Timber pile foundation piles are important structural components of historic buildings and constructions throughout the Netherlands. Many of these piles have been in service for a long time and start showing serious signs of biological degradation that affects their load-bearing capacity. It is essential to preserve these aged timber piles and, in order to make an estimate of the remaining functionality, it is essential to compute their wet mechanical properties. The conventional method for determining the wet compressive strength is by performing large-scale compression tests on segments from the pile. In this project it is researched whether it is also possible to determine the wet compressive strength by performing small-scale compression tests on discs taken from the pile, which could possibly save both time and resources during future investigations.

For this experimental study a total of 6 spruce foundation piles were selected that originated from 1727, 1886, 1922 and 2019. These piles brought forth 45 round wooden discs with each a height of 15 centimeters extracted from the pile head, middle and tip. The discs contained different amounts of bacterial degradation and high concentrations of knots in order to investigate their effects on the strength. The degradation was quantified using micro-drill measurements and the presence of the knots was specified as a knot ratio. From the results of the small-scale compression tests on the discs it can be concluded that the strength of the discs is well correlated with the strength from the large-scale tests. It was observed that the degraded wood hardly contributes to the strength of the pile and that the section with the highest knot ratio governs the strength of the pile. All in all, it was found possible to obtain accurate values for the wet compressive strength of aged timber piles by performing small-scale tests on discs from the piles, as long as the effects of the biological degradation and the knots are taken into account.

The increasing demand for sustainable and high-rise buildings has led to the development of hybrid concrete-timber structures. These buildings incorporate a concrete core and columns for stability, combined with timber and concrete floor systems, providing an opportunity to balance sustainability, structural efficiency, and cost-effectiveness. While this approach presents opportunities, it also introduces several challenges related to structural dynamics, fire safety, environmental impact, and construction costs.

A key issue in concrete-timber hybrid buildings is their lower weight due to timber floors that are lighter than concrete floors, which makes them more susceptible to wind-induced vibrations. Additionally, the irregular mass distribution caused by alternating timber and concrete floors over the height of the building influences the dynamic response of the building. From an environmental perspective, timber is often regarded as a sustainable material due to its carbon storage capability. However, the extent to which hybrid systems reduce overall carbon emissions compared to concrete buildings remains uncertain. Furthermore, construction costs are closely tied to structural and environmental performance, impacting the feasibility of such buildings.

Despite growing interest in hybrid concrete-timber high-rises, existing research lacks an integrated approach that examines the relationships between dynamic behavior, environmental impact, and construction cost. Although individual aspects have been studied, the correlation between these design factors remains unclear. Additionally, the influence of parameters such as building height, floor type, and concrete-timber distribution on these design aspects has not been extensively explored.

This research aims to support the integral design of hybrid concrete-timber high-rises by offering a structured approach to evaluating key design choices and their implications. The findings contribute to a more holistic approach to hybrid building design, supporting designers, policymakers, and researchers in optimizing hybrid systems.

This thesis explores the influence of key building parameters on the design aspects of tall concrete-timber buildings during the early design phase. The goal is to identify relationships between dynamic behavior, environmental performance, and building cost by analyzing various building variants. The studied parameters include building height, floor plan, floor type, and the percentage of concrete floors. To achieve this, three hypotheses are formulated that connect the design aspects with the percentage of concrete floors. By analyzing different percentage of concrete in the floor systems, the study aims to provide insights into the complex interactions between these aspects.

The methodology consists of three parts. First, building variants are designed based on predefined parameters, using structural calculations for floor systems, concrete cores, and foundations. Second, models are developed to determine the dependent variables: dynamic behavior (first natural frequency), environmental performance (Environmental Cost Index through Life Cycle Assessment), and construction cost. Based on the results of the models relationships between independent and dependent variables are analyzed to identify trends and interactions. Finally, correlations between the three design aspects are examined to provide insights into their interdependencies.

The results indicate that building height is the most significant factor influencing dynamic behavior, environmental performance, and construction cost. This is evident from the distinct scatter plots for each building height. The ECI value for buildings between 70 and 90m ranges from 12 to 28 €/m², while for buildings of 110m, it ranges from 20 to 33 €/m². Construction costs for buildings between 70 and 90m range from 735 to 875 €/m², and between 850 and 1000 €/m² for buildings of 110m. By analyzing the results, no significant correlation between construction cost and other parameters was found, as the effect ranges of the parameters are similar. Moreover, the dynamic behavior of the buildings remains within safe limits. Additionally, variations in foundation piles and core dimensions significantly impact the environmental cost index (ECI) and construction cost, making their inclusion essential for accurate comparisons. Finally, the model effectively analyzes specific parameters, thereby providing clear insights into their influence on design aspects.

The construction sector aims to reduce its environmental footprint to address climate change and material depletion, with an increasing focus on reducing embodied carbon. Simultaneously, there is a growing demand for affordable housing in the Netherlands. A significant part of the new housing stock needs to be mid-rise residential, efficient in both material and land use. Bio-based materials, such as timber, which are renewable and have relatively low carbon emissions, could play a key role in reducing embodied carbon for these types of buildings. Since structural systems often account for the majority of a building’s embodied carbon, using timber here can offer significant advantages. However, its application in practice remains relatively uncommon in the Netherlands.

Although existing research highlights the potential of timber in structural systems, challenges such as limited knowledge, lack of incentive and financial barriers are often cited as key reasons for its limited adoption. This research aims to address these challenges by exploring and quantifying to what extent a shift toward timber-based structural systems can reduce the environmental footprint of mid-rise residential buildings in the Netherlands, while maintaining economic feasibility. By doing so, this research aims to offer practical insights into the use of timber in construction, addressing knowledge gaps and identifying the conditions for its application in practice.

A comprehensive literature review was conducted on environmental regulations, assessment methods, structural systems, and suitable compositions of structural elements using timber. The insights gathered were applied to a case study, where various redesigns were developed and optimised under different boundary conditions. The environmental impact was quantified by a life cycle assessment using the Paris Proof Indicator (PPI, measured in GWP-GHG). Simultaneously, economic feasibility was quantified by an evaluation of construction costs. The scope of the assessments is limited to the life cycle stages from cradle to practical completion, emphasising the importance of direct impact.

As a result of the assessment of the case-study redesigns, several building concepts provided significant reductions in environmental footprint while being economically feasible. Compared to the original design, hybrid redesign concepts with calcium silicate brick walls and CLT-concrete composite floors can achieve PPI reductions up to 42% while being of equal or lower costs. Concepts with CLT walls and hollow core timber floors can even lead to reductions of PPI up to 55%. Within a 10% increase in costs, a wider range of concepts can lead to similar PPI reductions. All concepts with both CLT walls and CLT floors proved to be economically unfeasible within the stated cost thresholds.

The associated PPI values were found within the range of 82 and 114 kg CO2-eq./m², depending on the building concept. Accounting for design variations between mid-rise residential buildings, research uncertainties, and potential design optimisations, the building concepts researched could align with the Paris Agreement targets up to 2035. As the targets for 2050 are roughly twice as strict, it is unlikely that these are achievable within the researched design strategies. Incorporating reused or recycled materials and/or accounting for the benefits of temporary carbon storage in bio-based materials will likely be necessary to achieve these targets.

A large share of the buildings today is still masonry buildings, both reinforced and unreinforced. Post-earthquake reconnaissance studies have shown a remarkable difference between the performance of reinforced and unreinforced masonry buildings. While the unreinforced masonry buildings tend to suffer severe damage, even collapse, resulting in loss of innumerable and invaluable life; reinforced masonry buildings have often been reported to perform remarkably well under seismic events. Sometimes, this performance has exceeded performance of engineered buildings as well.

Himalayas are a highly seismic region in South Asia with multiple major earthquakes recorded across the past two centuries. The remoteness of the region and abundant availability of local materials along with frequent earthquakes has resulted in the development of a seismic culture of earthquake-resistant, timber-reinforced masonry buildings. Though these buildings have shown superior performance under seismic actions, little scientific research has been done to understand and analyse the reason behind this superior performance.

Across the different regions of Himalayas, timber has been used in different structural configurations to increase the seismic resistance of the masonry structures. These traditional building systems remain popular in the Himalayan region for their cheap and easy availability locally. This additional graduation project is a step towards understanding the behaviour of these masonry structures, and the role of timber in preventing catastrophic failure in the former.

In this study, different building typologies in the Himalayas that use timber as a structural element are identified and described. Failure mechanisms of masonry structures are widely studied and a brief overview is presented. In-plane, out-of-plane, combined in-plane and out-of-plane and local failure mechanisms of unreinforced masonry are discussed in detail. Furthermore, a literature review of post-earthquake reconnaissance surveys is conducted to understand different mechanisms through which masonry structures fail.

A review of state-of-the-art on experimental, analytical and numerical studies conducted on resistance of some of the building typologies of Himalayan region (for example, Bhatar, Dhajji Dewari, Ikra, Kath Kuni) is done in this study to understand work done previously. Finally, an analytical analysis is conducted on single room, one-storeyed Bhatar building to investigate the response of an in-plane wall to a lateral load exerted by earthquake excitation.

The buildings construction industry is demanded to reduce its ecological footprint to mitigate its contribution to climate change. In this context, a novel sustainable design strategy for the reuse of timber was developed in this Master thesis. The design strategy focuses on the utilization of the material “reclaimed timber” (RT) in the structural system “reciprocal frame” (RF). RT is timber which is harvested from the load bearing structure of dismantled buildings. Large quantities of RT are currently fixed in the building stock. RFs are a family of structures that boast with a rich variety of forms and diverse functions. The utilization of RT in RFs is favorable because RT items which are relatively short can span distances longer than their length when combined with RFs.

To inform the development of the design strategy a literature review on both RT and RFs was conducted. These theoretical studies were supplemented with more practical methods of investigation: RT was inspected first-hand during a visit of a salvage yard that stores RT. Throughout the project physical modeling was used as tool to explore and illustrate the characteristics of RFs. Moreover, during a three-day workshop in which a RF canopy structure from RT was built, important design aspects of RFs were investigated. This first part of the research concluded with describing the state-of-the art of the structural utilization of RT and providing a comprehensive overview of the structural design with RFs.

Key findings of the theoretical and practical studies on both RT and RFs were that the limited stock of available RT items and the geometric complexity of RFs are the two major problems when designing a RF with RT. To solve the two problems a novel RT database configuration that archives the properties of specific RT items was developed. This RT database was applied in conjunction with a novel bottom-up geometry generation model for Rainbow RFs. The Rainbow RF was identified as advantageous for the combination with RT. It can be used to generate expressive spatial assemblies with a relatively low geometric complexity and a high degree of regularity. From a structural perspective the Rainbow RF has the benefit of efficiently transferring axial forces, which reduces the bending action that is typical for RF. Moreover, it achieves flexural rigidity without using expensive moment resistant joints.

The key findings were integrated to form a preliminary design strategy. In a case study the preliminary strategy was used to design a RT RF for a railway station canopy that spans an area of 14.0 m x 27.0 m. The RT stock of the case study was defined by a database that is comprised of 30 stacks of RT items. Based on the material stock 118 geometric design proposals were generated using the bottom-up model. Three of the proposals were developed into safe structural designs. The three safe structural designs demonstrate that the RT items compensate their low strength grade with their relatively large cross-sections.

Based on a discussion of the case study’s design process, a complete design strategy for the structural utilization of RT in RF structures is derived. In the first design phase the shape of the building and the flow of forces through the structure are established. The material stock is defined using the novel RT database configuration. For each RT stack multiple geometric design proposals are developed with the bottom-up model in design phase 3. The bottom-up model is set up in “Grasshopper 3D” and “Python”. For the fourth phase, a versatile algorithm is programmed that automates the structural design to a large degree. This enables to assess many geometric design proposals with considerable accuracy in a short time. The Structural Design concludes with a complete design of the RF structure. The structural design algorithm is also programmed in Grasshopper 3D and Python, the plug-in “Karamba3D” is used for finite-element analyses. The Detail Design rounds the design strategy off by detailing the structure’s joints.

Timber usage in construction works has increased over the past years due to its better environmental performance. Applying timber elements instead of steel or concrete decreases the emissions impact of the built environment. Architect firm ZJA and Iv-consult are interested in investigating a timber railway bridge as part of the Norwegian infrastructure plan. A kilometre-long double-track railway bridge with 50 m spans is used as a case study to investigate the possibilities of timber application. The objective is to design and assess a timber beam bridge with steel sections at the support.

The aim of this research is to design the sections and their connection. The design requirements and calculation methods used are based upon the Eurocodes. The design is considered to be part of the preliminary design phase of a project. Unity checks of the cross-section and deflection are calculated by use of linear mechanics. An FE model with beam elements is created to determine the force distribution of the bridge and calculate deflection. The strength and stiffness of the connection are calculated using empirical and plastic mechanic methods given in the standards. The resulting stiffness is used in the model to determine the final deflection when accounting for the semi-rigid joint.

The design consists of timber and steel box girders that only carry a single track. On top of the support, a slender stiffened steel box girder of 10 m length is situated, 5 m to both sides. Between the steel sections, there are timber box girder sections of 40 m that have very thick flanges and webs. On top of the structure lies a slab track that is only considered as weight. A dowel-type connection is used with double slotted-in steel plates in all flanges and webs of the timber section. The slotted-in plates have a slightly smaller width than the timber elements and have a depth of around 2.7 m. The steel fasteners are simple dowels.

This thesis has found that a timber and steel beam bridge with box girder cross-sections is governed by the creep deflection, shear strength of the timber, fatigue strength of the steel, and the dimensional stability of the connection. Except for the last issue, each of these limits can be satisfied by increasing the dimensions of each cross-section. Dimensional stability is the timber size change due to moisture content variation. The perpendicular-to-grain stresses become too large due to the configuration of the steel in the connection. The use of modified timber, which decreases the dimensional stability effect drastically, is only suggested as a solution.

An architecturally pleasing structure is designed by adding very limited visual elements but mainly practical and structural elements that have two functions, shown in the figure below. The desired continuity and bridge rhythm is accomplished via a line concept. The abrupt material cross-section changes are partly covered by continuous timber elements. From the practical and architectural adjustments, new cross-section dimensions were determined. The governing unity checks of the new design were calculated and showed the possibility of the design under the assumption the connection shrinkage issue is resolved.

Thus a timber and steel railway bridge has potential. It should be stressed that methods and factors from the Eurocodes are assumed to be applicable to the large timber box girder sections. This assumption is recommended to be checked by means of experimental research on large timber specimens. Additional research on the semi-rigid is advised, as introducing slotted-in steel plates in the web and flange plane can significantly improve the moment capacity.

Finally, two alternative suggestions are given to avoid solving the dimensional stability issue. The first is to design a bridge with lower loading demands, like a road bridge. Secondly, the bridge can be made of only timber sections. Alternating spans would have two hinged connections to form a continuous cantilevered bridge. While the first alternative creates easier circumstances to solve for dimensional stability, the second alternative completely removes the issue by having a connection with lower demands. It is recommended to incorporate connections early on in timber design.

The demand to build with wood and other bio-based materials has increased rapidly the last decade, due to the ambition to build more with sustainable building materials. One of the major challenges in building with wood, is to account for the lower strength and stiffness perpendicular to the grain. Wood is an anisotropic material, meaning the material has different properties in different directions. Loading in the perpendicular to the grain direction is sometimes unavoidable and fracture often occurs in a brittle manner. Unfortunately, our understanding and knowledge of the perpendicular to the grain fracture is limited. This is especially the case for hardwoods, for which the material properties and the parameters important for the fracture process are often unknown.

The goal of this thesis is to reduce this knowledge gap on the material properties and the relevant parameters in mode-I (pure tension) fracture process of (tropical) hardwood. The knowledge gained in this research provides the answer to the main research question of this thesis: Which parameters should be considered when describing the constitutive model of a (tropical) hardwood in mode-I tension?

A single-end notch three-point bending (SEN-TPB) test demonstrated a strong influence of the orientation of the growth rings on the perpendicular to the grain fracture process of azobé. The value for the peak load and post-peak behaviour change significantly depending on the orientation in which the sample is placed. Furthermore, visual observations and results from a profilometer revealed that there is an inconsistency in the roughness of the cracked surface area between the different series. From the microscopic analysis is concluded that this inconsistency in general mechanical behaviour and the roughness of the cracked surface area is linked to the composition of ray and parenchyma cells. Moreover, the direction of the ray and parenchyma cells with respect to the fracture plane is different depending on the orientation of the sample. When the ray cells are orientated perpendicular to the crack plane, a higher strength is obtained. The thin-walled parenchyma cells significantly reduce the post-elastic stiffness if these cells are orientated perpendicular to the crack plane. The influence of the composition and orientation of both cells is reflected in the numerical value for the modulus of elasticity, the tensile strength and the fracture energy. This research showed that the composition of the cells in a wood specie and the orientation in which the growth rings are placed significantly influence the mode-I fracture process of a hardwood. This influence is reflected in the modulus of elasticity, the tensile strength, the fracture energy and the shape of the tension softening curve perpendicular to the grain. The results of this research provide new insight into the fracture modelling of hardwood. Both in numerical modelling and design considerations the variation in the material properties because of the orientation of the growth rings, should not be neglected.

The gas production in the Groningen gas field of the Netherlands has caused a significant amount of shallowhuman induced earthquakes. Among various building typologies, Groningen is home to many Dutch historical churches constructed by unreinforced masonry which has shown to be highly vulnerable to these earthquakes. From the perspective of conservation and prevention of loss of our historical and cultural heritage, the structural assessment of these churches and their monitoring is of importance. The assessment of the seismic performance of historic churches is a challenging task because of their unique design, governed by macro element behaviour and nonlinear material behaviour. An accurate and reliable earthquake resistant assessment with appropriate numerical modelling of the structure and proper assumptions of all the uncertainties is crucial. The structural monitoring cannot be applied to all historical churches. By selecting representative case studies, indepth study regarding both numerical modelling and structural monitoring are possible. This information can then serve engineers and professionals to evaluate similar structures. The research gap lies in accurate modelling of historical churches to achieve reliable and faster results by linear dynamic modelling. The fundamental modes, eigenfrequencies and modal shapes, geometry and material properties, boundary conditions, connections between structural elements and loading variations are studied using 3D models with shell elements of the casestudy. Although, the models described cannot closely represent the real structure. Firstly, a regular thickness has been assigned to masonry walls and piers despite their irregularities. Secondly, the material properties have been estimated from similar structures in Groningen, and may not represent the actual material characteristics of this case study. Thirdly, the cavity ties has been disregarded because they have been assumed to be corroded (no actual information was available). Finally, the concrete slab at the entrance of the church is disconnected to the foundation, which was an approximation from the drawings but could not be verified. For the casestudy prior structural retrofitting (models 15); Numerical Model 3 with eliminated foundation and timber flooring and a rigid base at the ground level is expected to give the best approximation of dynamic response of the church. The fundamental frequency in X direction of the casestudy prior structural retrofitting can be approximated between 2.30Hz to 2.75Hz and the fundamental frequency in Y direction between 3.0Hz to 3.45Hz. The fundamental global modes in this model show maximum deformation in the timber roof of the mainstructure and tip of the belltower in globalnd Y directions. This indicates weakness of the casestudy prior structural retrofitting. The Old Church has undergone structural retrofitting in July 2018, to prevent further seismic damage on the structure. From the survey of the casestudy and the retrofitting measures, the recent findings (eg., cavity walls, installation of steel frame, steel and timber columns) are incorporated into the finite element model of the casestudy and various modelling variations are presented in models 6 to 10. From comparing the results of these models post structural modifications, Numerical Model8 (or Model9 which has almost similar results) with degraded material properties of masonry and timber diaphragms, a shallow masonry step foundation and a rigid base at the foundation level are predicted as the closest approximation of the dynamic properties of the church. The fundamental frequency of the casestudy post structural retrofitting can be predicted to lie between 1.5Hz2.6Hz in global X direction and between 1.1Hz1.65 Hz in global Y direction. It can be observed that the implemented measures make the church stiffer and the weakness of the structure post structural retrofitting is localised at masonry facade walls of the belltower, cavity wall between the belltower and mainstructure, tip of the belltower, lateral walls and timber roofing of the mainstructure. This research on simulating a numerical model that closely represents the dynamic properties of the Old Church in Garrelsweer for achieving reliable, computationally effective and faster results. This can be used as a basis to compare the results of ambient vibration testing and operational modal analysis, and a relevant guide to study how the numerical models can be defined for modelling similar structures.

The infrastructure industry currently deals with two issues: the deterioration of (highway) bridges, and the urge to reduce emissions by the construction sector. Rijkswaterstaat must repair or replace hundreds of bridges in the upcoming decades. At the same time, the impact of human behaviour on climate change becomes more visible and must be reduced. The most structural solution to diminish the human impact on the environment is switching from a linear economy to a circular economy (CE).
This research aims to develop a system for circular highway bridges by both constructing with timber and extending the lifespan. The first contributes to a lower environmental impact as timber is a renewable material that captures carbon during growth. For an outdoor timber structure, protection is crucial to prevent the timber from deteriorating due to weather influences. The lifespan extension is obtained by applying three circular principles: (1) Design for Material Efficiency (DfME), (2) Design for Adaptability (DfA), and
(3) Design for Disassembly (DfD). Variant studies on typology, connections and material optimise for material efficiency. A flexible structure enables DfA: converting in function and expansion in length and width is possible. Furthermore, a modular system is developed to include DfD: connections between modules are demountable to disassemble, adapt and reuse the system. In summary, four design strategies are defined: efficient, protected, adaptable and demountable.
This research aims to provide an alternative for concrete highway bridges with a lower environmental impact.The timber bridge, a circular concrete bridge and a traditional concrete bridge are compared. The comparison includes the production (A1‐A3), construction (A4‐A5) and end of life (C1‐C4) stages. Timber results in a lower carbon footprint for all reference periods and lifespans. The study considers the third scenario most reliable, as the technical lifespans are most substantiated. In this scenario, reductions of 18% and 47% for respectively the circular and traditional concrete bridge are established.
This study concludes that Dutch highway bridges suit replacement with a modular timber alternative. The developed modular system covers 58% of the highway bridges stock owned by Rijkswaterstaat that were built in 1950‐1980. Moreover, timber shows substantial environmental benefits compared to concrete. The alternative reduces the carbon footprint by 47% compared to a traditional concrete bridge. Furthermore, this study observes additional benefits when one considers carbon emissions in time, as the structure
sequestrates carbon during use. Consequently, building with timber lowers the carbon concentration in the atmosphere, reducing the global warming effect. This study recommends Rijkswaterstaat to invest in the development of circular timber highway bridges. By changing the ’business as usual’ from concrete to a more sustainable alternative, the circular and climate goals can be obtained. Furthermore, the recommendation is made to clarify the regulations on quantification of environmental impact, both on data and methodology level.