Timber high-rise buildings have been gaining in popularity. However, due to the low material stiffness of timber the stability systems of these buildings are often made with steel or concrete. To avoid this the material efficiency of the timber stability systems must be improved. The most material efficient stability systems for timber high-rise are the externally braced systems according to literature. The externally braced systems are the diagrid and external braced frame stability systems. In literature the diagrid is concluded to be more material efficient than the external braced frame. Nonetheless, in practice only external braced frame systems are used for timber high-rise buildings. This disconnect could be caused by the steel connections which are often simplified or overlooked in literature studies but have a large influence on the material usage of a timber stability system. The connections can increase the timber element size because the required connection does not fit, and the connections will decrease the global stiffness of the stability system. For this reason, the connections must be regarded when comparing stability systems. One diagrid and two external braced frame designs will be compared with a parametric model. In this model other parameters will be studied as well. These parameters are: plot sizes of 27.2 x 27.2 m & 27.2 x 40.8 m, floor spans of 3.4 m & 6.8 m, permanent floor loads of 3.5 kN/m^2 & 5.3 kN/m^2 & 6.7 kN/m^2 and element widths ranging from 400 mm to 650 mm. The parametric model will first size the elements individually for the ULS checks and afterwards the elements will be sized per group for the SLS checks. The ULS checks start with a regular ULS member check, then a member check in the fire situation is performed and lastly the connection design component used. This connection design component will create slotted-in steel plate connections where the amount of steel per connection is calculated, and the timber element sizes are increased if needed. In the SLS checks the global lateral displacement is checked and the along-wind acceleration. The along-wind acceleration is often normative for the sizing of the elements in timber high-rise. With a higher global stiffness or higher building mass the acceleration decreases. To make a fair comparison in the results the amount of timber and steel of the internal structure is also added to the material required in the stability system in the façade. From the results it is seen that all buildings are sized on the connection design or on the along-wind acceleration. The diagrid designs have a higher global stiffness so they are sized more often on the connection design whereas the braced frame designs are sized more often on the along-wind acceleration. The diagrid designs use 3x more steel than the braced designs. The results for the other parameters are: Plot size: A smaller plot size requires a higher floor load to meet the acceleration requirement, therefore the large plot size is more material efficient. Floor span: The floor span in the external braced frame has a large influence on the designs with a small plot size. That is because the facade with the smaller span becomes normative for the global displacement. When this happens a smaller floor span decreases the material efficiency significantly. In the larger plot size the influence of the floor span on the braced frame designs is insignificant. For the diagrid designs the larger floor span causes higher normal forces in the diagonals. This increases the material usage in the facade. However, considering the internal structure of the building the large floor span is still more efficient. Floor weight: A higher floor weight is more timber efficient for a small plot size, and the lowest floor weight is the most material efficient for a large plot size. With a higher floor weight, the steel usage always increases since the connection designs are sized on the ULS checks only. Element width: The steel efficiency increases when the element width increases. This is a result of the chosen connection design. The timber usage is similar for all the element widths. Some of the designs with a small plot size and low floor weight are unfeasible since the elements in the facade are too large. This is a result of the choice to only increase the timber element heights and not the connection stiffness to improve the global stiffness. Therefore, it is recommended to study how the global stiffness can be improved more material efficiently. Other recommendations for further research are on the stability system design and the connection design. Since in this thesis many designs are fixed in simplified exploratory studies to decrease the design space of the parametric model.

Increasing housing demand in Europe and the need to be more sustainable are asking the construction industry to leave the traditional pathways and innovate. An emerging construction method with volumetric timber modules potentially offers the solution. However little is known about the robustness of this new innovation. Therefore, this thesis aims to advance the current research regarding collapse resistance in volumetric modular timber buildings. To achieve that goal, first, in this thesis, a literature study into robustness and modular buildings was performed. The study identified the importance of redundancy, proper connection design, ductility, and tying in modular structures for robustness. Secondly a case study was performed. The case study provided the structural design concept of a newly developed volumetric timber post and beam module by Lister Buildings, structurally designed by Pieters Bouwtechniek. The modules consist of glued laminated beams and columns with cross-laminated floor and ceiling slabs. With the modules, a hypothetical residential building of 5 storeys was created, which consecutively was decomposed into equivalent two-dimensional frame structures suited for 2D finite element analysis. To account for the mechanical behaviour of the connections in the models, nonlinear springs were used. To establish the springs, the component method was adopted. The spring behaviour was determined from the elastic, plastic and failure performance of the individual components of a connection in translational and rotational degrees of freedom. Then based on a notional element removal concept, multiple possible loss events of load bearing elements were analysed in the finite element software of Abaqus to examine the existence and development of alternative load paths. To do that, both nonlinear static and nonlinear dynamic analyses were performed. The results of this study indicate that the new design concept performs quite well on robustness. Several alternative load paths were identified, among which cantilever action, bridging action, and catenary action, depending on the removal event and scenario. In addition this thesis investigated the dynamic amplification factor (DAF) of the modular system. The results of this research imply that for alternative load path analysis of timber structures, a DAF of 2.0 should be applied in a (non)linear static analysis. More research will be necessary to examine whether a lower value than 2.0 can be used.

Currently, most of the modular building can be fabricated off-site, except for the stability system. Therefore, the question arises: Could modules be designed such that there is no need for an additional stability system? As modules are typically built in a rectangular shape, incorporating stability elements such as bracings along the longer side of the module is not the problem. The main challenge lies in the limited length available for stability elements on the shorter side of the module, combined with the fact that this shorter side is commonly used for windows and openings for door frames. This introduces a conflicting interest between structural capacity and daylight within the module. This conflicting interest becomes more and more prominent as the building height goes up. A possible solution to this problem can be found in the use of a load-bearing window frame with glass infill as a stability element, often referred to in literature as a timber-glass shear wall (TGSW). Therefore, this thesis will answer the main research question: 'To what extent can the structural performance of a timber-glass shear wall as a stability element in a timber module be used to accommodate for the stability of a mid-rise modular timber building?' The approach to answering the main research question consists of several steps. First, a literature study was conducted on modular buildings and TGSW's. The outcome of the study has provided insight into how modular buildings are constructed in general and how relevant aspects such as progressive collapse, fire safety design, and foundation design influence structural design. The study also resulted in an analytical prediction model for the load-bearing capacity and stiffness of the TGSW. Through this prediction model, it became clear how the properties of individual components relate to the load-bearing capacity and stiffness of the total TGSW-system. The second step was to propose a design for a modular timber building composed of timber modules. To save on computational time, the stability elements of the building are modelled using steel diagonals as an equivalent system for the TGSW. The cross-sectional area of the steel diagonals is directly related to the properties of the TGSW. Therefore, the steel diagonals have identical stability properties as the TGSW. In this study, varying the type of adhesive and the spacing of the screws was found to have the most significant impact on the overall structural properties of the TGSW. The horizontal connections are made of steel plates fastened with screws. The vertical connections are realised by shear plate connectors. The entire building was modelled in a 3D FEM programme to assess the structural behaviour of the building and its compliance with building regulations. Several building configurations ranging from 1:1 to 1:3 height-to-width ratio were investigated. For each building configuration, the cross-sectional area of the steel diagonals was adjusted within a specified range. This range corresponds to variations in adhesive type or screw spacing. As a result, design graphs were produced, which present the requirements for the load-bearing capacity and stiffness of the stability system. These can be compared to the load-bearing capacity and stiffness of the TGSW. This comparison can be used as a validation method to determine the viability of the TGSW stability element in a modular building. The results of this study indicate that a modular building can be stabilised by a TGSW up to six stories within the height-to-width ratio of 1:1 to 1:3. The minimum building configurations per story height are: 3 modules high by 5 modules wide, 4 by 8 modules, 5 by 12 modules, and 6 by 18 modules. These slenderness ratios were governed by the strength of the TGSW. The limiting factor in the load-bearing capacity is the shear strength of the adhesive. These slenderness ratios could only be reached with elastic adhesives such as silicones. The next step is to create a more extensive FEM model that could predict the load-bearing capacity and stiffness of the TGSW in a more accurate way compared to an analytical model. Furthermore, exploring the performance of the TGSW under different horizontal loads, such as earthquakes, would give valuable insight.

The Netherlands is grappling with a substantial housing crisis, marked by an estimated shortage of 380,000 houses. To address this issue, an annual creation of 100,000 new housing units is deemed necessary. However, the current construction rate stands at only 70,000 houses per year, indicating a considerable gap in resolving the housing crisis. Recognizing the potential of urban densification, especially through vertical extension using Cross-Laminated Timber (CLT), presents a sustainable solution. Nevertheless, challenges arise, such as the unique approach to vertical extension and the structural constraints posed by CLT's lower strength compared to materials like concrete. This research aims to identify the vertical extension potential of CLT in existing buildings by developing a parametric tool that considers various structural constraints. The ultimate goal is to contribute to informed decision-making practices for sustainable and effective structural design in vertical extensions. The methodology comprises four phases: analysis, synthesis, simulation, and evaluation. The analysis phase examines existing vertical extensions, structural context, and spare capacity concepts, forming the basis for synthesis. A parametric tool is then created using Grasshopper and Karamba, employed in the simulation phase to conduct a parameter study based on the analysis phase findings. This study assesses the effects of the original structure's base geometry on spare capacity and evaluates the design of the extension itself. The results of the parameter study reveal that the presence and placement of a stability core have the most significant impact on spare capacity in the existing building. The original construction grid and building height also influence spare capacity, though to a lesser extent. Additionally, wall layouts in the extension, such as core alignment, functional design, and façade-aligned layouts, significantly affect spare capacity utilization in both the original structure and the extension. Variations in extension grid show differences in spare capacity utilization, with effects smaller in magnitude compared to wall layout variations and displaying less dependence on the original structure's geometry. In the vertical extension itself, failure tends to concentrate on connections between CLT panels and floors, particularly with wall layouts emphasizing functional design. In conclusion, the research, coupled with the development of a parametric tool, successfully achieves its main goal. The tool's accuracy is validated through extensive assessments of horizontal load transfer from the extension to the original structure. The parameter study highlights the significant effects of various parameters on extension design and the original structure, emphasizing the tool's utility in exploratory design stages for vertical extensions.

Low-frequency sound transmission in a cross-laminated timber apartment building can result in annoyance, even if the acoustic requirements of the building code are fulfilled. Cross-laminated timber is an upcoming material in the building industry. But there are also problems arising when building with this relatively new material. CLT is a lightweight building material, which means that the mass itself is insufficient for meeting the acoustical requirements. The total sound transmission depends on the amount of direct sound and flanking sound transmission. The ISO 12354 standard used to determine the amount of sound transmission between rooms does not include frequencies below 100 Hz. Even though these low-frequency sounds are the main cause of annoyance in lightweight construction buildings. The low-frequency sound transmission is hard to measure because of the long wavelength. In this research, a numerical model was developed and used to determine the low-frequency sound transmission in CLT apartment buildings. The effect of the following sound-reducing measures are studied: the material properties of the material CLT, additional linings on the room separating elements, use of elastic interlayers between CLT panels and the type and number of connectors connecting the CLT panels. These are all common sound-reducing measures for lightweight constructions. The effect of the material properties of the CLT and the effect of additional linings are computed by a numerical direct sound transmission model. The effects of elastic interlayer and connectors between the CLT panels are computed with a numerical vibration reduction index model. The results of the numerical models are compared to measurements found in literature and the sound transmission according to the ISO standard. The results showed the importance of Young’s modulus in the y and z-direction, these influence the location of the resonance induced dips in the sound insulation. The internal loss factor of the CLT panels influenced the height of the dips. A loss factor of 20 % resulted in results most similar to the measurements. The direct sound transmission through a bare CLT panel can be predicted within a range of 3 dB difference with measurements. The prediction of the ISO standard is within a range of 5 dB with the measured values. The vibration reduction index between panels without interlayers is modelled with frictional contact regions between the panels. The numerical results showed similarities with the measurement results for the vibration reduction index of panels with screwed connectors. The ISO standard significantly overpredicts the vibration reduction index of CLT junctions. The effect of the elastic interlayer showed insignificant improvements in the frequency range 50-500 Hz, the additional reduction stays below 3 dB. The ISO standard does not include a method to determine the effect of elastic interlayers or connectors between CLT panels. The numerical models prove that is possible to predict the low-frequency sound transmission in CLT apartments. Important notes are that the CLT lamellas need to be modelled separately. Only in this way the model is able to capture the sound that goes through a structure within a range of 3 dB. In order to test the effect of additional lining, the material properties need to be known. The vibration transmission between panels in the junctions is more complex, as it depends on more design parameters. A frictionally bonded contact region between the panels results in vibration reduction indices that are in line with measurement results of panels with several connectors. The effect of the elastic interlayer is minimal in the low-frequency range, but the results are similar to measurement results. Both the direct sound transmission model and the vibration reduction model were influenced by the boundary conditions.

The importance of joints in timber structures is strongly emphasized in the existing literature (e.g., Blaß & Sandhaas, 2017; McLain, 1998). The aim of this project is to provide insight into whether the cross-sectional sizes of the member are dictated by the dimensional sizes of the laterally loaded dowel-type connection or the strength and stiffness requirements of the member itself in timber frame structures. In this research project, a parametric study is performed. The parameters in this study represent the global frame structure and the laterally loaded dowel-type connections. Together, these parameters form a parametric model that lays the foundation for the tool that is constructed in this study. This tool is built in order to generate a number of unique configurations that fulfill the design verifications. Using the tool, two analyses are performed. In analysis 1, the effect of different distances between the secondary beams is examined. In analysis 2, the effect of different grid sizes of the column in the frame structure is studied. In both analyses, two member sizes are first selected based on the criteria 'lowest cross-sectional area' (LCA) and 'lowest height beam' (LHB). These two member sizes form the starting point for generating different configurations of laterally loaded dowel-type connections. In this research project, three factors are found to contribute to the largest reduction in the number of unique configurations for all constructed cases examined in analysis 1 and 2. These three factors are small column widths combined with high shear forces, the effect of a 'compact' member, and the effect of 'brittle' failure mechanisms on the LCA-members, which was selected as a design constraint in this study. These factors may be relevant for engineers to take into account when designing the structural members. However, in this study, no constructed case is found in which the member needs to be redesigned in order to fit the connection. This means that one can conclude that the dimensional size of the structural member is dictated by the strength and stiffness requirements of the member itself. Important to note is that, although a large number of parameters was incorporated into this study, not all potentially relevant parameters were taken into account. When incorporating factors such as the horizontal forces in the connection, the effect of shrinkage and swelling, the level of difficultly in terms of assembling the joints on site, and adjustments to guarantee a certain level of fire resistance, certain turning points in the dimensional interaction between joints and members may be found. Finally, beyond allowing for the dimensional interaction between joints and members to be studied, the tool constructed in this study is also valuable to practical engineering. The large amount of data that is generated by the tool allows the engineer to explore the different possible configurations in the process of designing joints. By connecting the output of the tool to the Design Explorer interface, the engineer has the opportunity to search through all the individual characteristics or a specific range and examine different possible connections in an efficient manner. One of the main contributions of this research project, therefore, lies in the tool itself.

Currently, the building industry contributes to up to 50% of climate change. A way to reduce the impact is by replacing current building materials with more environmentally friendly materials, such as timber. Engineered wood products, such as cross-laminated timber (CLT) panels, have increased strength, stiffness, and stability which enables building higher buildings and floors with bigger spans. However, due to the low weight of timber, CLT floors are susceptible to unwanted high floor vibrations and therefore need to be verified on their footfall-induced vibration performance. Predicting the vibration performance is a complex problem as the load-bearing structure and architectural finishing have distinct structural behavior under small vibrations. Due to the novelty of the problem, the distinct behavior is not captured well in the current design codes. As a result, the Eurocode 5 guidelines on vibrations are currently being updated and extended. In support, this thesis addresses the critical issue of predicting the vibration performance of CLT floors, with a specific focus on the impact of architectural finishing. To achieve this goal, a literature review was conducted to identify structural components that are often overlooked, but may lead to inaccuracies in vibration predictions. These factors include the connections between CLT panels and different types of floor finishing. A case study was then carried out using the building HOUTlab, which features CLT floors with a concrete floating screed. On-site measurements were performed at key locations, including at the inter-panel connection line and in the middle of the panel. This was done before and after architectural finishing was placed. Subsequently, analytical and numerical calculations were used to gain insight into the structural behavior of the system subject to footfall-loading by investigating the accuracy of common engineering practices and other assumptions regarding their structural behavior. Onsite measurements, where the floor was loaded and the response was measured at the same location, showed that the root mean square velocity (vrms) values were much higher at the inter-panel connection line compared to in the middle of the panel. The vrms is a measure of the amplitude of the vibration. The initial finite element analysis (FEA), assuming a rigid inter-panel connection, inaccurately located the highest vrms values. When assuming a hinge, the FEA correctly allocated the critical vrms values but compromised the accuracy of frequency estimates. The experimental results revealed that adding architectural finishing increased the damping, reduced the vrms, and maintained a similar frequency, ultimately improving the vibration performance from level 3 to level 1 according to the preliminary Eurocode 5 (prEC5) standards. The prEC5 and FEA following common engineering practices accurately estimated the frequency before architectural finishing was placed but underestimated it by 39% after it was placed, indicating a higher increase in the bending stiffness of the floor than initially assumed. While prior calculations assumed slip between the floor layers due to the presence of the insulation layer, assuming full cooperation between the layers resulted in an overestimation of the frequency by 9%, suggesting that there is some cooperation, but the floors are not fully bonded...

To address the increasing housing demand in Europe and simultaneously tackle the challenge of creating a more sustainable construction industry, timber modular buildings present an innovative solution. However, before multi-storey modular buildings become a widespread practice, various engineering challenges need to be addressed. Ensuring robustness is one such challenge. This study focuses on the robustness of post-and-beam timber modular buildings, particularly through catenary action. The challenge with ensuring robust catenary action lies in designing connections with sufficient resistance and deformation capacity. This study proposes an optimisation process to determine the required mechanical properties of inter-module connections to enable robustness through catenary action. The principle of a catenary relies on the equilibrium between a vertical point load and the vertical component of the tie force in the deflected floor elements. Larger deflections result in a lower required tension resistance but demand a larger deformation capacity in the components. This study introduces a catenary equation to determine the required tensile resistance in a catenary at a specified elongation, creating a catenary requirement boundary. For a timber modular building to form robust catenary action, the axial force-elongation response in a catenary must meet this boundary. The catenary equation and the force-elongation response of the catenary form the basis of the connection optimisation, as the inter-module connection governs the response. To determine the optimised mechanical properties of an inter-module connection in a timber modular building, a case study was performed on a building consisting of twelve post-and-beam modules in width and five modules in height. To determine the effect of a change in the inter-module connection design on the force-elongation response of the buildings, quasi-static numerical analyses were conducted on 2D models, focussing on the frontal view frame of the building, and the floor plane. The load distribution through the floor system and corresponding deformation were added to the frame model by use of spring boundary constraints, after which the catenary could be examined. As a catenary can be formed by increasing the axial resistance, or its ductility, two optimisation methods were formulated, resulting in a high-strength inter-module connection and a ductile inter-module connection with a fuse. The optimisation process is based on iterations of the inter-module connection design. The resulting high-strength connection required a 143% increase in tension resistance, while the ductile connection relied on a 55% increase in resistance and a 550 mm fuse. This study underscores the complexity and critical importance of correct connection design to ensure structural robustness, emphasising the need for sufficient strength and deformation capacity. While the proposed methodology serves as a valuable tool for optimising connections in timber modular buildings, further research is recommended by including dynamic analyses in the optimisation process and experimental testing of inter-module connections to enhance the accuracy of the models.

Dynamic behaviour often is a topic of concern in the design of pedestrian bridges. It is time-consuming to assess and little is known about the way it is influenced by the characteristics of a bridge. In many cases, a bridge needs testing after is has been finished to determine the specifications of a damper. Striving to reduce the environmental impact of bridges, there lies a great potential in using materials with a low environmental impact, such as timber. This research combines the lack of knowledge about dynamic behaviour of footbridges with the need for using timber instead of other materials. It consists of two parts. The first part, the parameter study, investigates the influence of three preliminary design parameters on the dynamic behaviour of a long-span timber footbridge, namely the pylon height, the pylon shape and the amount of cables. The second part, the optimisation study, examines to what extent it is possible to design a long-span timber footbridge that does not need dampers to control excessive vibrations. To this end, a parametric model of a bridge was made in which parameters can be varied and optimised to create realistic design variants. To be able to optimise taking into account dynamic behaviour, a python script was written to automatically determine the type of modes. The results of the parameter study show that the dynamic behaviour can be influenced by the parameters, although the results depend on the specific model, dimensions, parameter values and damping value. The results of the second part show that a with a 14% increase in mass a design variant that does not need dampers to control excessive vibrations can be obtained.

This research looked into the influence of negative skin friction on timber piles in Amsterdam. Tensile load tests were performed on new, instrumented timber piles at Overamstel in Amsterdam. The negative skin friction calculated from the test data was compared to the negative skin friction from NEN 9997-1 for a single pile. The test results came close to the values from NEN 9997-1. A reduction of the factor required for timber piles when calculating negative skin friction using NEN 9997-1 seems necessary, but further studies are needed. Alpha factors were derived from the test data, and comparison to the alpha factors from compression load tests confirmed the influence of tapering on the timber piles. The research also confirmed the suitability of fibre optic sensors for pile load tests on timber piles.

The construction industry contributes significantly to global emissions. In response to the growing concern about climate change, new methods are being developed to reduce these emissions. Building with timber is one such approach, as it can be CO2 neutral if reforestation is practiced. Timber is a lightweight and flexible material compared to traditional construction materials like steel and concrete, which can result in high accelerations and deflections, negatively affecting user comfort. Engineered wood products such as CLT and GLT make it possible to construct larger panel sizes and spans, which can lead to more efficient building design. Many buildings utilize core systems to provide lateral stability and facilitate vertical transportation of goods and people. Therefore, replacing a conventional concrete core with a CLT core could be a viable solution to reduce the building’s environmental impact. Timber, being a flexible material, often lacks the necessary stability to meet user requirements for deflection and acceleration in high-rise buildings. An outrigger, similar to those used in concrete and steel structures, can provide the solution to enhance user comfort. The outrigger transfers bending moments from the core to the columns, reducing forces in the core and increasing overall stiffness. However it is unclear what the influence of the addition of a timber outrigger on a CLT core building is and how such a system can be improved. Therefore the purpose of this thesis is to evaluate the impact of a timber outrigger on a CLT core building, and provide guidance for structural engineers on how to improve the structural behaviour of such a system. The impact of adding an outrigger is evaluated through the comparison of different numerical case studies with and without timber outriggers. Additionally a sensitivity analysis is performed in which the influence of core joint design and the impact of outrigger design parameters is evaluated. By introducing a timber outrigger to a CLT core building bending moments are transferred from the core to the column, partially restricting rotation of the core. This will have the following effects on the behaviour of the structure. Firstly, the deflections due to lateral wind loading are reduced due to the increased global stiffness. Secondly, the increased stiffness of the structure will result in a reduction of peak lateral acceleration. Thirdly, by transferring loads from the core to the columns the strength requirements on the connections of the core are reduced. Finally, by introducing a timber outrigger system to a CLT core building horizontal forces are generated in the core at outrigger level, which should be accounted for in the design phase of the vertical core joints. Increasing the stiffness of the outrigger will further reduce deflections, peak lateral acceleration and strength requirements on the core joint, however strength requirements on the vertical core joints at outrigger level will further increase. An exponential relationship has been derived between the lateral deflections and the ratio between the effective bending stiffness of the outrigger and the effective bending stiffness of the core, a similar exponential relationship has been derived for the peak lateral accelerations Additionally it was investigated what the critical design parameters are and how the performance of a CLT core building with timber outriggers can be improved. For the design of a CLT core the connection between the core and foundation showed to be critical, having large effects on the lateral deformation. While increasing the stiffness of the vertical connections showed to have little influence on the interaction between core walls due to their respective high interaction factors. In the design of the outrigger it was shown that a two storey outrigger is able to more than double the reduction in deflections compared to a single storey outrigger, further increasing the overall effectiveness of the system. Finally the effectiveness of the system was found to be significantly influenced by the configuration of the outrigger truss, demonstrating a greater impact than increasing member size or connection stiffness.