Tunnel segment connections in cut-and-cover tunnels founded on shallow foundations are subjected to differential settlements during their service life. This research develops a systematic methodology for the assessment and selection of tunnel segment connections using a combination of geotechnical modeling, structural verification, and Multi-Criteria Decision Analysis (MCDA). The Oosterweelknoop project in Antwerp was used as a case study, considering four connection concepts: a shear key, collar construction, dowel connection, and free-settlement joint. The results show that the dowel connection provides the most suitable balance between robustness, feasibility, durability, sustainability, and cost. The developed methodology supports transparent and reproducible decision-making for similar tunnel projects. ... Read more

This dissertation investigates how proof load testing can be used to assess the reliability of existing structures. A flexible Bayesian methodology is proposed and applied to reinforced concrete road bridges and viaducts. Key contributions include:

• A demonstration of how proof load testing affects annual reliability, showing reductions during testing, but substantial gains after surviving target loads.

• An in-depth look at the conservative lower-bound estimation of structural reliability, revealing its assumptions and limitations.

• Combining in-situ monitoring and laboratory data for Bayesian updating during testing, enabling substantial reductions in required test loads.

• Hierarchical Bayesian modelling addressing spatial correlation and system reliability, enabling optimal testing strategies with a low number of tests, and the configuration of load testing vehicles.

This research positions proof load testing at the core of a Bayesian reliability-updating methodology, thereby providing a uniquely accurate procedure for assessing existing infrastructure. ... Read more

This study applied a Community-Based Participatory Research (CBPR) approach to assess water-related challenges on San Cristóbal Island, Galápagos, Ecuador. Data was collected by means of semi-structured interviews (74 households), stakeholder interviews, expert consultations, and additional 150 questionnaires (150 residents) regarding water vulnerability and flood risk. This research assessed lived experiences alongside governance mechanisms, investment plans, and socio-economic status and highlights the individual responsibility and adaptability requirements by residents of San Cristóbal in regards to water scarcity, quality and floods.

The island’s gravity-led distribution network covers 93.07% of households but operates intermittently (3 hours/day), necessitating storage at the household level and shifting maintenance responsibilities to residents. As a result, vulnerabilities differ across and within neighbourhoods according to storage type, cleaning practices, chlorine use and geographic location, none of which show consistent correlation Spatial mapping of the system revealed pressure-sensitive segments, indicating uneven performance across the system, where pressure fluctuations compromise delivery. Moreover, limited contingency support has made neighbourhoods still awaiting connection to the main supply overly dependent on limited sources, leaving them particularly vulnerable during service interruptions.

Reported system failures are widespread: 89% of interviewed households reported at least one problem, most commonly water shortages, high turbidity, and pipe breakages. Vulnerability varies between households depending on the capacity of water reserves and the potential of (re-)contamination. Even for households that report a rigid cleaning regime, these problems are present. The multiple mentions of pipe leakages and muddy water indicate seepage into the pipeline system, suggesting that water quality is compromised before it reaches the households. However, according to soe residents, contamination stems from the source, citing low efficiency at the drinking water treatment plant. This distrust in water quality translates to a high reliance on bottled water, which is uniform across the island despite its associated costs.

Reports on flood-related incidents are highly dependent on location, concentrated in places where local topography, incomplete drainage, or ravine bottlenecks amplify runoff. Notably, 23% of all questionnaire respondents reported that their homes suffer damage from flooding, highlighting the tangible impact of these events on residents. Despite significant municipal spending on flood relief, the creation of predictive flood models is restricted by limited technical knowledge and know-how, causing the infrastructural interventions to remain largely reactive, with affected areas identified only post-event. Comparing municipal investment plans with a resident weighted satisfaction index reveals that spending does not uniformly translate into higher satisfaction. Residents report greater value to reliability and communication with the community. Spatial analysis of the urban area Puerto Baquerizo Moreno shows that socio-economic vulnerability generally increases from coastal to peripheral neighbourhoods, but incomplete infrastructure, water shortages, and flooding do not always coincide with limited municipal support, meaning that some vulnerable areas still benefit from interventions while others remain underserved.

The results highlight how infrastructure performance and governance practices interact to shape everyday water-related vulnerability for the residents of San Cristóbal. The CBPR framework allows for enhancement of urban planning knowledge, with lived experiences of those most affected by it.
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In the more than sixty years of experience in forensic structural engineering of Adviesbureau Hageman, damages in underground concrete parking structures repeatedly passed by. In a master study, mainly based on the comprehensive archive of Adviesbureau Hageman, an overview of the various damages that can be distinguished, is made and causes for the occurrence and measures to prevent them, are addressed. Furthermore, one category of damages, that is not limited to only parking structures, but generally occurring in concrete structures, is damage to concrete corbels. In order to investigate the behaviour of such corbels, finite element analyses are performed with the FE Code ATENA. Its behaviour in case of a corbel and support according to the Codes is investigated, but also in case of a support close to the edge and applied horizontal loading due to imposed deformations in the elements that are supported by the corbel. In the thesis the overview of damages in concrete parking structures and the study into the behaviour of corbels will be presented. ... Read more

he growing demand for renewable energy sources has led to the deployment of wind turbines worldwide. One of the most critical parts of a wind turbine is the foundation, which plays an important role in maintaining the structural integrity and reliability of the towers throughout their service life. This research project is a case study that focuses on validating the numerical model against the experimental values from an operational onshore wind turbine foundation present at Riemst, Belgium, while considering the effect of hydration heat during the concrete curing process. The main aim of this research is to study and compare the behavior of the steel stresses in the on-site foundation with that of the numerical analysis and to see whether an adequate match can be obtained.

The study begins with the development of a three-dimensional symmetrical finite element model that captures its intricate geometrical and material properties. The structure’s behavior is simulated under realistic loading conditions to assess its structural performance and identify potential areas of concern. To validate the accuracy of the numerical analysis, experimental data obtained from fiber optic sensors are used. After converting the measured strains into stresses, they are carefully compared with the finite element analysis results to identify any variations and fine-tune the model. The validation of the FE model is performed using a 2D plate model in SCIA Engineering.

The research investigates the effects of hydration heat along with the structural analysis in FEA on the stresses experienced by the steel elements in the mass structure. This further extends to the effects of bedding and inclined piles combined with the thermo-mechanical analysis, where properties such as stiffness are varied in the simulations to study their influence on the structural response. It is imperative to note that utilizing the FE model with solely non-linear structural analysis can lead to a significant overestimation of the expected field results, up to 87 times. To mitigate this issue, the variant with thermo-mechanical analysis is implemented, reducing this estimation to a maximum factor of 58 compared to the field data.

It is crucial to achieve a satisfactory level of the project through iterative modifications. Implementing soil bedding on all sides in the thermo-mechanical model is one such step to effectively reduce steel stress to an acceptable level. The model shows steel stresses that are approximately 26 times higher than the actual experimental values. Along with reducing the steel stresses, the crack widths have decreased considerably from 3.4 mm to 2.35 mm. Hence, the effective way to perform the numerical simulation is to consider thermo-mechanical coupling along with minimizing assumptions and ensuring sufficient stiffness of the structure for reliable assessments of steel stresses and structural integrity of onshore wind turbine foundations.

The findings contribute valuable insights into the foundation’s structural behavior under varying operational conditions, highlighting areas of strength and potential advancement. Moreover, the outcomes from this investigation can assist engineers and designers in making informed decisions during the planning and construction phases of wind turbine foundations, leading to more cost-effective and robust structures. Additionally, the methodologies presented here may serve as a framework for future research in this field. ... Read more

In this project, student teams from Universidad San Francisco de Quito and Delft University of Technology worked together to provide safe drinking water in Ecuador. We used M-100 chlorinators from the company WaterStep, donated by Water Ambassadors Canada, to chlorinate water in schools and communities. The journey involved testing water quality, setting up the chlorination systems, and learning how to work in different communities. The key to success was testing water properly and setting up the system carefully. Learnings about working with local communities and organizations are included as well as the importance to understand each community’s needs to make a real difference. ... Read more

In this report, the applicability of Precast Concrete Sandwich panels (PCSPs) is analysed and improved. This is done by a multitude of methods: a literature study is performed, an advanced, non-linear Finite Element model and simple linear analytical model are developed, and calculations have been performed on a design-structure from Lievense | WSP. The literature study is performed to gain insight into the unique behavioural aspects of PCSPs, and to find where the current issues arise regarding the already-present prediction models. After the most important aspects of these floors have been determined, an advanced Finite Element model is developed to predict both the linear and non-linear behaviour of PCSPs. This FE-model has the possibility to include the non-linearity of all materials. In order to verify the correctness of the full behaviour of this model, it has been compared to experiments from literature. Additionally, a simple linear analytical model is developed, with the goal to make PCSPs easy-to-use in practice, so that people without knowledge about the background-calculations are still able to make use of these floors. This analytical model is compared to the linear version of the FE-model. On top of this, the Reinbouw project from Lievense | WSP is used to analyse what the bottlenecks are in their current design of a fully prefabricated structure. Based on these bottlenecks, a calculation is done to find the required resistances of the PCSPs to ensure a structurally verified structure. Both the linear prediction model and the Reinbouw project are combined at the end, where an advice is given on the PCSP-design in the Reinbouw project. All of these methods have the goal of increasing the applicability of PCSPs. ... Read more

Most bridges in the Western European road networks are ageing. The vast majority of about 90% of these bridges have reinforced concrete as a building material. The traffic intensity, as well as the axle, and the average vehicle weight have increased since these structures were opened to traffic. Furthermore, the structural (design) codes have changed over the years. Therefore, there is a need to investigate if existing structures meet the safety/reliability level described by the current codes. However, a frequently faced problem in practice is that the original design calculations and technical drawings of a large percentage of the existing bridges are unknown or lost. Especially for bridges in the lower road network, often designed for the lower load classes B/45 and maintained by a local government, the documentation is missing. The national road network, designed for load classes A/60 is maintained by the national government and faces the same problem but to a lesser extent. Bridges within this scope have different detailing rules and execution practices than used nowadays. Plain reinforcement was in general used which is bend-up at a support. Therefore, the study is twofold: first, Reverse Engineering is applied to determine the reinforcement of existing reinforced concrete slab bridges, second the capacity margin of RE bridges are examined with the current assessment codes. A Reverse Engineering-tool is developed to automate the dimensioning of the required reinforcement according to the former design codes. This tool uses the year of design, load class and the geometric dimensions of the bridge as input parameters. A parametric study is performed to examine bridges from different design periods. Consequently, the Reverse Engineering-tool is used to assess the Reverse Engineered bridge according to the current assessment codes. The validation of the model shows for the majority of the Reverse Engineered bridges that the Reverse Engineered reinforcement is slightly less than the reinforcement amounts from the technical drawings. This proves a conservative approach where the actual structural capacity is underestimated. Consequently, an assessment of the Reverse Engineered bridge can be performed with sufficient robustness.The computer code ran with the input parameters having a normal distribution, showed the largest effect for the uncertainty in the design year and load class especially around 1940 and 1962. Therefore, the design year and load class are crucial in Reverse Engineering and assessment of an existing bridge. The capacity margin of the Reverse Engineered bridges is assessed according to the current Eurocode based design codes. The traffic- and permanent load including load factors according to the general assessment codes from the NEN8700/NEN8701 and the RBK-1-1, and the decentralised load model from TNO are applied. The assessment with the Eurocode including the load factors from the NEN8700 showed Unity Checks for bending moment at the mid-supports and mid-spans of larger than 1.0, where the Unity Checks for shear forces resulted below 1.0. The assessment with the Decentralised load model showed Unity Checks for bending moment at the mid-supports and mid-spans and shear force below 1.0. In case the amount of support reinforcement is based on the amount of span reinforcement, the bending capacity margin at the mid-supports is insufficient for large spans. Significant bending capacity margins are obtained in structural design of RC slab bridges in the period 1930-1970. The main contribution of this research is that bridges designed between 1940 and 1962 show the most critical Unity Checks for bending in the assessed period. In this period account the following design methods: The dynamic amplification factor introduced in the GBV1940 for concrete bridges, the traffic load class from the VOSB1933, the N-method to determine the cross-section capacity and the effective width method from the GBV1940 and from the Guyon Massonnet method.The capacity margin for shear is found to be almost independent of the design period. Here can be concluded that the slenderness of the bridge deck is the main contribution in the shear capacity. Bridges designed in the period 1940-1962 with the support reinforcement based on the span reinforcement and with a span length >10m designed for load class B/45 or with a span length of >11m designed for load class A/60, form the group with the most critical bending capacity. However, the size of the group of former bridges designed according to these conditions is unknown.From the results can be concluded that bridges designed between 1940-1962 with RE reinforcement are found to be legally unsafe for bending according to the parametric assessment with the Eurocode. ... Read more

Finite element analysis is becoming a popular tool for engineers recently. Nonlinear finite element analysis is more advanced due to that it can deal with the nonlinearity of structures, which leads to more accurate approximation of structural behaviour. In Model Code 2010, nonlinear finite element analysis, which belongs to the higher level of approximation, can predict the structural behaviour with refined physical parameters but by devoting more time to the analysis. This leads to better accuracy. Thus, it is important to study how to apply nonlinear finite element analysis to approximate the structural strength.
When it comes to the existing design codes, the shear design methods of reinforced concrete slabs loaded in uniaxial in-plane force are developed from the tests of beams rather than slabs, which may lead to the underestimation of the design resistance. Through experiments of seven slabs, a related study of the validity of existing shear design methods has been performed by Bui et al. (2017). However, there is no existing literature about the application of nonlinear finite element analysis towards the reinforcement concrete slabs mentioned above so far. In this thesis, one single nonlinear finite element analysis is applied to seven slabs of experiment to study the validation of nonlinear finite element analysis on the RC slabs without shear reinforcement loaded in concentrated out-of-plane load and uniaxial in-plane loads. The validation is studied by comparing results from finite element analysis, experiment and finite element analysis from Nana et al. (2017), which mainly includes shear load – displacement curve, development of crack pattern, failure modes and the influence of uniaxial load on the structural behaviour. In addition, the shear capacity under uniaxial in-plane load is studied by comparing results from analytical assessment based on existing codes, experiment and nonlinear finite element analysis.
When compared with experiment, nonlinear finite element analysis shows a close shear capacity of all seven slabs but stiffer structural behaviour. The development of cracks is similar to the observation of experiment. The failure modes indicated by nonlinear finite element analysis is more likely punching shear rather than one-way shear that is demonstrated in the experiment. The influence of increasing uniaxial compression on shear capacity is larger than what is observed in experiment while increasing tension has smaller influence. By comparing the prediction of shear capacity from experiment, existing codes and nonlinear finite element analysis, it can be concluded that NLFEA is unconservative in prediction of shear capacity of the RC slabs without shear reinforcement loaded in concentrated out-of-plane loads and uniaxial in-plane loads. Some suggestions are given for further study. Improvement of modelling is suggested. For instance, finer mesh could lead to more accurate results, and insights of bond-slip reinforcement could generate more precise results. Furthermore, the study of safety formats is suggested in further study to consider the uncertainty due to random variation of material properties. In addition, more experiments and nonlinear finite element analysis are suggested to get insights of the influence of uniaxial loads on structural behaviour of RC slabs without shear reinforcement.
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