This research focuses on comparing Accoya® with unmodified wood and investigates Accoya®’s structural performance in environments with varying relative humidity levels. The wood’s moisture content, and consequently its swelling and shrinking behavior, fluctuates on an annual basis due to these varying relative humidity levels, especially when exposed to outdoor conditions. FEM analyses were conducted to investigate physical properties and the performance of moment-resistant connections, with their implementation aimed at incorporating rotational stiffness into a structural portal frame. Accoya® demonstrates excellent moisture resistance and an increase in dimensional stability of approximately 80%, based on Dutch climate conditions. The reduction in swelling alleviates internal stresses within the connections, enhancing the strength and stiffness of moment-resisting connections. Specifically, a clamped connection and a circular dowel connection were analysed using a linear elastic static FEM model, revealing internal stress reductions of 81% and 52%, respectively. This reduction was observed during the simulated initial annual swelling cycle that the wood may undergo. With the use of Accoya®, significantly less plastic deformation is expected in connections due to swelling issues compared to unmodified wood and reduced deflection in structures is expected. An increase of 219% and 58% in rotational stiffness was observed for the respective cases. To evaluate the impact on overall stiffness, these observed values were implemented in a portal frame structure. A reduction in horizontal displacement was observed ranging from 31% to 66%. This opens up new possibilities in structural wood design, allowing for slimmer and lighter wood constructions. Due to Accoya®’s lower property degradation and more stable structural performance in high-humidity conditions, an adjustment of the kmod and kddef factors is suggested; however, this is not sufficiently substantiated in the current study. Future research could explore long-term performance factors with experiments such as creep and fatigue to validate Accoya®’s structural reliability further.

This Master Thesis research is carried out to investigate the most efficient re-mountable timber car park in terms of feasibility and structural performance. Applying the re-mountability principle with a sustainable material like timber is important to help the construction industry tackle environmental problems like global warming. Specifically, re-mountability is important because it ensures a second use of the car park without applying environmentally affecting processes, like redesigning or repairing the gained elements, and without creating waste.
In summary, the research question is: What is the most suitable design for a timber re-mountable car park, including global structure and details based on structural performance and feasibility?
The first part of this research is determining the most suitable floor system. This is important because of the large floor span in a timber car park and the reduced stiffness of timber compared to concrete and steel. Information is gathered by investigating car park and floor system references and the boundary conditions from regulations, material behaviour, transportation, etc. Next, a preliminary design is made for the four largest potential floor systems.
Based on this preliminary design combined with the earlier gained knowledge, the most suitable floor system is chosen in a multi-criteria analysis. A spruce CLT floor system of 140 mm thick combined with 360 mm x 1040 mm glulam beams becomes the most suitable alternative. A Triflex coating is necessary on top to ensure sufficient moisture resistance and re-mountability of the floor system. The fire resistance does not affect the floor system design because the serviceability limit state is governing.
Then, the second part of this research uses the known floor system to design the re-mountable connections in a final design phase. Using the knowledge gained from the references and boundary conditions, a bolted connection is the most suitable re-mountable connection type. However, a console is most suitable for the column-to-beam connection due to the positive effect on the necessary crane operation time.

This thesis project proposes the introduction of bio-based materials in the design of unitised curtain wall façade systems. The work investigates a circular bio-based unitised façade design to understand its feasibility regarding thermal, technical, and environmental performance. The research is divided in four phases, including the material, system design, performance, and environmental assessment level.
The material phase serves as a literature review to study the current technologies and available bioproducts in the market to make an informed selection. Once the materials are selected, the system design phase starts with an emphasis on dynamic construction and design for disassembly features.
Overall, this study aims to minimize reliance on non-renewable resources such as aluminium in façade systems. Therefore, it is important to analyse the thermal and hygrothermal behaviour of the materials to integrate design characteristics that can improve their performance while protecting their structural integrity.
After the feasibility of the design concepts gets validated, a comparative environmental assessment against standard aluminium façade systems is conducted to quantify the sustainability impact of the proposed system. Ultimately, the research project proposes a detailed exploration into the feasibility of circular, bio- based unitised façade systems. Therefore, the introduction of bio-based systems that support sustainable methodologies and practices from the material, design, and system level is demonstrated.

Amsterdam and many other cities consist of a network of old quay walls, which sometimes have been constructed over a century ago. A large uncertainty exists concerning the current safety of these quay walls and their remaining service lifetime. In the current framework for the assessment of old urban quay walls, the influence of timber creep in the structure is being omitted. It had been expected that a part of the excessive deformations occurred are part of this timber creep as opposed to progressive failure. Hence, this research studied the influence of wood creep on the structural behaviour of old urban quay walls, using a case study based on the Herengracht. For the modelling of the quay walls, use has been made of the Embedded Beam Row (EBR) elements in Plaxis 2D. As this element type has no material model which takes into account creep,
use has been made of pseudo-elasticity. The behaviour over time had been modelled by reducing the elastic stiffness of the EBR elements with increasing creep factors. To force Plaxis to perform calculations, this stiffness reduction has been introduced as a reduced strength in the form of a custom moment-curvature diagram. At the time of writing, the Embedded Beam Row had not yet been validated for cohesive soils. Hence, a verification has been executed of the EBR using a full-scale load test performed on a pile group in Salt Lake City. In
this case, a 3x5 pile group driven in multi-layered cohesive and non-cohesive soils had been laterally loaded. The results included deformations, total horizontal load and bending moment distributions over depth. It
has been found that the EBR provides reasonable results when modelling laterally loaded pile groups. The force-displacement curve from the field test was only slightly stiffer compared to those obtained using Plaxis 2D. Maximum bending moments obtained using the EBR had been found to be 20 to 30% compared to the experimental data. The group efficiency of the pile group was initially lower for small displacements, which was likely caused by the lack of installation effects of driven piles in the Plaxis model. It has been observed
that the Interface Stiffness Factors (ISF) that are used to calibrate the EBR behaviour have a limited range. Increasing the ISF values beyond a certain limit will no longer affect results, as the interface connecting the EBR to the soil will have become practically rigid at this point. Nevertheless, it has been concluded the EBR can be used in this case to model laterally loaded pile groups. The influence of the timber creep on the structural behaviour of quay walls has been studied using a model based on the Herengracht in Amsterdam. A maximum creep factor has been applied of Φ=1.6. Two methods have been used to apply the final creep factor. With the "Direct" method, the maximum creep factor was
applied in the same phase as the load. With the "Indirect" method, the creep factor has been applied incrementally in steps of 0.1. It has been observed that the results from these methods deviate significantly. With the Indirect method, larger creep displacements have been calculated, as well as lower maximum compressive stresses in the piles. The creep behaviour has been studied in more depth using the Indirect method. In this case study, creep displacements of 2.22 times the initial displacement have been calculated. When plotted against the increasing creep factors, it has been observed a power function could be fitted to the data. In addition, a stress reduction of 0.590 times the initial maximum compressive stress has been observed in the front two pile rows. This stress reduction was achieved at φ=0.4. In the most landinwards pile row, stresses
continued to decrease, with a reduced rate beyond φ=0.4. A sensitivity analysis has been performed to study which parameters have significant influence on the creep behaviour. Conclusions were drawn based on the relative change in horizontal displacement and maximum compressive stress in the front pile row. It has been concluded that the shear strength parameters of the top layer, the elastic modulus of the timber, surface load and the geometry have the largest influence on the creep behaviour. Furthermore, it has been discovered
that the size of the creep factor steps influences the final stress and displacement. With decreasing stepsize, convergence occurred in the results. From the results it has been concluded that the structural behaviour of
old urban quay walls is significantly influenced by timber creep. The inclusion of timber creep resulted in large displacement increases, but also in stress reduction. The results suggest that excessive deformations of quay walls does not mean that an ultimate limit state has been reached. It is recommended to include the timber creep in the modelling and assessment of existing quay walls.

Timber bridges are much applied structures in the Dutch landscape. In contrast to the other two most common building materials, concrete and steel, the use of timber is however almost exclusively limited to bridges for lighter traffic, e.g. pedestrians and bicycles. Examples of timber traffic bridges in Germany, Scandinavia and even in the Netherlands, show however that, at least structuraly, timber can be perfectly used in the construction of bridges for heavier traffic. Although structuraly feasible, there are still a number of doubts and uncertainties that go hand in hand with timber bridges. One of them is the maximum reachable service life. This research focusses on the ability to estimate this service life with the help of so called factor methods. The service life of a timber element in the Netherlands, with respect to biological decay, is in the basis determined by two main factors: the natural durability of the timber specie, and the moisture and temperature levels of the timber during its service life. In the case of timber bridges, where the timber elements are subjected to the weather, this can be broken down in three main influencing factors, namely:
1. Natural durability of the used timber specie 2. Local climate (Temperature, rainfall and humidity) 3. Detailing of the bridge (Protection against water accumulation) With these three main influencing factors in mind, factor methods can be used to estimate the service life of bridge elements. These factor methods estimate the service life based on reference situations, and use modification factors to modify these reference situations into the actual situation of the element. In this research two different factor methods have been reviewed in depth: the DuraTB method, developed in Sweden, and the TimberLife method, developed in Australia. The two factor methods have in this research been compared with each other and after that their usability and accuracy has been tested with the use of two reality checks on existing bridges in Amsterdam. For the reality checks, first an expected bridge condition was determined with the help of the two factor methods. After this the actual condition of the bridge was determined by an in-field visual inspection. Then the expected and the actual conditions were compared in order to obtain insight in the correctness of the service life estimation of the two factor methods. In addition, the role of factor methods in the processes of service life planning and especially during the calculation of the total costs of ownership (TCO) has been discussed. An example of a TCO calculation has been performed for two bridge designs, in which the focus was put on the incorporation of both the DuraTB and the TimberLife factor methods. Even though this TCO example is not representative from a total cost point of view (since the values of the different costs were guessed), it does show how factor methods can be used in the calculation of these total costs.

Within the context of utilizing alternative materials to promote sustainable construction in the building industry, Living Architecture is a concept that uses living organisms as the building materials. As a rather unconventional approach, it possesses benefits such as low cost, not requiring considerable workforce or industrial material, carbon-free, and its ability to return to nature when no longer in use. As an essential part of Living Architectures, scientists and engineers have recognized the importance of fusion between trees. For instance, in projects such as the Baubotanik Tower and the Living Tree Pavilion, a design premise is that the structure becomes ready when the fusion between trees could provide sufficient strength to support the structure. However, little research has been conducted in terms of the fusion processes and the mechanical behaviours of tree connections, which is an essential step prior to designing Living Architecture. With crosswise tree connection as the main focus of this thesis, the following research question is formulated: What are the mechanical behaviours of a self-growing crosswise tree connection when utilized as load-bearing elements in a building structure, and how can such connections be modelled during the preliminary design phase of a building structure? To help answering the research question, literature studies are conducted. In chapter 1, from a botanical perspective, it is concluded that, in the event of two stems contacting with one another, the two stems would gradually fuse together. Such an event is triggered by the abrasion on the bark due to the rubbing between the stems; later, due to the secondary growth, fibers from both stems deviate and join together to form common growth rings, such event can also be verified by the micro-CT scans that have been conducted on the crosswise tree connections. Additionally, due to the nature of the connection, a certain eccentricity from the stems' piths exists, and it is important to acknowledge that the length of such eccentricity stays constant from the start of the fusion process. To investigate the influence of tree growth on the mechanical properties of trees and tree connections, which is needed for design purposes, chapter 2 investigates the growth model and the tapering geometry of living trees. With the help of the Urban tree growth model published by the United States Department of Agriculture and a series of simple tapering equations, the growth parameters of a growing tree can be computed. Part-II of the thesis explores deeper in terms of the mechanical behaviours of such crosswise connections. A simple analysis of two trees connected in a crosswise manner is first conducted in chapter 4. It is concluded that, under loading, the connection can be subjected to tensile stress perpendicular to the grain and rolling shear stress. As two of the weakest strength properties of wood, the crosswise connections should be treated with care by future designers. As a part of an entire building structure, it is essential to determine the rotational stiffness and strength of a structural connection; therefore, in chapter 5, an experimental design is proposed for such purpose. Due to the irregular geometry of the crosswise connection, the experiment makes use of digital image correlation so that the rotational stiffness of the connection under loading can be obtained. Since conducting the actual experiment falls out of this thesis scope, a finite element modelling analysis with similar boundary conditions is conducted in chapter 6. With the results obtained from FEM, it is found that, due to the nature of the connection, complex torsional behaviours occur to the connection. Additionally, with the connection under loading, it is found that non-uniform stress distribution and stress concentration occurs along the interface between two stems. Comparing with the strength properties of wood, it is discovered that the first incident that causes failure is tension perpendicular to the grain, which is the weakest strength property of wood. To conduct preliminary structural design and verification, wireframe modelling approach is often utilized. In chapter 7, it is concluded that it is most suitable to model the crosswise connection with a separate beam element that connects the two stems, for its ability to capture the complex torsional behaviours described in chapter 6.
Lastly, after investigating the local behaviours of crosswise connection, Part-III
investigates the feasibility of conducting a preliminary structural design and verification with such connections. With the case study analysis conducted in chapter 8, it is concluded that, by appropriately capturing the load effects on growing trees and tree connections, designers are able to predict when the structure would reach sufficient strength to be in service. This thesis positions itself as a part of a broader spectrum that examines the feasibility of utilizing tree connections as the load-bearing elements in structures, which can be seen as a step towards sustainable construction.

The structural reliability of the wooden tower of the Grote of St. BavoChurch in Haarlem has been assessed with the regular methods. In addition to the regular methods, some modern technologies have been used in the structural analysis. The mechanical properties of the timber have been determined with longitudinal vibration tests and visual grading. The inclination of the tower has been determined with a terrestrial laser scanner and the entire has been modeled and verified with a Finite Element Model. Conclusions are based on the results of the Finite Element Model, which takes the determined mechanical properties and inclination in consideration.

It is estimated that about 400.000 houses in the Netherlands – both shallow and wooden pile foundations – could be facing problems with their foundations. Although, house owners are becoming increasingly aware of the fact that problems (and thereby costs) can be prevented if remedial measures are taken in time. Monitoring of the foundation can possibly give insights in the remaining capacity of the foundation. In this thesis, research is performed into monitoring of foundations. The main research question is: Which methods can be used to monitor a foundation and to what extent are these useful and adequate? To answer this question, five different monitoring methods have been investigated: InSAR (Interferometric Synthetic-Aperture Radar), measurement bolts, a subsidence sensor, a groundwater level sensor and a tilt sensor. Other methods have not been considered and are beyond the scope of this research.
First, InSAR data has been compared to subsidence data gathered by measurement bolts in two different cases, one in Zaandam (Netherlands) and Amsterdam (Netherlands). Measurement bolts are used as golden standard in this comparison. The comparison of measurement bolts with INSAR data resulted in a maximum error margin of ± 0,86 mm/year for Case Study Block A and ± 1,31 mm/year for all measurements for the testcase in the Case Study Block B within a 95% confidence interval. Secondly, the measurement bolts method has been qualitatively compared to InSAR data. Also, the pros and cons have been discussed. Measurement bolts have a better precision (0,3-0,5 mm) than InSAR data (2-3 mm) for individual measurements. Possible errors that can influence the accuracy of this method are: personal errors, instrumental errors and natural errors. InSAR and measurement bolts both have their strengths and weaknesses. Prescreening is an easier application for InSAR but highly accurate measurements in a specific location is more reliable if measurement bolts are used. In a way, these methods complement each other rather than measuring the same way. The datasets collected by the subsidence, groundwater level and tilt sensors is made available for this research project by KennisCentrum Aanpak Funderingsproblematiek (KCAF) which is an independent knowledge and network organization funded by the government of the Netherlands. Generally, several factors can add noise to the signal. It is unknown if the signal of the sensors is calibrated to measure the right quantity. This research project has shown that the data showed a similar trend of the groundwater level as local monitoring wells. Therefore, it can be concluded that the sensors are adequate to measure the groundwater level if they are calibrated and referenced to NAP. Moreover, the groundwater level sensor can possibly be used to measure how long dry periods are and how much wood is exposed to air, in order apply measures well in time.
Tilt sensors are currently not used for monitoring of foundations. The factors that can be considered when a tilt sensor is used to monitor a foundation are investigated with a literature study and with expert opinion. As the results show the measured rotation can be related to the stiffness of the wall where the sensor is mounted on. As for all sensors, it has to be made sure if they are calibrated to actually measure what they observe. Further research could usefully explore how viable a system of sensors is. In general, classification or a prediction of the remaining service life of a foundation can be challenging. Further research might explore how useful it is when big dataset are combined to be able to give better judgement.

In this thesis the geotechnical bearing capacity of old timber piles in Amsterdam is studied. This is necessary because many structures such as quay walls, bridges and houses in the (historic) city centre of Amsterdam are founded on timber piles with ages ranging between 80 and 300 years old. The assessment of the foundation is currently done using many assumptions, these are needed because the piles are not easily accessible and old construction drawings are not always available or accurate. Furthermore, the effect that bacterial degradation of the wood has on the interface friction between soil and wood has never been studied in detail. In the assessment it is currently assumed that degradation has no effect on the geotechnical bearing capacity (Kalt and Dusseldorp (2018)), while in the old Dapperbuurt tests it was found that old piles had a reduced shaft capacity of 40% (Korff (2013)). The study is split into two parts; firstly a laboratory study into the effect of bacterial degradation on the interface friction between sand and wood has been performed, and secondly a sensitivity analysis into the geotechnical bearing capacity of timber piles in Amsterdam soil has been carried out.

W/C is a fundamental parameter for concrete mix design, it defines the properties in the fresh and hardened state as well as the durability of the material. Nevertheless, once the concrete has hardened, it is very difficult to estimate the W/C in the original mix design, so far only 2 methodologies has been accepted as a standards. Because of this, the aim of the research is to use 4 methodologies, circular polarization microscopy (CPL), thermogravimetric analysis (TGA), UV light microscopy and scanning electron microscopy (SEM) + Powers and Brownyard approach to estimate the W/C of different concrete samples from a Round Robin Test done by the Applied Petrography Group (APG). The results showed that all the techniques have a correlation with the W/C. The CPL on its own and in combination with the UV light can be a feasible technique to estimate this value. Furthermore, since there were several techniques, it was decided to choose which one gave the best results using three guidelines, representativeness, reproducibility and reliability. The technique with the highest score was the combination of CPL+UV light.

This research focused on the question whether it is possible to predict the density of tropical hardwoods with acceptable accuracy based on drill resistance measurements. To assess the feasibility, the influence of the characteristics of the drill resistance measurement tool; the Resistograph® and the wood species have been investigated. With respect to the measurement tool, drill sharpness, feed speed and rotation rate were examined. For the wood samples, the influence of extractives, moisture content, drill direction and density were investigated. It was found that the influence of drill sharpness cannot be ignored and a calibration procedure was developed. No significant difference in drill resistance was observed between drilling in radial and tangential directions; however, drilling in the longitudinal direction resulted in a significant higher drill resistance. Moisture content influences the drill resistance; however, the effect is small and not statistically significant, it can usually be ignored. The influence of extractives on the drill resistance most likely depends not only on the mass fraction of extractives but also on the sort and the composition of the cell wall. Meranti has a typical density within the range 350 to 860 kg/m3. With an appropriate calibration procedure, it is possible to predict the density of meranti with 95% confidence to an accuracy of ± 70 kg/m3

Wood is an important building material that has been used for thousands of years throughout the world. It is the most widely used building material and due to its characteristics suitable for a wide range of applications. Still, for the last century steel and concrete have been the materials of choice for large buildings. Part of the reason for this is the lack of knowledge in the industry regarding timber construction. Now that the environmental problems such as climate change get more and more attention, there is an opportunity for timber as a building material and the manufacturers of timber products to increase its popularity.
Cross-Laminated Timber, or CLT, is a relatively new product. First introduced in the early 1990’s in Austria and Germany, now gaining popularity in residential and non-residential applications in several countries around the world. The panels normally have 3 or more layers of side-by-side placed boards, that are stacked crosswise at a 90 degree angle. The boards are glued on their wide faces and may or may not be glued together on their narrow faces.
The Derix Group, a company with a vast experience in the timber industry, specializes in laminated timber constructions and are interested in developing a new panel configuration. The idea is that by relocating boards from the middle layer of a CLT element, to a more favourable position, material usage can be optimized.
A problem definition is formulated and used to derive the research questions that form the direction of the thesis. The research questions are related to the possible advantages and the consequences of the Hollow Core Cross-Laminated Timber (HCCLT) configuration.
The first thing that is done in order to investigate the possibilities, is research into the manufacturing process and the structural design of CLT. As a relatively flexible building material with a low dead weight, the design of CLT is often determined by serviceability criteria, such as deformation and vibration. However, the rolling shear properties of the cross-layers can control the design, it influences the effective bending stiffness and stress distribution. It also causes a larger deformation due to shear than for other wood based products. Since there is not one specific design method, the most common methods are researched and described.
 The composite theory
 The mechanically jointed beams theory
 The shear analogy

To determine how the existing methods perform and to investigate the structural behaviour of a HCCLT element compared to a CLT element, the methods are used to calculate different configurations in order to compare the results.
The knowledge obtained during the research and calculations is then used to model a HCCLT element. Different models are made in order to investigate the behaviour during manufacturing and for when the element is in use.