Among the current targets of the building sector, one major goal is to maximize the resource efficiency (in terms of material use and in terms of energy used to produce the buildings); furthermore, the circular economy model aims for maximizing the reuse of the structural elements; thus, minimizing the material waste and avoiding a second production of elements. The high-rise building sector faces the challenge of considering a design that is flexible and adaptable to meet the functional requirements along its life span; and additionally, to consider a design for deconstruction, where the benefits and challenges that arise form reusing and recycling the material can be considered and addressed from early design stages.
This research addresses these trends and challenges by evaluating and comparing the environmental impact of different structural systems for a high-rise building in the Netherlands (151m). The comparison of four different structural systems with two core variations provides eight different stability systems. The scope of the stability systems considers foundations, core, columns, beams, bracings and floor slabs. The design of the structural systems was performed by the elaboration of 3D FEM models with parametrical tools to ensure the structural safety and serviceability of the building. Furthermore, the assessment of the environmental impact (global warming potential) was performed by means of a Life-Cycle Aseessment comparing three scenarios of the structure: cradle to gate, cradle to cradle, and cradle to cradle with 100% reuse of the structural elements; with data from the Nationale Milieu Database and with information from a technical report from the Joint Research Center.
The analysis of the results demonstrated that the environmental impact of the structural systems with steel core is 21% higher than the one that corresponds to the structures with concrete core, However, this variation is only 4% for the two variants of the diagrid structure. Furthermore, by including the average recycle and reuse rates form the market and current construction practices, the benefits at the end-of-life stage of the building can represent up to 17% of the impacts from the production phase. Moreover, when the reuse rate is considered as 100% the benefits increase up to 42% of the impacts from the production phase.
The results indicate that the improvement of the environmental impact of high-rise buildings can be achieved by means of sustainable structural design from the early phases of the design; where the choice of materials and of the structural system play and important role on the outcome of the total environmental impact of the building, which is becoming an important driver for the decision-making of new projects.

A parametric study, using the FEM-software package ABAQUS, validated on experimental results found by Abspoel, was conducted on S690 steel plate girders to address if the results of the previous researches was valid. Using a slightly different analytical model the results show the maximum web slenderness of this steel grade in both 6000 mm2 and 12000mm2 was the same. It was shown that the maximum bending moment was found when the top flange was able to yield, shortly followed by sudden collapse.
A new parametric study, to expend the optimizing plate girders using S890 steel was conducted as well to address the usefulness of steels with higher yield strength in plate girders subjected to bending. This study again used the geometry used by Abspoel. The results showed a decrease in maximum web slenderness, but still a significant increase in bending moment capacity compared to the S690 plate girders. It was shown that using an optimized S890 plate girders compared to hot rolled section made also from S890 steel, could reduce the use of steel by more than 80%.
After the parametric studies showed increasing capacity, the geometry used to numerically model the plate girders, was critically addressed, using small scale numerical studies using FEM-software. These tests showed that not only the slenderness of the web was a factor in the bending moment capacity of a plate girder, but also the flange geometry plays a significant role. It was shown that increasing the length of the tested part of the girder, the failure mode could change from flange yielding to an instable mode in which the flange rotated around its longitudinal axis, resulting in a much lower bending moment capacity.
An extra investigation in using a hybrid steel composition resulted in showing the potential of this optimization. Because by adding lower grade steel, more ductility was shown due to these parts yielding prior to yielding of the compressive flange, resulting in possible safer design.

The re-use of building components and structural elements is an underdeveloped practice which could be an important strategy in the global paradigm shift towards a circular economy. Steel is one of the most important structural building materials which combines incredible strength, favourable mechanical properties and excellent durability characteristics. It is practically infinitely recyclable and raw materials required for the production of steel are abundantly available in the Earth’s crust. This makes steel one of the most interesting sustainable engineering materials. However, the production process requires vast energy investments and produces considerate environmental pollution. To make steel an increasingly sustainable material and a frontrunner in the global transition towards a circular economy, significant investments and process improvements are necessary. The global environmental challenges of the 21st century demand rapid and far-reaching changes from the steel industry but it also poses opportunities for creative thinking and development of alternative strategies. The re-use of structural steel elements could offer great potential in reducing both the embodied environmental impact of construction works as well as the vast waste streams that result from demolition. There is general consensus on the technical feasibility of this circular alternative across academic literature and the idea enjoys widespread scientific support. Actual implementation is however limited, presumably due to the existence of several multi-level barriers. A diversity of actors along the value chain have indicated that various attitudinal, financial, structural, operational, technological and legislative barriers are preventing widespread adoption. Although some of the identified issues are of a practical nature, various perceived barriers have been identified which were found to be rather subjective. It is to be expected that providing additional information on the risks and opportunities, and by quantitative demonstration of the potential benefits of re-use, several of these perceived barriers could be alleviated. This thesis aims to integrate the potential use of circular steel elements in the structural design process for steelworks as a sustainable alternative to the use of new steel. The developed method allows structural design & engineering professionals to assess the environmental impact of structural steel frameworks with increasing accuracy. Furthermore, it improves the current practice by making the design process reuse-inclusive. It thereby provides design professionals with a tool to assess and communicate the possibilities of improving a design with regard to their inherent sustainability. It was found that the currently prescribed ‘fast-track’ LCA method, aimed at quantifying the embodied environmental impact of building structures, is highly sensitive and the current method could be leading to large inaccuracies and spread of misinformation. Two dominant national LCIA methodologies have been extensively compared and a sensitivity analysis has been performed for a variety of data resources. It could be concluded that the prescribed national data for steel products contained in the NMD is unverifiable and inconsistent with other resources. This raises serious concerns with regard to the accuracy and reliability of currently used ‘fast-track’ LCA methods for the Netherlands. It was calculated that the specific LCIA method used and the selection of modules included in the assessment can cause deviations of the estimated shadowprice up to approximately 424%. Subsequently, a tool was developed based on the CML methodology to validate the potential deviations that could arise from selecting a specific data resource. The application analyses and evaluates structural steel frameworks with regard to their inherent environmental impact. Furthermore it allows the engineer to select and substitute new steel elements with remanufactured counterparts found in a circular steel database. A case study was performed for four different scenarios. Both the LCIA method as well as the considered modules were consistent for all scenarios. From the results it could be concluded that the estimated shadowprice is also highly sensitive to the specific data considered. It was indicated that the input data can lead to deviations of the shadowprice of up to approximately 281%. Furthermore, it was calculated what the potential benefits of reuse would be. It was calculated that substituting 25% of the required steel could lead to reductions of approximately the same magnitude by eliminating the required process for production and cutting the transportation requirements. From the results of this thesis it could be concluded that there is serious inconsistency and limited transparency among the various data resources used for quantifying the environmental impact of steelworks. It is to be expected that the actual shadowcosts deviate significantly from the estimations provided by current assessment methods used in the Netherlands. Failure to accurately quantify the impact of primary building products could lead to significant errors as these materials have a relatively large contribution to the total impact of a building structure. Subsequently, this could lead to misinterpretation of LCA results thereby providing a misleading message for policy- and decision makers. However, it was also illustrated that the remanufacturing and reuse of structural steel profiles could offer significant environmental benefits and has the potential to significantly cut the environmental impact of structural steel framework constructions.

Today, society is becoming more and more aware of the environment and the (negative) influence we have on it. Especially the current workings of our economy have a detrimental effect on the environment. To reduce these effects, a transition is being made towards a circular economy. The construction sector plays a big role in the degradation: in the Netherlands the sector accounts for 50% of the raw material use, 40% of the energy consumption, 40% of the waste production and 35% of the CO2 emission. For the construction sector, one of the changes to establish a more circular economy, is the adoption of a circular design method. This method consists of the construction of buildings, building systems and building elements being designed for disassembly and reuse. This reduces raw material use and the expel of harmful emissions. While we see some developments being made in the construction sector regarding circularity, not many developments can be found in the field of reusable floor systems. For the sizable use of raw materials and expel of harmful emissions during the manufacturing process of floors, a more circular design for floor systems can (eventually) contribute to the sectors transition to circularity. Therefore, this research is focussed on developing demountable connections which can be used in such a circular floor system. The result is a system comprising a prefabricated timber-concrete composite (hereafter: TCC) floor slab connected to steel edge beams with toothed-plate connectors. An important aspect taken into account in the development of this design is the efficiency of erecting, disassembling and reassembling the floor. A multi-criteria analysis is conducted to determine floor slabs viable for use in a reusable floor system. A timber-concrete composite floor slab is chosen and designed. The slab is verified using analytical calculations. Design variants are made for demountable connections at the slab-beam positions at the head end and the side of the slab and for the slab-slab position. A choice between design variants is made by reviewing the fabrication and assembly tolerances and by assuring a non-destructive disassembly procedure. Analytical calculations are performed to verify the chosen connections. A case study building is used for the development of the floor system. The TCC floor slab spans 10.8m, has a total height of 510mm and a width of 1800mm. The used edge beam is an L-section. On the web a toothed-plate connector is adhesively bonded onto which the timber beams are placed to enable shear force transfer between the timber beams and the edge girder. At the top of the web a compression bolt is installed which is fastened after instalment of the floor slabs to ensure force transfer between the bolt and the concrete slab. Two angle sections are screwed to the outer sides of the outer timber beams and bolted to the edge girder to guide the slab to its intended position and to ensure structural soundness by vertically fixing the floor slab to the girder. Lastly the limits of the developed floor system are determined by performing a parameter study of the floor slab and the connection. The floor slab can be designed to span 12.6m. The connection still meets the structural requirements when the system is used in a building of maximally 70m high. This is applicable on many combinations of the building length (10m to 70m) and width (6m to 12.6m), if the right cross-sectional dimensions are used.

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

The research concentrated on a behavior of the deep composite deck ComFlor210 under a concentrated force. The distribution of a concentrated force in ComFlor210 was studied numerically and analytically.
The finite element model of a composite slab with 5.4m span showed good agreement with test results in the elastic stage. The parametric study of composite slab ComFlor210 revealed that in a slab with span 3.2m and 5.4m the load is distributed over three middle ribs. In a slab with 7.2m span, the load was spread over all five ribs. The bending resistance of the rib was exceeded for slab with 7.2m span.
In the elastic part of the load-deflection curve, the variation in cross-sectional properties causes a minor change in a slab response.
The proposed engineering model was unable to predict the deflection of the composite slab under concentrated load with the desired accuracy.

Monopiles will be installed in more difficult terrain since space in the 'ideal' locations is reduced by the rapidly increasing development of wind farms in the ideal areas. In difficult terrain, the amount of obstacles or hard layers increase, leading to an increased risk of pile tip damage. Also the ever increasing D/t ratio of the pile leads to piles more vulnerable to damage to the pile tip. Already, damage to the pile tip was encountered in projects such as the Goodwyn A and Valhall projects, resulting in financial burdens. The design codes show close to zero design guidance regarding pile tip deformation when hard driving is expected. There is a demand for research to understand these deformations at the pile tip. The main goal of this research is to obtain insight in the potential deformations at the pile tip as a result of collision with an obstacle.

To identify the pile tip deformation, a finite element model is established. Six volume elements over the thickness are required at the contact zone to model the pile-boulder interaction accurately. Axial- and lateral soil support is included in the model by using non-linear Winkler springs. Lateral soil support inside the pile is included by transferring the results of a volume element model into linear springs.
A parametric study is performed to investigate the influence of different parameters on damage to the pile tip. It is noticed that a fully geometric- and material nonlinear analyses is required to performs these simulations. Also, it is shown that in contrast with what is frequently done and also mentioned in design standards, the D/t ratio of the pile cannot be used as single parameter to design monopiles. Both D and t should be independently taken into account. Furthermore, it is seen that relatively large pile-boulder contact angles or low steel-rock friction causes the pile to slip over the boulder’s surface. Higher friction or smaller contact angles are likely to result in rippling or local in- or outward (local ovalisation) deformation of the wall. Although the larger contact angles and lower friction causes the pile to slip over the boulder’s surface, the horizontal reaction is shown to be large enough to push the boulder away, reducing the damage to the tip.

Based on a pile drive-ability analyses it is pointed out that current offshore hydraulic hammers are able to deliver the load that is needed to initiate the investigated local tip damage. Furthermore, based on Terzaghi's bearing formulation and the Brazilian Tensile Test it is demonstrated that local penetration of the pile into the boulder is likely to happen for softer rocks and that splitting the boulder is not likely to occur. Finally, one dynamic simulation is run to compare the static and dynamic simulation. It seems possible to investigate failure mechanisms using statics. Accurate results and propagation should be obtained in dynamic analyses. Detailed dynamic analyses is left for future work.

Two polluted Ghanaian lagoons are investigated and possible engineering solutions are suggested and researched.
The first lagoon is the Sakumo lagoon, located between Accra and Tema. This lagoon is connected to the sea through a small culvert, which enables a limited amount of water exchange. Since a few years, fishermen have been unable to catch fish in this lagoon, because of invasive plants restraining them from entering the basin. The siltation rate is high due to increasing friction because of these plants and limited sediment outflow through the small culvert. Furthermore, the water quality in the lagoon is poor. An overland flow model and a mixing model are used to evaluate the effects of a change in layout of the lagoon mouth. From this, it follows that a larger connection to the sea is beneficial to the water quality while still maintaining flood safety. However, decisions on the redesign of this lagoon mouth should be made with close regard to stakeholder interests.
The second lagoon is the Klottey lagoon, located in the city centre of Accra. The surroundings of this lagoon are planned to become an area of tourism. Neighbouring the lagoon, a new fishing harbour is planned. The water quality in this lagoon is poor and its water flows along the shore of Accra. The water quality in and near the lagoon is investigated with the development plans of the area in mind. Furthermore, the shoreline response as a result of these interventions is assessed.

The standard sign gantries at the highways in the Netherlands have different geometrical and structural characteristics than sign gantries in other countries. The sign gantries have in total four oblique columns instead of two straight columns and have a triangular shaped spatial truss beam. The design loads that are currently taken into account include the effects of the self weight, natural wind and settlements. This research focuses on the structural response to vehicle induced wind loads.

The vehicle induced wind loads cause a vibration of the truss beam mainly in its first horizontal mode. The vibration of the beam can be modelled by discretizing a simply supported Euler-Bernoulli beam with rotational springs at the supports that take into account the rotational stiffness of the columns. From literature the vehicle induced wind load is characterized as a pulse load, which is applied to the discrete beam model. The mass, stiffness and damping matrices are used to compute the structural response numerically in the time domain using MATLAB. This numerical calculation model is verified and fitted to the full scale measurements. The measurements were performed with multiple video cameras that were focussed on specific details of the structure and the vehicles that pass the structure. It was found that it is possible to approximate the amplitude of vibration in time using a single pulse load for trailer trucks and trucks.

The stresses in the structure are calculated by applying a deformation that was caused by vehicle induced wind loads to a calculation model with bar elements in MatrixFrame. These stresses are compared with the cut off limit for fatigue detail classes. Based on the preliminary measurements and the calculation model it can be concluded that no fatigue damage is caused by vehicle induced wind loads for the newer series of structures (2012). The older series (2005) could encounter fatigue damage, but it depends on the span length of the beam.

For the E39 highway in Norway a project is underway to replace the ferry crossing in the Sognefjord with a fixed crossing. Previous thesis projects have resulted in a design for a 4500 m long buoyancy bridge which consists of 22 concrete pontoons that carry a steel truss superstructure. To reduce lateral movements the pontoons are fixed to a submerged anchoring cable system. In the middle of the bridge a 400 m wide, 70 m high ship fairway is created. In previous bridge designs the superstructure consisted of separate girders for every span which were connected to the pontoons through hinges. The purpose of this research was to investigate the structural feasibility of creating a continuous superstructure without internal hinges for the Sognefjord bridge. After making a design for a continuous CHS steel truss superstructure, behaviour of the whole Sognefjord bridge with the new superstructure was researched for different load combinations. It was found that maximum lateral displacement of the bridge is 27 m, while maximum longitudinal displacement is 46 m. These were deemed acceptable values. A research was conducted into which parameters influence bridge behaviour the most. It was found that of the bridge structure, rotational stiffness of the pontoons influences bridge deformations the most. A two times higher rotational stiffness of the pontoons leads to a maximum reduction in lateral bridge displacements of 44%. The stiffness of the superstructure was found to have only minor effect on bridge behaviour. Internal loads in the superstructure were found to be mainly determined by displacements of the top of the pontoons, upon which the superstructure rests. Internal loads in individual truss members under a ULS storm situation were investigated. Member stress levels under a ULS storm are very diverse in value, with a maximum peak member stress of 590 N/mm², resulting in a unity check for stability of 1.36. Under reduced bridge deformations from double rotational stiffness of the pontoons, member stress in de superstructure on average drops by half. Peak member stress in the superstructure under a ULS storm with double pontoon rotational stiffness is 293 N/mm², resulting in a unity check for stability of 0.67. Preliminary investigations into bridge dynamics and ship collision were performed. Vortex-induced vibrations of structural elements, as well as pontoon displacements and shockwave effects under ship impact are challenges that require more investigation. The results of this research suggest that creating a continuous bridge girder without internal hinges for the Sognefjord buoyancy bridge is structurally feasible. This would require doubling the rotational stiffness of the pontoons, which is expected to come with large material costs. More in-depth research into other load situations is recommended.

Wind energy plays an important role in the global energy supply and is obtained by wind turbines placed on- and offshore. The expected growth of offshore wind farms will generate a lot of work in the future. Seaway Heavy Lifting is an offshore company which offers Engineering, Procurement, Construction and Installation (EPCI) solutions worldwide for oil, gas and renewables projects.

Offshore wind turbines are most commonly placed on a monopile foundation. The installation of monopile foundations used for offshore wind turbine farms is the main part of the projects Seaway Heavy Lifting is executing. The installation of monopiles is done using an installation vessel, which needs to be anchored during installation. The anchoring is done in order to cooperate with external forces on the side shell due to the installation of the monopile. The installation of the monopile is done using a frame which is connected to the side shell of the vessel. In order to stay competitive in the business, the company has been doing research to how to decrease the amount of installation time of their projects. It is concluded that profit can be gained by reducing the necessary time to anchor the installation vessel.

To install monopiles without anchoring the vessel, the monopile installation frame (MIF) was designed. The MIF can be placed onto the seabed after which the monopile can be hoisted inside of the frame. The frame will support the monopile during hammering. No external forces will be acting on the side shell of the vessel when using the MIF during hammering, which rules out the need for anchoring the vessel. Instead of anchoring, dynamic positioning will be used. Since the installation of monopiles will occur in different water depths, the MIF needs to be modular. An extension piece will be used in order to change the height of the frame.

The goal of this thesis is to obtain a structural optimized design of the MIF. The connections needed to connect and disconnect the extension piece are critical sections of the MIF. During the lifetime of the MIF, fatigue due to waves, wind and current loading will play a role. Therefore, this thesis has focused on the structural optimization of the connection with respect to fatigue loading. A bolted flange connection will be used in order to connect the members, which will be machined and then welded to the tube end. An initial geometry of the connection was designed with help of design rules stated by ir. M. Seidel.

The finite element program ANSYS will be used for the calculation of stress distributions. The decision was made to verify ANSYS, which was done by studying the accuracy of ANSYS, its way of working and to get used to the program. The verification has been done using a reference project.

The fatigue analysis of the connection started first of all with a global load analysis. This was done with help of the program SACS, which uses wave heights and wind speeds together with currents data as input. A calculation model of the MIF was built in SACS. Once the input was completed, the internal forces of the MIF were calculated. The global load analysis is necessary in order to obtain the loads in the members that will be connected by the bolted flange connection. These loads were used as input for ANSYS.

To check whether the initial design could be used as a starting point, the 3 failure modes of a bolted flange connection have been explained and verified for the initial design. Once it was verified, it was used as input in ANSYS in order to study the stress distribution of the model. The initial geometry has a negligible radius between the tube and the flange of the connection. Therefore, it was expected that a high concentration of stresses would occur in the junction between the tube and the flange of the connection. In order to find the stress concentration factor (SCF) in this junction, the maximum stress occurring in the junction needs to be divided by the stress applied to the tube.

Once the SCF was known the fatigue analysis could be performed. The fatigue analysis was done for two details: the junction between the tube and the flange and the welded connection between the tube and the machined part. Firstly, the amount of actual cycles was calculated for a certain time period with help of the wave scatter diagram, after which the corresponding stress ranges during these cycles was obtained. The stress ranges were multiplied with the SCF for the tube-to-flange junction, the SCF was obtained using ANSYS. Once the stress ranges were known, the amount of cycles until failure was calculated using S-N-curves that fit the two studied details. The actual damage to the structure was determined by dividing the actual number of cycles happening by the amount of cycles until failure. With the damage known for a certain time period, the life time of the structure was calculated.

The MIF will be used for a period of more or less 8 years, so the design lifetime was set at 9 years.
The initial geometry had an extremely low lifetime. Therefore, the connection needed to be optimized in order to improve the lifetime. The optimization of the connection was done by increasing the radius of the tube-to-flange junction to lower the SCF. A lower SCF value resulted in a longer lifetime. The design has been optimized until an optimum radius of 36 mm was found. The final design has a lifetime of 9 years.

Limitations in the modern housing market supply and the high demand for city centre living space ask for a robust urban densification way of building. This results in the exploration of innovative vertical extension projects, such as the ’De Karel Doorman’ case in Rotterdam. However, demanding the construction method to be extreme light-weight revealed an unexpected normative serviceability phenomenon. The reducedmass did not dissipate enough vibrational energy induced by human activities such as walking, leading to an excessive and disturbing perception of vibrations. This caused nuisance for both the home situation where the motion takes place as for the neighbouring floor fields. The critical motion-related limit state has to be satisfied to create a comfortable living environment. This thesis aims to further develop the concept of light-weight steel and timber building structures focussing on vibration comfort. This is done by exploring structural measures that can steer the vibrational floor response for both the induced situation as for the transmittance to adjacent fields. Broadening research shows the general impact of the damping, natural frequency and modal mass. From this starting point, new practical building tools are developed to affect and control the path and magnitude of vibrations positively. General guidelines are provided that show the demands for a structural assembly to create suitable apartments. The proposed measures to steer the vibration comfort were researched using both the conventional handcalculation method from the SBR-guideline and by more accurate finite element analyses from SoViST and Autodesk Robot. The resulting OS-RMS90 values indicate the response velocity of the floor and have to meet the limit criteria proposed for the specific function of a building. For the light-weight residential building concept, these criteria were set to 0,8 [-] and 0,2 [-] for respectively the home and neighbouring situation. It was found that for light-weight building structures the implementation of a large amount of stiffness is inevitable in both the floor assembly as in the junction. The consequence of additionalmass and height can be balanced by using efficiently shaped profiles and smart placement of the joists. For the supporting beams, these demands encourage the use of rectangular hollow structural sections whereas for the floor assembly I-joists are recommended. Additional transverse stiffness stretches the clustering of natural frequencies for orthotropic plates but is most effective for two-way span floors. A smaller span will result in improved comfort levels but will complicate the structural assembly by introducing more elements and connections. Besides the overall performance enhancing measures, it was found that the limit criterion for neighbouring apartments is harder to achieve without additional interventions. Introducing more substantial obstacles for the vibrations to overcome along the path, will reflect the transmittance and hence steer the floor response towards improved comfort levels. The use of an alternating floor field can provide in this issue as it avoids the mode-coupling of natural frequencies from adjacent elements. One other recommendation is the differentiation of the home-separating and in-home junctions. This results in maintaining more vibration energy in the home situation and limits the nuisance caused from excitements in a neighbouring apartment. The as-built ’De Karel Doorman’ revealed the impact of additional stiff elements in the wall that substantially increase the bending and torsional stiffness in the junction. It was found that these elements mitigate the nuisance caused by footfalls to imperceptible values for adjacent floor fields. However, these elements do leave a mark on the flexibility of the floor plan. Light-weight building structures face new challenges and acknowledge the shift from strength-design to serviceability-design criteria. Regarding vertical extension projects, not just the building engineering aspects but also the practical implementation was found to contribute in the consideration for structural assembly measures.

More than 50 locks owned by Rijkswaterstaat need replacement or renovation in the coming 40 years. Due to this fact an opportunity for changing the traditional way of building and maintaining navigational locks has arisen. Because of the replacement/renovation of locks in the coming time, implementing a new owning and building strategy is relatively easy. Rijkswaterstaat is interested in how standardization could be applied to (some) lock components to save costs, and increase reliability and availability.
The lock gates are the lock components with the highest potential for standardization. A parametric model for several lock gates is made in order to compare these gate types for a range of boundary conditions. The comparison of several gate types which can be made by the parametric model, could lead to a prescription of a standard gate type for specific boundary conditions. With this prescription, standardization could be implemented in the design process for navigational lock gates. The parametric model can also be used to assess the impact of design choices on the standard design. A parametric model is made to assess rolling gates and mitre gates (with and without clearance at the pivots) made in steel. The model has led to a way of optimising one design (in terms of steel volume used) per gate type for these gates for a range of boundary conditions. The model is able to prescribe a gate type for the case study used, the Prinses Marijkesluizen. The model is unable to prescribe a gate type for bilateral retaining gates, since the results of the design are too close to each other to prescribe one variant as the best variant. It is recommended to record more data, since costs can be added as optimisation criteria (instead of material volume) when this data is known.

Sustainability concerns steer the construction sector towards adopting a circular economy philosophy. Steel-concrete composite beams are extensively used in multi-story buildings and bridges due to their competitive construction and efficient material use. Currently the composite action is mainly achieved by headed shear connectors welded to the top flange of the beam, obstructing the non-destructive demountability. Demountable shear connectors can be used in order to open up the composite con-struction for reusability. Demountable shear connectors can take the form of a bolted connection which requires a tight control of construction tolerances. This thesis is fo-cused on studying a bolt coupler connector which is seen as a valuable alternative to the more conventional embedded bolt. The proposed shear connector consists of a bolt and coupler embedded in prefabricated concrete decks which are connected through the top flange of the steel section by an injection bolt.
Full-scale experiments have been performed to investigate the feasibility of construc-tion of a demountable car park. The demountable flooring was obtained by large pre-fabricated concrete decks in combination with tapered beams. Experimental research has confirmed the possibility of assembly and disassembly of the system if construction tolerances are appropriately designed. The most influential factors were quantified based on experimental observations, measurements and finite element models. The hole clearance should be designed keeping in mind the deformability of the system during construction, the manufacturing tolerances and the speed of construction. Experiments show that resin injection can be reliably and labour efficiently used for large oversized holes which allow for higher fabrication imperfections and reduced construction while at the same time enabling composite action of the connectors under live load.
The reusability of the structure was confirmed by a set of eight four-point bending tests considering uniform and non-uniform connector arrangements. Finite element models closely match the experimental results in terms of deflection, stresses and curva-ture. However, the end slip is overpredicted which is in line with research performed by other authors. The efficiency of the non-uniform connector arrangements was studied experimentally and numerically to reduce the construction costs. Concentrating the shear connectors toward the supports will bring the highest benefit in terms of beam bending stiffness without the need of a large number of connectors to prevent uplift.
An extensive cost analysis was performed based on a database of 15500 beam solu-tions generated by a design algorithm develop as part of this thesis. The case study provides a preliminary cost assessment of two demountable steel-concrete composite floorings in order to quantify their economic viability. It was shown that the system constructed with prefabricated solid slabs is more viable compared to the demountable profiled sheeting slab. The most influential contribution to the final cost of the struc-ture comes from the steel work and the labour intensive manufacturing.

There is currently increasing interest in making a transition towards a circular economy, to improve resource efficiency and to reduce harmful emissions to the environment. The European Union adopted a Circular Economy package in 2015, while the Dutch government introduced a programme to achieve a circular economy by 2050. The construction industry is regarded in particular, being responsible for the use of about 50% of all raw materials. Innovation in the field of demountable and reusable structural elements is therefore of importance. By connecting composite (steel-concrete) slabs to steel beams using shear studs, composite beams are created. This results in a structurally efficient composite flooring system. However, demounting and reusing this system is very difficult due to the welded connection of the shear studs to the steel beam and the embedment of the studs in the concrete. This research aims to provide recommendations for the design of a demountable composite flooring system in which both the steel beams and the composite slab can be reused, while its structural efficiency is retained. Additionally, the environmental benefits of this system are assessed.

To quantify the environmental advantages of a composite flooring system, a Life Cycle Assessment (LCA) has been conducted based on a case study of the Temporary Courthouse building in Amsterdam. For this building, it is found that the use of a composite flooring system instead of hollow core slabs leads to a reduction in environmental impact of 16-37%. For a building with main spans of 16.2 m instead of the original 10.8 m, this reduction increases to 35-51%. This is mainly caused by the reduction in the amount of concrete in the composite slab. Additionally, the weight reduction of 40-50% compared to hollow core slabs is beneficial for the transport-related environmental impact. Furthermore, it is found that the importance of the steel beams for the total environmental impact of the composite flooring system is limited: a reduction in steel section size due to shear interaction between the beam and the
slab only leads to a reduction of 2-6% in environmental impact. However, a cost analysis shows that material costs are reduced with €12 - €31 per square metre when shear interaction is achieved. This shows that the use of demountable shear connectors between the beam and the slab can be viable, as long as the costs of the shear connectors are kept below these amounts.

The structural behaviour of a composite beam with a composite slab and M20 grade 8.8 bolts as demountable shear connectors has been analyzed in more detail by means of analytical calculations and finite element analysis. It is found that initial slip due to bolt-to-hole clearances must be prevented in order to avoid larger deflections than allowed. A demountable composite flooring system is proposed in which the slab is cast in-situ for the first use, after placing the shear connectors, and reused as prefab elements without the shear connectors. In this way, bolt-to-hole clearances are avoided, while the main advantages of composite slabs are retained. Design recommendations are provided as a framework for the future development of a demountable composite flooring system.