http://hdl.handle.net/10993/84 Search this channel search http://orbilu.uni.lu/simple-search http://hdl.handle.net/10993/41924 Title: Continuous solution of poroelastic problems using Artificial Neural Networks <br/> <br/>Author, co-author: Dehghani, Hamidreza; Zilian, Andreas http://hdl.handle.net/10993/41912 Title: Poroelastic material characterisation by means of Artificial Neural Network <br/> <br/>Author, co-author: Dehghani, Hamidreza; Zilian, Andreas <br/> <br/>Abstract: Poroelastic problems require multiscale and multiphysics techniques that are expensive and time-consuming, which result in either several simplifications or costly experimental tests. The latter motivates us to develop a more efficient approach to address more complex problems with an acceptable computational cost. In this manuscript, first, the necessary equations derived from Asymptotic homogenisation for poroelastic media are mentioned. Then, the variational formulation of the cell problems is carried out and solved by the open-source FE package FEniCS. This is followed by presenting the advantages and downsides of macroscale properties identification via asymptotic homogenisation and the application of Artificial Neural Network (ANN) to solve the issues stated as its downsides by means of bypassing the process of solving the cell problems. Finally, we study a practical example, namely, spatial dependent porosity (in macroscale) to demonstrate the feasibility of using the provided framework to include more details. Further applications, including growth and remodelling, are subjects of future articles. http://hdl.handle.net/10993/41898 Title: Inbetriebnahme und Monitoring einer Feldtestfläche zur außenliegenden Lufttemperierung <br/> <br/>Author, co-author: Schmidt, Christoph Wilhelm; Altgeld, Horst; Groß, Bodo; Hähn, Felix; Maas, Stefan; Scholzen, Frank <br/> <br/>Abstract: Der Beitrag ist inhaltlich dem Forschungsprojekt „Low Exergy Utilisation - Einsatz von außen-liegender Wandtemperierung bei der Gebäudesanierung - Feldtest, CO2- Wärmepumpe mit Eisspeicher“ (kurz LEXU II, Förderkennzeichen 0327370Y) zugeordnet. Im Rahmen des Pro-jektes wurde ein Großdemonstrator mit außenliegender Wand- und Lufttemperierung (kurz aWT & aLT) zusammen mit einem niederexergetischen Versorgungssystem, bestehend aus Eisspeicher, Wärmepumpe und PVT-Hybridkollektoren realisiert. Zur Heizperiode 2018/19 wurde die „Feldtestanlage“ in Betrieb genommen, sodass derzeit Messdaten generiert wer-den. In dem Forschungsprojekt wird der Demonstrator über eine Heizperiode und eine Kühl-periode messtechnisch begleitet und ausgewertet. Dabei wird der Großdemonstrator und alle Komponenten umfassend messtechnisch ausgewertet (~300 Messwerte). Ziel des Beitrags ist eine Darstellung der Grundlagen der außenliegenden Lufttemperierung, als niederexergetische und schnell regelbare Ergänzung zur außenliegenden Wandtemperie-rung. Bei der außenliegenden Lufttemperierung wird zwischen thermisch aktivierter Be-standswand und neuem Wärmedämm-Verbundsystem ein Luftspalt geschaffen, durch den Außenluft geführt und temperiert werden kann. Diese temperierte Außenluft wird dem dahin-terliegenden Raum (im Feldtest ein Büroraum mit rund 20 m² Grundfläche und zwei Arbeits-plätzen) als Frischluft zur Verfügung gestellt. Aufbauend auf den Grundlagen wird die Inbe-triebnahme der bereits umgesetzten Feldtestfläche mit möglichen Regelstrategien geschildert. Abschließend sollen erste Messergebnisse der Feldtestfläche dargestellt und diskutiert wer-den. Interessant sind hier vor allem (im Vergleich zur außenliegenden Wandtemperierung) die möglichen Zeitkonstanten und die erreichbaren Wärmeströme nach Innen (z.B. mögliche Wärmeübertragung als Kombination aus Konvektion im Luftspalt und Wärmeleitung durch die Bestandswand). Themengebiet: Energieeffiziente Gebäude & Bauphysik und Sanierung & Behaglichkeit und Raumklima http://hdl.handle.net/10993/41897 Title: Auswertung eines Großdemonstrators mit außenliegender Wandtemperierung, Wärmepumpe, Eisspeicher und PTV-Hybridkollektoren <br/> <br/>Author, co-author: Schmidt, Christoph Wilhelm; Altgeld, Horst; Groß, Bodo; Maas, Stefan; Scholzen, Frank <br/> <br/>Abstract: Der Beitrag ist inhaltlich dem Forschungsprojekt „Low Exergy Utilisation - Einsatz von außen-liegender Wandtemperierung bei der Gebäudesanierung - Feldtest, CO2- Wärmepumpe mit Eisspeicher“ (kurz LEXU II, Förderkennzeichen 0327370Y) zugeordnet. Im Rahmen des Pro-jektes wurde ein Großdemonstrator mit außenliegender Wand- und Lufttemperierung (kurz aWT & aLT) zusammen mit einem niederexergetischen Versorgungssystem, bestehend aus Eisspeicher, Wärmepumpe und PVT-Hybridkollektoren realisiert. Zur Heizperiode 2018/19 wurde die „Feldtestanlage“ in Betrieb genommen, sodass derzeit Messdaten generiert wer-den. In dem Forschungsprojekt wird der Demonstrator über eine Heizperiode und eine Kühl-periode messtechnisch begleitet und ausgewertet. Dabei wird der Großdemonstrator und alle Komponenten umfassend messtechnisch ausgewertet (~300 Messwerte). Ziel des Beitrags ist eine Darstellung der messtechnischen Auswertung des Großdemonstra-tors über die aktuelle Heizperiode (2018/19) und die anstehende Kühlperiode (2019). Der Fo-kus der Auswertung liegt auf der Feldtestfassade der außenliegenden Wandtemperierung und adressiert die folgenden Fragestellungen: - Konnten die theoretischen Ergebnisse aus Berechnung und Simulation reproduziert werden? - Welche Heizleistungen sind über die außenliegende Wandtemperierung übertragbar? - Welches Fazit kann nach dem Betrieb der Anlage/Feldtestfläche über ca. ein Jahr ge-zogen werden? Je nach aktuellem Stand der begleitenden Simulations- und Potentialstudien können auch hier erste Ergebnisse präsentiert werden. Inhaltlich baut der Beitrag auf dem Beitrag „Außen-liegende Wand- und Lufttemperierung: Umsetzung eines Großdemonstrators“ von den Bau-physiktagen 2017 in Kaiserslautern auf. Im Anschluss an die dort beschriebene Umsetzung soll nun ein Fazit bzgl. Umsetzung, Monitoring und Simulation gezogen werden. http://hdl.handle.net/10993/41889 Title: Feldtest und dynamische Simulation der außenliegenden Wandtemperierung <br/> <br/>Author, co-author: Schmidt, Christoph Wilhelm http://hdl.handle.net/10993/41829 Title: Characterising the influent macro-substrates of wastewater treatment plants and the impact of DOC portions on the degradation of xenobiotics during biological treatment <br/> <br/>Author, co-author: Christen, Anne http://hdl.handle.net/10993/41749 Title: Non-localised contact between beams with circular and elliptical cross-sections <br/> <br/>Author, co-author: Magliulo, Marco; Lengiewicz, Jakub; Zilian, Andreas; Beex, Lars <br/> <br/>Abstract: The key novelty of this contribution is a dedicated technique to e fficiently determine the distance (gap) function between parallel or almost parallel beams with circular and elliptical cross-sections. The technique consists of parametrizing the surfaces of the two beams in contact, fixing a point on the centroid line of one of the beams and searching for a constrained minimum distance between the surfaces (two variants are investigated). The resulting unilateral (frictionless) contact condition is then enforced with the Penalty method, which introduces compliance to the, otherwise rigid, beams' cross-sections. Two contact integration schemes are considered: the conventional slave-master approach (which is biased as the contact virtual work is only integrated over the slave surface) and the so-called two-half-pass approach (which is unbiased as the contact virtual work is integrated over the two contacting surfaces). Details of the finite element formulation which is suitably implemented using Automatic Di fferentiation techniques are presented. A set of numerical experiments shows the overall performance of the framework and allows a quantitative comparison of the investigated variants. http://hdl.handle.net/10993/41711 Title: Vierte Reinigungsstufe für kleine und mittlere Kläranlagen <br/> <br/>Author, co-author: Hansen, Joachim http://hdl.handle.net/10993/41361 Title: Development of an innovative U-shaped steel-concrete composite beam solution: Experimental and numerical studies on the mechanical behaviour <br/> <br/>Author, co-author: Turetta, Maxime <br/> <br/>Abstract: An innovative solution of steel-concrete composite beam was developed taking into consideration the fire situation and the construction stage. The beam is composed of a U-shaped steel part connected to a reinforced concrete part. In the construction phase, the beam is supporting the slab and constitutes a formwork for the reinforced concrete part. The U-shaped beam withstands the construction loads without any temporary propping system. When casting concrete, the steel beam is filled at the same time as the slab, this allows considerable time-saving on site. In exploitation stage, the beam behaves as a steel-concrete composite beam. The connection between the two materials is made by welded headed studs on the lower part of the U-shaped beam. In fire situations, the composite beam satisfies conventional fire stability durations due to the longitudinal reinforcements inside the concrete downstand part with sufficient covers. A literature review focuses on modern solutions that fulfils the criteria of the thesis is performed in order to develop an innovative solution optimised. In construction stage, the U-shaped steel beam without restraints is prone to lateral torsional buckling instability. In order to characterise the stability of the beam, a full-scale test is carried out at the Laboratory of the University of Luxembourg. The test clearly showed the lateral torsional buckling of the steel beam. The test results are compared to numerical simulations and analytical studies. A parametrical study, covering 200 geometrical configurations of the U-shaped beam, is carried out to validate the use of the curve "b" for the design of the steel beam for lateral torsional buckling according to Eurocodes 3. In the exploitation phase, once the concrete hardens, the beam has a steel-concrete composite behaviour provided by the shear connection between the two materials. For manufacturing reasons, the connection is located in a zone where the concrete is subjected to tension forces induced by the bending of the beam. The concrete in this zone is potentially cracked, thus the efficiency of the connection and therefore the mechanical steel-concrete composite behaviour is investigated. Another test is therefore carried out in the Laboratory of the University of Luxembourg, this time the specimen tested is made of concrete and steel. The failure mode is a shear mechanism of the composite beam at very large displacements. However, the beam specimen exhibited a real steel-concrete composite behaviour with high ductility, the connection is therefore very efficient. The test results are compared to numerical simulations in order to validate the finite element model developed. From numerical results and test results, an analytical method, based on EN 1994-1-1, is proposed to find the bending resistant of this composite beam by taking into account the partial yield of the side plates of the U-shaped steel section. A global analytical design method is proposed for the developed solution based on the Eurocodes with additional considerations and constructional guidelines. http://hdl.handle.net/10993/41220 Title: Dismountable Flooring Systems for Multiple Use <br/> <br/>Author, co-author: Odenbreit, Christoph; Kozma, Andras <br/> <br/>Abstract: Steel shapes our modern world as an integral part of the global construction economy. In the last decades, the sustainability of steel grew and turned from a linear to a circular business, where the material is fully recovered and recycled after use. The RFCS Research Project “REDUCE” of the European Commission goes one step beyond the mere material recycling and investigates, how the circular economy’s philosophy can be used to reduce the carbon footprint furthermore. On that basis, one target of the research was to develop basic modular and standardised structural load bearing elements which can be adapted in the building or assembled, properly disassembled and partly or entirely be reused again in a subsequent building. This paper presents the respective research results of demountable flooring- and beam systems: 15 large scale push-out tests and two large scale composite beam tests as well as numerous finite element simulations with ABAQUS have been performed at the Laboratory of the ArcelorMittal Chair of Steel and Façade Engineering. The suitability for dis- and re-assembly as well as the strength, stiffness, slip capacity and ductility have been determined. The investigated systems included pre-stressed and epoxy injected systems, as well as solid slabs and composite slabs with profiled decking. The results showed sometimes higher resistances and smaller displacement capacities than conventional systems. The numerical simulation results were presented as well as the results of the laboratory tests. First assessments were given about the respective consequences and about how these consequences could be considered in the layout of future steel composite structures. http://hdl.handle.net/10993/41219 Title: Push-out tests on demountable shear connectors of steel concrete composite structures <br/> <br/>Author, co-author: Kozma, Andras; Odenbreit, Christoph; Braun, Matthias Volker; Veljkovic, Milan; Martin, Nijgh <br/> <br/>Abstract: Circular Economy refers to a move from linear business models, in which products are manufactured from raw materials, used and then discarded, to circular business models where products or parts are re-used, remanufactured or recycled. Structural steel is highly compatible with this concept; however, when steel-concrete composite structures are used, recycling becomes difficult and the potential for reuse is lost. In order to make steel-concrete composite structures reusable, bolted connections should replace the commonly used welded headed studs. Furthermore, the reusable parts should be designed to withstand repeated use. This paper presents a desktop study and the corresponding laboratory experiments on demountable shear connectors that facilitate recyclability and even provide the potential for reusing complete structural elements. In the Laboratory of Steel and Composite Structures of the University of Luxembourg 15 push-out tests have been carried out using different bolted connection systems suitable for multiple use. The shear connectors have been evaluated based on their shear strength, stiffness, slip capacity, ductility and ability of demounting. The investigated systems included pre-stressed and epoxy resin injection bolts, solid slabs and solid slabs in combination with profiled steel sheeting. The results showed that the tested demountable shear connections could provide higher shear resistance than conventional shear connections. The critical failure mode was the shear failure of the bolts, which is a brittle failure. There was no visible damage observed on the connected members. The application of epoxy resin in the hole clearance resulted in lower slip capacity. The outcome provides an important basis for the justification of the forthcoming enhancement and validation of numerical models of the demountable shear connections. The failure behaviour, the observed damages and the resulting ability of the elements for re-use are discussed in detail. http://hdl.handle.net/10993/41218 Title: Parametric study on non-ductile demountable shear connectors <br/> <br/>Author, co-author: Odenbreit, Christoph; Kozma, Andras <br/> <br/>Abstract: The basic principle of the circular economy is to reduce or totally eliminate waste and carbon dioxide production with the help of a multiple, efficient usage of resources. The application of reusable structural elements plays an important role and can contribute essentially to a low-carbon future. Within the European research project REDUCE (Grant Agreement number: 710040), composite beams and steel-based flooring systems, which are demountable and reusable, have been developed and investigated. The experimental investigations showed that the structural behaviour of the newly developed shear connectors differs from the behaviour of the traditionally applied welded studs. Some behave in a non-ductile way. In order to assess, how far the regulations of EN1994-1-1 for shear connections can still be applied, parametric studies have been conducted. The respective numerical models were developed with the use of the commercially available finite element software ABAQUS® and were validated against the experimental observations. The effects of the lack of ductility of the shear connectors on the structural behaviour of the entire composite beam was examined with different types of shear connectors, shear connector layouts and material grades. This contribution presents the underlying laboratory tests as well as the results of the supplementing numerical parameter studies. The outcome provides valuable information for future design guidance concerning the use of demountable shear connectors in composite beams. http://hdl.handle.net/10993/41217 Title: Characterisation of demountable shear connector systems in composite beams <br/> <br/>Author, co-author: Kozma, Andras; Odenbreit, Christoph; Braun, Matthias Volker <br/> <br/>Abstract: Reusable structures can contribute to a resource-efficient low-carbon future on the basis of the principles of the circular economy. This paper presents a comparison of different demountable shear connector systems that facilitate recyclability and reusability of steel-concrete composite structures with the performance of traditional ones. In the Laboratory of the ArcelorMittal Chair of Steel and Façade Engineering at the University of Luxembourg 15 push-out tests and 2 full-scale beam tests have been carried out using different bolted shear connection systems suitable for reuse after the end of life of the respective building. The analysed shear connector systems have been evaluated based on their resistance, slip capacity, stiffness, ductility and ease of fabrication, assembly and disassembly. The experimental work was supplemented by numerical simulations performed with the finite element software Abaqus®. The developed numerical models were validated against the experimental observations. The experimental and numerical results provide information for future design guidance concerning the use of demountable shear connectors in composite beams. http://hdl.handle.net/10993/41199 Title: Phase field simulation of early-age fracture in cement-based materials (Top 10%) <br/> <br/>Author, co-author: Nguyen, Thanh-Tung; Waldmann, Danièle; Bui, Tinh Quoc <br/> <br/>Abstract: In this paper, a new computational approach, which is based on a multi-physics coupling of the chemo-thermo-mechanical process, is developed for modeling failure mechanism in cement-based materials at early-age hydration. A new constitutive law describing mechanical behavior of young concrete is thus derived, taking into account the effects of several factors including thermal expansion, shrinkage, damage, and both basic and transient thermal creeps. A strongly coupled model describing the interaction between fracture and multi-physics problems of cement hydration is obtained. The present phase field model in terms of smeared crack approach is highly suitable for simulating crack, especially when considering the unilateral contact conditions at crack surfaces. The capability of the proposed model in modeling complex crack initiation and propagation under arbitrary boundary conditions is highlighted. Fracture phenomena at both macroscopic and mesoscopic scales are considered and analyzed. The effects of creep and microstructural heterogeneity in different length scale are investigated, showing the great potential of the developed approach. http://hdl.handle.net/10993/41195 Title: The impact of macro-substrate on micropollutant degradation in activated sludge systems <br/> <br/>Author, co-author: Christen, Anne <br/> <br/>Abstract: Wastewater treatment plants are designed as a first barrier to reduce xenobiotic emission into rivers. However, they are not sufficient enough to fully prevent environmental harm of emerging substances in the water body. Therefore, advanced treatment processes are currently being investigated but their implementation is cost-intensive. The optimisation of the activated sludge treatment to enhance biological micropollutant removal could reduce operating costs and material. Although the impact of operational parameters, such as sludge retention time and hydraulic retention time on the xenobiotic removal have been investigated, the influence of the macro-substrate composition and load on micropollutant elimination causes a high degree of uncertainty. This study focuses on the latter by analysing 15 municipal wastewater treatment plants, where variations in load and composition of the macro-substrate were expected. Assuming that macro-substrate shapes the biomass and triggers their activity, the impact of macro-substrate composition and load on xenobiotic degradation by microorganisms was analysed. It was hypothesised that on the one hand, a high dissolved organic carbon concentration might lead to enhanced xenobiotic degradation for certain substances due to a high microbial activity. The latter is assumed to be caused by a high labile dissolved organic carbon portion and the tendency for a shorter sludge retention time. On the other hand, a low dissolved organic carbon concentration, probably containing a predominant recalcitrant substrate portion, tends to a longer sludge retention time. Consequently, slow-growing and specialised microorganisms may develop, able to degrade certain xenobiotics. As a second question, the contribution of the autotrophic biomass to xenobiotic degradation was tested by inhibiting the autotrophic microorganisms during the degradation test. To additionally test the hypothesis, the impact of a readily biodegradable substrate (acetate) on the xenobiotic degradation was tested and the sensitivity of the fluorescence signal of tryptophan was used to analyse the impact of tryptophan on xenobiotic degradation. Degradation tests focusing on the removal of macro-substrate and micropollutants within 18 hours incubation in the OxiTop® system were performed. The OxiTop® system is known as fast and easy method for organic matter analysis in the wastewater. To assess the macro-substrate composition prior to and after the degradation test, three characterisation methods were applied. Firstly, to determine the labile and the rather recalcitrant portion in the dissolved organic carbon, absorbance was measured at 280 nm and further analysed. This was verified by the characterisation of both portions based on the oxygen consumption measurements. Secondly, to analyse the organic matter concerning its fluorescent properties, excitation-emission scans were run and analysed using the parallel factor analysis approach. Lastly, the chromophoric and fluorescent organic matter was separated via size-exclusion chromatography to investigate the macro-substrate composition. Micropollutant elimination efficiency was followed by measuring initial and final concentrations of the targeted substances using liquid chromatography tandem-mass spectrometry and calculating pseudo-first-order degradation rates. To distinguish between the contribution of the heterotrophic biomass and the total biomass on xenobiotic degradation, allylthiourea was added to inhibit the autotrophic biomass. No significant composition changes of the chromophoric macro-substrate were observed. A higher initial dissolved organic carbon concentration led to higher chromophoric and fluorescent properties. The same was found for the degraded dissolved organic carbon amount and the loss of signal within the chromophoric and fluorescent portions. Variations in the macro-substrate load or rather concentration were tracked. Derived from the oxygen consumption measurements, a prominent labile and non-chromophoric portion was present at higher dissolved organic carbon levels, impacting the microbial activity. However, a characterisation of the non-chromophoric macro-substrate composition was not done within the study. Regarding the micropollutant removal, varying elimination rates were observed. For 4 out of 17 substances, distinct degradation dynamics were found, suggesting a possible impact of the present macro-substrate load. However, no overall impact of the macro- substrate on xenobiotic removal was observed. Atenolol, bezafibrate and propranolol showed a negative correlation with the initial dissolved organic carbon concentration, meaning higher degradation rates at a lower substrate load. This might indicate the presence of specialised microorganisms and a higher microbial diversity. Furthermore, inhibition studies using allylthiourea suggest a contribution of the autotrophic biomass to xenobiotic degradation. Sulfamethoxazole showed a positive trend with the initial dissolved organic carbon concentration, possibly indicating co-metabolic degradation of sulfamethoxazole by the autotrophic and heterotrophic biomass. Thus, it seemed that the removal efficiencies of sulfamethoxazole benefited from higher substrate loads. With respect to the short term experiments with acetate, higher degradation efficiencies were observed for several substances in the presence of acetate. Ketoprofen and bezafibrate showed in all tested wastewaters enhanced removal efficiencies. The tryptophan test indicated the presence of tryptophan in wastewater, but no clear contribution to the xenobiotic degradation was seen. The presented findings substantially contribute to the understanding of the influencing parameters on xenobiotic degradation in activated sludge systems. By using the OxiTop® application for xenobiotic degradation tests, an easy and fast method was established. Absorbance and fluorescence measurements proved to be a sufficient method for characterisation and biodegradability estimation of organic matter, which could be further applied as online measurements on wastewater treatment plants. Thus, the current study will serve as a base for future work investigating the influencing parameters on the xenobiotic degradation pathways and focusing on the optimisation of the biological and advanced treatment process to overcome current limitations. http://hdl.handle.net/10993/41178 Title: Influence of Macro-Substrate Composition in Wastewater on Micropollutant Removal <br/> <br/>Author, co-author: Christen, Anne; Gallé, Tom; Köhler, Christian; Wilmes, Paul; Frkova, Zuzana; Hansen, Joachim http://hdl.handle.net/10993/40939 Title: IMPROVED DESIGN METHODS FOR THE BEARING CAPACITY OF FOUNDATION PILES <br/> <br/>Author, co-author: Rica, Shilton <br/> <br/>Abstract: Pile foundations are often used for civil structures, both offshore and onshore, which are placed on soft soils. Nowadays, there are many different methods used for the prediction of the pile bearing capacity. However, the resulting design values are often different from the values measured at pile load field tests. A reason for this is that there are many pile installation effects and (unknown) soil conditions which influence the pile bearing capacity. Another problem is that for many pile load field tests in the past, the residual stresses at the pile after pile installation, have been ignored unfortunately. This ignoring leads to a measured tip bearing resistance which is lower than the real tip bearing resistance (capacity), and a measured pile shaft friction which is higher than the real pile shaft friction. The main aim of this thesis is, to come to a better understanding of the pile performance and especially the pile bearing capacity. In order to achieve this aim, many numerical loading simulations were computed for small displacements with the Finite Element Model Plaxis and many existing pile design methods have been studied. The pile installation process itself was modelled and simulated with the help of the material point method, MPM, which is able to handle large displacement numerical simulations. The used version of this MPM method was recently developed at the research institute Deltares in the Netherlands. The results from the MPM simulations showed that there is a big difference between the bearing capacity of a pre-installed pile (no installation effect are taken into account) and the bearing capacity of a pile where the installations effects are taken into account. This proves in a numerical way the importance of the pile installation effects on the pile bearing capacity. However, the MPM numerical simulations were done only for jacked piles. Therefore, impact piles, vibrated piles etc., were not simulated. For this reason, there is not a detailed numerical study for the effect of each installation method specific on the pile bearing capacity. The fact that the installation effects, in general, has an important influence on the pile bearing capacity was already proven by field tests and centrifuge tests, and has been published before by several authors. The performed numerical simulations show that during the loading and failure of a pile, a balloon shaped plastic zone develops around the pile tip, which is in fact the failure mechanism. A better understanding of this zone could lead to a better estimation of the pile tip bearing capacity because the size and position of this plastic zone are directly related to the pile tip bearing capacity. Therefore, this plastic zone has been studied for different soil and pile parameters. Also, the influence of each parameter has been studied and discussed. A similar balloon shaped plastic zone was found for both small and large displacement simulations. The tip bearing capacity of a pile is regarded to depend only on the soil in a certain zone around the pile tip. This zone is called the influence zone. The influence zone is found to be similar to the plastic zone of a pile tip. Therefore, the influence of a soft soil layer, near the influence zone of the pile tip, has also been studied. The numerical results have been validated with laboratory tests made by Deltares. The influence zone is roughly from 2 times the pile diameter, 𝐷, above the pile tip, to 5 or 6 times 𝐷 below the pile tip. Laboratory tests, using the direct shear test machine, have been performed in order to define the difference between the soil-pile friction angle and the soil-cone friction angle. The tests were done for different surface roughnesses and for three different sand types. The results were compared with the roughness of the sleeve of the Cone Penetration Test (CPT) apparatus. Based on the numerical simulations and the laboratory tests of Deltares, a new design method has been proposed for the estimation of the pile bearing capacity. This method has as main input value, the CPT results, therefore it is a CPT-based design method. The proposed method has been validated using pile field tests that were performed in Lelystad in the Netherlands. During this research, several axial and lateral pile field tests were performed at the West Coast of Mexico. Their results have been reported and discussed in the appendices. http://hdl.handle.net/10993/40934 Title: Numerical parametric study on minimum degree of shear connection in steel-concrete composite beams <br/> <br/>Author, co-author: Romero Guzman, Alfredo <br/> <br/>Abstract: In steel-concrete composite beams, the mechanical shear connectors are used to provide the shear transfer at the steel-concrete interface by connecting the concrete slab and the steel beam. Eurocode 4 (EN 1994-1-1), provides the design rules to achieve an adequate degree of shear connection. In recent years, revised rules have been proposed for the new generation of Eurocodes and research has been done to assess their suitability. The aim of this study is to complement previous studies and to evaluate the revised rules for minimum degree of shear connection of propped composite beams with ductile shear connectors and symmetric cross sections. First, a simple and comprehensive numerical model of a simply supported composite beam was developed in the finite element software ABAQUS and validated against previous numerical studies. Then, a parametric study was performed to evaluate the proposed rules on solid composite beams and composite beams with profiled steel sheeting for four span lengths (i.e. Lₑ= 6, 9, 12, and 15 m). For each span length, ten distinct configurations were analysed and each configuration was evaluated for five different degrees of shear connection (i.e. η= 0.20, 0.40, 0.60, 0.80, and 1.0). Thus, more than 200 simulations were completed in this parametric study. The results were post-processed and the suitability of the proposed rules was assessed in terms of end slip and midspan deflection at ULS and SLS respectively. The design rules led to adequate results in terms of midspan deflection. However, in some cases the end slip at ULS exceeded the 6 mm upper bound given in EN 1994-1-1 for ductile shear connectors. In order to properly identify and limit the end slip of the unsafe cases, the data from previous studies focusing on long span beams (i.e. 15m<Lₑ≤25m) was gathered with the results of the present study. Based on the assessment of the results, additional limitations to the revised rules were provided for the unsafe configurations. In these cases, the load level shall be limited by a reduction factor βₓ varying between 0.85 and 1, as a function of the plastic neutral axis depth to the overall height ratio (i.e. xₚₗ/h) and the composite to steel beam plastic bending resistance ratio (i.e. Mpl,Rd/Mpl,a,Rd). The effectiveness of this condition was re-evaluated and the results showed that more than 90% of the cases exhibited a maximum allowable end slip lower than 6 mm. Finally, a design proposal that accounts for the reduction factor βₓ was developed. http://hdl.handle.net/10993/40777 Title: A stochastic Galerkin cell-based smoothed finite element method (SGCS-FEM) <br/> <br/>Author, co-author: Mathew, Tittu; Beex, Lars; Bordas, Stéphane; Natarajan, Sundararajan <br/> <br/>Abstract: In this paper, the cell based smoothed finite element method is extended to solve stochastic partial diff erential equations with uncertain input parameters. The spatial field of Young's moduli and the corresponding stochastic results are represented by Karhunen-Lo eve expansion and polynomial chaos expansion, respectively. The Young's Modulus of structure is considered to be random for stochastic static as well as free vibration problems. Mathematical expressions and the solution procedure are articulated in detail to evaluate the statistical characteristics of responses in terms of static displacements and free vibration frequencies. The feasibility and eff ectiveness of the proposed SGCS-FEM method in terms of accuracy and lower requirement on the mesh size in the solution domain over that of conventional FEM for stochastic problems are demonstrated by carefully chosen numerical examples. From the numerical study, it is inferred that the proposed framework is computationally less demanding without compromising accuracy. http://hdl.handle.net/10993/40747 Title: MULTILINE HOLDING CONTROL AND INTEGRATION OF COOPERATIVE ITS <br/> <br/>Author, co-author: Laskaris, Georgios <br/> <br/>Abstract: Transportation is an important sector of the global economy. The rapid urbanization and urban sprawl comes with continuous demand for additional transportation infrastructure in order to satisfy the increasing and variable demand. Public transportation is a major contributor in alleviating traffic congestion in the modern megacities and provide a sustainable alternative to car for accessibility. Public transport operation is inherently stochastic due to the high variability in travel times and passenger demand. This yields to disruptions and undesired phenomena such as vehicles arriving in platoons at stops. Due to the correlation between the headway between vehicles and passenger demand, bunching leads to long waiting time at stops, overcrowded vehicles, discomfort for the passengers and from the operators side poor management of available resources and overall a low of service of the system. The introduction of intelligent transport systems provided innovative applications in order to monitor the operation, collect data and react dynamically to any disruption of the transit system. Advanced Public Transport Systems extended the range of control strategies and their objectives beyond schedule adherence and reliance on historical data alone. Among strategies, holding is a thoroughly investigated and applicable control strategy. With holding, a vehicle is instructed to remain at a designated stop for an additional amount of time after the completion of dwell time, until a criterion is fulfilled. Depending on the characteristics of the line the criterion aim for schedule adherence or regularity or minimization of passenger costs and its components. So far, holding is used for regulating single line operation. Beyond single line, it has been used for transfer synchronization at transfer hubs and recently has been extended to regulate the operation on consecutive stops that are served by multiple lines. The first part of this dissertation is dedicated to real time holding control of multiple lines. A rule based holding criterion is formulated based on the passenger travel time that accounts for the passengers experiencing the control action. Total holding time is estimated based on the size of all passenger groups that interact. The formulated criterion can be applied on all different parts of trunk and branch network. Additionally, the criterion is coupled with a rule based criterion for synchronization and the decision between the two is taken based on the passenger cost. The criterion has been tested for different trunk and branch networks and compared with different control schemes and its performance has been assessed using regularity indices as well as passenger cost indicators for the network in total but also per passenger group. Finally, an analysis has been conducted in order to define under which network and demand configuration multiline control can be preferred over single line control. Results shown that under specific demand distributions multiline control can outperform single line control in network level. Continuously new technologies are introduced to transit operation. Recently, Cooperative Intelligent Transport Systems utilized in the form of Driver Advisory Systems (DAS) shown that can provide the same level of priority with transit signal priority without changing the time and the phases of a traffic light. However, until now the available DASs focus exclusively on public transport priority neglecting completely the sequence of the vehicles and the effects on the operation. In the second part of the dissertation, two widely used DASs are combined with holding in order to meet both the objective of reducing the number of stops at traffic signals and at the same time maintain regularity. Two hybrid controllers are introduced, a combination of two holding criteria and a combination of holding and speed advisory. Both controllers are tested using simulation in comparison to the independent application of the controllers and different levels of transit signal priority. The hybrid controllers can drastically reduce transit signal priority requests while they manage to achieve both objectives.