion assessment in the fatigue calculation. Fatigue assessments are based on stress ranges in structural members. Corrosion leads to a reduction in the cross sectional area, increasing the stress and thus stress ranges occurring in the critical structural details.
The design, decomposition, loading history and technical condition of the eastern Van Brienenoord are analysed. After critical review of the Van Brienenoord the structural elements of the bridge deck are selected to investigate further. Inspection reports by Rijkswaterstaat and Nebest are used to locate corrosion damage on the Van Brienenoord. The corrosion damage is determined using functions for uniform surface corrosion for steel. The critical structural details of the selected elements in the bridge deck are identified. Using the fatigue assessment procedure described in the Eurocode in combination with the reduced cross section the remaining service life of the structural elements is determined.
According to the results of the proposed assessment method in this research, all structural elements of the eastern Van Brienenoord bridge deck have significant service life left and are therefore suitable for reuse after disassembly. However, certain specific details that have a higher calculated fatigue damage may need to be repaired or removed.

Rijkswaterstaat aims to build circularly from 2030 onward, with the purpose of having a fully circular economy by 2050. Therefore, the aim of this study is to design a reusable modular superstructure, with a small span, which can replace an existing so-called volstortligger superstructure. This is a structure that Dura Vermeer often uses and it regularly happens that these constructions are demolished after a lifespan of, for example, 10 years. This is a waste of materials and therefore an alternative will be investigated in this research. The following research question guides this study:

What is the optimal structure, in terms of shadow costs, mass and financial costs, for a modular superstructure?

In order to answer this question, a parametric study is performed using the software Grasshopper, using the Finite Element Model plug-in Karamba3D. In this way, quick structural analyses were performed, to explore multiple options. In total, more than 11.000 bridge design variants have been generated, divided over 12 different runs. The model allowed targeted optimization of shadow costs, weight and financial costs. Optimization is achieved by varying the following input parameters: number of steel girders, steel profile girders, outrigger deck, concrete deck thickness, concrete class, outrigger deck, FRP sandwich panel height, facing thickness, web thickness, and fibre volume.

In total, 6 different variants would be developed in this way, 3 with a concrete deck and 3 with an FRP deck. However, the optimization results in only 4 different variants, 3 with a concrete deck and just one with an FRP deck. The results show that the variant with the FRP deck is indicative for Shadow costs, Financial costs and weight.

After the four pre-designs had been developed, these variants were weighed against each other by means of a Trade-Off Matrix (TOM). Using this method, a distinction is made between the variants based on the pre-chosen performance indicators. All performance indicators have a weighting that adds up to a total of 100.

This study concludes that it can be advantageous to replace the traditional design with a demountable design, with the assumed boundary conditions of this study. All developed variants have an advantage with regard to environmental impact and financial costs compared to the traditional design, assuming a lifespan of 100 years in which it is moved 10 times.

The current understanding of auxetic metamaterials in structural engineering applications is limited. Auxetic materials exhibit lateral contraction under compressive loads, possessing a negative Poisson's ratio. The research addresses this gap, focusing on the use of auxetics for steel reinforcement in structural concrete elements to enhance sustainability by reducing material usage without compromising safety.

The research goals include:

Describing the state of the art in auxetic materials for concrete structural elements.
Investigating auxetic behavior under different loading conditions (compression, tension, shear, and bending).
Developing a geometrical design for auxetic steel reinforcement, considering practical aspects like manufacturability and mortar flow.
Performing numerical analyses on proposed beams under various loading conditions, comparing Young's modulus and Poisson's ratio.
Exploring upscaling solutions for architected metamaterials.

The research follows a systematic approach:

Literature Study:
Examines the use of auxetics in concrete structural elements.
Selects a bow-tie architecture for its adaptability and manufacturability using Laser Powder Bed Fusion (LPBF).

Geometrical Study:
Focuses on a cantilever beam subjected to rotation, ensuring pure bending with a linear geometry.
Chooses a range of unit cell angles for desired structural behavior.
Designs unit cells and beams, considering compatibility, continuous lattice, and manufacturability.

Numerical Study:
Utilizes FEM software (ABAQUS) to analyze effective Young's modulus and Poisson's ratio.
Validates models against literature using Euler-Bernoulli beam theory.
Studies the influence of boundary conditions on results.

Upscaling Technologies:
Explores technologies for upscaling auxetic lattices beyond current LBPF methods.
Proposes multi-robotic fabrication for automated assembly using conventional rebar.

Findings and conclusions include:

Selected Architecture:
Chooses bow-tie architecture for its modifiability and manufacturability.
Proposes "single cells" and "three angle" units for different loading conditions.

Design Expansion:
Develops a stacking sequence for a 3D lattice, considering dimensions and relative density.
Creates beams with auxetic, cubic, non-auxetic, combined, and gradual behaviors.

Numerical Model Conclusions:
Affirms constant moment and zero shear in designed beams.
Emphasizes the dominance of effective modulus in lattice geometry.
Validates Poisson's ratio behavior in different beams under pure bending.

Upscaling Proposal:
Recommends multi-robotic fabrication for full-scale lattice construction.
Uses software like Rhinoceros 7 and COMPAS FAB for design and control.

In summary, the research contributes to understanding auxetics in structural applications, providing insights into their behavior under various loads, proposing practical designs, and exploring upscaling possibilities. The proposed approach and findings aim to advance the use of auxetics in steel reinforcement for sustainable and safe construction practices.

The evolution of ships requires larger depth or larger terrain loads in ports. Therefore, the existing quay walls require reinforcements. An effective way of reinforcing the structure are underwater anchors, requiring holes in existing sheet piles at the location of significant bending moment. Since this is a new area of expertise, the influence of the hole is still unknown. This report discusses a developed finite element model to study the influence of hole weakening of sheet pile and studies the influence of hole weakening on the sheet pile resistance and behaviour with the discussed model.

The 3DSSI model includes soil modelled by the subgrade reaction model (spring model) the steel sheet pile is modelled with shell elements in the finite element software DIANA FEA. The model includes both physical nonlinear and geometrical nonlinear behaviour and captures the soil-structure interaction. Also oblique bending, which is an existing phenomena of older, existing double U-sheet piles, can be captured with interface elements in the 3DSSI model. Nowadays, sheet piles are also designed using the subgrade reaction model and the sheet pile is modelled as a beam with the appropriate stiffness. The 3DSSI model is able to illustrate the 3D behaviour of the sheet pile, without having to model the soil with solid elements as well. This is beneficial with respect to calculation time.

With the 3DSSI model, the hole weakening of sheet piles can be studied. The influence of different parameters on the sheet pile resistance and behaviour is studied. The parameters studied, based on literature findings, are: hole diameter, hole location (level of the hole in depth), hole spacing (hole centre to centre distance in width), hole in-pan (compression zone) or out-pan (tension zone), sheet pile cross-section class 2 and 3 and oblique bending.

The influence of hole weakening on sheet pile behaviour and resistance is studied by finding in the parameter study for each case the load-displacement curve and from this load-displacement curve, the stiffness is derived. The load-displacement curve and stiffness curve include both steel and soil behaviour.
Resulting from the parameter study, the holes significantly reduce the sheet pile resistance and behaviour. The cases with holes in tension show less reduction in resistance and stiffness reduction. The hole diameter is also influencing the results, but the influence of hole location and hole spacing is relatively small. The failure modes are for holes in compression zone is plasticity around the hole and local buckling in the webs. For holes in tension zone, the failure mode is also plasticity around the hole, but also local buckling in the compression flange. For cases including oblique bending and holes in tension zone do not show local buckling in the compression flange, but in the compression web, due to the inclined neutral axis caused by oblique bending.

With the effects of climate change being more and more frequent, the European union, and other governments world-wide are looking for sustainable alternatives for processes and products that are part of the daily requirements of people. Among these requirements, the construction industry plays a vital role, as it accounts for the consumption of about 50% of the total raw materials. In
line with its targets of 100% recycling by 2050, the industry in Europe, and particularly in the Netherlands is shifting towards the use of circular and sustainable construction products. This thesis investigates into both these aspects: Circularity by addressing the requirements for demountable structural elements, thus providing scope for reusing, and Sustainability by addressing the impact of substituting concrete and steel with timber products.

Structural timber products obtained from sustainable forestry are considered as eco-friendly construction products. The benefits are two-fold: First of all, it is produced or grown naturally, and thus avoids the emission of harmful gases during production. Second, growing timber products helps in CO2 storage for the duration of the technical service life of the product. Thus, increasing the market share of timber products in the construction industry can play a huge and decisive role to achieve the targets of sustainability.

The focus of this thesis is on steel-timber floor systems i.e., a floor system with timber slabs supported by steel beams. There are many timber products available that can be used as slabs, as a substitute to hollow core slabs and steel-concrete composite slabs, which are the conventional solutions for floor systems in the Netherlands (the former more than the latter). Owing to the disadvantage of timber in stiffness, coupled with the effects of creep, steel beams are considered for traversing larger spans.

From the plethora of steel and timber products that can be coupled together to form a floor system, the best solution is obtained with the help of a Multi Criteria Analysis. This is done by scoring the different floor systems on the aspects of utility, circularity and sustainability. The obtained solution is a conventional non-integrated floor system with Lignatur surface elements as the slab, supported by steel I beams. Lignatur elements are box-shaped slabs that can span over large
distances typically required for office use. Being made of sawn timber, it boasts the advantage of being more sustainable than other timber products made of cross laminated timber and laminated veneer lumber. I beams were found to perform better than other steel beams, posing as more accessible for demounting, over the other beams.

With the help of a case study, the benefits of the chosen steel-timber floor system were evaluated and compared against the hollow core slabs and steel-concrete composite slabs. Owing to the lightweight nature of timber, the chosen floor system was approximately 45% lighter than hollow core slabs, and 25% lighter than composite slabs. They were comparable in terms of floor height,
to the composite slabs.

The main benefit was the fact that the use of concrete and/or steel could be substituted with the use of timber slabs, and the supporting steel frame could be lighter owing to the lightweight nature of timber. A life cycle analysis was done to compare the different floor systems. Due to the use of sustainably produced timber, the steel-timber floor system had the least environment impact. Considering the effects of carbon storage meant that the total environmental footprint of the floor system could be negative. On further analysis, by excluding the benefit of carbon storage, the steel-timber floor system was still found to have the least impact (39% lesser than hollow core slabs, 31% lesser than steel-concrete composite slabs).

Another aspect that was investigated in this thesis was whether the consideration of composite action (similar to that in steel-concrete) could lead to any benefits i.e., composite action between the timber slab and the supporting steel beam. Based on the calculations in the case study, it was concluded that there were no such benefits i.e., the reduction in size of the steel beams was not
enough to justify the use of added shear connectors.

Another limitation of timber was found to be its lack of reusability. Being a biomaterial, timber is associated with a large reduction in strength for each reuse (although this reduction cannot be quantified using the present state of the art). Other materials such as steel and concrete do not experience this strength loss, and thus assume to have better performance than timber regarding this aspect.

The main barrier for implementing a steel-timber floor system would be in terms of costs. Though not explicitly investigated into in this thesis, it is expected to be more than that for its conventional counterparts. Currently, hollow core slabs are the most widely used, in the Netherlands, which is mainly owed to its low costs. Thus, the circulation of a product is closely related to its costs in the
market. By showing light on the benefits of the steel-timber floor system, it is expected that the results of this thesis will help the industry shift to the more responsible choice, in the near future. Wider circulation of steel-timber floors can help in reducing its costs, thus making it more desirable.

The need for sustainable solutions in the energy sector has led to the rapid increase of offshore windfarms around the globe. The areas with ideal soil conditions are gradually being occupied, pushing the offshore wind industry to search for methods of installing wind turbines in hard terrain. So far, the installation of monopiles in weak rock, if successful, required the use of additional casings and grouting. In this thesis project, an alternative installation method is investigated, in which the monopile itself is used as casing, avoiding the waste of extra material.

The ‘drill-drive’ installation method under investigation consists of an initial drill-out of the rock from the inside of the pile and its subsequent driving into the seabed with a hydraulic hammer. No casing is used and a cutting toe is equipped in the bottom circumference of the pile, being responsible for breaking through the rock.

Through finite element analysis, the structural integrity of both the monopile and the cutting toe during the drill-drive process is assessed. A driveability analysis is conducted for a seabed of different types of rock and the first conclusions on the feasibility of this novel installation method are drawn.

In this thesis an investigation into the buckling behaviour of steel trusses with eccentric joints is performed.
In recent years, Ampelmann motion compensated gangway systems have been pivotal to the advancement of offshore personnel transfers. These systems for functionality reasons require the use of eccentric joints. The behaviour of such joints is not a well-studied topic, and little is known of their effect on the buckling behaviour of structures. Buckling of trusses using conventional centric (non-eccentric) joints has been examined extensively in the literature. This work aims to answer what the effects of using eccentric joints compared to centric are, on the stability of steel truss structures. Additionally, a reduction of the computational and design time is attempted, by extending a simplified approach developed for centric joints, to eccentric joints.
The main investigation is performed on a simply supported truss comprised from eccentric K-joints and square hollow sections (SHS). Detailed models are used, with the joints being modelled by shell elements. The results are compared to equivalent trusses with centric joints. The main conclusions are that due to the eccentric joints, a better buckling behaviour can be realised for the truss members in the case of in-plane buckling. This improvement is more evident for the buckling of the braces and for combinations of chords and braces with γ>8 and 0.30<β<0.70 respectively. In those cases, a decrease of the buckling length of at least 5% is observed and reaching nearly 20% for γ=15.9 and β=0.4. In the case of out of plane buckling, the observed behaviour is slightly worse. The difference is considered negligible in practice, with all configurations checked giving a difference of less than 2% between the buckling lengths.
The simplified design approach, which uses beam elements and rotational springs, is validated, by comparing literature results with detailed shell element models. It is, also, further improved by performing new research on individual centric K-joint models. Having validated the approach for centric joints, three different modifications are proposed to extend it to eccentric joints. None of the proposed modifications give the validation required but insight is gained regarding the behaviour of eccentric K-joint trusses. It is concluded that eccentric joints require non-symmetric stiffness matrices for their behaviour to be captured.

The development towards a circular economy has many hurdles to overcome. For the construction sector an important step in this process is the transition towards reusing structural elements. Prefabrication of elements is a significant step towards achieving this concept. However, a case where both prefabrication and reuse are limited is the replacement of bridge decks. Headed bolts are welded to the steel supporting elements and encased in grout to connect them to the concrete deck elements. This method prevents reuse of the deck elements and hinders reuse of the steel supporting elements.

Research and literature exists on a number of alternative shear connectors that increase the modularity of these elements. The best alternatives have a single limitation in common: the allowed deviation for the placement of the shear connectors and bolt holes is smaller than is feasibly possible. The variances of element placement during construction add up to make it incredibly hard for these low tolerance connections to be made. The bolt hole diameter can be increased to increase the deviation tolerances. The large nominal hole clearance this results in needs to be considered. This can be done by using either resin injected bolts or High Strength Friction Grip (HSFG) bolted connections. Using HSFG bolted connections is preferred due to the shorter time spent on site and minimal waste, but research on the subject is sparse.

A proposed HSFG bolted connection that implements significantly oversized holes, defined as bolt holes with a nominal hole clearance roughly equal to the bolt diameter, and cover plates was designed together with both a control and regular connection to compare its behaviour with. The control connection is identical to the proposed connection with the exception of its holes which are normal sized. The regular connection has normal holes and does not include cover plates. Finite Element Models (FEM) were made of these connections that were subjected to static loading in a Finite Element Analysis (FEA). Test specimens of these connections were made and subjected to fatigue loading.

The numerical results of the static FEA showed that the use of cover plates reduced the stiffness and slip load of the connection. The second observation was the small impact that the hole size had on the slip load when using cover plates. This small impact becomes negligible at design preload.

The experimental results showed that the impact of larger bolt holes increased the loss of preload by roughly 1% during both short term relaxation and fatigue loading. The effect of the bolt hole size on the slip after fatigue loading was also concluded to be negligible, but the effect of the cover plates was concluded to be detrimental.

It was overall concluded that the use of significantly oversized holes in HSFG bolted connections with cover plates is viable. The negative effects caused by the cover plates and required longer bolt make it preferrable for large disc springs to be used instead of thick cover plates. The viability of the concept allows for further research on the subject.