The lack of insight regarding the stability of many dolmen in the Netherlands is problematic. In 2019, a capstone fell down dolmen D14, greatly damaging this cultural heritage. In order to decide on whether it would be wise to reconstruct this dolmen, it is useful to understand the stability of potential reconstruction scenarios without having to perform invasive tests that could damage the structure. To this end, this research has focused on the application of non-destructive, digital methods to analyze the stability of dolmen D14. Laser scanners were used to obtain point cloud data from the zone around the dislocated capstone, with which 3D meshes were created. Furthermore, tests were conducted to estimate the relevant parameters to quantify the shear strength of the rock contact areas. This was done in the field using the Equotip and Barton’s comb and by performing tilt tests and Golder shear box tests in the laboratory. For the rock parameters, a basic friction angle of 33° was found with tilt tests and a residual friction angle of 31.2° and 30.5° was found for the Golder shear box on a flat sample. The meshes and rock parameters were used as input to conduct stability analyses in 3DEC. Two different models were analyzed, one based on the rock configuration as it was in 2019 (Model 1) and the second model with a rock configuration as it was in 1925 (Model 2). In the stability analysis, it was found that Model 1 is much more unstable compared to Model 2. The minimum pushing force for instability of the structure was 2 kN for Model 1 and 94 kN for Model 2, for the conditions under research. Furthermore, it was found that the number of cycles used in the analysis, mesh coarseness and rock joint friction angle all have a significant impact on the model results. All in all, this research has demonstrated the potential for using digital and non-destructive methods to analyze the stability of megalithic structures.

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.

This research is about which geometry of FRP slabs is the most optimal, in terms of costs, to use for a given load and boundary conditions taking the occurring uplift bolt forces into account. The first part of the report focuses on the calculation of the uplift forces in the bolted connections caused by the moving loads. For this, first a detailed numerical model is made in Abaqus. Based on this most detailed numerical model, different simplifications are made to make the calculations easier and less time-consuming. Numerical models with linear bolts instead of non-linear bolts and with load superposition using a one-wheel load instead of a complete vehicle are considered. Next to this, equivalent material properties are calculated to make a model with an orthotropic deck plate instead of modeled geometry of skins and webs. For the numerical model with this orthotropic deck, the same simplifications are applied. Next to the numerical models, different analytical beam and plate models are considered. All different numerical and analytical models made, are compared on possibilities, calculation and modeling time and accuracy. Based on the comparison between the models and the capacity of the connections, it is concluded that the uplift design of the bolted connections does not need to be taken into account in the optimization of the slabs. The second part of the graduation work is about the optimization of the FRP slabs considering the global behavior of the deck, for which a genetic algorithm is used to detect the most optimal geometry. The most important parameters for the design are the height of the deck, the spacing of the webs and the layup of the topskin, bottomskin and webs. The layup of the different elements is dependent on the number of plies, the ply orientation and the overlapping length. During the optimization process, design and initial (global) strength, stability and stiffness checks are performed. First, optimization is done for the same deck that is considered in part one of the research. Next to this case, different cases for the distance between the supports are considered for which standardization is done with respect to engineering and production of the slabs. Based on the performed research it is concluded that the uplift bolt forces are in a range of 0.5 to 21.5 kN. Simplifications can be done by the use of an orthotropic deck with equivalent material properties. The maximum difference using this simplification is 2.9 kN, while the calculation time needed is reduced by a factor of 4-5. Other simplifications that can be done are the use of linear bolts and/or load superposition. Using linear bolts gives a maximum difference of 0.5 kN and load superposition a maximum difference of 0.3 kN, both without an improvement of the calculation time. The optimal geometry for different boundary conditions is given as a standard design with a variable number of plies for the topskin and a variable height based on intervals for the distance between the supports.

The extraction of natural gas in the northern part of the Netherlands, from the region of Groningen, has been causing human-induced seismic activities for the past several decades. This is a problem since the existing building stock in this region, which consists of mainly unreinforced masonry buildings and historical structures, are not designed to withstand seismic events due to the lack of empirical earthquake-resistant design features. Further, the combination of a soft topsoil and the gas extraction, is responsible for ground settlements which may compromise the capacity of the existing buildings. The bed-joint reinforcement technique is a strengthening method which consists of cutting a slot in the bed-joints and installing steel bars embedded in a high-strength repair mortar. Although this strengthening method is commonly applied in the Netherlands to counteract settlement damage, limited investigations on the performance against seismic loading are available in the literature. Therefore, an experimental campaign (Licciardello et al., 2021) was conducted at Delft University of Technology in which a quasi-static cyclic in-plane test on a full scale wall was performed to characterize the performance of the bed-joint reinforcement technique. The wall featured artificially introduced cracks (pre-damage), achieved by the inclusion of plastic sheets between bricks and mortar, to account for the settlement-induced damage. Compared to the un-strengthened walls, tested in a previous experimental campaign (Korswagen et al., 2019) under similar conditions, it is observed that the bed-joint reinforcement technique can provide a significant increment in terms of displacement capacity and ductility of the wall but not in terms of the force capacity. In this thesis, numerical simulations of both un-strengthened and strengthened walls from the experiments were performed using 2D-models and the nonlinear static analyses (monotonic and cyclic) were carried out in the finite element software DIANA. The objective of this research was to compare different numerical modeling approaches and material models to find the best suited one for simulating the in-plane seismic response of both un-strengthened and strengthened masonry walls. Moreover, the objective was also to extrapolate the experimental results to other wall configurations, which are not experimentally tested, to investigate the combined effect of the bed-joint reinforcement technique and the change in size and location of the window opening on the in-plane response of the wall (parametric study). In the scope of this thesis, three numerical modeling approaches were investigated (Figure i). The bricks and mortar joints are modeled as one homogeneous continuum in the macro-model. On the other hand, the bricks and mortar joints are modeled separately for the continuous and detailed micro-model where interface elements are included at the brick-mortar bonds for the latter one. The discrete (simplified) micro-model was not investigated because the reinforcement bars cannot be connected to the mortar joints since they are substituted by zero-thickness interface elements. Moreover, the Discrete modeling approach of the reinforcement was used in order to simulate the pull out behavior of the bars. Cracks were modeled using the discrete cracking approach and the smeared cracking approach where the former one was used at the brick-mortar interfaces and the latter one was used for cracking in the mortar joints (micro-models) and in the masonry composite (macro-model)…

Climate change is changing the world. Where previously efficient use of materials was mainly applied to realize cost savings, this can also help to reduce the footprint of a construction. There is a rather direct and obvious relationship between the amount of material required in a construction and its environmental impact. Of course, the environmental impact is not solely dependent on this metric, but minimizing the weight of the structure is a great starting point. This thesis focusses on minimizing the environmental impact of a welded truss bridge. In addition to the required volume of construction material, the environmental costs for the welding and conservation are also taken into account. A case study is performed on a bicycle bridge crossing a highway that is built in the Netherlands. The thesis starts with a review of multiple methods that minimize the weight of a structure. Within the field of structural optimization, The Ground Structure Method (GSM) appears to be the most suitable method for large structures that consist of slender structural elements. Making utterly high refinements in the GSM-model will result in a structure with definitely the lowest volume possible. However, this structure will have lots of smaller and shorter elements that will require in total more welding and conservation. This will not lead to a least-environmental-impacting structure. Thus the main question arises: Will, within the ground structure method, minimizing on the environmental impact result in a significantly different structure than a minimization on weight? The objective function for the environmental impact consists of the three considered contributing factors: the construction material, welding and the conservation. The environmental impact for the three factors is determined with a Life Cycle Assessment (LCA). Finally, every contributing factor is unified into a single indicator value through the Environmental Cost Indicator (ECI) method. The objective function also consists of three variables which represent: the volume of construction material, the welding volume and the surface of the structure. The volume is already known, since it is the regular GSM minimization. The welding volume can be determined through the joint-cost method, which is adding an artificial length to each member. The surface area of the structure is harder to determine. The relation of the volume of a construction element and its surface area is generally speaking non-linear. Multiple implementations were investigated. The aim is to perform the optimization on a fully connected ground structure, and so the assumption is made to make the relation between the volume and surface area linear. A circular hollow cross section with a variable radius and a constant wall thickness is implemented into the optimization method. The final objective function to minimize the ECI costs is a mixed-integer linear programming problem (MILP). This method is tested on the established benchmark for a cantilever structure and on a case study for a bicycle bridge. The shape of the optimal structure is dependent on the amount of nodes within the design domain. The results for the cantilever structure does clearly reflect this. Depending on the amount of nodes in the design domain, the minimization of the environmental impact is decreased between 0 and 37%, while the weight is at most 2.5% higher. The difference of the environmental impact between the least-weight and least-environmental-impacting structure keeps increasing as the node density increases. The bicycle bridge is optimized in a 2D and 3D design domain. The design domain of the bicycle bridge appeared to be too big to be solved by the MILP formulation optimization, thus the domain is reduced to a single span of the bridge. Furthermore, the amount of nodes in the design domain is limited to improve the computability of the problem. In both the 2D and 3D variant the regular minimization on weight requires only a fraction of the time to solve the problem successfully. For the 2D case there is a difference between the minimization of the weight and ECI. The number of members in the least-environmental-impacting structure is reduced by 40%, which results in a 1% lower environmental impact. The MILP could not converge properly in 4 hours in the 3D design domain. This is mainly because the model size did increase a lot compared to the 2D design domain. Going from 2D to 3D adds a third axis, which increases the amount of constraints by 50%. Likewise, the number of nodes in a 3D domain increase more rapidly than in a 2D domain. All in all, the method is implemented successfully and validated with the cantilever structure. The proposed method will result in a structure with an equal or lower environmental impact compared to the regular least-weight minimization. However the minimization of the environmental cost with the proposed optimization method is able to solve problems with around 5,000 variables. To solve larger models successfully it is advised to either reduce the connectivity of the ground structure or to apply the joint-cost method with an LP.

With the advent of Computer-Aided Design, the design and fabrication of complex free-form shells have become easier to achieve. However, this results in extensive usage of custom-made formworks for the production of shell components and falseworks which provide support for the shell during the construction process. Therefore, a modular design method is proposed for generating form-active spatial structures out of stackable blocks of a few types, having in mind its potential applications such as housing. Instead of shells, spatial masonry structures are thus the main consideration in the design process considering building on top of a vaulted ceiling. By designing a 3D interlocking grid and introducing a four-step topological design that is coupled with structural verification processes based on finite element modelling and discrete element modelling simulations, the geometry of interlocking stackable modular blocks can be automatically generated for constructing such spatial masonry structures. The proposed method ensures that the designed vaults are modular, reconfigurable, and self-supporting during construction, thus increasing the efficiency of mass production while allowing for combinatorial mass customization in designs.

Structural health monitoring of buildings is useful for a few reasons. It provides information on the usage and cause of damage to a building. This can result in targeted maintenance or allow for potential improvements. Traditionally, a building can be monitored by installing sensors during construction or maintenance work. These can be strain gauges, inertial measurement units or surveying equipment. However, not all buildings have such sensors installed due to lack of space or the cost of the equipment. To overcome this, a spaceborne technique shows potential, namely multi-temporal interferometric synthetic aperture radar (MT-InSAR). This technique has already been applied to monitor damage to sections of buildings or large structures, for instance facades or deformations of bridges. In the context of entire buildings, the result of an MT-InSAR analysis has not yet been paired with a computational model. This is mainly due to the relatively small scale of a building and low spatial density of the displacement data. This thesis integrates remote sensing data, acquiring displacements due to mining, with a computational structural finite element model of a church structure. The displacements have been interpolated using MT-InSAR data, which contains projections of nonlinear displacements in vertical and West-East directions. The interpolation has been performed using two techniques. The first is Ordinary Kriging, which is used to obtain a general insight into the deformations and the shape of the deformed region near the church. The second uses the least squares method to fit polynomial shape functions. The resulting displacements of the least squares analysis have been integrated into a nonlinear structural finite element model. The structural model consists of a soil-structure interaction model and nonlinear material properties, and is used to assess crack propagation. Integrating remote sensing with computational modelling, shows potential in providing a monitoring technique for buildings. The interpolation method can be used to obtain displacements at a building, even when the spatial density of the InSAR analysis is limited. The main limitation is the information on the horizontal displacements obtained by the InSAR technique, where the displacement along the North-South is unknown. Furthermore, the structure and integration can then be performed using a finite element model, which can follow crack propagation and account for soil-structure interaction.

Concrete half-joints are a specific support detail in reinforced concrete structures, which reduce the construction height of the total structure. The use of concrete half-joints became popular around 1950s, but decreased its interest as a result of new insights on structural behaviour and collapses of these structures. Typical issues regarding concrete half-joints are either due to inadequate reinforcement detailing or due to deterioration mechanisms. The most critical deterioration is when a crack at the re-entrant corner allows for water ingress and thus corrosion of the rebars. This thesis focuses on the negative influence of this corrosion on the load bearing capacity and proposes an assessment method, which includes the reinforcement detailing. Firstly, problematic half-joints have been categorised and studied for reinforcement detailing. Subsequently, they have been analysed using an analytical tool, in which corrosion was implemented on the rebars. The outcomes were validated numerically. For this thesis research, a series of Dutch concrete bridges has been studied to identify general reinforcement issues and categorise concrete half-joints. It has been observed that the majority showed short transfer- and/or anchorage lengths of the rebars and that all of them showed no shear stirrups as hanger-reinforcement. In stead, only a horizontal- and hanger rebar are present, which can be accompanied with a diagonal rebar, prestressing at the top or nib (or combinations in between). An analytical tool is designed to calculate the load bearing capacity of (un)corroded concrete half-joints. The analysis is based on a lower-bound approximation using a strut-and-tie approach and an upper-bound approximation using a kinematic approach. The analytical tool is used to determine the load bearing capacity of the series of investigated Dutch concrete half-joints. Both approximations are comparable when rebar failure is the governing failure mechanism. The strut-and-tie approach also incorporates detailing checks, which are not considered in the kinematic approach. Therefore large differences occur when detailing governs the capacity. The nodes in the strut-and-tie model, in which two ties are connected to one concrete strut, appear to be critical in the lower-bound solutions. The capacity depends on the concrete strength and dimensions of the node. The dimensions are influenced by the mandrel diameter of the hanger-rebar and anchorage length of the horizontal rebar. In order to study the influence of corrosion on the load bearing capacity, the effect of a reduced rebar capacity due to an increasing corrosion rate was implemented in the analytical tool. The kinematic approach appears to be more sensitive to load bearing capacity loss, as this calculation depends mainly on the strength of the rebars. The strut-and-tie approach is able to redistribute forces over the struts and ties and is less sensitive. In order to verify the analytical results, a numerical study is performed. The specimens are modelled in such a way that rupture of one of the rebars at the re-entrant corner is governing. Both analytical solutions appear to be conservative compared to the numerical results, in which the lower-bound solutions are very conservative. Different crack’s angles have been found between the upper-bound calculation and numerical results. If the same angle is applied in the analytical tool, the difference reduces from 7% to 2% for an uncorroded concrete half-joint without diagonal. The differences can be explained by the simplification in the kinematic approach, in which the concrete compression zone is not able to transfer shear stresses. Based on the conclusions of the analytical tool and numerical verification, an assessment method is proposed in which the upper-bound solution is combined with the lower-bound solution. If the load on the concrete half-joint is lower than the calculated lower-bound solution, the concrete half-joint is safe. However, questions arise if the load is between the lower- and upper-bound solution, in which structural safety cannot be guaranteed. The analytical tool is still a useful tool to understand the behaviour and vulnerabilities of the concrete half-joint. The analytical tool is even more useful if the strut-and-tie approach is governed by rupture of the horizontal-, diagonal- or hanger-rebar. The kinematic approach can be extended by implementing the same crack’s angle, which occurs in the existing concrete half-joint.

Cracks in masonry structures are a cause for concern as they signal a potential lack of functionality and/or aesthetics. It thus becomes important to identify the cause of damage in order to mitigate it and to prevent its occurrence in the future. Similarities in crack patterns may correlate to similarities in the damage cause. Currently, the assessment of similarities in crack patterns and their corresponding damage causes is done by masonry experts and structural engineers. This process is often expensive and subjective. The use of a Convolutional Neural Network (CNN) may offer an alternate robust and dependable means to automate the assessment of masonry crack patterns by processing their images. The main research goal of this MSc thesis is to answer how accurately can the CNN -- fitted to data generated from finite element models -- estimate masonry crack pattern similarities. To develop a neural network that can perform such an automated assessment of masonry crack patterns with a high degree of accuracy, a large number of crack patterns with similarity ratings given by human experts are required. This data is collected in increasing complexity, first from a statistics-based approach by generating synthetic crack patterns from Markov walks. This is followed by a computational physics-based approach, such as the Finite Element Method (FEM), that generates crack patterns on 2D masonry façades subjected to differential settlements and out-of-plane loads. Finally, real-world data is also collected. This data is used to fit and test a convolutional neural network developed by Kleijn (Kleijn, 2022). Continuing along the previous line of research done at TNO (where 12 crack patterns were chosen and developed using the statistics-based approach), this thesis focuses on developing parametric finite element models of 8 out of these 12 Pattern IDs. Additionally, real-world images are also collected from Gouda in The Netherlands. This data is then used to form crack pattern image pairs that can be assessed for their similarities by 28 raters using three similarity label categories: crack pattern similarity label, damage severity label, and the overall similarity label. Using these labels, the raters assessed 2587 image pairs generated from the statistics-based approach, 500 image pairs from the computational physics-based approach, and 50 image pairs from the combination of images from the statistics-based approach, computational physics-based approach, and the real-world cases. An inter-rater agreement analysis is performed on the similarity assessments using Krippendorff’s alpha measure. Additionally, the agreement of each rater with a chosen standard rater is studied using Lin’s Concordance Correlation Coefficient (CCC). Using Lin’s CCC, the intra-rater agreement is also assessed for the standard rater to see how consistent a rater is with their own annotations. These labelled image pairs are then used to fit and test the regression neural network to evaluate its accuracy in predicting the similarity labels. The neural network is also fitted to and tested with various combinations of labelled data to study its generalisability. It is found that in all three sets of data, Krippendorff’s alpha is less than 0.80 for all the labels, which indicates an insufficient agreement among the raters. It is also seen that, in general, agreement among the raters increases with their experience level, i.e. the descending order of agreement within the rater group is: industry experts, PhD students, and MSc students. Studying the Lin’s CCC of each rater’s performance compared to that of the standard rater helps to choose the raters who can be considered as reliable as the standard rater. Additionally, the intra-rater agreement analysis of the chosen standard rater shows that the highest self-consistency (agreement) is achieved for the crack pattern similarity label, followed by the overall similarity label and finally the damage severity label, with corresponding Lin's CCC values of 0.96, 0.86 and 0.72, respectively. The neural network is tasked to predict the similarity level in each similarity rating for each image pair in the test sample. The ground truth of this neural network is established by averaging the similarity ratings given to each image pair by multiple raters. It is found that the neural network is able to achieve a sufficiently high degree of accuracy when fitted to and tested with all the image pairs generated from the computational physics-based approach. The crack pattern similarity label, the damage severity label, and the overall similarity label achieve an accuracy of 87%, 82%, and 69%, respectively. However, the generalisability experiments on the neural network that consist of predicting the similarity of a type of crack pattern image pair that is not included in the fitting data set, show very poor performance with respect to the prediction accuracy of the similarity labels. When the neural network attempts to predict the similarity of Pattern ID or a façade geometry that it did not see in the fitting procedure, it predicts all three labels with an accuracy that varies from 40% to 50%. Additionally, the neural network is also fitted to images generated from the computational physics-based approach and then tested with a pool of image pairs generated from the statistics-based approach, computational physics-based approach, and real-world images. The average accuracy with which the three similarity labels are predicted is even lower, lying between 25% and 40%. This MSc thesis concludes that the neural network fitted to data generated from the computational physics-based approach and assessed by all the raters is able to predict the crack pattern similarity label, the damage severity label and the overall similarity label with sufficiently high degrees of accuracy. However, the generalisability experiments on the neural network show very poor results. This indicates that in order to achieve a greater prediction accuracy, the neural network may need to be fitted to a considerably larger sample of crack patterns that covers all of the relevant situations. Furthermore, the substantial inter-rater variability in the labelling of crack pattern image pairs suggests that even an ideal neural network architecture may not be able to overcome the inconsistencies in the fitting data.

The light and frequent earthquakes in the north of the Netherlands, particularly in the province of Groningen, have recently exposed the unreinforced masonry structures to seismic activities. Since these structures do not adhere to seismic regulations, they are considered vulnerable to seismicity. The ultimate state capacity of the structures is important for an individual's safety, however, these earthquakes are of low intensity and cause aesthetic damage. In order to investigate the light damage initiation and development, TNO has performed shaking table tests on an unreinforced masonry (URM) cavity wall specimen in out-of-plane (OOP) one-way bending with small increments in intensity. The test specimen consisted of calcium silicate brick inner leaf and perforated clay brick outer leaf. The damage development in the outer leaf was monitored during these tests using a high-speed digital image correlation (DIC) technique to study the initiation and development of damage in the outer leaf of the specimen. The experimental tests showed damage initiation at the mid-height of the outer leaf. The tests could not capture the development of cracks through the thickness of the cavity wall. The scope of this research is a numerical assessment of the experimental study by using a Non-Linear Time History (NLTH) analysis of light damage initiation and development of a URM cavity wall under out-of-plane loading. The high-resolution experimental results are used as a basis for the development and calibration of models which can better predict the crack initiation and development in URM. The finite element software DIANA 10.5 FEA was used to set up the numerical model and conduct transient analysis. The seismic signal as an input loading and the top boundary condition of the test specimen. The acceleration data measured from the shaking table tests at the base was used as an input seismic signal for the transient analysis of the models. The input signal needed to be processed before application as the presence of low-frequency content leaded to inaccurate results. Different approaches are discussed in this thesis regarding the processing of the input acceleration signal. The experimental tests were modeled along the cross-section of the test specimen, thereby highlighting the thickness of the inner leaf and the outer leaf. This enabled tracking the light damage initiation and propagation through the thickness of the cavity wall. A total of thirteen shaking table tests were conducted on the experimental setup. In order to gain insight into the behavior of the specimen during each shaking table test, a model was created corresponding to each shaking table test. Preliminary analysis schemes were set in order to check the validity of all thirteen models. The two cases of top boundary conditions were checked, roller support and spring-mass support. The roller boundary condition proved to be stiff in comparison to the experimental results. The numerical results were calibrated on the basis of material properties. The results were compared to experimental results by checking the dynamic behavior at the mid-height, dynamic behavior over the height, and light damage initiation and development of the specimen. The results of the numerical models were stiff in comparison to the experimental results. According to the conclusions, it is recommended to research further regarding the boundary conditions, especially the bottom boundary condition due to the formation of a rocking crack. Another important aspect to focus on is the combination of all input signals, thereby, taking into consideration the damage accumulation.

For the first time since the 1970s, concrete plans are in motion to bring humans back to the Moon through the Artemis programme. The dawning era of space exploration aims to set the groundwork for long-term off-Earth settlement, with sights on bringing the first humans to Mars. In order to provide a safe means of inhabiting extraterrestrial (ET) environments, a self-supporting habitat shield concept has been developed by the Specialist Modelling Group at Foster + Partners, which is based on the use of mechanically interlocking masonry manufactured from in-situ resources. Significant progress must still be made in the structural design and validation of such systems, however, before they can be safely implemented. Due to the novelty of the proposed structure, existing research does not provide numerical evidence of its stability under self-weight, or under seismic loading. Research in this direction is valuable, as it explores alternatives to popular design concepts based on monolithic additive manufacturing and addresses research gaps related to the analysis of mechanically interlocking structures. The aim of this project is to provide novel insight into the stability of self-supporting dry-stone vaults under the influence of microgravity and ground motions. This is achieved through a three-part analysis approach, which starts with an investigation into the fundamental structural behaviour of dry-stone, Nubian-type vaults based on a series of parametric studies. Key geometric parameters of the vaults are varied, and the resulting distinct element models are subjected to quasi-static pushover-type analysis in 3DEC. The parametric studies indicate what configuration of the vault geometry can maximise seismic capacity. This optimal vault geometry is modelled in Rhino using geometric constraint solving, which is used to produce a model which can be assembled from mechanically interlocking components. Through pushover-type testing and dynamic time history analysis, the performance of the resulting vault model is assessed with respect to possible moonquake loading. The final part of the design process accounts for uncertainties in material properties by conducting sensitivity studies, which indicate what degree of variation in performance is possible. After completing the three mains sets of analysis needed to design a moonquake-resistant vault, several comparative analyses are carried out to provide context to the structural performance of the Nubian-type vault. The first of these additional investigations models an equivalent monolithic vault geometry in DIANA and conducts finite element analysis to determine its capacity for lateral acceleration. The second comparative study determines how covering the vault in loose regolith may influence its structural performance. The third study investigates how the variation of gravity affects the stability and seismic performance of the vault. Several key findings are obtained in this project, leading to an understanding of the structural behaviour of Nubian-type vaults and how they may be a possible solution to shielding demands in ET contexts. The final vault model was shown to remain stable under a uniform lateral acceleration equivalent to the PGA for a possible moonquake with a 475 year return period. Dynamic analysis conducted using an artificial ground motion record obtained for the same return period produced less favourable results, resulting in partial collapse of the outermost six courses of the vault. Computational constraints necessitated the implementation of an undamped analysis, however, so these results are considered to be conservative. Further analysis is needed, but these results suggest that with minor adjustments, the vault may be able to safely resist moonquake loading. The comparative monolithic vault analysis demonstrates that an additively manufactured vault may provide slightly better resistance to static lateral acceleration than a component-based vault. When considering the structural redundancy and energy dissipation necessary for safe seismic design, however, the discrete vault is expected to perform better. Results show that covering the vault in loose regolith is expected to reduce its overall stiffness. Conclusions about changes in stability cannot be made with confidence due to modelling issues at the interface between the regolith and the structure. By studying the influence of gravitational variation on the vault, results indicate that it may perform favourably on the Earth or on Mars, though the possibility of material damage must be studied further.

For the renovation of the Suurhoff bridge, Arup decided to design and propose a new, innovative strengthening scheme, which improves the fatigue performance of the bridge deck and extends the design life of the bridge by at least 15 years. In this strengthening scheme, a steel plate is placed on top of the existing deck plate with a layer of epoxy in between. Preloaded injection bolts are also used to connect the strengthening plate with the deck plate. This strengthening techniques has clear advantages over the current alternatives with regard to weight, execution time, risks and flexibility in the design. In order to better understand the behaviour of the renovated bridge deck, verify the effectiveness of the strengthening scheme and check the accuracy of the numerical models, a monitoring scheme is desirable. This is an important step in the development and optimisation of the strengthening approach, especially when the goal is to apply the scheme more often on future bridge renovation projects. To achieve this, the two research questions of this thesis are formulated as follows: What is the effectiveness of strengthening an orthotropic steel deck with a bonded & bolted strengthening plate? How can the behaviour of the bridge be numerically modelled to accurately capture the improved fatigue resistance? This question will be answered through a combination of monitoring and finite element modelling. First, a monitoring scheme is set up with 16 strain gauges that are installed on the deck plate, troughs and cross girder. Quasi-static load tests are executed using a truck with known weight, both before and after the application of the strengthening scheme. The load tests were successfully and accurately carried out and the results show a large reduction in the stress cycle. Stresses in the troughs are alleviated by 45-55% and stresses in the deck plate are reduced by 85-90%. This is largely in line with what was expected during the design. Furthermore, the used FE models are validated so that more confidence can be gained in the design decisions. The full influence line is simulated, with the truck positioned at more than 120 longitudinal locations. The numerical modelling was able to accurately predict the shape and magnitude of the influence line generated by the truck loading. A difference in peak value between experimental and numerical results of no more than 25% was observed. The largest differences are observed for local bending in the deck plate of the unstrengthened bridge, but this is largely explained by the large sensitivity to the exact wheel position. For the strengthened bridge, a very good match is obtained in almost all locations. A difference between numerical and experimental results of no more than 10% is observed when not considering the area close to the bolts. Close to the bolted connection (±200 mm), no accurate results can be obtained with a simplified modelling approach that uses shear springs to model the bolts. However, the obtained numerical results are conservative compared to the experimental results. Some simple modelling adjustments have been applied but are unable to significantly improve the results. A detailed modelling approach has successfully been applied in which the bolt has been modelled fully in solid elements. The preload is implemented through a dynamic relaxation phase, so the bolt force is transferred through friction of the plates without any relevant increase in computation time. Therefore, this modelling technique can relatively easily be applied in a global FE model. This modelling technique is more accurate, and analyses have successfully managed to reduce the error by 50%. However, stresses close to the bolt are still overestimated even with this advanced modelling approach and more research is needed for a complete match in this area. In conclusion, the largely matching results reinforce the decisions from the design report. More confidence is gained in the static and fatigue design life, acknowledging the potential of this new strengthening scheme for future applications. As recommendations for future research, more testing and design work could be carried out to further optimise the design of the strengthening scheme. Furthermore, the temperature loading can be investigated through testing and monitoring in order to reduce this critical load case. Lastly, more detailed local FE modelling around the bolted connection can help understand the behaviour in this area. This can further increase the potential of the strengthening scheme when bolts are applied in close proximity of critical fatigue details.

Designing structures that are more sustainable is a relevant topic within the construction industry. By choosing materials that have a low embodied energy value and optimizing the structures that can be constructed by these materials, one could potentially minimize the economical and environmental footprint of a structural design. As burnt clay bricks have a relatively low embodied energy value, are relatively cheap as a construction material and are relatively durable, it is interesting to investigate the optimization of masonry structures. To achieve this, use is made of topology optimization. To accurately optimize the topology of masonry structures however, this optimization must be performed based on the results of a discrete element analysis. This thesis presents several methods to set up such a model based on masonry structures of arbitrary size and lay-out, departing from the smallest scale: the individual brick. First, a method is developed to create arbitrary shapes for bricks. An algorithm is developed to parametrically create structures for two distinct shapes. A procedure to abstract these structures and translate their geometrical representation to a simplified numerical model is then presented. Several methods for structural analyses are detailed and their results are evaluated and compared. The results of these analyses are used to optimize the topology of the initial structure by means of the Method of Moving Asymptotes. The resulting structures are then verified using 3DEC. Finally, some applications of the developed method are presented along with future visions.