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The accelerated urbanization has led to increasing tension on urban land use. In this context, more and more slender high-rise buildings are being built worldwide in pursuit of better economic benefits. However, these structures are susceptible to wind excitation due to their lower first natural frequency. Different passive, semi-active, and active damping systems have been developed to reduce wind-induced structural vibration. Among them, the tuned mass dampers are widely used and proved as a very effective method in practice. However, this system requires a large additional damping mass. This also causes additional reinforcement, which increases the cost and carbon footprint. A huge space near the top story of the building is needed for the installation. In this research, a novel system named distributed-Multiple Tuned Facade Damping (d-MTFD) system is proposed by using specially designed parallel moveable Double-Skin Facade (DSF) outer skin as damping mass. These moveable facade elements can be installed on the upper stories of the high-rise building. Smooth-running guide rail systems are used to achieve the parallel moveability. Multi-objective optimization based on the Genetic Algorithm (GA) is applied to reduce the maximum top floor acceleration (Objective I) and to reduce the maximum facade relative displacement (Objective II) simultaneously. The optimization results for the passive and semi-active systems are presented in the form of the Pareto front. The trade-off between these selected two competing optimization objectives is observed. This approach was first validated in a simulation using a 306 m tall reference building for a wind speed of 13.5 m/s at 10 m above ground level with a return period of 10 years. Acceptable peak accelerations at the top story for hotel use and a maximum facade relative displacement of less than ±0.5 m could be achieved for the benchmark building with the d-MTFD system. For semi-active control, the variable damping coefficient can be achieved by using stepper motors in generator mode. The electrical damping coefficient can be continuously adjusted by the developed power electronics. In addition, electrical energy can be generated and stored in a battery. A full-scale prototype with one parallel moveable facade element was built. Based on the prototype, the functionality of the semi-active control using a stepper motor and its energy harvesting performance was tested by applying Hardware-in-the-Loop (HiL) simulations. Greybox system identification was used to estimate some parameters (spring stiffness, friction, etc.) in the connection. The accurate system identification results ensure further validation using HiL simulations. The HiL simulations successfully demonstrated the feasibility of a self-powered semi-active d-MTFD system., In Metropolen ist die Flächennutzung aufgrund der Urbanisierung eingeschränkt, was den Bau von schlanken Hochhäusern weltweit gefördert hat. Jedoch sind sie anfällig für dynamische Windlasten. Um dies zu bekämpfen, wurden passive, semi-aktive und aktive Dämpfungssysteme entwickelt, wobei sich abgestimmte Massendämpfer als sehr wirksam erwiesen haben. Dieses System erfordert jedoch eine große zusätzliche Dämpfungsmasse. Dies führt auch zu einer zusätzlichen Verstärkung des Tragwerks, was die Kosten und den CO2-Fußabdruck erhöht. Für die Installation wird ein großer Raum in den obersten Stockwerken des Gebäudes benötigt. In dieser Arbeit wird ein innovatives System mit der Bezeichnung "distributed-Multiple Tuned Facade Damping (d-MTFD) System" vorgestellt, bei dem eine speziell entwickelte, parallel bewegliche Außenhaut der Doppelfassade (DSF) als Dämpfungsmasse verwendet wird. Diese beweglichen Fassadenelemente können in den oberen Stockwerken des Hochhauses installiert werden. Um die parallele Verschiebbarkeit zu erreichen, werden leichtgängige Führungsschienensysteme eingesetzt. Eine multikriterielle Optimierung mittels des genetischen Algorithmus (GA) wird angewandt, um gleichzeitig die maximale Beschleunigung im obersten Stockwerk (Ziel I) und die maximale Verschiebung zwischen der Primarstruktur und der beweglichen Außenhaut (Ziel II) zu reduzieren. Die Optimierungsergebnisse für die passiven und semiaktiven Systeme werden in Form der Pareto- Front dargestellt. Der Kompromiss zwischen diesen beiden ausgewählten konkurrierenden Optimierungszielen wird beobachtet. Dieser Ansatz wurde zunächst in einer Simulation mit einem 306 m hohen Referenzgebäude für eine Windgeschwindigkeit von 13,5 m/s in 10 m Höhe über Grund mit einer Wiederkehrperiode von 10 Jahren validiert. Mit dem d-MTFD System konnten für das Referenzgebäude akzeptable Spitzenbeschleunigungen im obersten Stockwerk für die Hotelnutzung und eine maximale Fassaden-Relativverschiebung von weniger als ±0, 5 m erreicht werden. Bei der semiaktiven Regelung kann der variable Dämpfungskoeffizient durch den Einsatz von Schrittmotoren im Generatorbetrieb erreicht werden. Der elektrische Dämpfungskoeffizient kann durch die entwickelte Leistungselektronik stufenlos eingestellt werden. Darüber hinaus kann elektrische Energie erzeugt und in einer Batterie gespeichert werden. Ein maßstäblicher Prototyp mit einem parallel beweglichen Fassadenelement wurde gebaut. Anhand des Prototyps wurden die Funktionalität der semiaktiven Regelung unter Verwendung eines Schrittmotors und die Leistung der Energiegewinnung mittels Hardware-in-the-Loop (HiL)-Simulationen getestet. Die Grey-Box-Systemidentifikation wird zur Schätzung der Parameter (Federsteifigkeit, Reibung, usw.) in der Verbindung verwendet. Die genauen Ergebnisse eine weitere Validierung durch HiL-Simulationen. Die HiL-Simulationen haben erfolgreich die Machbarkeit eines autarken semiaktiven d-MTFD Systems demonstriert., Schriftenreihe Hybride Konstruktionen - Massivbau; 15

A number of major fire incidents in recent decades, particularly in tunnels and indoor car parks, have increased the awareness among construction designers towards the potential susceptibility of concrete to fire-induced explosive spalling. In some fields of application, this violent breaking-off of concrete layers may reduce the fire resistance time of fire-exposed construction elements. The mechanisms causing explosive spalling are not yet fully understood and discussed controversially among scientists. In cement production, a steadily increasing proportion of the market volume is constituted by cement types with several main constituents. In these types of cement, Portland cement clinker is replaced by granulated blast furnace slag, lime stone, fly ash or other inorganic materials. Fire tests of concrete specimens presented in a previous publication and the present paper have shown that the type of cement may have a marked influence on the susceptibility of concrete to explosive spalling. The main objectives of this thesis were therefore to: - determine the way in which the physical and chemical properties of the hardened cement paste influence the spalling propensity of heated concrete; and in this manner - contribute to a better understanding of the mechanisms causing explosive spalling. A particular focus was placed on the way in which the moisture present in the concrete pores promotes spalling. Three common characteristics of those concretes that were found to have an increased susceptibility of spalling were identified. For each of the three common characteristics, a corresponding hypothesis describing its possible contribution to the fire-induced concrete spalling was proposed. Each of the three hypotheses in turn was verified through a dedicated experimental programme. The evaluation of the experiments showed that explosive spalling was caused by the following principal mechanisms: • In the concretes that showed explosive spalling in the corresponding tests, the interfacial transition zone (ITZ) between the aggregate particles and the hardened cement paste was only weakly developed, and hence there was no pronounced interfacial porosity. Consequently, the differences in thermal strain between the expanding aggregates and the shrinking cement paste caused relevant tensile stresses in the cement paste. • Due to their pore size distribution, the concretes that showed explosive spalling had a comparably high moisture content. The moisture in the concrete pores caused an increase in the thermal gradients in the heated specimens. Beyond that, pressure from trapped water vapour enhanced the local stresses at the contact areas between the aggregate particles and the hardened cement paste. Eventually, this resulted in the formation of fracture planes and the spalling of near-surface concrete layers. The tests carried out confirmed that explosive spalling can be reliably prevented through the addition of polypropylene fibres to the concrete mix. Based on the results of the experimental programme, further potential ways to mitigate spalling are proposed., Einige größere Brandereignisse der letzten Jahrzehnte, insbesondere solche in Tunneln und Parkhäusern, haben das Bewusstsein von Planern bezüglich der möglichen Neigung von Beton zu explosiven Abplatzungen im Brandfall erhöht. In bestimmten Anwendungsbereichen können diese die Feuerwiderstandsdauer brandbeanspruchter Bauteile verkürzen. Welche Mechanis-men für die explosiven Abplatzungen verantwortlich sind, wird unter Wissenschaftlern kontro-vers diskutiert. In der Zementproduktion entfällt ein stetig wachsender Anteil des Marktvolumens auf Zemente mit mehreren Hauptbestandteilen. Bei diesen Zementarten wird Portlandzementklinker durch Hüttensand, ungebrannten Kalkstein, Flugasche oder andere anorganische Stoffe ersetzt. In einer früheren Veröffentlichung und der vorliegenden Arbeit beschriebene Brandversuche an Betonprobekörpern haben gezeigt, dass die Zementart einen deutlichen Einfluss auf die Nei-gung von Beton zu explosiven Abplatzungen haben kann. Das Hauptziel dieser Dissertation war es daher - zu bestimmen, in welcher Weise die physikalischen und chemischen Eigenschaften des Zementsteins die Neigung von erhitztem Beton zum Abplatzen beeinflussen; und auf diese Weise - zu einem besseren Verständnis der Mechanismen beizutragen, die explosive Betonab-platzungen verursachen. In diesem Zusammenhang wurde ein besonderes Augenmerk auf die Frage gelegt, auf welche Weise die in den Betonporen vorhandene Baustofffeuchte Betonabplatzungen begünstigt. Drei gemeinsame Merkmale wurden für diejenigen Betone identifiziert, die eine erhöhte Anfällig-keit für Abplatzungen aufwiesen. Für jedes dieser drei Merkmale wurde eine entsprechende Hypothese hinsichtlich seines möglichen Beitrags zum Betonabplatzen im Brandfall aufgestellt. Jede der drei Hypothesen wurde wiederum durch ein entsprechendes Versuchsprogramm über-prüft. Als Ergebnis der Untersuchungen wurden die folgenden Hauptmechanismen identifiziert, durch die Abplatzungen ausgelöst werden: • Bei den Betonen, bei denen Abplatzungen auftraten, war die Übergangszone (ITZ) zwi-schen Gesteinskörnung und Zementstein nur schwach ausgebildet. Im Bereich um die Gesteinskörner lag somit keine ausgeprägte Porosität vor. Als Folge verursachten die Unterschiede der thermischen Dehnung zwischen der sich ausdehnenden Gesteinskör-nung und dem schwindenden Zementstein maßgebliche Zugspannungen im Zement-stein. • Die Betone, bei denen Abplatzungen auftraten, hatten zu Beginn der Versuche aufgrund ihrer Porengrößenverteilung einen vergleichsweise hohen Feuchtegehalt. Die Feuchte in den Betonporen verursachte eine Erhöhung der Temperaturgradienten in den erhitzten Probekörpern. Darüber hinaus verstärkte der Druck des eingeschlossenen Wasser-dampfs die lokalen Spannungen an den Kontaktflächen zwischen Gesteinskörnung und Zementstein. Dies führte schließlich zur Bildung von Bruchflächen und zum Abplatzen der oberflächennahen Betonschicht. Die durchgeführten Versuche bestätigten, dass explosive Abplatzungen durch die Zugabe von Polypropylenfasern zur Betonmischung zuverlässig verhindert werden können. Basierend auf den Ergebnissen des Versuchsprogramms werden weitere Möglichkeiten zur Vermeidung von Abplatzungen vorgeschlagen.

Self-reconfigurable batteries represent a new and promising technique of electrochemical storage. The application of self-reconfigurable batteries can resolve the challenge of efficient renewable storage in solar-powered installations. In this paper, the problem of solar panel’s Maximum Power Point (MPP) tracking utilizing self-reconfigurable batteries is explored through modeling. The efficiency of energy storage is improved by removing the intervening DC/DC converter, which is usually necessary for solar PV applications. To make such a system functional, a Switching Battery Management System (SBMS) is proposed instead of a traditional couple of DC/DC converter and usual BMS. This system allows the series connection of multiple battery modules of different sizes, States-of-Charge (SoC), and States-of-Health (SoH). Two main challenges arise by the proposed implementation: tracking MPP of solar panels through battery cell switching and maintaining an equal (balanced) SoC of the separate cells/modules. The theoretical investigation includes developing the distinct software parts: digital twins of the battery module and solar PV modules that interact with the SBMS and the algorithm according to which the proposed SBMS will operate. The SBMS algorithm, based on sortingthe battery cells according to their SoC, resolves both challenges. Having this promising theoretical starting point, a working prototype was developed. The prototype worked as expected and was tested under field conditions, beingintegrated into the power grid as part of a virtual power plant.

Additive manufacturing with steel offers new opportunities for the construction sector. In particular, direct energy deposition (DED) processes such as Wire Arc Additive Manufacturing (WAAM or DED-Arc), are able to create large structures with a high degree of geometric freedom, like force-flow-optimized steel nodes and frameworks, as well as truss structures. By using high-strength steel, manufacturing times can be shortened because less material has to be applied. In order to enable the usage of WAAM components in the construction industry, profound knowledge of the material behavior is necessary. Based on reliable process parameters, extensive experimental and numerical investigations are carried out to characterize the influence of layer orientation and overhang angle on the mechanical parameters of WAAM high-strength low-alloy steel (HSLA) walls. The results have been compared to HSLA steel sheet material. It is shown that comparable characteristics exist for Young’s modulus E, yield strength Rp,0.2 and tensile strength Rm with regard to civil engineering applications. The influence of the loading direction on the material level is similar. Only the yield strength shows a slight dependence on the layer orientation for WAAM walls (difference 4.5%). The overhang angle has no influence on the material parameters.

Monopiles are the preferred foundation for offshore wind turbines in Europe. These large-diameter pipe piles transfer predominantly horizontal loads to the soil by means of lateral bedding. The piles are commonly installed by impact driving. Vibratory driving as alternative installation method has advantages regarding installation time, fatigue and environmental aspects. However, the experiences with this installation technique for offshore foundations are limited. There are concerns regarding the influences on the load-bearing behaviour. To close this gap, comparing scale model tests were carried out with impact and vibratory driven pipe piles. During the installation of the model piles, forces and motions were measured at the pile head and radial stresses were measured in the soil. Soil stress developments known from impact driven piles were also witnessed in certain cases of vibratory installation. In such cases, a specific 'vibratory driving mode' could be identified from the pile head motion. After end of driving, increased soil stresses remained especially near the pile toe ('installation effect'). During subsequent cyclic loading, the load-displacement behaviour of the first cycle, the displacement accumulation as well as lateral stiffness over cycle count and the further development of soil stresses were analysed. Different lateral behaviour depending on the installation parameters could be identified. The 'certain' vibrated piles mentioned above showed similar lateral behaviour as impact driven piles while other vibrated piles behaved softer. Due to changes of loading direction, a back-accumulation of pile head displacement together with re-arrangements of soil stresses could be witnessed. The increased soil stresses near the pile toe observed at certain piles largely remained after cyclic loading. For the static lateral calculation of monopile foundations, a one-dimensional bedded beam (Winkler foundation) on nonlinear springs (p-y curves) is commonly used. A modified p-y approach considering the soil stresses due to pile installation effects was developed and shows good agreement with the first loading cycle of each model test. For offshore cases, the influence of increased soil stresses near the pile toe on the static lateral behaviour was predicted as well. The activation of lateral bedding below the point of zero displacement ('toe kick') is decisive for this behaviour. For the lower displacement accumulation during cyclic loading in case of increased soil stresses, a possible explanation could be found as well., Monopfahlgründungen stellen die Vorzugsvariante bei Gründung von Offshore-Windenergieanlagen dar. Diese Stahlrohrpfähle großen Durchmessers tragen die vornehmlich horizontalen Lasten durch laterale Bettung in den Baugrund ab. Die Installation der Pfähle erfolgt mittels Schlagrammung. Die Vibrationsrammung als alternatives Einbringverfahren hat Vorteile hinsichtlich Installationszeit, Stahlermüdung und Umwelteinwirkungen. Die Erfahrungen mit dem Verfahren für Offshore-Gründungspfähle sind jedoch begrenzt und Bedenken bestehen insbesondere hinsichtlich er Auswirkungen auf das Tragverhalten. Um diese Lücke zu schließen wurden vergleichende Modellversuche mit geschlagenen und vibrierten Rohrpfählen durchgeführt. Während der Installation der Modellpfähle wurden die am Pfahlkopf angreifenden Kräfte und resultierenden Bewegungen sowie die radial auf den Pfahl wirkenden Spannungen im Boden gemessen. Von geschlagenen Pfählen bekannte Spannungsentwicklungen im Boden wurden auch bei vibrierten Pfählen gemessen, bei denen anhand der Pfahlbewegungen ein bestimmter 'Vibrationsmodus' identifiziert werden konnte. Nach Ende der Pfahlinstallation blieben insbesondere im Bereich des Pfahlfußes erhöhte Bodenspannungen erhalten ('Installationseffekt'). Für die anschließende zyklisch laterale Belastung wurden das Last-Verformungsverhalten des ersten Belastungszyklus, die Verformungsakkumulation und die Entwicklung der Systemsteifigkeit infolge zyklischer Belastung sowie die weitere Entwicklung der Bodenspannungen ausgewertet. Ein unterschiedliches laterales Verhalten konnte in Abhängigkeit der gewählten Installationsparameter festgestellt werden. Die o.g. 'bestimmten' vibrierten Pfähle zeigten dabei ein ähnliches Verhalten wie geschlagene Pfähle, während andere vibrierte Pfähle sich 'weicher' verhielten. Infolge mehrerer Richtungswechsel der zyklisch lateralen Belastung konnten ein Rückgang der zuvor akkumulierten Verformungen und gelichzeitig Spannungslagerungen im Boden festgestellt werden. Die bei bestimmten Pfählen auftretenden erhöhten Bodenspannungen im Bereich des Pfahlfußes blieben auch nach der zyklischen Belastung weitestgehend erhalten. Die statische laterale Berechnung von Monopfahlgründungen erfolgt i.d.R. als eindimensionaler, gebetteter Balken (Winkler-Balken) mit nichtlinearen Federkennlinien (p-y-Kurven). Ein modifizierter p-y-Ansatz zur Berücksichtigung der Bodenspannungen infolge der Pfahlinstallation wurde entwickelt und zeigt gute Übereinstimmungen mit dem jeweils ersten Belastungszyklus der Modellversuche. Auch für Monopfahlgründungen im Offshore-Maßstab wurde ein Einfluss erhöhter Bodenspannungen im Bereich des Pfahlfußes auf das statisch laterale Tragverhalten prognostiziert. Die Aktivierung lateraler Widerstände unter dem Nulldurchgang der Biegelinie des Pfahls ('toe kick') ist hierfür entscheidend. Für die geringeren Verformungen infolge zyklischer Belastung bei erhöhten Bodenspannungen konnte ebenfalls ein Erklärungsansatz gefunden werden., Mitteilung des Instituts für Geomechanik und Geotechnik, vol. 112

The thesis illustrates the Life-Cycle Cost Analysis of road bridges equipped with Structural Health Monitoring systems (defined LCCA-SHM) framework developed in the research project. LCCA-SHM framework is designed as a support tool for the infrastructures management. The main intent of the research is to promote the implementation in the common practice of the alert devices to develop the realization of smart structures capable to timely predict the structural damages and to impose the most cost and safety effective operation and maintenance planning based on the collected data., Die Dissertation veranschaulicht die Lebenszykluskostenanalyse von Straßenbrücken, die mit Structural Health Monitoring-Systemen (definiert als LCCA-SHM) ausgestattet sind, die im Rahmen des Forschungsprojekts entwickelt wurden. Der LCCA-SHM-Rahmen ist als Hilfsmittel für das Infrastrukturmanagement konzipiert. Das Hauptziel der Forschung ist es, die Implementierung von Warngeräten in die gängige Praxis zu fördern, um die Realisierung von intelligenten Strukturen zu entwickeln, die in der Lage sind, strukturelle Schäden rechtzeitig vorherzusagen und die kosten- und sicherheitseffektivste Betriebs- und Instandhaltungsplanung auf der Grundlage der gesammelten Daten vorzuschreiben.Die Dissertation veranschaulicht die Lebenszykluskostenanalyse von Straßenbrücken, die mit Structural Health Monitoring-Systemen (definiert als LCCA-SHM) ausgestattet sind, die im Rahmen des Forschungsprojekts entwickelt wurden. Der LCCA-SHM-Rahmen ist als Hilfsmittel für das Infrastrukturmanagement konzipiert. Das Hauptziel der Forschung ist es, die Implementierung von Warngeräten in die gängige Praxis zu fördern, um die Realisierung von intelligenten Strukturen zu entwickeln, die in der Lage sind, strukturelle Schäden rechtzeitig vorherzusagen und die kosten- und sicherheitseffektivste Betriebs- und Instandhaltungsplanung auf der Grundlage der gesammelten Daten vorzuschreiben.

Advanced science 10(17), 2206342 (2023). doi:10.1002/advs.202206342, Published by Wiley-VCH, Weinheim

Nowadays, more and more complex interdependent infrastructures and networks are developed in engineering. The design and maintenance of such systems increasingly call for advanced computational models to optimize their performance and assess their reliability under various operational conditions. Unlike many conventional simulators that are deterministic, stochastic simulators feature intrinsic stochasticity. More precisely, they produce different results when run multiple times with a given set of input parameters. Due to this random nature, repeated model evaluations of the stochastic model with the same input value, called replications, are necessary to fully characterize the probability distribution of the associated model response. For the purpose of optimization or uncertainty quantification (e.g., uncertainty propagation or sensitivity analysis), computational models typically need to be evaluated a large number of times. The additional layer of randomness due to the intrinsic stochasticity of stochastic simulators makes it even more computationally demanding to perform these complex analyses. A common practice to alleviate the prohibitive cost associated with expensive simulators is to build surrogate models, which behave similarly to the original model but are much cheaper to evaluate. Contrary to the deterministic case, surrogate modeling of stochastic simulators has only emerged in the past decade. The main challenge in this field is that one model evaluation yields only a single realization of the random model response associated with the given input value. In other words, one run of a stochastic simulator provides proportionally much less information than that of a deterministic one. This thesis focuses on developing efficient and accurate surrogate models to emulate the response distribution of stochastic simulators, combining statistical methods with state-of-the-art deterministic surrogate modeling techniques. To this end, we propose two new approaches: the generalized lambda model (GLaM) and the stochastic polynomial chaos expansion (SPCE). The first one capitalizes on the use of the generalized lambda distribution to characterize the random nature of the simulator response. The distribution parameters are functions of the input variables and are represented by polynomial chaos expansions (PCEs). We explore replication-based methods to build GLaMs and improve their performance by an additional joint optimization of the overall likelihood function. We further elaborate this idea and develop a new method that does not require replications. Using this surrogate, we investigate sensitivity analysis for stochastic simulators. The second class of stochastic surrogates, SPCE, overcomes the main shortcoming of GLaM, which is unable to represent multimodal distributions. In this more versatile stochastic emulator, we extend PCE by introducing an artificial latent variable to the expansion and an additive noise variable to mimic the intrinsic stochasticity of the simulator. We also propose an adaptive algorithm to construct the surrogate model without the need for replications. For both stochastic surrogate models, we investigate basic theoretical properties of the primary estimation method. Analytical examples and engineering applications, including wind turbine design and seismic fragility analysis, are used to validate and illustrate the performance of the new approaches. Furthermore, these engineering case studies provide valuable insights into the applicability of the developed framework to real-world industrial problems.

Masonry structures are ubiquitous in our society, serving as housing for millions worldwide and forming a large part of the world's built heritage. Their assessment and preservation are essential to achieving a more sustainable and resilient built environment. This dissertation presents a novel computational approach to assess unreinforced vaulted masonry structures. A novel limit-analysis-based framework is developed to search for admissible equilibrium states. The equilibrium solutions considered are represented by compressive thrust networks within the structure's geometry, representing their compressive flow of forces. A modular multi-objective constrained nonlinear optimisation problem is formulated and solved using interior point and sequential least-square quadratic programming techniques to search for admissible networks. Different objective functions are implemented in the optimisation framework, including the minimum and maximum horizontal thrust states, the maximum Geometric Safety Factor (GSF), maximum vertical and horizontal load multipliers, and the complementary energy minimisation for prescribed foundation displacements. The problem's constraints are formulated to translate the limit analysis admissibility criteria to thrust networks. Gradient vectors and Jacobian matrices are described analytically and computed modularly based on the objective, variables, and constraints selected. The present formulation requires minimal input, encouraging its future application as a practical numerical tool to assess existing masonry structures. Only the structural envelope, typically obtained through surveys, and the topology and planar geometry of the thrust network are needed for the analysis. The networks' topology is explored, quantifying different patterns. Pattern modification strategies are developed for problems involving different objectives. A new algorithm is described to identify the degrees of freedom in the networks necessary to analyse general topologies. A convex load-path optimisation is formulated and used as starting point for the nonlinear problems. The framework developed provides a single approach which contributes to three critical open questions in the field: 1. Computing the level of stability of vaulted masonry structures by introducing the stability domain, enabling to compute global safety factors and evaluating the structural robustness. 2. Estimating a lower bound of horizontal and vertical collapse loads by directly maximising a scalar load multiplier, contributing to protecting structures against extreme external actions and evaluating newly imposed loads. 3. Understanding the effects of foundation settlements on crack patterns by investigating minimum energy solutions arising after differential displacements, which can inform the identification and evolution of pathologies in masonry structures. Throughout the dissertation, several examples are presented to demonstrate the possibilities of the framework. Finally, the implementation is offered as an open-source Python package, enabling future collaboration and further development.

The finite element method is the most widely used numerical method for progressive collapse analysis and analysis of structures subjected to extreme loading. However, it is computationally expensive for problems where discontinuities occur. In progressive collapse analysis, an example of a discontinuity is when two or more elements separate because of failure. Variations of the finite element method, such as the extended finite element method and other numerical methods, can model such discontinuities but become computationally expensive. For large-scale analyses of progressive collapse, the method must be computationally efficient and be able to model relevant discontinuities. In this paper, a discrete method called the mixed element method is presented and compared with the finite element method in a case study. Results from the case study demonstrate small deviations between the two methods in modal analyses and different static and transient loading situations. The mixed element method uses elements that are available in common finite element software and can therefore be implemented in any finite element software., Lecture Notes in Civil Engineering, 326, ISSN:2366-2557, ISSN:2366-2565, Proceedings of the 2022 Eurasian OpenSees Days, ISBN:978-3-031-30125-4, ISBN:978-3-031-30124-7

In nonlinear response history analysis, equivalent viscous damping is often used with Rayleigh damping. For inelastic structures, this may lead to spurious damping forces. Moreover, the equivalent viscous damping is often based on vibration measurements of elastic structures. Consequently, the use of equivalent viscous damping assumes that the damping properties are identical in the elastic and inelastic range. To avoid these issues, hysteresis can be implemented explicitly in the material behavior. Because of the limited ductility of timber members, the connections often provide the ductility and energy-dissipating capacity of a timber structure. For such structures, a lumped plasticity model with hysteretic connection behavior is suitable. In this paper, a semi-analytical hysteretic model for laterally loaded timber connections with dowel-type fasteners is presented based on the individual fastener behavior. The model includes damage from cyclic loading and can be generalized to an arbitrary connection layout., Experimental Mechanics in Engineering and Biomechanics - Proceedings ICEM20, ISBN:978-989-54756-6-7

This dissertation presents a new numerical solver with an assembly-aware design workflow to help users better design and build discrete shell structures. Discrete shell structures are aesthetically ravishing but challenging to design and build efficiently. Although discrete structures can be prefabricated using efficient material and increasing productivity on-site, building discrete shell structures typically requires extensive scaffolding during their assembly process, which is associated with massive material and energy waste. Moreover, discrete shell structures usually require additional design steps normally not necessary with standard continuous structures, such as shape discretisation and stability analyses during and after construction. The state-of-the-art stability solver rigid-block equilibrium (RBE) method uses quadratic programming with penalty formulation to measure structural infeasibility. For unstable structures, RBE provides a solution with a tensile force at the unstable regions, which gives a quantified measure of instability. Moreover, this dissertation extends the RBE method with some prominent features to thoroughly understand its optimisation results and mechanical meanings. Several experiments are performed and studied, including comparing the original quadratic with a linear function to illustrate nodal forces and interface resultants’ roles and reducing the structure’s contact interface into its kern area to explore different admissible internal stress states. However, although RBE has various benefits that can be applied to the design problem, it incorrectly assesses unstable structures as stable when complex interface geometries are involved. Therefore, this dissertation provides insight into the RBE flaws, builds upon its strengths, and presents a new robust solver that overcomes the problem. Our newly proposed coupled rigid-block analysis (CRA) solver combines equilibrium and kinematics in a nonlinear programming problem. Furthermore, similar to RBE, CRA with penalty formulation makes it possible to measure infeasibility and gives valuable information to users to change their design. Comparing a wide range of benchmarks with commonly used commercial software shows CRA’s robustness and accurate mechanical description of the complex three-dimensional discrete-element assemblies formed by rigid blocks. Utilising CRA, this dissertation proposes a stability-aware design process to iteratively help the user and guide their design towards structurally-sound assemblies. Embedding stability-aware design process, an assembly-aware design (AAD) is further proposed to allow the user to consider the assembly sequence while designing discrete shell structures. Several computational and physical models were designed and assembled with limited scaffolding using our proposed workflow to verify our research findings in real-world scenarios. Finally, our CRA solver is publically available as an open-source Python package — COMPAS CRA — to help researchers and designers around the globe to build better discrete shell structures upon our work., In dieser Dissertation wird ein neuer numerischer Löser eines montagegerechten Entwurfsablaufs vorgestellt, der BenutzerInnen unterstützt, diskrete Schalentragwerke besser zu entwerfen und zu erbauen. Diskrete Schalentragwerke sind ästhetisch reizvoll, jedoch schwierig zu entwerfen und effizient zu bauen. Diskrete Tragwerke können unter Verwendung effizienter Materialien vorgefertigt werden und erhöhen so die Produktivität auf der Baustelle. Jedoch erfordert der Montageprozesses diskreter Schalentragwerke in der Regel einen umfangreichen Gerüstbau, der mit einer massiven Material- und Energieverschwendung einher geht. Darüber hinaus erfordern diskrete Schalentragwerke in der Regel zusätzliche Entwurfsschritte, die bei herkömmlichen kontinuierlichen Tragwerken nicht erforderlich sind, wie beispielsweise die Diskretisierung der Form und Stabilitätsanalysen während und nach Abschluss des Bauprozesses. Das hochmoderne Stabilitätslösungsverfahren Rigid-Block-Equilibrium (RBE) verwendet eine quadratische Programmierung mit Straffunktionen, um die strukturelle Undurchführbarkeit zu messen. Für instabile Tragstrukturen liefert die RBE-Methode eine Lösung mit Zugkraft in den instabilen Regionen, die ein quantifiziertes Maß für die Instabilität darstellt. Darüber hinaus wird in dieser Dissertation die RBE-Methode um einige bedeutende Merkmale erweitert, um ihre Optimierungsergebnisse und ihre mechanische Bedeutung gründlich zu verstehen. Experimente untersuchen den Vergleich der ursprünglichen quadratischen Funktion mit einer linearen Funktion um die Rolle der Knotenkräfte und der Schnittstellenresultierenden zu veranschaulichen. Des Weiteren wird die Reduzierung der Kontaktflächen des Tragwerks auf ihren Kernbereich untersucht, um verschiedene zulässige Eigenspannungszustände zu ergründen. Obwohl RBE diverse Vorteile hat, die auf das Bemessungsproblem angewendet werden können, werden instabile Tragwerke bei komplexen Geometrien der Kontaktflächen fälschlicherweise als stabil eingestuft. Daher gibt diese Dissertation einen Einblick in die Schwachstellen der RBE-Methode, baut auf ihren Stärken auf und stellt einen neuen robusten Löser vor, der das Problem überwindet. Unser neu vorgeschlagener gekoppelter Coupled-Rigid-Block-Analysis (CRA)-Löser kombiniert Gleichgewicht und Kinematik in einem nichtlinearen Programmierproblem. Ähnlich wie bei RBE ermöglicht CRA mit einer Straffunktion die Messung der Nichtdurchführbarkeit und liefert BenutzerInnen wertvolle Informationen, um den Entwurf anzupassen. Der Vergleich einer breiten Palette von Benchmarks mit gängiger kommerzieller Software zeigt die Robustheit von CRA und die genaue mechanische Beschreibung eines komplex dreidimensionalen, aus diskreten starren Blöcken bestehenden Tragwerks. Unter Verwendung von CRA wird in dieser Dissertation ein stabilitätsbewusster Entwurfsprozess vorgeschlagen, der BenutzerInnen iterativ unterstützt und zu strukturell soliden diskreten Tragwerken führt. Zur Einbettung des stabilitätsbewussten Entwurfsprozesses wird außerdem ein Assembly-Aware-Design (AAD) vorgeschlagen, der es BenutzerInnen ermöglicht, die Montagereihenfolge beim Entwurf diskreter Schalenstrukturen zu berücksichtigen. Mehrere rechnerische und physische Modelle wurden mit limitierten Gerüsten unter Verwendung unseres vorgeschlagenen Arbeitsablaufs entworfen und montiert, um unsere Forschungsergebnisse mit realen Szenarien zu verifizieren. Schlussendlich ist unser CRA-Löser als Open-Source-Python-Paket COMPAS CRA öffentlich verfügbar, um ForscherInnen und KonstrukteurInnen weltweit zu helfen, bessere diskrete Schalenstrukturen auf der Grundlage unserer Arbeit zu entwickeln.

Dynamische Beanspruchungen können das Ergebnis natürlicher oder vom Menschen verursachter Aktivitäten sein. Partikeleigenschaften wie Korngröße, Korngrößenverteilung, Mineralogie, Feinkorngehalt und Kornform spielen hierbei eine wichtige Rolle und beeinflussen das mechanische Verhalten der Böden. In dieser Arbeit wird der Einfluss verschiedener Partikeleigenschaften wie Korngröße, Korngrößenverteilung und Kornform auf das inhärente, statische, zyklische und dynamische Verhalten granularer Materialien untersucht. Neben der Kornform wird der Einfluss der Korngrößenparameter auf die Lagerungsdichte von granularen Böden untersucht. Darüber hinaus wurde eine Reihe von Triaxial- und Resonanzsäulenversuchen unter verschiedenen Randbedingungen an drei Materialien mit sehr unterschiedlichen durchgeführt, um den Einfluss der Kornform auf verschiedene Bodeneigenschaften zu quantifizieren. Am Ende, die experimentellen Ergebnisse wurden anschließend im Kontext der Mikromechanik diskutiert., Schriftenreihe des Lehrstuhls für Bodenmechanik, Grundbau und Umweltgeotechnik, 75

In this paper, a test setup for conducting impact testing of full-size timber beams is presented. The test setup comprises a pendulum impact hammer with an effective length of 4750 mm, mass of 3475 kg, and can be released from a near-horizontal position. On the impact hammer, 100g accelerometers and a shock-resistant high-speed camera with a capacity of up to 5700 pictures per second were installed. In addition, other cameras were installed, as well as an angular encoder to record the position of the pendulum impact hammer. The pendulum impact hammer was released using an electromechanical release system attached to a crane. The impact hammer was designed for impact tests on timber beam specimens with cross-sections ranging from 160x160 mm to 200x320 mm and lengths between 2700 and 4300 mm. The results include the energy release of the specimens upon failure, peak impact forces, time to failure, and high-speed imagery. With the test setup, similar knowledge can be gained for other engineered wood products., World Conference on Timber Engineering WCTE 2023, ISBN:9781713873273

Concrete hinges are monolithic connections in structural concrete, shaped to carry high axial compressive forces and undergo significant rotations while developing little moment resistance about at least one hinge axis. This behaviour is particularly useful for articulating linear elements under high axial compressive loads, such as bridge piers and arches. It is achieved by suitably tapering the member section and centring forces and deformations in a small zone, referred to as the hinge throat. Nowadays, concrete hinges are mainly used to reduce restraint stresses in monolithic structures (e.g. integral bridges) as an alternative to conventional bearings. Despite the century-long experience, which confirms the numerous advantages of concrete hinges over conventional bearings (particularly in terms of cost-effectiveness, durability, robustness, sustainability, and appearance), engineers are often still reluctant to opt for concrete hinges. The primary reasons are the limited mechanical understanding of their structural behaviour and the lack of sufficient experimental data, which is reflected in inadequately substantiated design guidelines. A remarkable knowledge gap exists even for the hinge behaviour under the fundamental loading case of axial compression without hinge rotation, which essentially corresponds to that of a partially loaded area. The behaviour under general loading (i.e. bending moments and shear forces) entails even greater uncertainties and open questions. Due to these issues, the potential of concrete hinges is far from being adequately exploited. This thesis aims at alleviating the uncertainties arising when designing and assessing concrete hinges by theoretically and experimentally investigating the underlying mechanisms governing their structural behaviour and proposing mechanically substantiated and experimentally validated models for their analysis and design. To this end, the first part of the thesis is devoted to an in-depth investigation of the structural behaviour of partially loaded areas, i.e. regions where high, concentrated compressive forces are applied over limited contact areas. The accurate understanding and modelling of this fundamental structural engineering problem are of paramount importance to be able to consistently model the more complex behaviour of concrete hinges under general loading. Several discontinuous stress field solutions are proposed to consistently account for the multiaxial strength of concrete and the favourable effect of confinement reinforcement. The results from an extensive experimental campaign conducted on 62 partially loaded concrete blocks show that, compared to the existing, semi-empirical design rules, the proposed stress fields yield very accurate and significantly less conservative predictions of the bearing capacity, thereby enabling a much better exploitation of the structural capacity with reduced uncertainties. The second part of the thesis investigates the structural behaviour of one-way concrete hinges under general loading. In order to extend the very scarce available test data, seven large-scale concrete hinges with light reinforcement crossing their throat were tested in the Large Universal Shell Element Tester at ETH Zurich. The specimens were subjected to multi-stage load histories targeting various failure types (due to axial compression, hinge rotation, shear force parallel or perpendicular to the hinge axis, bending moment about the strong axis, and torque). The experiments (i) confirm the remarkably high compressive strength and deformation capacity of the confined concrete in the hinge throat observed in previous studies, (ii) demonstrate that the hinge can sustain large shear forces and torques if sufficient axial compression is provided, and (iii) reveal that a moderate reinforcement crossing the hinge throat considerably increases the shear resistance at low axial stresses and prevents brittle shear failures. Building on the insights gained from the experiments and previous theoretical studies, the analytical modelling of concrete hinges is revisited using approaches compatible with current design standards. A cross-sectional analysis with confined concrete properties is proposed for the behaviour under axial forces and bending moments, where the strength of the triaxially compressed concrete in the hinge throat and the adjacent blocks is determined with the stress fields developed in the first part of the thesis. The shear strength of concrete hinges is investigated with failure mechanisms inspired by failure modes observed in experiments. Based on the shear strength, a simple approach to estimate the torsional resistance of the throat is also proposed. Overall, the proposed models are mechanically more consistent and agree better with the available experimental data than previously proposed modelling approaches. Moreover, they predict significantly higher resistances, allowing for a more efficient design and potentially fostering the application of concrete hinges in future projects.

Die hybride Brandsimulation (HFS) ist eine neuartige Methode zur Analyse der Gesamtstrukturen im Brandfall. Bei dieser Methode wird der Teil eines Bauwerks, das einem Brand ausgesetzt ist, in einem Brandversuch physikalisch getestet, während der Rest des Bauwerks numerisch modelliert wird. Bei HFS als erweiterter FE-Simulation kontrolliert und aktualisiert das numerische Modell kontinuierlich die Daten des laufenden Brandversuchs. In dieser Dissertation wird ein kleines Benchmark-Problem mit einem Freiheitsgrad verwendet. Es werden eine Reihe von hybriden Brandsimulationen durchgeführt und die Robustheit und Genauigkeit des implementierten HFS-Frameworks wird durch die Untersuchung verschiedener Parameter, wie z.B. des angewandten Lastverhältnisses, der Aufheizrate sowie einflussreicher rechnergestützter Faktoren, validiert. Darüber hinaus wird der Einfluss des Wärmeübergangs an der Schnittstelle von Substrukturen im Hybridmodell durch einen virtuellen HFS-Ansatz dargestellt., Hybrid fire simulation (HFS) is a novel method for analysis of global performance of structures in fire. In the principles of this method, the part of a structure subjected to fire is physically tested in a fire test while the rest of the structure is numerically modeled. In HFS as an extended FE simulation, the numerical model continuously controls and updates the data of the ongoing fire test. In this dissertation, a small-scale one-degree-of-freedom benchmark problem is applied. A series of hybrid fire simulations are performed and the robustness and accuracy of the implemented HFS framework are validated by investigating various parameters as applied load ratio, heating rate as well as influencing computational factors. Additionally, the influence of heat transfer at the interface of substructures in hybrid model is also presented by a virtual HFS approach.

The reduction of the concrete volume used in the construction sector – triggered by the urgent demands on sustainability – has become one of the critical drivers for developing new composite materials and structural typologies. This thesis presents a novel approach for stay-in-place fexible formworks with integrated textile reinforcement based on the KnitCrete technology, reducing the environmental footprint of concrete structures through structurally informed geometries and slender dimensions, enabled by the use of weft-knitted fabrics and non-corrosive high-strength fbrous materials. The frst part of the thesis explores the possibilities arising from knitted textiles – including the feasibility of creating doubly curved geometries and introducing continuous rovings and spatial ribs – and revisits conventional reinforcement types and their suitability for complex geometries, proposing two directions for lean reinforcement strategies: (i) use of high-strength fbrous materials for the manufacturing of weft-knitted textiles and (ii) guiding conventional reinforcement (i.e. deformed steel bars or post-tensioning tendons) with integrated features within the fexible formworks. The second part of the thesis aims at characterising the mechanical behaviour of weft-knitted textile reinforced concrete regarding the (i) strength, (ii) stifness, (iii) bond, and (iv) deformation capacity. To this end, several experimental campaigns are conducted to prove the feasibility of the manufacturing procedure and examine the structural response under various loading conditions, including uniaxial tension, bending, and shear. The investigations focus on various knitting patterns, textile materials, coating types, and the infuence of shear connectors to enhance the bond conditions and the addition of short fbres to the concrete to improve the post-cracking behaviour. Furthermore, the combination of brittle and ductile reinforcement materials and the optimisation of the geometry by means of thinwalled cross-sections are studied. The load-deformation and failure behaviour is evaluated using refned measuring techniques, i.e. digital image correlation and distributed fbre optical sensing, which allow assessing the mean strains in the reinforcement and the crack kinematics. Analytical methods following the Tension Chord Model, which considers the stress transfer between the reinforcement and the concrete based on mechanically consistent assumptions, allow the adaptation to the specifc geometry of the weft-knitted textile reinforcement, the back-calculation of bond shear stresses, and the consideration of the short fbres in the concrete. The resulting predictions are validated with the experimental results. The load-bearing capacity of concrete beams with integrated transverse textile reinforcement is analysed regarding various contributions from the concrete and the high-strength rovings to the shear transfer across the governing crack and modelled using numerical simulations based on the Compatible Stress Field Method. The third part of the thesis discusses potential structural applications based on the fndings on the mechanical behaviour obtained from the experimental investigations. The implications of using brittle reinforcement materials are addressed, and various means to implement ductility in the global structural response are discussed, eventually proposing a classifcation framework for safe and reliable design principles to achieve an adequate post-cracking behaviour. The thesis concludes with a case study examining the structural behaviour of doubly curved concrete shells using non-linear fnite element analyses, highlighting the potential of the developed reinforcement approach for structures with complex geometries.

Carbon dioxide (CO2) capture, utilization, and storage (CCUS) by mineralization has been shown to reduce greenhouse gas (GHG) emissions not only in stand-alone plants but also in large-scale climate-optimal supply chains. Yet, implementing the large-scale supply chain for CCUS by mineralization requires a substantial financial investment and, thus, a deep understanding of its economics. The current literature estimates the economics of CO2 mineralization for stand-alone plants. While CO2 mineralization plants have their specific a) CO2 supply, b) solid feedstock supply, c) energy supply, and d) product market, the plant-level cost estimation does not account for a large and potentially shared supply chain. In our study, we assess the economics of mineralization by designing and analyzing cost-optimal supply chains for CCUS by mineralization in Europe. Our results show that the CO2e abatement costs of individual mineralization plants in a supply chain range from 110 to 312 €/ton CO2e avoided. The proposed supply chains for CCUS by mineralization can avoid 60 Mt CO2e/year in Europe at CO2e abatement costs comparable to CO2 capture and geological storage. Furthermore, we identify five locations that could offer a robust business case for CO2 mineralization. The analysis thus shows pathways on how to add CO2 mineralization to the GHG mitigation portfolio of Europe., Journal of CO2 Utilization, 72, ISSN:2212-9820, ISSN:2212-9839

This database compiles over 1000 entries on pore solution compositions of cementitious systems, from early ages to years. The data were obtained through a literature review of 58 studies published between 1981 and 2021. Systems include a diversity of cementitious materials (mainly Portland cement mixed with silica fume, fly ash, slag, and fillers), mix proportioning, curing conditions, carbonation, experimental extraction procedures, and analytical techniques employed on pore solution characterization. The ionic concentrations reported are on OH-, Na+, K+, Ca2+, sulfur species, eventual minor ions, measured and calculated pHs, and ionic strength. Thus, the database is a comprehensive source of information on the ionic concentration of the concrete pore solution, summarized in a single file. It can support the investigation of these features’ influence on the solution, clarifying trends in literature based on diversified data. A detailed interpretation of the data and its possibilities is provided in an article published in Cement and Concrete Research. There, part of the database was applied to train Machine Learning models for predicting the pore solution composition of hardened cementitious systems. Furthermore, these data can support research on deteriorative processes in concrete, considering the relevance of pore solution composition on corrosion processes, alkali-aggregate reaction, sulfate attack, and others.

This work reports about preparation of W/Fe co-sputtered layers between tungsten and steel in order to ease their coefficient of thermal expansion mismatch.Iron and tungsten have been gradually co-sputtered on W tiles with real time deposition parameters changing to obtain a graded interlayer: SEM, EDS, XPS, HR-TEM have been used to characterize the W/Fe co-sputtered layer.W tiles co-sputtered with the W/Fe layers have been hot pressed to steel tiles: morphology and mechanical strength have been investigated for joints with and without W/Fe co-sputtered layer.Lap-shear tests in compression at room temperature have been made on hot pressed W/steel joints with and without W/Fe co-sputtered layer, showing a different behaviour.High flux test on joints with and without W/Fe co-sputtered layer are reported and discussed. The mechanical test results of manufactured joints are in good accordance with high heat flux test results, showing that the behaviour of hot-pressed joints with W/Fe co-sputtered layer was slightly worse if compared to joints without co-sputtered layer at the interface.

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2023; Aachen : RWTH University Aachen Online-Ressource : Illustrationen, Diagramme (2023). = Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2023, This thesis describes the development of a closed-loop model for the virtual application of the air con-ditioning system for vehicles. Virtual application describes the design and development of the control behavior of a system by a virtual model. To be able to observe the behavior of the controlled system, the model must be in a closed-loop state, since this is the only way to represent the complete control loop. Within the literature research conducted at the beginning of the thesis, mainly models where found in which either the control system, the air conditioning system in connection with the air vents or the cabin model were simplified to an extent that a closed-loop state is not possible. First, different parts of the air conditioning system were investigated by measurements to enable their modeling. To measure the air and temperature distribution of the HVAC Unit, a test setup of the distribution tract was built to measure the distribution of the flow variables for different representative flap positions. Since the accuracy of the existing measurement methods was not sufficient, special attention was paid to the development of a new measurement method. Furthermore, a measurement of the leakage enables the integration of the leakage air rate into the simulated models. In addition to the distribution tract, a test setup was created to measure the delivery characteristic of the blower. Training data is needed as a basis for building machine learning models. In this work, the models used to generate this data are referred to as baseline models. Derived equivalent pressure drops for diffusers and air ducts significantly reduced the computational time of the baseline CFD model used for the re-quired number of data points, allowing an HVAC fluid model to be derived in STARCCM+. In addition, a baseline blower model was also created in STARCCM+ and validated using the blower characteristics. Due to the complex flow processes in the area of the blower tongue, the delivery characteristic of the blower can only be calculated with the required accuracy by scale-resolving simulations. Based on the validation of the baseline models, reduced metamodels from the field of machine learning were built using the Python Toolbox P7. Here, the air handling unit consists of several submodels based on Gauss-ian processes. The initial model of the distribution tract does not achieve the necessary accuracy for the virtual application. To increase the accuracy, a resampling algorithm and a linear error condition were designed and implemented in an extended model. The different submodels were interconnected in a HVAC-metamodel. The modeling used results that have no information about the multi-dimensional flowfield at the cabin vents. The flow field of the outlets is relevant for the thermal comfort in the cabin. To compensate for this effect and to avoid having to calculate the outlets in the overall vehicle model due to the different geometric length dimensions, a reduced model was derived for the outlets based on a principal component analysis. The flow fields were decomposed into their characteristic eigenmodes and eigenvalues and the eigenvalues were represented by a regression model. A model of a Porsche 911 4S (992) with a high level of detail was built as the controlled system in this work. The model consists of a weathering model, vehicle model and cabin model. The software of the climate con-troller was derived as an FMU model and coupled with the complete vehicle model, the reduced mod-els and a residual bus simulation. For representative load cases, the closed-loop composite model was validated using a climatic wind tunnel measurement. The load cases correspond to the VDI specifica-tions for summer and winter load cases for the representation of heating and cooling processes. The validation demonstrated the suitability of the model for virtual application., Published by RWTH University Aachen, Aachen

The construction industry faces the challenge of reducing its large environmental impact while at the same time providing housing and infrastructure to a growing global population. One of the main causes of the negative impact is the vast amount of reinforced concrete used. Digital fabrication with concrete (DFC) might offer a path towards more sustainable construction by producing structurally optimised shapes without extra cost or effort. However, DFC technologies have been mainly applied to date to produce elements with low structural demand. One of the main reasons for this limited applicability is the challenge of integrating reinforcement to comply with existing building codes. This thesis thus aims at advancing the application of DFC for load-bearing applications by developing and assessing reinforcement strategies based on sound structural principles. To this end, five experimental campaigns were designed, examining various fabrication approaches and reinforcement strategies and assessing their performance based on established models for reinforced concrete. In its first part, the thesis is contextualised based on the two identified current challenges, i.e., (i) of the construction industry to reduce its environmental impact and (ii) of DFC to reach structural integrity. The need for consistent structural testing of large-scale components with simple geometries is identified based on the state-of-the-art of various DFC technologies and corresponding reinforcement strategies. The second part of the thesis presents five experimental campaigns exploring and assessing various reinforcement strategies. In the first campaign, the feasibility of aligned interlayer fibre reinforcement as shear reinforcement is explored. These fibres are combined with unbonded post-tensioning and bonded passive deformed steel reinforcing bars as longitudinal reinforcement of 3D concrete printed beams, and the resulting behaviour is compared to that of beams without and with steel cables as shear reinforcement. In the second campaign, the versatility of aligned interlayer fibres as shear reinforcement is examined for the Eggshell technology on rectangular beams and compared to fibres in the mix and conventionally cast specimens. The insights from these beams are then applied for material optimisation resulting in a T-beam with almost 50% volume reduction. The bond between 3D printed concrete and conventional reinforcement or cables is assessed on pull-out tests produced with high yield stress or set on-demand concrete in the third campaign. The fourth campaign investigates conventional reinforcement cages designed according to established building codes to fabricate an optimised T-beam with 3D concrete printing. The last campaign explores the use of reinforcing bar meshes fixed by shotcreting to an unreinforced printed shell as a reinforcement solution for water tank walls, with the structural performance being evaluated with a series of direct tension tests. The results of these five experimental campaigns allow (i) gaining insights into the efficiency of the reinforcement strategies, (ii) assessing the influence of fabrication parameters, (iii) comparing the results to models for conventional reinforced concrete, and where needed, (iv) developing new models based on established structural principles. The lessons learnt are discussed in the third part of the thesis and put into context with other reinforcement approaches and DFC technologies, comparing the various reinforcement strategies and identifying their advantages and drawbacks, highlighting the complexity of choosing the right fabrication parameters and finally proposing future research areas for structural applications of DFC.

Um die bestehenden Unsicherheiten bei der Beurteilung der Tragsicherheit vieler bestehender Winkelstützmauern zu beseitigen, die von lokaler Korrosion der Bewehrung oberhalb der Arbeitsfuge am Wandfuss betroffen sind, wurden vom Astra mehrere Forschungsprojekte lanciert. Der vorliegende Bericht fasst die Ergebnisse des in diesem Zusammenhang durchgeführten Forschungsprojekts AGB 2015/028 zusammen, welches die Auswirkungen der lokalen Korrosion auf das Last-Verformungsverhalten untersuchte. Ergänzende Resultate sind in der ETH-Dissertation „Load-deformation behaviour of reinforced concrete structures affected by local corrosion“ von S. Haefliger enthalten, welche diesem Bericht angehängt ist. Ein lokaler Querschnittsverlust der Bewehrung vermindert offensichtlich den Tragwiderstand von Stahlbetontragwerken. Andererseits reduziert er aber auch – infolge der Lokalisierung der Verformungen – in nochmals stärkerem Ausmass ihr Verformungsvermögen. Letzteres ist bei Stützbauwerken äusserst relevant, da der Erddruck als primäre Einwirkung dieser Bauwerke stark verformungsabhängig ist: Die bei der Bemessung von Stützmauern übliche Annahme des aktiven oder erhöhten aktiven Erddrucks setzt ein ausreichendes Verformungsvermögen voraus, welches bei korrodierenden Stützmauern mutmasslich nicht vorhanden ist. Wird bei der Überprüfung solcher Mauern eine geringere Belastung als der Erdruhedruck angesetzt, muss daher ein ausreichendes Verformungsvermögen nachgewiesen werden. Im vorliegenden Projekt wurden dazu benötigte Grundlagen erarbeitet. Die Resultate aus den Versuchen und theoretischen Untersuchungen zeigen, dass Tragwiderstand und Verformungsvermögen massgeblich von der Verteilung des Gesamtquerschnittsverlusts auf die einzelnen Bewehrungsstäbe abhängen, die Angabe eines mittleren oder gesamten Querschnittsverlusts also nicht ausreichend für eine realitätsnahe Beurteilung ist. Weiter beeinflussen lokale Effekte rund um die Korrosionsstelle (dreidimensionaler Spannungszustand und Biegeeffekte) das Last-Verformungsverhalten des Tragwerks und können das Verformungsvermögen günstig beeinflussen. Modelle, die lediglich die Verformungslokalisierung berücksichtigen, unterschätzen demnach das verbleibende Verformungsvermögen. Aus den Erkenntnissen des Projekts wurde in Zusammenarbeit mit der Forschungsstelle des vor dem gleichen Hintergrund durchgeführten Projekts AGB 2015/029 „Bruchverhalten von Winkelstützmauern – Boden-Wand Interaktion“, das auf die geotechnischen Aspekte (u.a. verformungsabhängiger Erddruck) fokussierte, eine mehrstufige Strategie abgeleitet, die für die Überprüfung von Winkelstützmauern mit lokal korrodierender Bewehrung herangezogen werden kann. Weiter werden Empfehlungen für die Projektierung und Ausführung neuer Winkelstützmauern und Hinweise für die weitere Forschung zu korrodierenden Bauwerken gegeben., Afin d’éliminer les incertitudes lors de l’évaluation de la sécurité structurale des murs de soutènement à semelle affectés par la corrosion des armatures au-dessus du joint de construction à la base du mur, plusieurs projets de recherche ont été lancés par l’OFROU. Ce rapport résume les résultats du projet de recherche AGB 2015/028, qui a étudié les effets de la corrosion locale sur le comportement charge-déformation de ces murs. Les résultats complémentaires sont compris dans la dissertation ETH „Load-deformation behaviour of reinforced concrete structures affected by local corrosion“ de S. Haefliger, qui est jointe à ce rapport. Une réduction locale de la section de l’armature réduit évidemment la résistance ultime des structures en béton armé. Toutefois, elle réduit encore davantage la capacité de déformation des structures, en raison de la localisation des déformations. Ceci est particulièrement important pour les structures de soutènement, parce que la poussée des terres, charge primaire de ces structures, dépend fortement des déformations: L’hypothèse habituelle de la poussée active ou d’une poussée active majorée présuppose une capacité de déformation suffisante, qui n’existe supposément pas dans les murs de soutènement corrodés. Si la poussée des terres considérée lors de la vérification de ces murs est inférieure est à celle au repos, il faut donc vérifier que la capacité de déformation soit suffisante. Le présent projet a permis d’élaborer les bases de calcul requises pour cette preuve. Les résultats des essais et des recherches théoriques montrent que la résistance ultime et la capacité de déformation dépendent de la distribution de la réduction de la section totale sur différentes barres d’armature. L’indication d’une réduction de section moyenne ou totale ne suffit donc pas pour une évaluation réaliste. De plus, les effets locaux autour de la zone corrodée (état de contrainte tridimensionnel et effets de flexion) influencent le comportement charge-déformation de la structure, pouvant améliorer la capacité de déformation. Les modèles qui regardent seulement l’effet de localisation sous-estiment donc la capacité de déformation résiduelle. Sur base des conclusions du présent projet et en collaboration avec l’équipe de recherche du projet AGB 2015/029 „Comportement de rupture des murs de soutènement à semelle – Intéraction sol-mur“, réalisé dans le même contexte et centré sur les aspect géotechniques (notamment la poussée des terres en fonction des déformations), une stratégie en plusieurs étapes a été élaborée pour la vérification des murs de soutènement à semelle affectés par la corrosion locale. De plus, des recommandations pour la conception et la réalisation de nouveaux murs de soutènement cantilever ont été données, ainsi que des indications pour la poursuite des recherches sur les ouvrages affectés par la corrosion., The Federal Roads Office FEDRO launched several research projects to reduce the present uncertainties regarding the structural safety assessment of many cantilever retaining walls affected by local corrosion of the reinforcement above the construction joint at the wall base. The present report summarises the results of the research project AGB 2015/028, which investigated the effects of local corrosion on the load-deformation behaviour. The ETH dissertation „Load-deformation behaviour of reinforced concrete structures affected by local corrosion“ by S. Haefliger contains supplementary results and is added to the appendices of this report. A local cross-section loss of the reinforcement obviously reduces the load-carrying capacity of reinforced concrete structures. On the other hand, and to an even greater extent, it also reduces their deformation capacity due to the localisation of the deformations. The latter is highly relevant for retaining walls since the earth pressure – as primary load of these structures – strongly depends on the deformation: The usual assumption of an active or increased active earth pressure in the design of retaining walls relies on a sufficient deformation capacity, which is presumably strongly impaired in case of corrosion. Therefore, the deformation capacity needs to be assessed carefully if a lower load than the earth pressure at rest is assumed for corroding retaining walls. For this purpose, the necessary basics were developed within this project. The results of the experiments and theoretical investigations show that the load-carrying and deformation capacity significantly depend on the distribution of the total cross-section loss over the individual reinforcing bars. Therefore, merely indicating a mean or total crosssection loss is not sufficient for a realistic assessment of corroding structures. Moreover, local effects at the corrosion pits (triaxial stress state and bending moments) influence the load-deformation behaviour and can have a favourable effect on the deformation capacity. Models solely considering the strain localisation thus underestimate the residual deformation capacity. Based on the findings of this project, a multilevel strategy for the assessment of cantilever retaining walls affected by local corrosion was elaborated in close collaboration with the research team of the project AGB 2015/029 „Failure of Cantilever Retaining Walls – SoilRetaining Wall Interaction“, which was carried out against the same background but focusing on the geotechnical aspects (including the deformation-dependent earth pressure). Furthermore, recommendations for the design and construction of new cantilever retaining walls and for further research on corroding structures are given.

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2023; Aachen : RWTH Aachen University 1 Online-Ressource : Illustrationen, Diagramme (2023). = Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2023, Wind energy is one of the main contributors to the worldwide transition towards renewable energies. To increase the generation capacity, wind turbine rotors and towers have become increasingly larger, making modern wind turbines highly sensitive to aerodynamic and aeroelastic effects. Some of these effects, especially those acting on tubular steel towers, have been studied in this thesis through wind tunnel measurements.Firstly, the tower along-wind aerodynamic damping has been determined using the forced oscillations method. Surface roughness modification techniques have been used to reduce Reynolds number scale effects. The aerodynamic damping has been determined in wind tunnel tests, applied in a study case, and described analytically. Its relevance is limited to parked conditions and extreme wind speeds. For the first time, the forced oscillations method has been used to determine the aerodynamic damping of wind turbine rotors and their blades, and the results have been proved to reflect the predictions from multi-body simulations and well-known analytic approaches from the literature. The methodology, equations and scaling laws required for wind tunnel measurements of wind turbine models using the forced oscillations method have been developed and documented in detail.%It is concluded that the forced oscillation method can be used for the determination of the aerodynamic damping of wind turbines.Secondly, the characteristics of vortex-induced vibrations in parked wind turbines have been studied using an aeroelastic wind tunnel model, and the most critical rotor positions have been identified. For some configurations, the measurements show VIV occurrences at Strouhal numbers around St=0.14 or at two different Strouhal numbers, being this a singularity of parked wind turbines. The results have been applied to a study case, and a reduction of VIV amplitudes due to rotor blade disturbances has been observed in most cases.Finally, the blade passing effects on the wind turbine tower aerodynamics have been determined in wind tunnel measurements for one operation state. The resulting tower aerodynamic coefficients have been averaged for one blade passing and given at five tower heights for its implementation in multi-body-simulations. The blade passing effects have been quantified in a study case. A light reduction of the average along-wind tower base moment, an increase of the average and RMS cross-wind tower base moments, and a small increase of the estimated fatigue damage is observed near the cut-of speed., Published by RWTH Aachen University, Aachen

Journal of CO2 utilization : JCOU 69, 102423 (2023). doi:10.1016/j.jcou.2023.102423, Published by Elsevier, Amsterdam [u.a.]

Advanced science 10(6), 2205890 (2023). doi:10.1002/advs.202205890, Nanoporosity is clearly beneficial for the performance of heterogeneous catalysts. Although exsolution is a modern method to design innovative catalysts, thus far it is predominantly studied for sintered matrices. A quantitative description of the exsolution of Ni nanoparticles from nanoporous perovskite oxides and their effective application in the biogas dry reforming is here presented. The exsolution process is studied between 500 and 900 °C in nanoporous and sintered La$_{0.52}$Sr$_{0.28}$Ti$_{0.94}$Ni$_{0.06}$O$_{3±δ}$. Using temperature-programmed reduction (TPR) and X-ray absorption spectroscopy (XAS), it is shown that the faster and larger oxygen release in the nanoporous material is responsible for twice as high Ni reduction than in the sintered system. For the nanoporous material, the nanoparticle formation mechanism, studied by in situ TEM and small-angle X-ray scattering (SAXS), follows the classical nucleation theory, while on sintered systems also small endogenous nanoparticles form despite the low Ni concentration. Biogas dry reforming tests demonstrate that nanoporous exsolved catalysts are up to 18 times more active than sintered ones with 90% of CO$_2$ conversion at 800 °C. Time-on-stream tests exhibit superior long-term stability (only 3% activity loss in 8 h) and full regenerability (over three cycles) of the nanoporous exsolved materials in comparison to a commercial Ni/Al$_2$O$_3$ catalyst., Published by Wiley-VCH, Weinheim

One of the major design limitations for tokamak fusion reactors is the heat load that can be sustained by the materials at the divertor target. Developing a full understanding of how machine or operation parameters affect the conditions at the divertor requires an enormous number of simulations. A promising approach to circumvent this is to use machine learning models trained on simulation data as surrogate models. Once trained such surrogate models can make fast predictions for any scenario in the design parameter space. In future such simulation based surrogate models could be used in system codes for rapid design studies of future fusion power plants. This work presents the first steps towards the development of such surrogate models for plasma exhaust and the datasets required for their training. Machine learning models like neural networks usually require several thousand data points for training, but the exact amount of data required varies from case to case. Due to the long runtimes of simulations we aim at finding the minimal amount of training data required. A preliminary dataset based on SOLPS-ITER simulations with varying tokamak design parameters, including the major radius, magnetic field strength and neutral density is constructed. To be able to generate more training data within reasonable computation time the simulations in the dataset use fluid neutral simulations and no fluid drift effects. The dataset is used to train a simple neural network and Gradient Boosted Regression Trees and test how the performance depends on the number of training simulations.

A significant part of the existing building stock in Europe has been designed without modern seismic considerations and is, in the meantime, exceeding its design life-span. Even in sites of moderate seismicity, earthquakes bear large loss potential, driven by low-probability but high-impact events. Reducing seismic risk remains a major scientific frontier and reliable estimation of building vulnerability prior to and in the direct aftermath of earthquakes is a fundamental step towards quantifying and, eventually, reducing seismic risk. Structural Health Monitoring (SHM) offers tools to leverage measurement data to accelerate evaluations and reduce the uncertainty pertaining to engineering models. Despite recent advances in sensor technology and computational capabilities, SHM retains unexploited potential and is often limited to the research domain. This is mainly attributed to missing guidelines and standardized frameworks for efficient treatment and robust interpretation of monitoring data, as well as to the limited amount of recordings from real buildings. This thesis aims to provide practical techniques to support the seismic evaluation of existing buildings with monitoring data, as well as to develop robust post-earthquake damage indicators. A first step towards this goal consists in collecting data from real buildings with higher amplitudes than ambient vibrations and in different damage states. To facilitate and formalize data collection, a framework for monitoring unreinforced masonry (URM) buildings prior to and during planned demolitions is proposed. URM buildings comprise a significant part of the existing building stock in Europe, one that is particularly vulnerable to earthquakes. Vibration-based monitoring in operating buildings is hindered by accessibility issues and is limited to low-amplitude ambient vibration measurements. Demolitions of URM buildings are conducted progressively with an excavation shovel, providing a cost-efficient way to collect vibrational data. Studying the dynamic response at various amplitude levels in the commonly assumed linear-elastic regime exposed reversible stiffness reduction, which affects the predicted seismic performance and is mainly attributed to “breathing” cracks in masonry. Based on monitoring recordings from nine URM buildings undergoing demolition, a Bayesian model-updating framework is proposed and implemented, demonstrating a significant reduction in uncertainties related to predicted seismic performance. This enables the direct comparison of multiple buildings featuring either similar or different structural characteristics. Furthermore, by extrapolating the information extracted from monitored buildings that are representative of a broader typological class, provides the means to dynamically update vulnerability and risk maps at regional scale. Clustering together buildings featuring similar seismic performance is eminent, to define representative buildings at regional scale, thus paving the way to data-informed regional post-earthquake loss assessment. Therefore, damage-sensitive features (DSFs) derived from vibrations are used to quantify the damaging impact of ground motions. An extensive set of DSFs computed on low-amplitude response prior to and directly after earthquakes is evaluated in terms of damage-prediction accuracy. The predictive performance of fragility functions involving individual DSFs is compared with Engineering Demand Parameters (EDPs) and intensity Metrics (IMs). DSFs are shown to outperform peak ground acceleration, which is a typical IM and is currently used in regional risk and damage assessment. Gradientboosted decision trees and convolutional neural networks are deployed to fuse multiple DSFs into robust damage classifiers. Owing to the uncertainties arising when simulating nonlinear building responses to earthquakes, a domain adaptation framework is proposed and enables successful transfer of the knowledge obtained from physics-based simulation models to real data. While such techniques are very promising when applied to available data, long-term monitoring application are undermined by the limited life-cycle of sensors compared to the monitored structures. To alleviate this issue, timely identification of sensor faults and robust characterization of their origin are required. A semi-supervised framework for sensor fault detection is combined with an approach to interpret black-box model predictions, on the basis of the herein proposed “decision trajectories”. Additionally, a measure of correlation, namely the Decision Trajectory Assurance Criterion (DTAC), which enables the characterization of new fault types and the automatic classification of anomalies to known fault classes. The framework is designed to be independent of structure-specific characteristics and the type, amount, and locations of sensors used, providing an easy to train, project-agnostic tool, which can be seamlessly integrated into the pre-processing part of many SHM applications. This thesis contributes to seismic vulnerability assessment, by confronting the main challenges that currently limit the broad application of vibrationbased SHM for data-driven enhancement of seismic evaluation before and after earthquakes. Extensive monitoring data from real structures has been acquired during demolitions and used to validate the proposed frameworks, together with benchmark monitoring data from long-term monitored structures and a large-scale shake-table test. Thorough comparisons with the state of practice have been conducted to quantify the benefit of data-informed engineering solutions. Overall, the outcome of this work sheds light on the practical value of integrating SHM in seismic evaluation, towards SHM-based vulnerability assessment, and provides a baseline for the broad establishment of vibration-based SHM as a valid tool in the engineering community.

The interaction of reinforcement and concrete through bond is fundamental to the structural behaviour of reinforced concrete structures and must be preserved throughout their service lives. Bond behaviour has, thus, been the subject of intensive investigations since the advent of reinforced concrete. However, many aspects still lack a clear, mechanically consistent characterisation due to limitations of the conventional measurement techniques and the difficulty to obtain measurements at the reinforcement-concrete interface without modifying its structural behaviour. Consequently, the complex bond mechanisms are predominantly idealised as nominal bond shear stresses with a uniform distribution along the reinforcing bar perimeter, of which the magnitude is expressed as a function of the relative displacement between concrete and reinforcement. This thesis provides new insights into the bond behaviour through the application of fibre optical sensors mounted directly on the reinforcing steel bars embedded in concrete. The focus of the investigation is to characterise the effects of repeated tensile loading and unloading on bond and their implications for the tension stiffening. In the first part of the thesis, the potential of distributed fibre optical sensing in the field of reinforced concrete research is explored. An optimal instrumentation of reinforcing bars as well as the data acquisition and post-processing methods, as identified in a series of pilot tests, are described. Subsequently, the performance of fibre optical sensors applied to measure elastic strains in high-cyclic tests and strains exceeding the yield limit of the reinforcement is assessed. The second part of the thesis presents the results of a comprehensive experimental programme comprising a total of 31 pull-out tests and 28 reinforced concrete ties subjected to monotonic, cyclic and high-cyclic loading. Detailed measurements obtained in the former test configuration allow reconsidering the suitability of this test set-up for the description of the bond behaviour. The assessment of local strains observed in the reinforced concrete ties allows a qualitative description of the bond deterioration mechanism under repeated loading. From these observations, two approaches are proposed to account for the effects of repeated loading in the load-deformation analysis. The first approach is centred around solving the differential equation of slip using various bond stress-slip relationships accounting for bond degradation near the cracks and through repeated loading. The second approach is based on the Tension Chord Model, which considers the interaction in a simplified, yet mechanically consistent way. This model is amended to account for repeated loading and calibrated with the experimental results presented in this thesis. The final part describes the yield phenomenon in bare and embedded reinforcing steel bars with a defined yield plateau. Discrepancies between the presented experimental results and the currently accepted bond theory are addressed and their implications are discussed.

Advanced science 2205012 (2022). doi:10.1002/advs.202205012, Published by Wiley-VCH, Weinheim

Advanced science 10(15), 2300901 (2023). doi:10.1002/advs.202300901, Published by Wiley-VCH, Weinheim

In particular during storm events an accumulation of excess pore pressures may occur in the soil around cyclically loaded offshore foundations. The excess pore pressure build-up reduces the effective stresses in the soil and, hence, may negatively affect the structural integrity by influencing the soil-structure interaction. Besides a loss in bearing capacity, large plastic deformations may occur to the structure. Especially for offshore wind turbines an accurate estimation of such deformations is of great importance. Even though the consideration of this degradation effect on the bearing capacity is commonly demanded by the involved certification or approval bodies, no general applicable and accepted method for the calculative verification currently exists. Over the past decades several researchers investigated the excess pore pressure build-up around offshore foundations due to environmental cyclic loads. They tried to capture the loss of bearing capacity, the accumulation of plastic rotation and the essential influence on the serviceability limit state and fatigue design. However, even if there are some sophisticated concepts, none of them is seen as the simple general applicable choice. Within this thesis a new numerical method – termed Excess Pore Pressure Estimation method (EPPE) – is presented in great detail. This method allows for the transfer of the soil behaviour obtained in cyclic simple shear tests to the bearing behaviour of the entire foundation. Herein, the numerical model accounts for the cyclic excess pore pressure accumulation by respecting the element-based mean stress and stress amplitude as well as an equivalent number of load cycles. The simulation of the excess pore pressure build-up due to certain cyclic loading is based on undrained conditions, i.e. the excess pore pressure build-up due to cyclic loading is derived by disregarding the simultaneous consolidation process. The respected transfer method, in the form of contour plots, enables the consideration of site-specific cyclic direct simple shear and triaxial test results from laboratory devices to elements within the finite element model. Each integration point is evaluated individually. Based on the derived excess pore pressure field, a consolidation analysis takes place in the second step. The actual accumulated excess pore pressure in each element at the end of the storm (or cyclic loading event) is then found by analytically superposing the excess pore pressure decay curves from the consolidation analysis. For a deeper understanding of cyclic soil behaviour, the cyclic response in different laboratory devices with different densities and under varying stress states was investigated by the author. A contour approach based on cyclic load- and displacement-controlled test results is derived to study the element response from the numerical point of view and use these for the calibration of an implicit model. Moreover, different explicit approaches are presented and compared in terms of their estimation behaviour of cyclic excess pore pressure generation, their predicted foundation capacity and their model assumptions. The intention is hence to examine existing approaches and their applicability by means of an elaborate comprehensive study. A simple modular explicit model is presented which can be easily assessed with engineering judgment. If needed, the different individual calculation steps can be exchanged with more sophisticated ones. For a reference sandy soil, results of cyclic laboratory tests are presented and used on a reference monopile foundation for a predefined storm event. The EPPE approach helps to quantify the risk of capacity degradation as well as to evaluate an appropriate safety margin. It is possible with the current methodology to evaluate the degradation potential for different sites quite easily and fast., Insbesondere bei Sturmereignissen kann es im Boden an zyklisch belasteten Offshore-Fundamenten zu einer Akkumulation von Porenwasserüberdrücken kommen. Der Porenwasserüberdruck reduziert die effektiven Spannungen im Boden und kann daher die strukturelle Integrität negativ beeinflussen, indem dieser die Boden-Bauwerk-Interaktion zusätzlich beeinträchtigt. Insbesondere für Offshore-Windenergieanlagen ist eine genaue Abschätzung von Verformungen von großer Bedeutung. Obwohl die Berücksichtigung dieses Degradationseffekts auf die Tragfähigkeit von den beteiligten Zertifizierungs- oder Genehmigungsstellen gefordert wird, existiert derzeit keine allgemein anwendbare und akzeptierte Methode für den rechnerischen Nachweis. In den vergangenen Jahrzehnten untersuchten mehrere Forschende die zyklische Porenwasserüberdruckakkumulation, die sich um Offshore-Windenergieanlagen aufgrund von zyklischen Belastungen aufbaut. Sie versuchten, den Verlust der Tragfähigkeit und die Akkumulation der plastischen Rotation zu quantifizieren. Auch wenn einige Konzepte existieren, so wird keines als allgemeingültige Methodik angesehen. In dieser Arbeit wird eine neue numerische Methode – die sogenannte Excess Pore Pressure Estimation Methode (EPPE) – vorgestellt, die es erlaubt, das in zyklischen Einfachscherversuchen ermittelte Bodenverhalten auf das Tragverhalten des gesamten Fundaments zu übertragen. Dabei berücksichtigt das numerische Modell die zyklische Porenwasserüberdruckakkumulation unter Verwendung der element-spezifischen mittleren Spannung und Spannungsamplitude sowie der äquivalenten Zyklenzahl. Die Simulation des Porenwasserüberdruckaufbaus infolge bestimmter zyklischer Beanspruchungen basiert auf undrainierten Bedingungen, d.h. der Porenwasserüberdruckaufbau infolge bestimmter zyklischer Beanspruchungen wird unter Vernachlässigung des gleichzeitigen Konsolidierungsprozesses abgeleitet. Die Übertragung von Laborergebnissen auf Elemente innerhalb des Finite-Elemente-Modells in Form von Konturdiagrammen ermöglicht die Berücksichtigung von standortspezifischen zyklischen Einfachscher- und Triaxialversuchsergebnissen. Jeder Integrationspunkt wird individuell auf der Grundlage von last- oder weggesteuerten zyklischen Laborversuchsergebnissen ausgewertet. Die gesamte Porenwasserüberdruckakkumulation während eines Sturmereignisses, wird dann für einen bestimmten Bemessungssturm ermittelt. Auf Grundlage des abgeleiteten Porenwasserüberdruckfeldes wird im zweiten Schritt eine Konsolidierungsanalyse durchgeführt. Als Ergebnis der Analyse werden elementbasierte Porenwasserdruckabbaukurven abgeleitet. Der Verlauf des akkumulierten Porenwasserüberdrucks bis hin zum Ende des Sturms (oder des zyklischen Belastungsereignisses) wird durch analytische Superposition ermittelt. Für ein tiefgehendes Verständnis des zyklischen Bodenverhaltens wird das zyklische Antwortverhalten in verschiedenen Laborgeräten bei unterschiedlichen Lagerungsdichten und unter verschiedenen Spannungszuständen untersucht. Ein Konturansatz, der auf last- und verschiebungsgesteuerten Versuchsergebnissen basiert, wird abgeleitet. Um die Elementantwort aus numerischer Sicht zu untersuchen, wurde auch ein implizites Modell kalibriert. Die Ergebnisse werden im Detail erläutert. Anschließend werden verschiedene explizite Ansätze vorgestellt und hinsichtlich ihres Abschätzungsverhaltens der zyklischen Porenwasserüberdruckerzeugung, ihrer prognostizierten Gründungskapazität und ihrer Modellannahmen verglichen. Damit ist beabsichtigt, bestehende Ansätze und deren Anwendbarkeit in einer umfassenden Gesamtstudie zu untersuchen. Es wird ein generisches und modulares, explizites Modell vorgestellt, das leicht mit fachspezifischem Sachverstand bewertet werden kann. Die verschiedenen Berechnungsschritte können nach Bedarf durch weitere Schritte ergänzt werden. Im Rahmen dieser Arbeit werden Ergebnisse aus zyklischen Laborversuchen für einen beispielhaften Nordseesand vorgestellt und auf eine Referenz-Monopile-Gründung innerhalb eines vordefinierten Sturmereignisses angewendet. Der EPPE-Ansatz hilft bei der Quantifizierung des Verflüssigungsrisikos und der Ermittlung eines angemessenen Sicherheitsniveaus. Mit der aktuellen Methodik ist es möglich, das Degradationspotenzial für verschiedene Standorte einfach und schnell zu bewerten.

Structural robustness of timber buildings is becoming increasingly relevant because of the increasing use of timber in the built environment. An important tool for assessing the robustness of any structure is an efficient numerical model capable of simulating progressive collapse. With such a model, physical tests can be limited to a few carefully selected validation tests and the robustness of a wide range of building typologies and geometries can be investigated efficiently. In this paper, a parametric nonlinear dynamic model for simulating progressive collapse of timber buildings is presented. Because of the parametric capabilities of the model, a vast range of buildings can be modelled. Moreover, the entirety of a collapse can be simulated with the recently developed mixed element method and the implementation of stress- and energy-based failure criteria for normal loading and impact loading. To demonstrate the capabilities of the model, a case study is presented on a symmetrical three-dimensional frame building with varying cross-sectional member dimensions. The model is an indispensable tool for investigating the robustness of timber buildings., World Conference on Timber Engineering WCTE 2023, ISBN:9781713873273

Mobility simulations are crucial for research, industry, and governance. However, simulating mobility systems with reasonable accuracy requires large-scale efforts of data collection, data transformation, data analysis, and data visualization. The paradigm of the digital twin offers a novel perspective on how to manage the data efficiently and make the simulations available more steadily at a lower cost. We introduce the first prototype of the “CH on the move” digital twin that is designed to be openly available to all interested parties to enable a common baseline for transport research in Switzerland. This digital twin is based on the extensible Open Digital Twin Platform (ODTP) that uses containerization, loose coupling, and micro-services to provide dynamically composable digital twins. In its first iteration, “CH on the move” provides an easy-to-use version of the eqasim pipeline for MATSim making it possible to initiate simulations of Switzerland with one click. Future versions of “CH on the move” aim to include a rich set of relevant data sources and analytical pipelines related to transport and mobility and make them easily accessible to research, industry, and governance., ISBN:https://zenodo.org/communities/open-digital-twin-platform

This study presents the results of a large-scale experimental investigation of low-cost, high-performance seismic isolators based on deformable rolling rubber spheres. The spheres roll on flat or concave concrete surfaces. Different types of spheres and design scenarios were examined. A potential application of the proposed isolator could be in low-rise structures in regions where conventional seismic isolators are unaffordable. The spheres were initially subjected to monotonic uniaxial compression and sustained compression under vertical load to examine their compressive behavior. Subsequently, lateral cyclic tests under large displacements were performed. Finally, a total of 1170 shake-table tests were performed in 1:2 scale, with various different isolators subjected to a large number of ground motion excitations. Results showed that the compressive strength of the spheres was substantially higher than the design load. The lateral cyclic response differs substantially from the one that a rigid body model would suggest due to the non-negligible deformability of the spheres. The rolling friction coefficient ranged between 3.7% and 7.1%. Hence, it is suitable for seismic isolation applications. The spherical concrete plates increase the restoring force of the system. When tested in a shake table under 1170 ground motions, the isolators substantially reduced the acceleration transmitted to the superstructure (to less than 0.2 g) while maintaining reason-able peak and zero residual displacements. Notably, the shake table tests were repeatable, and the isolators did not deteriorate even after subjected to 65 ground motion excitations., COMPDYN Proceedings, COMPDYN 2023

Advanced science 10(17), 2206325 (2023). doi:10.1002/advs.202206325, Metal halide perovskites are an emerging class of crystalline semiconductors of great interest for application in optoelectronics. Their properties are dictated not only by their composition, but also by their crystalline structure and microstructure. While significant efforts are dedicated to the development of strategies for microstructural control, significantly less is known about the processes that govern the formation of their crystalline structure in thin films, in particular in the context of crystalline orientation. This work investigates the formation of highly oriented triple cation perovskite films fabricated by utilizing a range of alcohols as an antisolvent. Examining the film formation by in situ grazing-incidence wide-angle X-ray scattering reveals the presence of a short-lived highly oriented crystalline intermediate, which is identified as FAI-PbI$_2$-xDMSO. The intermediate phase templates the crystallization of the perovskite layer, resulting in highly oriented perovskite layers. The formation of this dimethylsulfoxide (DMSO) containing intermediate is triggered by the selective removal of N,N-dimethylformamide (DMF) when alcohols are used as an antisolvent, consequently leading to differing degrees of orientation depending on the antisolvent properties. Finally, this work demonstrates that photovoltaic devices fabricated from the highly oriented films, are superior to those with a random polycrystalline structure in terms of both performance and stability., Published by Wiley-VCH, Weinheim

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2023; Aachen : RWTH Aachen Univsersity 1 Online-Ressource : Illustrationen, Diagramme, Karten (2023). = Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2023, Anthropogenic impacts on rivers date back several millennia BC, starting with agricultural land use and deforestation. In Europe, many of today’s measures, like mill ditches, still used by industries for process and cooling water today, originate from medieval times. With Industrialization, rivers were regulated, and large dams were constructed. Until today, several resulting morphodynamic processes from former and recent measures overlap, and it is almost impossible to determine how the river’s morphology will develop in the future. Thus, systematically evaluating the river’s morphological behavior supports sustainable water resources management. The Rur River (North Rhine-Westphalia, Germany) is a model example for a typical mid-sized mid-European low-mountain to lowland river whose catchment has been affected by industrial development, including the construction of seven reservoirs. In this thesis, anthropogenic impacts are evaluated qualitatively and quantitively on different spatial scales. We identify the morphological developments from different eras affecting the Rur River until today, specific measures of water resources management impacting the sediment connectivity, and long-term impacts of damming to assess boundaries for a river’s morphological development. Morphological changes over the last 200 years are determined in GIS. Changes in river straightening and structural diversity are described by structural indicators and correlated with eras of water resources management. The most severe measures affecting sediment transport are identified by modifying the sediment rating curve. A hybrid examination of field measurements and numerical modeling investigates the impact of large dams on the downstream’s morphology. We identified five eras characterized by priority shifts in water resources management during the last 200 years: The Pre- Industrial Era (mid-18th – mid-19th century), the Industrial Era (mid-19th century – WWI), the Agricultural Era (after WWI – 1980s), the Era of Ecological Improvement (1980s – 2000), and the Era of EU-WFD (from 2000 to the present). The Industrial and Agricultural Era led to river straightening, even without direct hydraulic measures. The suspended sediment transport as the main morphodynamic driver could be described more accurately with the sediment rating curve when incorporating parameters for the length of a river’s section and damming. Results are river specific as they are closely linked to connectivity behavior. For the Rur River, the construction of large dams leads to a sediment deficit, increased mean sediment diameters downstream of the reservoir, and an alteration of the flow regime. The local lithostratigraphy superimposes the sedimentological changes downstream of the dam. The changes in the flow regime, however, lead to severe floodplain decoupling. Natural boundaries pose the foundation on which a river develops. Geomorphological boundaries primarily operate on different scales and, amongst other boundaries, lead to a specific fingerprint in a river’s connectivity, which determines responses to anthropogenic measures. However, the socio-economic era determines priorities in water resources management. To achieve sustainable river development, we need a shift in the socio-economic priorities of the present era and the implementation of water resources management in current political agendas. Further, evaluating a river’s connectivity behavior on different scales needs to be incorporated into water resources management to achieve development within the river’s natural boundaries., Published by RWTH Aachen Univsersity, Aachen

A growing number of ageing structures is affected by pitting corrosion due to the ingress of chlorides or structural defects such as honeycombs. The resulting local damage reduces their load-carrying capacity and – even more pronouncedly – their deformation capacity due to the corresponding strain localisation. The latter is particularly critical for statically indeterminate structures whose structural safety relies on plastic load redistributions or for structures whose main loading is deformation-dependent, such as the earth pressure in the case of retaining walls. In fact, many design rules in current codes are based on the lower bound theorem of the plasticity theory (though often implicitly, e. g. by neglecting initial internal or external restraint stresses), which requires a sufficient deformation capacity as commonly available in uncorroded elements. These rules are, however, no longer applicable to locally corroded structures unless their deformation capacity is carefully assessed. Unfortunately, and despite much research conducted over the past decades, no mechanically consistent, generally applicable assessment strategies in case of local corrosion exist. This thesis addresses this knowledge gap by investigating the influence of local corrosion on the load-deformation behaviour of reinforced concrete structures, focusing on the practical case of corroding cantilever retaining walls. A comprehensive series of tensile tests on artificially damaged bare reinforcing bars revealed the influences of (i) strain rate, (ii) varying microstructural layers over cross-section, and (iii) the pit geometry on their load deformation behaviour. Whereas the varying strain rate (i) along the bar axis tends to increase the tensile strength at the corrosion pit, it is potentially reduced for increasing cross-section loss in modern reinforcing bars exhibiting a varying microstructure (ii) over the cross-section, as it is characteristic for quenched and self-tempered (“Tempcore”) reinforcing bars. Depending on the pit geometry (iii), the apparent uniaxial tensile strength and the deformation capacity in the pit and in its vicinity increase due to a triaxial stress state. This effect counteracts strain localisation and leads to a significantly higher deformation capacity of affected bars than assumed by common strain localisation models. A series of large-scale tests on cantilever retaining wall segments with artificially damaged reinforcing bars confirmed a pronounced influence of the effective corrosion distribution among the reinforcing bars, as anticipated based on a preliminary theoretical analysis: the load-carrying and deformation capacity of structures containing many slightly corroded bars differs significantly from that of structures with only a few but severely corroded bars, even if the total cross-section loss is equal in both cases. Hence, merely indicating the mean cross-section loss is inappropriate to conclude on the load-deformation behaviour of a structure. Two hybrid tests, where the corrosion damage was increased at simultaneously decreasing load simulating the earth pressure, revealed that the deformation increase caused by an increasing cross-section loss is very limited even for considerable damage (approximately 1 mrad rotation for 40% cross section loss). Deformations might notably increase only very close to failure, which challenges the successful application of monitoring systems relying on deformation measurements. Finally, a mechanically consistent model enabling the reliable assessment of the structural safety and the load-deformation behaviour of locally corroded reinforced concrete structures was developed: the Corroded Tension Chord Model. In its basic version, this model combines the effects of tension stiffening and strain localisation. Based on the experimental observations, it was enhanced to account for the effects of a triaxial stress state at the corrosion pit, considering axisymmetric damage. The model predictions of the experimental results are very promising, with the comparison indicating an additional softening effect – exceeding that of the triaxial axisymmetric stress state – at the corrosion pit, probably caused by superimposed bending stresses due to unilateral corrosion. The deformation capacity of the specimens was thus clearly less impaired than predicted by established strain localisation models.

Dowelled steel-to-timber connections have been successfully used in timber construction for decades due to their ease of installation and high performance. The steel dowels provides some ductility to the load-bearing behaviour of the connections, where timber by itself largely fails in brittle manner. However, modelling the behaviour of dowelled connections is complex due to stress peaks, anisotropic material behaviour and the variability of mechanical properties. Current design models are based on rigid-plastic material behaviour, which simplifies calculation of ultimate load-carrying capacity but not deformation. Empirical formulae exist for linear load-displacement relationships. The non-linear load-deformation behaviour and load-carrying capacity under eccentric loading is not addressed by design models. Timber trusses with dowelled connections are therefore designed with simplified procedures. The simplified design method for trusses accounts for the load-carrying capacity of individual component but not their load-deformation behaviour or system effects of the entire structure. This thesis presents a modelling approach for simulating the load-deformation behaviour and load-carrying capacity of dowelled steel-to-timber connections under eccentric loading. The approach consists of two main components: (1) a model to simulate the load-deformation behaviour and load distribution within the connection, based on the load-deformation behaviour of individual dowels, and (2) a model to calculate the stresses within the timber part of the connection. The developed modelling framework is calibrated and validated through a comprehensive experimental test campaign on dowelled connections at the material, fastener and connection level. The model shows good agreement compared to the the experimental results and design models. The simulations show the potential of the model for the investigation of the structural behaviour and reliability of timber trusses with dowelled steel-to-timber connections.

Modelling ecosystem services (ES) has become a new standard for the quantification and assessment of various ES. Multiple ES model applications are available that spatially estimate ES supply on the basis of land-use/land-cover (LULC) input data. This paper assesses how different input LULC datasets affect the modelling and mapping of ES supply for a case study on Terceira Island, the Azores (Portugal), namely: (1) the EU-wide CORINE LULC, (2) the Azores Region official LULC map (COS.A 2018) and (3) a remote sensing-based LULC and vegetation map of Terceira Island using Sentinel-2 satellite imagery. The InVEST model suite was applied, modelling altogether six ES (Recreation/Visitation, Pollination, Carbon Storage, Nutrient Delivery Ratio, Sediment Delivery Ratio and Seasonal Water Yield). Model outcomes of the three LULC datasets were compared in terms of similarity, performance and applicability for the user. For some InVEST modules, such as Pollination and Recreation, the differences in the LULC datasets had limited influence on the model results. For InVEST modules, based on more complex calculations and processes, such as Nutrient Delivery Ratio, the output ES maps showed a skewed distribution of ES supply. Yet, model results showed significant differences for differences in all modules and all LULCs. Understanding how differences arise between the LULC input datasets and the respective effect on model results is imperative when computing model-based ES maps. The choice for selecting appropriate LULC data should depend on: 1) the research or policy/decision-making question guiding the modelling study, 2) the ecosystems to be mapped, but also on 3) the spatial resolution of the mapping and 4) data availability at the local level. Communication and transparency on model input data are needed, especially if ES maps are used for supporting land use planning and decision-making. The research leading to these results has received funding from the European Union, under the programme Pilot Project — Mapping and Assessing the State of Ecosystems and their Services in the Outermost Regions and Overseas Countries and Territories: establishing links and pooling resources, MOVE Project (MOVE-Facilitating MAES to support regional policy in Overseas Europe: mobilizing stakeholders and pooling resources, grant agreement Nº 07.027735/2018/776517/SUB/ENV.D2, www.moveproject.eu). info:eu-repo/semantics/publishedVersion

Formed where the water from rivers meets the sea, processes in estuaries are driven by the mixing between freshwater and seawater. Being home to diverse plant and animal communities, which have adapted to this unique environment, estuaries are one of the most productive ecosystems in the world. Providing a multitude of ecosystem services, estuaries are also of high economic value and contribute to human well-being. Besides providing habitats to aquatic species, estuaries are a source of food and raw materials while also cycling nutrients and contributing to coastal protection by damping the damaging effects of extreme events (e.g., storm surges). In addition, estuaries ensure safe navigation to and from ports and are used for recreational activities. However, with many of the world’s largest cities located on estuaries, they are directly exposed to impacts from human activity, such as overexploitation of resources or pollution. Being located in low-lying coastal areas, estuaries are also vulnerable to sea-level rise while simultaneously being impacted by climate change-induced alterations in hydrology. The combination of human-driven and climate-induced changes may lead to the degradation or loss of estuarine ecosystems and the services they provide. In order to minimize negative impacts and to promote a sustainable management of estuaries, it is thus important to investigate how estuarine environments respond to drivers of contemporary and future changes. Since no two estuaries are alike, examples from the Yellow River Delta (China), the Mekong Delta (Vietnam), and the German Bight are presented in this thesis. Major drivers, which impact these focus regions, include: sand mining/dredging, damming, climate change-induced alterations in hydrology, and sea-level rise. The aim of this thesis is to improve the understanding of how the selected estuaries are impacted by predominant contemporary and projected future drivers. This is accomplished by addressing different research questions with a focus on: (i) improving methods for assessing the present-day impact of selected drivers, (ii) improving projections by addressing less visible impacts and by integrating recently identified relevant processes, and (iii) applying different scenarios of plausible future developments in estuarine environments. (i) In a first study focusing on the Vietnamese Mekong Delta, improved methods were used to gain new insights into the intensity of regional sand mining activity. It was shown that the regional extraction of sand from the Mekong riverbed, which is driven by socio-economic developments in the region, is significantly higher than the river’s natural supply of sand. These findings have strong implications for the stability of the Vietnamese Mekong Delta, which is already subject to riverbank and coastal erosion under present-day conditions. (ii) Projections of future developments in estuaries were improved by addressing less visible impacts in numerical models and by integrating previously unaddressed processes. A second study concentrating on the Vietnamese Mekong Delta was used to project, for the first time, the morphodynamic evolution of the Mekong in response to a combination of major drivers, including sand mining, damming, climate change-induced alterations in hydrology, and sea-level rise. In a third study, which focuses on the North Sea, it could also be shown that the morphological evolution of intertidal flats in the Wadden Sea has a significant impact on the tidal dynamics in the region when considering future sea-level rise. (iii) By applying numerous plausible scenarios of future developments, the second study concentrating on the Mekong was able to identify the operation of hydropower dams as the major driver for future morphodynamic changes in the region, followed by sand extraction. Furthermore, this approach enabled to investigate the local interactions between different drivers. By combining different rates of sea-level rise with various rates of vertical accretion in the intertidal flats of the Wadden Sea, several plausible scenarios were also addressed in the study focusing on North Sea tides. If no vertical accretion is assumed in the intertidal flats, sea-level rise will lead to enhanced tidal asymmetry in the German estuaries Elbe, Weser, and Ems, potentially leading to increased sediment import. In contrast, tidal asymmetries resemble present-day conditions if intertidal flats are able to keep up with sea-level rise.

The objective of the contribution is to understand the fatigue bond behaviour of brass-coated high-strength micro steel fibres embedded in ultra-high performance concrete (UHPC). The study contains experimental pullout tests with variating parameters like load amplitude, fibre orientation, and fibre-embedded length. The test results show that fibres are generally pulled out of the concrete under monotonic loading and rupture partly under cyclic tensile loading. The maximum tensile stress per fibre is approximately 1176 N/mm2, which is approximately one third of the fibre tensile strength (3576 N/mm2). The load-displacement curves under monotonic loading were transformed into a bond stress-slip relationship, which includes the effect of fibre orientation. The highest bond stress occurs for an orientation of 30° by approximately 10 N/mm2. Under cyclic loading, no rupture occurs for fibres with an orientation of 90° within 100,000 load changes. Established S/N-curves of 30°- and 45°-inclined fibres do not show fatigue resistance of more than 1,000,000 load cycles for each tested load amplitude. For the simulation of fibre pullout tests with three-dimensional FEM, a model was developed that describes the local debonding between micro steel fibre and the UHPC-matrix and captures the elastic and inelastic stress-deformation behaviour of the interface using plasticity theory and a damage formulation. The model for the bond zone includes transverse pressure-independent composite mechanisms, such as adhesion and micro-interlocking and transverse pressure-induced static and sliding friction. This allows one to represent the interaction of the coupled structures with the bond zone. The progressive cracking in the contact zone and associated effects on the fibre load-bearing capacity are the decisive factors concerning the failure of the bond zone. With the developed model, it is possible to make detailed statements regarding the stress-deformation state along the fibre length. The fatigue process of the fibre-matrix bond with respect to cyclic loading is presented and analysed in the paper.

In this thesis, a novel approach is developed for visco-plasticity and nonlinear dynamics problems. In particular, variational equations are elaborated following the Helligner-Reissner principle, so that both stress and displacement fields appear as unknown fields in the weak form. Three novel finite elements are developed. The first finite element is formulated for the axisymmetric problem, in which the stress field is approximated by low-order polynomials such as linear functions. This approach yields accurate solutions specifically in incompressible and stiff problems. In addition, a membrane and plate bending finite element are newly designed by discretizing the stress field using the lowest order Raviart-Thomas vector space RT0 This approach guarantees the continuity of the stress field over an entire discrete domain, which is a significant advantage in the numerical method, especially for the wave propagation problems. The developments are carried out for the viscoplastic constitutive behavior of materials, where the corresponding evolution equations are obtained by appealing to the principle of maximum dissipation. To solve the dynamic equilibrium equations, energy conserving and decaying schemes are formulated correspondingly. The energy conserving scheme is unconditional stable, since it can preserve the total energy of a given system under a free vibration, while the decaying scheme can dissipate higher frequency vibration modes. The last part of this thesis presents procedures for upscaling of the visco-plastic material behavior. Specifically, the upscaling is performed by stochastic identification method via Baysian updating using the Gauss-Markov-Kalman filter for assimilation of important material properties in the elastic and inelastic regimes., In dieser Arbeit wird ein neuartiger Ansatz für Viskoplastizitäts- und nichtlineare Dynamikprobleme entwickelt. Insbesondere werden Variationsgleichungen nach dem Helligner-Reissner-Prinzip aufgestellt, so dass sowohl Spannungs- als auch Verschiebungsfelder als unbekannte Felder in schwacher Form erscheinen. Drei neuartige finite Elemente werden entwickelt. Das erste finite Element wird für das axialsymmetrische Problem formuliert, bei dem das Spannungsfeld durch Polynome niedriger Ordnung wie lineare Funktionen angenähert wird. Dieser Ansatz liefert genaue Lösungen speziell bei inkompressiblen und steifen Problemen. Darüber hinaus wird ein finites Element mit Membran- und Plattenbiegung neu entworfen, indem das Spannungsfeld unter Verwendung des Raviart-Thomas-Vektorraums RT0 niedrigster Ordnung diskretisiert wird. Dieser Ansatz garantiert die Kontinuität des Spannungsfeldes über eine gesamte diskrete Domäne, was insbesondere bei Wellenausbreitungsproblemen ein wesentlicher Vorteil der numerischen Methode ist. Die Entwicklungen erfolgen für das viskos-plastische Materialverhalten, wobei die entsprechenden Evolutionsgleichungen unter Berufung auf das Prinzip der maximalen Dissipation erhalten werden. Um die dynamischen Gleichgewichtsgleichungen zu lösen, werden entsprechende Energieerhaltungs- und -zerfallsschemata formuliert. Das energieerhaltende Schema ist bedingungslos stabil, da es die Gesamtenergie eines gegebenen Systems unter einer freien Schwingung erhalten kann, während das abklingende Schema höherfrequente Schwingungsmoden zerstreuen kann. Im letzten Teil dieser Arbeit werden Verfahren zum Upscaling des viskoplastischen Materialverhaltens vorgestellt. Konkret erfolgt die Hochskalierung durch stochastische Identifikationsverfahren mittels des Baysian Update unter Verwendung des Gauss-Markov-Kalman-Filters zur Assimilation wichtiger Materialeigenschaften im elastischen und inelastischen Bereich.

PIn der vorliegenden Arbeit werden mehrere statistische Methoden, die in verschiedensten Forschungsbereichen eingesetzt werden, im Hinblick auf ihren Nutzen im Zusammenhang mit geotechnischen Problemen betrachtet, bei denen die Unschärfe der Bodenparameter maßgebend ist und Messdaten oft nur in geringem Umfang über größere Modell-/Systembereiche verteilt sind. Die verwendeten Methoden zur statistischen Versuchsplanung (OED) sind die globale Sensitivitätsanalyse, die Bootstrap-Auswertung und das Bayes'sche Verfahren. Diese Methoden werden im Detail vorgestellt und auf repräsentative Probleme wie ein geotechnisches Laborgerät, die auf einen Deich wirkende Wasserabsenkung und den maschinellen Tunnelbau angewendet. Um die mit der Finite-elemente-Methode erstellten Modelle dieser Probleme systematisch zu bewerten, werden weitere mathematische Werkzeuge wie Metamodellierung und Optimierungsalgorithmen eingesetzt und in einem zusätzlichen Kapitel vorgestellt., Schriftenreihe des Lehrstuhls für Bodenmechanik, Grundbau und Umweltgeotechnik, 71

A substantial part of corrosion research relies on the analysis of polarization curves to obtain corrosion currents, Tafel slopes, and other parameters, such as exchange current densities. This, often manual, analysis remains highly subjective, which hampers the reproducibility of corrosion research and makes a comparison of reported Tafel slopes, corrosion rates, or exchange current densities from different literature sources difficult. One reason is that the analysis is strongly influenced by the selected range of the measured data. To improve this, we developed a Python library for the reliable analysis of polarization curves. A particular novelty is an algorithm designed to fit polarization curves under mixed activation-diffusion control, which is a situation often encountered in corrosion research. This algorithm reduces the subjectivity related to the measured or selected potential range. Moreover, the algorithm offers the possibility to diagnose and quantify the accuracy of the fit. We use experimentally measured polarization curves to test the proposed approach and show that for curves without a clear, purely activation-controlled Tafel region in the cathodic branch, accurate and consistent analysis is only possible by applying the mixed activation-diffusion control technique. Re-evaluation of literature data shows that by applying the library the variability in reported Tafel slopes can be greatly reduced. Thus, here the proposed approach and the related open-access Python library for the analysis of polarization curves may foster reproducibility and enhance the comparability of data measured in corrosion research ISSN:0010-9312 ISSN:1938-159X

A wide part of the European built heritage consists of masonry constructions originally designed with very limited if not completely absent earthquake resisting criteria, exposing the structures to possible fragile collapse mechanisms during earthquakes. Therefore, it is evident that the evaluation of the health state of these types of buildings after a seismic event plays a fundamental role in the preservation of human life and the historical and cultural building heritage. Structural Health Monitoring (SHM) systems represent a possible solution to this problem by allowing the assessment of the structural performance of the monitored construction during its service life, even in real-time or rapidly after an earthquake, as well as enabling scheduling of maintenance and retrofitting interventions. Although the usefulness of such systems is widely recognized, their application on masonry constructions is still limited due to practical drawbacks experienced in the use of the off-the-shelf sensing technologies. Recent developments in materials engineering introduced in the field of SHM the use of smart materials obtained by doping traditional construction materials, such as cement-based ones, with conductive fillers capable of improving the electrical and sensing properties of the base matrix, giving to the composite the capability of detecting changes in its strain conditions through the output of specific electrical signals. This Ph.D. thesis extends a similar concept to masonry buildings investigating the innovative smart brick technology, which consists of clay bricks doped with suitable conductive fillers and thus capable of revealing changes in their strain conditions by leveraging on their improved piezoresistive capability, i.e. by varying their electrical outputs accordingly. The Thesis aims to promote the development of this newly conceived technology by addressing the missing/incomplete aspects in the reference literature, with the main objective of comprehensively designing, producing, and characterizing a reliable smart sensing device suitable for seismic SHM of masonry constructions. The obtained results demonstrate that the proposed new formulation of smart bricks can be effectively employed for the post-earthquake assessment of masonry constructions, bringing the technology to a readiness level that is mature for field validation., Ein großer Teil des europäischen Bauerbes besteht aus Mauerwerkskonstruktionen, die ursprünglich mit sehr begrenzten, wenn nicht sogar völlig fehlenden Erdbebensicherheitskriterien entworfen wurden, wodurch die Strukturen bei Erdbeben möglichen fragilen Einsturzmechanismen ausgesetzt sind. Es liegt daher auf der Hand, dass die Bewertung des Gesundheitszustandes dieser Gebäudetypen nach einem Erdbeben eine grundlegende Rolle für den Erhalt des menschlichen Lebens und des historischen und kulturellen Bauerbes spielt. Structural Health Monitoring (SHM)-Systeme stellen eine mögliche Lösung für dieses Problem dar, indem sie die Bewertung der baulichen Leistung des überwachten Bauwerks während seiner Nutzungsdauer, auch in Echtzeit oder schnell nach einem Erdbeben, sowie die Planung von Wartung und nachträgliche Eingriffe. Obwohl die Nützlichkeit solcher Systeme allgemein anerkannt ist, ist ihre Anwendung auf Mauerwerkskonstruktionen aufgrund praktischer Nachteile, die bei der Verwendung von Standard-Sensortechnologien erfahren werden, immer noch begrenzt. Jüngste Entwicklungen in der Werkstofftechnik führten auf dem Gebiet der SHM die Verwendung intelligenter Materialien ein, die durch Dotieren traditioneller Baumaterialien, wie z die Fähigkeit, Änderungen seiner Dehnungsbedingungen durch die Ausgabe spezifischer elektrischer Signale zu erkennen. Dieser Ph.D. Dissertation erweitert ein ähnliches Konzept auf Mauerwerksgebäude, in dem die innovative Smart Brick-Technologie untersucht wird, die aus Ziegeln besteht, die mit geeigneten leitfähigen Füllstoffen dotiert sind und so in der Lage sind, Änderungen ihrer Dehnungsbedingungen durch Ausnutzung ihrer verbesserten piezoresistiven Fähigkeit, dh durch entsprechende Variation ihrer elektrischen Leistungen, aufzudecken . Die Arbeit zielt darauf ab, die Entwicklung dieser neu konzipierten Technologie zu fördern, indem die fehlenden/unvollständigen Aspekte in der Referenzliteratur angesprochen werden, mit dem Hauptziel, ein zuverlässiges intelligentes Sensorgerät, das für seismische SHM von Mauerwerkskonstruktionen geeignet ist, umfassend zu entwerfen, herzustellen und zu charakterisieren. Die erzielten Ergebnisse zeigen, dass die vorgeschlagene neue Formulierung von Smart Bricks effektiv für die Bewertung von Mauerwerkskonstruktionen nach Erdbeben eingesetzt werden kann, wodurch die Technologie auf einen für die Feldvalidierung reifen Reifegrad gebracht wird.

The majority of offshore wind farms (OWFs) are equipped with Structural Health Monitoring (SHM) system. However, since most of them are implemented to only fulfill the minimum requirement, the benefits that could have been obtained from SHM are not yet being fully utilized. The presented work used SHM data from several operating offshore wind turbines (OWTs) in the North Sea to show the added value of SHM for effective operational life cycle management of OWFs. The developed three-stage data analysis approach is used to investigate several application cases to highlight the benefits. Furthermore, an artificial neural network is developed to extrapolate the SHM results from the monitored to the unmonitored OWTs. To make up for the absence of monitored damage scenarios, a validated FE model is used to simulate damages and observe their effect on damage sensitive parameters. In addition, a procedure is outlined to incorporate SHM based stress magnitude for risk based inspection planning., Die meisten Offshore-Windparks sind mit einem Structural Health Monitoring (SHM)-System ausgestattet. Die Vorteile von SHM-Systemen werden jedoch noch nicht in vollem Umfang genutzt. In der vorliegenden Arbeit werden SHM-Daten von Offshore-Windenergieanlagen (OWEA) in der Nordsee verwendet, um den Mehrwert von SHM für ein effektives Management des Lebenszyklus aufzuzeigen. Um dies zu verdeutlichen, wird ein Datenanalyseansatz entwickelt, der für die Untersuchung verschiedener Anwendungsfälle verwendet wird. Darüber hinaus wird ein künstliches neuronales Netz aufgebaut, das die Extrapolation von SHM-Ergebnissen der überwachten OWEA auf die nicht überwachten OWEA ermöglicht. Da es keine überwachten Schadensszenarien gibt, wird ein validiertes FE-Modell verwendet, um Schäden zu simulieren. Dies erlaubt die Beobachtung der Beeinflussung schadensempfindlicher Parameter. Zudem wird eine Methode zur Einbeziehung von SHM-basierten Spannung für risikobasierte Inspektionsplanung dargestellt.