TY - JOUR A1 - Lizarazu, Jorge A1 - Harirchian, Ehsan A1 - Shaik, Umar Arif A1 - Shareef, Mohammed A1 - Antoni-Zdziobek, Annie A1 - Lahmer, Tom T1 - Application of machine learning-based algorithms to predict the stress-strain curves of additively manufactured mild steel out of its microstructural characteristics JF - Results in Engineering N2 - The study presents a Machine Learning (ML)-based framework designed to forecast the stress-strain relationship of arc-direct energy deposited mild steel. Based on microstructural characteristics previously extracted using microscopy and X-ray diffraction, approximately 1000 new parameter sets are generated by applying the Latin Hypercube Sampling Method (LHSM). For each parameter set, a Representative Volume Element (RVE) is synthetically created via Voronoi Tessellation. Input raw data for ML-based algorithms comprises these parameter sets or RVE-images, while output raw data includes their corresponding stress-strain relationships calculated after a Finite Element (FE) procedure. Input data undergoes preprocessing involving standardization, feature selection, and image resizing. Similarly, the stress-strain curves, initially unsuitable for training traditional ML algorithms, are preprocessed using cubic splines and occasionally Principal Component Analysis (PCA). The later part of the study focuses on employing multiple ML algorithms, utilizing two main models. The first model predicts stress-strain curves based on microstructural parameters, while the second model does so solely from RVE images. The most accurate prediction yields a Root Mean Squared Error of around 5 MPa, approximately 1% of the yield stress. This outcome suggests that ML models offer precise and efficient methods for characterizing dual-phase steels, establishing a framework for accurate results in material analysis. KW - Maschinelles Lernen KW - Baustahl KW - Spannungs-Dehnungs-Beziehung KW - Arc-direct energy deposition KW - Mild steel KW - Dual phase steel KW - Stress-strain curve KW - OA-Publikationsfonds2023 Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20231207-65028 UR - https://www.sciencedirect.com/science/article/pii/S2590123023007144 VL - 2023 IS - Volume 20 (2023) SP - 1 EP - 12 PB - Elsevier CY - Amsterdam ER - TY - THES A1 - Shamskooshki, Hanieh T1 - Perception of Socio-Spatial Segregation: The Interaction of Physical and Social Urban Space-Study case of Tehran Neighborhoods N2 - “How to understand the interaction between urban space and social processes” is a significant question in urban studies. To answer that, the city needs to be recognized as both a physical and a social entity and urban theory and practice need to connect these (Hillier 2007). The present research aims to re-examine the complex correlation between spatial and social inequality manifestations in the city of Tehran regarding the concept of segregation. It observes the causes and consequences of segregation in Tehran and provides an insight into both concepts of socio-spatial segregation and neighborhood effects and creates a link between them. First, I argue when, where, and for whom spatial locations affect the chances of social networks in Tehran. Then, I discuss how neighborhood effects can emerge via social network mechanisms and thus affect the perceptions of residents in the neighborhoods. KW - Soziales Netzwerk KW - Socio-spatial Segregation KW - Urban Space KW - Neighborhood Effects KW - Social Networks Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20210802-44666 ER - TY - THES A1 - Alkam, Feras T1 - Vibration-based Monitoring of Concrete Catenary Poles using Bayesian Inference N2 - This work presents a robust status monitoring approach for detecting damage in cantilever structures based on logistic functions. Also, a stochastic damage identification approach based on changes of eigenfrequencies is proposed. The proposed algorithms are verified using catenary poles of electrified railways track. The proposed damage features overcome the limitation of frequency-based damage identification methods available in the literature, which are valid to detect damage in structures to Level 1 only. Changes in eigenfrequencies of cantilever structures are enough to identify possible local damage at Level 3, i.e., to cover damage detection, localization, and quantification. The proposed algorithms identified the damage with relatively small errors, even at a high noise level. KW - Parameteridentifikation KW - Bayesian Inference, Uncertainty Quantification KW - Inverse Problems KW - Damage Identification KW - Concrete catenary pole KW - SHM KW - Inverse Probleme KW - Bayes’schen Inferenz KW - Unschärfequantifizierung KW - Schadenerkennung KW - Oberleitungsmasten Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20210526-44338 UR - https://asw-verlage.de/katalog/vibration_based_monitoring_of_co-2363.html VL - 2021 PB - Bauhaus-Universitätsverlag CY - Weimar ER - TY - THES A1 - Goswami, Somdatta T1 - Phase field modeling of fracture with isogeometric analysis and machine learning methods N2 - This thesis presents the advances and applications of phase field modeling in fracture analysis. In this approach, the sharp crack surface topology in a solid is approximated by a diffusive crack zone governed by a scalar auxiliary variable. The uniqueness of phase field modeling is that the crack paths are automatically determined as part of the solution and no interface tracking is required. The damage parameter varies continuously over the domain. But this flexibility comes with associated difficulties: (1) a very fine spatial discretization is required to represent sharp local gradients correctly; (2) fine discretization results in high computational cost; (3) computation of higher-order derivatives for improved convergence rates and (4) curse of dimensionality in conventional numerical integration techniques. As a consequence, the practical applicability of phase field models is severely limited. The research presented in this thesis addresses the difficulties of the conventional numerical integration techniques for phase field modeling in quasi-static brittle fracture analysis. The first method relies on polynomial splines over hierarchical T-meshes (PHT-splines) in the framework of isogeometric analysis (IGA). An adaptive h-refinement scheme is developed based on the variational energy formulation of phase field modeling. The fourth-order phase field model provides increased regularity in the exact solution of the phase field equation and improved convergence rates for numerical solutions on a coarser discretization, compared to the second-order model. However, second-order derivatives of the phase field are required in the fourth-order model. Hence, at least a minimum of C1 continuous basis functions are essential, which is achieved using hierarchical cubic B-splines in IGA. PHT-splines enable the refinement to remain local at singularities and high gradients, consequently reducing the computational cost greatly. Unfortunately, when modeling complex geometries, multiple parameter spaces (patches) are joined together to describe the physical domain and there is typically a loss of continuity at the patch boundaries. This decrease of smoothness is dictated by the geometry description, where C0 parameterizations are normally used to deal with kinks and corners in the domain. Hence, the application of the fourth-order model is severely restricted. To overcome the high computational cost for the second-order model, we develop a dual-mesh adaptive h-refinement approach. This approach uses a coarser discretization for the elastic field and a finer discretization for the phase field. Independent refinement strategies have been used for each field. The next contribution is based on physics informed deep neural networks. The network is trained based on the minimization of the variational energy of the system described by general non-linear partial differential equations while respecting any given law of physics, hence the name physics informed neural network (PINN). The developed approach needs only a set of points to define the geometry, contrary to the conventional mesh-based discretization techniques. The concept of `transfer learning' is integrated with the developed PINN approach to improve the computational efficiency of the network at each displacement step. This approach allows a numerically stable crack growth even with larger displacement steps. An adaptive h-refinement scheme based on the generation of more quadrature points in the damage zone is developed in this framework. For all the developed methods, displacement-controlled loading is considered. The accuracy and the efficiency of both methods are studied numerically showing that the developed methods are powerful and computationally efficient tools for accurately predicting fractures. T3 - ISM-Bericht // Institut für Strukturmechanik, Bauhaus-Universität Weimar - 2021,1 KW - Phasenfeldmodell KW - Neuronales Netz KW - Sprödbruch KW - Isogeometric Analysis KW - Physics informed neural network KW - phase field KW - deep neural network KW - brittle fracture Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20210304-43841 ER - TY - THES A1 - Bianco, Marcelo José T1 - Coupling between Shell and Generalized Beam Theory (GBT) elements N2 - In the last decades, Finite Element Method has become the main method in statics and dynamics analysis in engineering practice. For current problems, this method provides a faster, more flexible solution than the analytic approach. Prognoses of complex engineer problems that used to be almost impossible to solve are now feasible. Although the finite element method is a robust tool, it leads to new questions about engineering solutions. Among these new problems, it is possible to divide into two major groups: the first group is regarding computer performance; the second one is related to understanding the digital solution. Simultaneously with the development of the finite element method for numerical solutions, a theory between beam theory and shell theory was developed: Generalized Beam Theory, GBT. This theory has not only a systematic and analytical clear presentation of complicated structural problems, but also a compact and elegant calculation approach that can improve computer performance. Regrettably, GBT was not internationally known since the most publications of this theory were written in German, especially in the first years. Only in recent years, GBT has gradually become a fertile research topic, with developments from linear to non-linear analysis. Another reason for the misuse of GBT is the isolated application of the theory. Although recently researches apply finite element method to solve the GBT's problems numerically, the coupling between finite elements of GBT and other theories (shell, solid, etc) is not the subject of previous research. Thus, the main goal of this dissertation is the coupling between GBT and shell/membrane elements. Consequently, one achieves the benefits of both sides: the versatility of shell elements with the high performance of GBT elements. Based on the assumptions of GBT, this dissertation presents how the separation of variables leads to two calculation's domains of a beam structure: a cross-section modal analysis and the longitudinal amplification axis. Therefore, there is the possibility of applying the finite element method not only in the cross-section analysis, but also the development for an exact GBT's finite element in the longitudinal direction. For the cross-section analysis, this dissertation presents the solution of the quadratic eigenvalue problem with an original separation between plate and membrane mechanism. Subsequently, one obtains a clearer representation of the deformation mode, as well as a reduced quadratic eigenvalue problem. Concerning the longitudinal direction, this dissertation develops the novel exact elements, based on hyperbolic and trigonometric shape functions. Although these functions do not have trivial expressions, they provide a recursive procedure that allows periodic derivatives to systematise the development of stiffness matrices. Also, these shape functions enable a single-element discretisation of the beam structure and ensure a smooth stress field. From these developments, this dissertation achieves the formulation of its primary objective: the connection of GBT and shell elements in a mixed model. Based on the displacement field, it is possible to define the coupling equations applied in the master-slave method. Therefore, one can model the structural connections and joints with finite shell elements and the structural beams and columns with GBT finite element. As a side effect, the coupling equations limit the displacement field of the shell elements under the assumptions of GBT, in particular in the neighbourhood of the coupling cross-section. Although these side effects are almost unnoticeable in linear analysis, they lead to cumulative errors in non-linear analysis. Therefore, this thesis finishes with the evaluation of the mixed GBT-shell models in non-linear analysis. T3 - ISM-Bericht // Institut für Strukturmechanik, Bauhaus-Universität Weimar - 2021,2 KW - Biegetheorie KW - Finite Elemente Methode KW - Generalized Bean Theory KW - Finite Element KW - Thin-walled Structures KW - Cross-Section Warping KW - Cross-Section Distortion KW - Verallgemeinerte Technische Biegetheorie Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20210315-43914 ER - TY - THES A1 - Bielik, Martin T1 - FORM-ACTIVITY-MOVEMENT INTERACTION MODEL N2 - This dissertation investigates the interactions between urban form, allocation of activities, and pedestrian movement in the context of urban planning. The ability to assess the long-term impact of urban planning decisions on what people do and how they get there is of central importance, with various disciplines addressing this topic. This study focuses on approaches proposed by urban morphologists, urban economists, and transportation planners, each aiming the attention at a different part of the form-activity-movement interaction. Even though there is no doubt about the advantages of these highly focused approaches, it remains unclear what is the cost of ignoring the effect of some interactions while considering others. The general aim of this dissertation is to empirically test the validity of the individual models and quantify the impact of this isolationist approach on their precision and bias. For this purpose, we propose a joined form-activity-movement interaction model and conduct an empirical study in Weimar, Germany. We estimate how the urban form and activities affect movement as well as how movement and urban form affect activities. By estimating these effects in isolation and simultaneously, we assess the bias of the individual models. On the one hand, the empirical study results confirm the significance of all interactions suggested by the individual models. On the other hand, we were able to show that when these interactions are estimated in isolation, the resulting predictions are biased. To conclude, we do not question the knowledge brought by transportation planners, urban morphologists, and urban economists. However, we argue that it might be of little use on its own. We see the relevance of this study as being twofold. On the one hand, we proposed a novel methodological framework for the simultaneous estimation of the form-activity-movement interactions. On the other hand, we provide empirical evidence about the strengths and limitations of current approaches. KW - Stadtplanung Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20210407-43970 ER - TY - JOUR A1 - Lashkar-Ara, Babak A1 - Kalantari, Niloofar A1 - Sheikh Khozani, Zohreh A1 - Mosavi, Amir T1 - Assessing Machine Learning versus a Mathematical Model to Estimate the Transverse Shear Stress Distribution in a Rectangular Channel JF - Mathematics N2 - One of the most important subjects of hydraulic engineering is the reliable estimation of the transverse distribution in the rectangular channel of bed and wall shear stresses. This study makes use of the Tsallis entropy, genetic programming (GP) and adaptive neuro-fuzzy inference system (ANFIS) methods to assess the shear stress distribution (SSD) in the rectangular channel. To evaluate the results of the Tsallis entropy, GP and ANFIS models, laboratory observations were used in which shear stress was measured using an optimized Preston tube. This is then used to measure the SSD in various aspect ratios in the rectangular channel. To investigate the shear stress percentage, 10 data series with a total of 112 different data for were used. The results of the sensitivity analysis show that the most influential parameter for the SSD in smooth rectangular channel is the dimensionless parameter B/H, Where the transverse coordinate is B, and the flow depth is H. With the parameters (b/B), (B/H) for the bed and (z/H), (B/H) for the wall as inputs, the modeling of the GP was better than the other one. Based on the analysis, it can be concluded that the use of GP and ANFIS algorithms is more effective in estimating shear stress in smooth rectangular channels than the Tsallis entropy-based equations. KW - Maschinelles Lernen KW - smooth rectangular channel KW - Tsallis entropy KW - genetic programming KW - artificial intelligence KW - machine learning KW - big data KW - computational hydraulics Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20210504-44197 UR - https://www.mdpi.com/2227-7390/9/6/596 VL - 2021 IS - Volume 9, Issue 6, Article 596 PB - MDPI CY - Basel ER - TY - THES A1 - Spröte, Daniel T1 - Immobilienportfoliomanagement öffentlicher musealer Schlösserverwaltungen - Daten zur Investitionssteuerung N2 - Die Arbeit leistet einen wissenschaftlichen Beitrag zur Erforschung der Einsatzmöglichkeiten eines Immobilienportfoliomanagements für öffentliche museale Schlösserverwaltungen in Deutschland. Insbesondere wird ein für deren Organisation spezifisches Modell zur Investitionssteuerung herausgearbeitet und dessen Anwendbarkeit in der Praxis mit Experten diskutiert. KW - Unbewegliche Sache KW - Portfoliomanagement KW - Museum KW - Schloss KW - Investition Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20210510-44260 ER - TY - JOUR A1 - Harirchian, Ehsan A1 - Lahmer, Tom A1 - Rasulzade, Shahla T1 - Earthquake Hazard Safety Assessment of Existing Buildings Using Optimized Multi-Layer Perceptron Neural Network JF - Energies N2 - The latest earthquakes have proven that several existing buildings, particularly in developing countries, are not secured from damages of earthquake. A variety of statistical and machine-learning approaches have been proposed to identify vulnerable buildings for the prioritization of retrofitting. The present work aims to investigate earthquake susceptibility through the combination of six building performance variables that can be used to obtain an optimal prediction of the damage state of reinforced concrete buildings using artificial neural network (ANN). In this regard, a multi-layer perceptron network is trained and optimized using a database of 484 damaged buildings from the Düzce earthquake in Turkey. The results demonstrate the feasibility and effectiveness of the selected ANN approach to classify concrete structural damage that can be used as a preliminary assessment technique to identify vulnerable buildings in disaster risk-management programs. KW - Erdbeben KW - Maschinelles Lernen KW - earthquake damage KW - seismic vulnerability KW - artificial neural network KW - OA-Publikationsfonds2020 Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20200504-41575 UR - https://www.mdpi.com/1996-1073/13/8/2060/htm VL - 2020 IS - Volume 13, Issue 8, 2060 PB - MDPI CY - Basel ER - TY - THES A1 - Schmitz, Tonia Annick T1 - Entwicklung und Bilanzierung eines Photobioreaktorsystems zur Makroalgenkultivierung am Standort einer landwirtschaftlichen Biogasanlage N2 - Marine Makroalgen besitzen vielversprechende Eigenschaften und Inhaltsstoffe für die Verwendung als Energieträger, Nahrungsmittel oder als Ausgangsstoff für Pharmazeutika. Dass die Quantität und Qualität der in natürlicher Umgebung wachsenden Makroalgen schwankt, reduziert jedoch deren Verwertbarkeit und erschwert die Erschließung hochpreisiger Marktsegmente. Zudem ist eine Ausweitung der Zucht in marinen und küstennahen Aquakulturen in Europa gegenwärtig wenig aussichtsreich, da vielversprechende Areale bereits zum Fischfang oder als Erholungs- bzw. Naturschutzgebiete ausgewiesen sind. Im Rahmen dieser Arbeit wird demzufolge ein geschlossenes Photobioreaktorsystem zur Makroalgenkultivierung entwickelt, welches eine umfassende Kontrolle der abiotischen Kultivierungsparameter und eine effektive Aufbereitung des Kulturmediums vorsieht, um eine standortunabhängige Algenproduktion zu ermöglichen. Zur Bilanzierung des Gesamtkonzeptes einer Kultivierung und Verwertung (stofflich oder energetisch) werden die spezifischen Wachstumsraten und Methanbildungspotentiale der Algenarten Ulva intestinalis, Fucus vesiculosus und Palmaria palmata in praktischen Versuchen ermittelt. Im Ergebnis wird für den gegenwärtigen Entwicklungsstand der Kultivierungsanlage eine positive Bilanz für die stoffliche Verwertung der Algenart Ulva intestinalis und eine negative Bilanz für die energetische Verwertung aller untersuchten Algenarten erzielt. Wird ein Optimalszenario betrachtet, indem die Besatzdichten und Wachstumsraten der Algen in der Zucht erhöht werden, bleibt die Energiebilanz negativ. Allerdings summieren sich die finanzielle Einnahmen durch einen Verkauf der Algen als Produkt auf jährlich 460.869€ für Ulva intestinalis, 4.010€ für Fucus vesiculosus und 16.913€ für Palmaria palmata. Im Ergebnis ist insbesondere eine stoffliche Verwertung der gezüchteten Grünalge Ulva intestinalis anzustreben und die Produktivität der Zuchtanlage im Sinne des Optimalszenarios zu steigern. N2 - Marine macroalgae have renown properties as feedstock for fuel, food or pharmaceuticals. However, since the quantity and quality of naturally grown algae vary widely, their exploitability is reduced – especially for producers in high priced markets. Moreover, the expansion of marine or shore-based cultivation systems is unlikely in Europe, since promising sites either lie in fishing zones, recreational areas or natural reserves. The aim of this thesis was therefore to develop a closed photobioreactor system enabling full control of abiotic environmental parameters and an effective reconditioning of the cultivation medium in order to produce marine macroalgae at sites distant from shore. Using environmental management accounting methods, the potential output of macroalgae cultivation and valorization (product- or energy-based) is being assessed based on the specific growth rates and methane yields achievable with the species Ulva intestinalis, Fucus vesiculosus and Palmaria palmata. The balancing results for the status quo of the developed cultivation system show a positive outcome for a product-based valorization of the species Ulva intestinalis and a negative outcome for an energy-based valorization of all species investigated. Considering an optimum scenario providing an increase of growth rates and culture density, the balance of an energy-based valorization remains negative for all three species. However, the financial income by selling the cultivated macroalgae as a product sums up to a yearly amount of 460.869€ for Ulva intestinalis, 4.010€ for Fucus vesiculosus and 16.913€ for Palmaria palmata. Concluding, a product-based valorization seems promising – especially for the green algae Ulva intestinalis – when the productivity of the developed cultivation system is increased in accordance to the framework of the optimum scenario. KW - Makroalgen KW - Photobioreaktor KW - Biogas KW - Makroalgen KW - Photobioreaktorsystem KW - Biogasproduktion Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20200604-41774 ER - TY - THES A1 - Hossein Nezhad Shirazi, Ali T1 - Multi-Scale Modeling of Lithium ion Batteries: a thermal management approach and molecular dynamic studies N2 - Rechargeable lithium ion batteries (LIBs) play a very significant role in power supply and storage. In recent decades, LIBs have caught tremendous attention in mobile communication, portable electronics, and electric vehicles. Furthermore, global warming has become a worldwide issue due to the ongoing production of greenhouse gases. It motivates solutions such as renewable sources of energy. Solar and wind energies are the most important ones in renewable energy sources. By technology progress, they will definitely require batteries to store the produced power to make a balance between power generation and consumption. Nowadays,rechargeable batteries such as LIBs are considered as one of the best solutions. They provide high specific energy and high rate performance while their rate of self-discharge is low. Performance of LIBs can be improved through the modification of battery characteristics. The size of solid particles in electrodes can impact the specific energy and the cyclability of batteries. It can improve the amount of lithium content in the electrode which is a vital parameter in capacity and capability of a battery. There exist diferent sources of heat generation in LIBs such as heat produced during electrochemical reactions, internal resistance in battery. The size of electrode's electroactive particles can directly affect the produced heat in battery. It will be shown that the smaller size of solid particle enhance the thermal characteristics of LIBs. Thermal issues such as overheating, temperature maldistribution in the battery, and thermal runaway have confined applications of LIBs. Such thermal challenges reduce the Life cycle of LIBs. As well, they may lead to dangerous conditions such as fire or even explosion in batteries. However, recent advances in fabrication of advanced materials such as graphene and carbon nanotubes with extraordinary thermal conductivity and electrical properties propose new opportunities to enhance their performance. Since experimental works are expensive, our objective is to use computational methods to investigate the thermal issues in LIBS. Dissipation of the heat produced in the battery can improve the cyclability and specific capacity of LIBs. In real applications, packs of LIB consist several battery cells that are used as the power source. Therefore, it is worth to investigate thermal characteristic of battery packs under their cycles of charging/discharging operations at different applied current rates. To remove the produced heat in batteries, they can be surrounded by materials with high thermal conductivity. Parafin wax absorbs high energy since it has a high latent heat. Absorption high amounts of energy occurs at constant temperature without phase change. As well, thermal conductivity of parafin can be magnified with nano-materials such as graphene, CNT, and fullerene to form a nano-composite medium. Improving the thermal conductivity of LIBs increase the heat dissipation from batteries which is a vital issue in systems of battery thermal management. The application of two-dimensional (2D) materials has been on the rise since exfoliation the graphene from bulk graphite. 2D materials are single-layered in an order of nanosizes which show superior thermal, mechanical, and optoelectronic properties. They are potential candidates for energy storage and supply, particularly in lithium ion batteries as electrode material. The high thermal conductivity of graphene and graphene-like materials can play a significant role in thermal management of batteries. However, defects always exist in nano-materials since there is no ideal fabrication process. One of the most important defects in materials are nano-crack which can dramatically weaken the mechanical properties of the materials. Newly synthesized crystalline carbon nitride with the stoichiometry of C3N have attracted many attentions due to its extraordinary mechanical and thermal properties. The other nano-material is phagraphene which shows anisotropic mechanical characteristics which is ideal in production of nanocomposite. It shows ductile fracture behavior when subjected under uniaxial loadings. It is worth to investigate their thermo-mechanical properties in its pristine and defective states. We hope that the findings of our work not only be useful for both experimental and theoretical researches but also help to design advanced electrodes for LIBs. KW - Akkumulator KW - Battery KW - Batterie Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20200214-40986 ER - TY - THES A1 - Kavrakov, Igor T1 - Synergistic Framework for Analysis and Model Assessment in Bridge Aerodynamics and Aeroelasticity N2 - Wind-induced vibrations often represent a major design criterion for long-span bridges. This work deals with the assessment and development of models for aerodynamic and aeroelastic analyses of long-span bridges. Computational Fluid Dynamics (CFD) and semi-analytical aerodynamic models are employed to compute the bridge response due to both turbulent and laminar free-stream. For the assessment of these models, a comparative methodology is developed that consists of two steps, a qualitative and a quantitative one. The first, qualitative, step involves an extension of an existing approach based on Category Theory and its application to the field of bridge aerodynamics. Initially, the approach is extended to consider model comparability and completeness. Then, the complexity of the CFD and twelve semi-analytical models are evaluated based on their mathematical constructions, yielding a diagrammatic representation of model quality. In the second, quantitative, step of the comparative methodology, the discrepancy of a system response quantity for time-dependent aerodynamic models is quantified using comparison metrics for time-histories. Nine metrics are established on a uniform basis to quantify the discrepancies in local and global signal features that are of interest in bridge aerodynamics. These signal features involve quantities such as phase, time-varying frequency and magnitude content, probability density, non-stationarity, and nonlinearity. The two-dimensional (2D) Vortex Particle Method is used for the discretization of the Navier-Stokes equations including a Pseudo-three dimensional (Pseudo-3D) extension within an existing CFD solver. The Pseudo-3D Vortex Method considers the 3D structural behavior for aeroelastic analyses by positioning 2D fluid strips along a line-like structure. A novel turbulent Pseudo-3D Vortex Method is developed by combining the laminar Pseudo-3D VPM and a previously developed 2D method for the generation of free-stream turbulence. Using analytical derivations, it is shown that the fluid velocity correlation is maintained between the CFD strips. Furthermore, a new method is presented for the determination of the complex aerodynamic admittance under deterministic sinusoidal gusts using the Vortex Particle Method. The sinusoidal gusts are simulated by modeling the wakes of flapping airfoils in the CFD domain with inflow vortex particles. Positioning a section downstream yields sinusoidal forces that are used for determining all six components of the complex aerodynamic admittance. A closed-form analytical relation is derived, based on an existing analytical model. With this relation, the inflow particles’ strength can be related with the target gust amplitudes a priori. The developed methodologies are combined in a synergistic framework, which is applied to both fundamental examples and practical case studies. Where possible, the results are verified and validated. The outcome of this work is intended to shed some light on the complex wind–bridge interaction and suggest appropriate modeling strategies for an enhanced design. T3 - Schriftenreihe des DFG Graduiertenkollegs 1462 Modellqualitäten // Graduiertenkolleg Modellqualitäten - 21 KW - Brücke KW - Bridge KW - Computational Fluid Dynamics KW - Aerodynamics KW - Aeroelasticity KW - Category Theory KW - Aerodynamik KW - Aeroelastizität Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20200316-41099 UR - https://asw-verlage.de/katalog/?id=2255 SN - 978-3-95773-284-2 PB - Bauhaus-Universitätsverlag CY - Weimar ER - TY - JOUR A1 - Harirchian, Ehsan A1 - Lahmer, Tom A1 - Buddhiraju, Sreekanth A1 - Mohammad, Kifaytullah A1 - Mosavi, Amir T1 - Earthquake Safety Assessment of Buildings through Rapid Visual Screening JF - Buildings N2 - Earthquake is among the most devastating natural disasters causing severe economical, environmental, and social destruction. Earthquake safety assessment and building hazard monitoring can highly contribute to urban sustainability through identification and insight into optimum materials and structures. While the vulnerability of structures mainly depends on the structural resistance, the safety assessment of buildings can be highly challenging. In this paper, we consider the Rapid Visual Screening (RVS) method, which is a qualitative procedure for estimating structural scores for buildings suitable for medium- to high-seismic cases. This paper presents an overview of the common RVS methods, i.e., FEMA P-154, IITK-GGSDMA, and EMPI. To examine the accuracy and validation, a practical comparison is performed between their assessment and observed damage of reinforced concrete buildings from a street survey in the Bingöl region, Turkey, after the 1 May 2003 earthquake. The results demonstrate that the application of RVS methods for preliminary damage estimation is a vital tool. Furthermore, the comparative analysis showed that FEMA P-154 creates an assessment that overestimates damage states and is not economically viable, while EMPI and IITK-GGSDMA provide more accurate and practical estimation, respectively. KW - Maschinelles Lernen KW - Machine learning KW - Erdbeben KW - buildings KW - earthquake safety assessment KW - earthquake KW - extreme events KW - seismic assessment KW - natural hazard KW - mitigation KW - rapid visual screening Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20200331-41153 UR - https://www.mdpi.com/2075-5309/10/3/51 VL - 2020 IS - Volume 10, Issue 3 PB - MDPI ER - TY - JOUR A1 - Harirchian, Ehsan A1 - Lahmer, Tom T1 - Improved Rapid Visual Earthquake Hazard Safety Evaluation of Existing Buildings Using a Type-2 Fuzzy Logic Model JF - Applied Sciences N2 - Rapid Visual Screening (RVS) is a procedure that estimates structural scores for buildings and prioritizes their retrofit and upgrade requirements. Despite the speed and simplicity of RVS, many of the collected parameters are non-commensurable and include subjectivity due to visual observations. This might cause uncertainties in the evaluation, which emphasizes the use of a fuzzy-based method. This study aims to propose a novel RVS methodology based on the interval type-2 fuzzy logic system (IT2FLS) to set the priority of vulnerable building to undergo detailed assessment while covering uncertainties and minimizing their effects during evaluation. The proposed method estimates the vulnerability of a building, in terms of Damage Index, considering the number of stories, age of building, plan irregularity, vertical irregularity, building quality, and peak ground velocity, as inputs with a single output variable. Applicability of the proposed method has been investigated using a post-earthquake damage database of reinforced concrete buildings from the Bingöl and Düzce earthquakes in Turkey. KW - Fuzzy-Logik KW - Erdbeben KW - Fuzzy Logic KW - Rapid Visual Screening KW - Vulnerability assessment KW - OA-Publikationsfonds2020 Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20200331-41161 UR - https://www.mdpi.com/2076-3417/10/7/2375 VL - 2020 IS - Volume 10, Issue 3, 2375 PB - MDPI CY - Basel ER - TY - THES A1 - Radmard Rahmani, Hamid T1 - Artificial Intelligence Approach for Seismic Control of Structures N2 - Abstract In the first part of this research, the utilization of tuned mass dampers in the vibration control of tall buildings during earthquake excitations is studied. The main issues such as optimizing the parameters of the dampers and studying the effects of frequency content of the target earthquakes are addressed. Abstract The non-dominated sorting genetic algorithm method is improved by upgrading generic operators, and is utilized to develop a framework for determining the optimum placement and parameters of dampers in tall buildings. A case study is presented in which the optimal placement and properties of dampers are determined for a model of a tall building under different earthquake excitations through computer simulations. Abstract In the second part, a novel framework for the brain learning-based intelligent seismic control of smart structures is developed. In this approach, a deep neural network learns how to improve structural responses during earthquake excitations using feedback control. Abstract Reinforcement learning method is improved and utilized to develop a framework for training the deep neural network as an intelligent controller. The efficiency of the developed framework is examined through two case studies including a single-degree-of-freedom system and a high-rise building under different earthquake excitation records. Abstract The results show that the controller gradually develops an optimum control policy to reduce the vibrations of a structure under an earthquake excitation through a cyclical process of actions and observations. Abstract It is shown that the controller efficiently improves the structural responses under new earthquake excitations for which it was not trained. Moreover, it is shown that the controller has a stable performance under uncertainties. KW - Erdbeben KW - seismic control KW - tuned mass damper KW - reinforcement learning KW - earthquake KW - machine learning KW - Operante Konditionierung KW - structural control Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20200417-41359 ER - TY - THES A1 - Hoinkis, Jule Hannah T1 - Hitze in der Stadt Jena BT - Eine Untersuchung des städtischen Mikroklimas von Jena, dessen Veränderungen infolge des Klimawandels, städtebaulicher Anpassungsstrategien & Anwendung der Ergebnisse anhand eines städtebaulichen Konzeptes zur Neugestaltung des Bachstraßenareals. N2 - Die vorliegende Arbeit befasst sich mit den spezifischen Faktoren und Wechselwirkungen des städtischen Klimas und Strategien zur Prävention und Kompensation lokaler Klimaveränderungen. Problematische Merkmale des Stadtklimas werden sich infolge des Klimawandels stärker ausprägen. Insbesondere die Hitzebelastung wird zunehmen und die Lebensbedingungen in der Stadt negativ beeinflussen. Infolge höherer Temperaturen in Städten und einer höheren Temperaturdifferenz zum Umland verändern sich Windströme und die Wasserbilanz. Es sind Strategien notwendig, um den Schadstoffausstoß, die Flächeninanspruchnahme, die Abfallproduktion und den Wasser-, Energie- und Ressourcenverbrauch zu verringern, um sowohl langfristig den Klimawandel als auch dessen bereits unvermeidbaren Auswirkungen auf Städte zu begrenzen. Beispielhaft untersucht die Arbeit das Stadtklima, dessen zukünftige Veränderungen infolge des Klimawandels, bauliche Maßnahmen und Anpassungsstrategien der Stadt Jena. Jena ist die zweitgrößte Stadt im Bundesland Thüringen und gehört heute zu den wärmsten und trockensten Großstädten Deutschlands. Die Ergebnisse der Arbeit werden anschließend anhand eines städtebaulichen Konzepts und Entwurfs angewendet. Das Bachstraßenareal liegt in der Innenstadt, dem am stärksten von Hitze betroffenen Stadtteil. Als ehemaliger Hauptstandort des Jenaer Universitätsklinikums, soll es zu einem nachhaltigen Wissenschaftscampus der Lebenswissenschaften umgebaut werden, wobei ein Großteil der denkmalgeschützten, ehemaligen Klinikgebäude erhalten bleibt. Der Fokus liegt dabei auf der Umsetzung der zuvor formulierten, nachhaltigen Strategien zur Verbesserung des lokalen Stadtklimas und einer Abschwächung der Auswirkungen des Klimawandels auf den besonders stark betroffenen Innenstadtbereich Jenas. KW - Hitze KW - Jena KW - Stadtklima KW - Klimawandel Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20220414-46323 ER - TY - JOUR A1 - Pollack, Moritz A1 - Lück, Andrea A1 - Wolf, Mario A1 - Kraft, Eckhard A1 - Völker, Conrad T1 - Energy and Business Synergy: Leveraging Biogenic Resources from Agriculture, Waste, and Wastewater in German Rural Areas JF - Sustainability N2 - The imperative to transform current energy provisions is widely acknowledged. However, scant attention has hitherto been directed toward rural municipalities and their innate resources, notably biogenic resources. In this paper, a methodological framework is developed to interconnect resources from waste, wastewater, and agricultural domains for energy utilization. This entails cataloging existing resources, delineating their potential via quantitative assessments utilizing diverse technologies, and encapsulating them in a conceptual model. The formulated models underwent iterative evaluation with engagement from diverse stakeholders. Consequently, 3 main concepts, complemented by 72 sub-concepts, were delineated, all fostering positive contributions to climate protection and providing heat supply in the rural study area. The outcomes’ replicability is underscored by the study area’s generic structure and the employed methodology. Through these inquiries, a framework for the requisite energy transition, with a pronounced emphasis on the coupling of waste, wastewater, and agriculture sectors in rural environments, is robustly analyzed. KW - Energiewende KW - Energieplanung KW - Abfallwirtschaft KW - organischer Abfall KW - Biomasse KW - Regionalentwicklung KW - biogene Abfallstoffe KW - Abwassermanagement KW - OA-Publikationsfonds2023 Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20231222-65172 UR - https://www.mdpi.com/2071-1050/15/24/16573 VL - 2023 IS - volume 15, issue 24, article 16573 SP - 1 EP - 25 PB - MDPI CY - Basel ER - TY - THES A1 - Rabizadeh, Ehsan T1 - Goal-oriented A Posteriori Error Estimation and Adaptive Mesh Refinement in 2D/3D Thermoelasticity Problems T1 - Zielorientierte a posteriori Fehlerabschätzung und adaptive Netzverfeinerung bei 2D- und 3Dthermoelastischen Problemen N2 - In recent years, substantial attention has been devoted to thermoelastic multifield problems and their numerical analysis. Thermoelasticity is one of the important categories of multifield problems which deals with the effect of mechanical and thermal disturbances on an elastic body. In other words, thermoelasticity encompasses the phenomena that describe the elastic and thermal behavior of solids and their interactions under thermo-mechanical loadings. Since providing an analytical solution for general coupled thermoelasticity problems is mathematically complicated, the development of alternative numerical solution techniques seems essential. Due to the nature of numerical analysis methods, presence of error in results is inevitable, therefore in any numerical simulation, the main concern is the accuracy of the approximation. There are different error estimation (EE) methods to assess the overall quality of numerical approximation. In many real-life numerical simulations, not only the overall error, but also the local error or error in a particular quantity of interest is of main interest. The error estimation techniques which are developed to evaluate the error in the quantity of interest are known as “goal-oriented” error estimation (GOEE) methods. This project, for the first time, investigates the classical a posteriori error estimation and goal-oriented a posteriori error estimation in 2D/3D thermoelasticity problems. Generally, the a posteriori error estimation techniques can be categorized into two major branches of recovery-based and residual-based error estimators. In this research, application of both recovery- and residual-based error estimators in thermoelasticity are studied. Moreover, in order to reduce the error in the quantity of interest efficiently and optimally in 2D and 3D thermoelastic problems, goal-oriented adaptive mesh refinement is performed. As the first application category, the error estimation in classical Thermoelasticity (CTE) is investigated. In the first step, a rh-adaptive thermo-mechanical formulation based on goal-oriented error estimation is proposed.The developed goal-oriented error estimation relies on different stress recovery techniques, i.e., the superconvergent patch recovery (SPR), L2-projection patch recovery (L2-PR), and weighted superconvergent patch recovery (WSPR). Moreover, a new adaptive refinement strategy (ARS) is presented that minimizes the error in a quantity of interest and refines the discretization such that the error is equally distributed in the refined mesh. The method is validated by numerous numerical examples where an analytical solution or reference solution is available. After investigating error estimation in classical thermoelasticity and evaluating the quality of presented error estimators, we extended the application of the developed goal-oriented error estimation and the associated adaptive refinement technique to the classical fully coupled dynamic thermoelasticity. In this part, we present an adaptive method for coupled dynamic thermoelasticity problems based on goal-oriented error estimation. We use dimensionless variables in the finite element formulation and for the time integration we employ the acceleration-based Newmark-_ method. In this part, the SPR, L2-PR, and WSPR recovery methods are exploited to estimate the error in the quantity of interest (QoI). By using adaptive refinement in space, the error in the quantity of interest is minimized. Therefore, the discretization is refined such that the error is equally distributed in the refined mesh. We demonstrate the efficiency of this method by numerous numerical examples. After studying the recovery-based error estimators, we investigated the residual-based error estimation in thermoelasticity. In the last part of this research, we present a 3D adaptive method for thermoelastic problems based on goal-oriented error estimation where the error is measured with respect to a pointwise quantity of interest. We developed a method for a posteriori error estimation and mesh adaptation based on dual weighted residual (DWR) method relying on the duality principles and consisting of an adjoint problem solution. Here, we consider the application of the derived estimator and mesh refinement to two-/three-dimensional (2D/3D) thermo-mechanical multifield problems. In this study, the goal is considered to be given by singular pointwise functions, such as the point value or point value derivative at a specific point of interest (PoI). An adaptive algorithm has been adopted to refine the mesh to minimize the goal in the quantity of interest. The mesh adaptivity procedure based on the DWR method is performed by adaptive local h-refinement/coarsening with allowed hanging nodes. According to the proposed DWR method, the error contribution of each element is evaluated. In the refinement process, the contribution of each element to the goal error is considered as the mesh refinement criterion. In this study, we substantiate the accuracy and performance of this method by several numerical examples with available analytical solutions. Here, 2D and 3D problems under thermo-mechanical loadings are considered as benchmark problems. To show how accurately the derived estimator captures the exact error in the evaluation of the pointwise quantity of interest, in all examples, considering the analytical solutions, the goal error effectivity index as a standard measure of the quality of an estimator is calculated. Moreover, in order to demonstrate the efficiency of the proposed method and show the optimal behavior of the employed refinement method, the results of different conventional error estimators and refinement techniques (e.g., global uniform refinement, Kelly, and weighted Kelly techniques) are used for comparison. N2 - Einleitung und Motivation: 1- Im Laufe der letzten Jahrzehnte wurde den Mehrfeldproblemen und ihrer numerischen Analyse große Aufmerksamkeit gewidmet. Bei Mehrfeldproblemen wird die Wechselwirkung zwischen verschiedenen Feldern wie elastischen, elektrischen, magnetischen, chemischen oder thermischen Feldern untersucht. Eine wichtige Kategorie von Mehrfeldproblemen ist die Thermoelastizität. In der Thermoelastizität werden neben dem mechanischen Feld (Verschiebungen) auch das thermische Feld (Temperatur) und deren Auswirkungen aufeinander untersucht. 2- In fortgeschrittenen und sensible Anwendungen mit Temperaturänderung (z. B. LNG-, CNG- oder LPG-Speichertanks bei Sonnentemperatur im Sommer) ist die Elastizitätstheorie, die nur Verschiebungen berücksichtigt, nicht ausreichend. In diesen Fällen ist die Verwendung einer thermoelastischen Formulierung unumgänglich, um zuverlässige Ergebnisse zu erzielen. 3- Da eine analytische Lösung für thermoelastische Probleme sehr selten bestimmbar ist, wird sie durch numerische Methoden ersetzt. Allerdings sind die numerischen Ergebnisse nicht exakt und approximieren nur die exakte Lösung. Daher sind Fehler in den numerischen Ergebnissen unvermeidlich. 4- In jeder numerischen Simulation ist die Genauigkeit der Approximation das Hauptanliegen. Daher wurden verschiedene Fehlerschätzungstechniken entwickelt, um den Fehler der numerischen Lösung zu schätzen. Die herkömmlichen Fehlerschätzungsmethoden geben nur einen allgemeinen Überblick über die Gesamtgenauigkeit einer Näherungslösung. Bei vielen realen Problemen ist jedoch anstelle der Gesamtgenauigkeit die örtliche Genauigkeit (z. B. die Genauigkeit an einem bestimmten Punkt) von großem Interesse 5- Herkömmliche Fehlerschätzer berechnen Fehler in gewissen Normen. In der Ingenieurpraxis interessieren allerdings Fehler in anderen Zielgrößen, beispielsweise in der Last-Verformungs-Kurve oder in gewissen Spannungs-komponenten und speziellen Positionen. Dafür wurden sog. zielorientierte Fehlerschätzer entwickelt. 6- Die meisten numerischen Methoden unterteilen das Gebiet in kleine Teile (Element/Zelle), um das Problem zu lösen. Die Verwendung sehr feiner Elemente erhöht die Simulationsgenauigkeit, erhöht aber auch die Rechenzeit drastisch. Dieses Problem wird durch adaptive Methoden (AM) gelöst. AM können die Rechenzeit deutlich verringern. Bei adaptiven Methoden spielt die Fehlerschätzung eine Schlüsselrolle. Die Verfeinerung der Diskretisierung wird von einer Fehlerschätzung der Lösung kontrolliert und gesteuert (Elemente mit einem höheren geschätzten Fehler werden zur Verfeinerung/Aufteilung ausgewählt). Problemstellung und Zielsetzung der Arbeit 7- Die thermoelastischen Probleme können in zwei Hauptgruppen eingeteilt werden: Klassische Thermoelastizität (KTE) und klassische gekoppelte Thermoelastizität (KKTE). In jeder Gruppe werden verschiedene thermoelastische Probleme mit verschiedenen Geometrien, und Rand-/Anfangsbedingungen untersucht. In dieser Untersuchung werden die KTE- und KKTE-Probleme numerisch gelöst und alle numerischen Lösungen durch Fehlerschätzung bewertet. 8- In dieser Arbeit werden die Gesamtgenauigkeit der numerischen Lösung durch herkömmliche globale Fehlerschätzverfahren (auch als recovery-basierte Methoden bekannt) und die Genauigkeit der Lösung in bestimmten Punkten durch neue lokale Methoden (z. B. Dual-gewichtete Residuumsmethode oder DWR-Methode) bewertet. 9- Bei den dynamischen thermoelastischen Problemen ändern sich die Problembedin-gungen und anschließend die Lösung mit der Zeit. Daher werden die Fehler in jedem Zeitschritt geschätzt, um die Genauigkeit über die Zeit zu erhalten. 10- In dieser Dissertation wurde eine neue adaptive Gitter-Verfeinerung (AGV)-Technik entwickelt und für thermoelastische Probleme implementiert. Stand der Wissenschaft 11- Da die Thermoelastizität im Vergleich zu anderen mechanischen Bereichen wie der Elastizität nicht so umfangreich untersucht ist, wurden nur sehr begrenzte Untersuchungen durchgeführt, um die numerischen Fehler abzuschätzen und zu kontrollieren. Alle diese Untersuchungen konzentrierten sich auf die konventionellen Techniken, die nur den Gesamtfehler abschätzen können. Um die lokalen Fehler (wie punktweise Fehler oder Fehler an einem bestimmten Punkt) abzuschätzen, ist die Verwendung der zielorientierten Fehlerschätzungstechniken unvermeidlich. Die Implementierung der recovery-basierten zielorientierten Fehlerschätzung in der Thermoelastizität wird vor diesem Projekt nicht untersucht. 12- Viele numerische Analysen der dynamischen thermoelastischen Probleme basieren auf der Laplace-Transformationsmethode. Bei dieser Methode ist es praktisch nicht möglich, den Fehler in jedem Zeitschritt abzuschätzen. Daher wurden bisher die herkömmlichen globalen oder lokalen zielorientierten Fehlerschätzungsverfahren nicht in der dynamischen Thermoelastizität implementiert. 13- Eine der neuesten fortgeschrittenen zielorientierten Fehlerschätzungsmethoden ist die Dual-gewichtete Residuumsmethode (DWR-Methode). Die DWR-Methode, die punktweise Fehler (wie Verschiebungs-, mechanische Spannungs- oder Dehnungsfehler an einem bestimmten Punkt) abschätzen kann, wird bei elastischen Problemen angewendet. Es wurde jedoch kein Versuch unternommen, die DWR-Methode für die thermoelastischen Probleme zu formulieren. 14- In numerischen Simulationen sollte das Gitter verfeinert werden, um den Fehler zu verringern. Viele Verfeinerungstechniken basieren auf den globalen Fehlerschätzern, die versuchen, den Fehler der gesamten Lösung zu reduzieren. Daher sind diese Verfeinerungsmethoden zum reduzieren der lokalen Fehler nicht effizient. Wenn nur die Lösung an bestimmten Punkten interessiert ist und der Fehler dort reduziert werden will, sollten die zielorientierten Verfeinerungsmethoden angewendet werden, die vor dieser Untersuchung nicht in thermoelastischen Problemen entwickelt und implementiert wurden. 15- Die realen Probleme sind in der Regel 3D-Probleme, und die Simulation mit vereinfachten 2D-Fällen zeigt nicht alle Aspekte des Problems. Wie bereits erwähnt, sollten in der numerischen Simulation zur Erhöhung der Genauigkeit Gitterverfeinerungstechniken eingesetzt werden. Die konventionell verfeinerten Gitter, die durch gleichmäßige Aufteilung aller Elemente erreicht werden, erhöhen die Rechenzeit. Diese Simulationszeiterhöhung bei 3D-Problemen ist enorm. Dieses Problem wird durch die Verwendung der intelligenten Verfeinerung anstelle der globalen gleichmäßigen Verfeinerung gelöst. In diesem Projekt wurde erstmals die zielorientierte adaptive Gitterverfeinerung (AGV) bei thermoelastischen 3D-Problemen entwickelt und implementiert. Forschungsmethodik 16- In dieser Arbeit werden die beiden Haupttypen der thermoelastischen Probleme (KTE und KKTE) untersucht. Das System der partiellen Differentialgleichung der Thermoelastizität besteht aus zwei Hauptgleichungen: der herkömmlichen Gleichgewichtsgleichung und der Energiebilanzgleichung. 17- In diesem Projekt wird die Finite-Elemente-Methode (FEM) verwendet, um die Probleme numerisch zu simulieren. 18- Der Computercode zur Lösung von 2D- und 3D-Problemen wurde in den Program-miersprachen MATLAB bzw. C++ entwickelt. Um die Rechenzeit zu verkürzen und die Computerressourcen effizient zu nutzen, wurden Parallelprogrammierungs- und Optimierungsalgorithmen eingesetzt. 19- Nachdem die Probleme numerisch gelöst wurden, wurden zwei verschiedene Arten von globalen und lokalen Fehlerschätzungstechniken implementiert, um den Fehler zu schätzen und die Genauigkeit der Lösung zu messen. Der globale Typ ist die recovery-basierte zielorientierte Fehlerabschätzung, die wiederum in drei Unterkategorien von SPR-, L2-PR- und WSPR-Methoden unterteilt ist. Der lokale Typ ist die dual-gewichtete residuumsbasierte zielorientierte Fehlerabschätzung. Die Formulierung dieser Methoden wurde für thermoelastische Probleme entwickelt. 20- Schließlich wurde nach der Fehlerschätzung die entwickelte AGV-Methode implementiert. Wesentliche Ergebnisse und Schlussfolgerungen 21- In diesem Projekt wurde die Fehlerschätzung der Thermoelastizität in den folgenden drei Schritten untersucht: 1- Recovery-basierte Fehlerschätzung in statischen thermo Problemen (KTE), 2- Recovery-basierte Fehlerabschätzung in dynamischen thermo Problemen (KKTE), 3- Residuumsbasierte Fehlerschätzung in statischen thermo Problemen (KTE), 22- Im ersten Schritt, wurde das recovery-basierte Fehlerschätzverfahren auf mehrere stationäre thermoelastische Probleme angewendet. Einige der untersuchten Probleme verfügen über analytische Lösungen. Der Vergleich der numerischen Ergebnisse mit der analytischen (exakten) Lösung zeigt, dass die WSPR-Methode die genaueste unter den SPR, L2-PR und WSPR Techniken ist. 23- Darüber hinaus schließen wir aus den Ergebnissen des ersten Schritts, dass die zielorientierte Verfeinerung, im Vergleich zur herkömmlichen gleichmäßigen Total-Verfeinerungsmethode, nur ein Drittel der Unbekannten erfordert, um das Problem mit der gleichen Genauigkeit zu lösen. Daher benötigt die zielorientierte Adaptivität im Vergleich zu herkömmlichen Methoden viel weniger Rechenzeit, um die gleiche Genauigkeit zu erreichen. 24- Im zweiten Schritt, sind die Fehlerschätzungstechniken dieselben wie im ersten Schritt, aber die untersuchten Probleme sind dynamisch und nicht statisch. Der Vergleich der numerischen Ergebnisse mit den analytischen Ergebnissen in einem Benchmark-Problem bestätigt die Genauigkeit der verwendeten Methode. 25- Die Ergebnisse des zweiten Schritts zeigen, dass die geschätzten Fehler in allen gekoppelten Problemen niedriger sind als die ähnlichen ungekoppelten. Bei diesen Problemen reduziert die Implementierung der entwickelten adaptiven Methode den Fehler erheblich. 26- Im dritten Schritt wurde das residuumsbasierte Fehlerabschätzungsverfahren auf mehrere thermoelastische Probleme im stationären Zustand angewendet. In allen Beispielen wird die Genauigkeit der Methode durch analytische Lösungen überprüft. Die numerischen Ergebnisse zeigen eine sehr gute Übereinstimmung mit der analytischen Lösung sowohl bei 2D- als auch bei 3D-Problemen. 27- Im dritten Schritt werden die Ergebnisse der DWR-Verfeinerung mit Kelly-, W-Kelly- und gleichmäßigen Total-Verfeinerungstechniken verglichen. Die entwickelte DWR-Methode zeigt im Vergleich zu den anderen Methoden die beste Effizienz. Um beispielsweise die Fehlertoleranz von 10-6 zu erreichen, enthält das DWR-Gitter nur 2% unbekannte Parameter im Vergleich zu einem gleichmäßig verfeinerten Gitter. Die Verwendung des DWR-Verfahrens spart daher erhebliche Rechenzeit und Kosten. KW - Mesh Refinement KW - Thermoelastizität KW - Goal-oriented A Posteriori Error Estimation KW - 2D/3D Adaptive Mesh Refinement KW - Thermoelasticity KW - Deal ii C++ code KW - recovery-based and residual-based error estimators Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20201113-42864 ER - TY - THES A1 - Salavati, Mohammad T1 - Multi-Scale Modeling of Mechanical and Electrochemical Properties of 1D and 2D Nanomaterials, Application in Battery Energy Storage Systems N2 - Material properties play a critical role in durable products manufacturing. Estimation of the precise characteristics in different scales requires complex and expensive experimental measurements. Potentially, computational methods can provide a platform to determine the fundamental properties before the final experiment. Multi-scale computational modeling leads to the modeling of the various time, and length scales include nano, micro, meso, and macro scales. These scales can be modeled separately or in correlation with coarser scales. Depend on the interested scales modeling, the right selection of multi-scale methods leads to reliable results and affordable computational cost. The present dissertation deals with the problems in various length and time scales using computational methods include density functional theory (DFT), molecular mechanics (MM), molecular dynamics (MD), and finite element (FE) methods. Physical and chemical interactions in lower scales determine the coarser scale properties. Particles interaction modeling and exploring fundamental properties are significant challenges of computational science. Downscale modelings need more computational effort due to a large number of interacted atoms/particles. To deal with this problem and bring up a fine-scale (nano) as a coarse-scale (macro) problem, we extended an atomic-continuum framework. The discrete atomic models solve as a continuum problem using the computationally efficient FE method. MM or force field method based on a set of assumptions approximates a solution on the atomic scale. In this method, atoms and bonds model as a harmonic oscillator with a system of mass and springs. The negative gradient of the potential energy equal to the forces on each atom. In this way, each bond's total potential energy includes bonded, and non-bonded energies are simulated as equivalent structural strain energies. Finally, the chemical nature of the atomic bond is modeled as a piezoelectric beam element that solves by the FE method. Exploring novel materials with unique properties is a demand for various industrial applications. During the last decade, many two-dimensional (2D) materials have been synthesized and shown outstanding properties. Investigation of the probable defects during the formation/fabrication process and studying their strength under severe service life are the critical tasks to explore performance prospects. We studied various defects include nano crack, notch, and point vacancy (Stone-Wales defect) defects employing MD analysis. Classical MD has been used to simulate a considerable amount of molecules at micro-, and meso- scales. Pristine and defective nanosheet structures considered under the uniaxial tensile loading at various temperatures using open-source LAMMPS codes. The results were visualized with the open-source software of OVITO and VMD. Quantum based first principle calculations have been conducting at electronic scales and known as the most accurate Ab initio methods. However, they are computationally expensive to apply for large systems. We used density functional theory (DFT) to estimate the mechanical and electrochemical response of the 2D materials. Many-body Schrödinger's equation describes the motion and interactions of the solid-state particles. Solid describes as a system of positive nuclei and negative electrons, all electromagnetically interacting with each other, where the wave function theory describes the quantum state of the set of particles. However, dealing with the 3N coordinates of the electrons, nuclei, and N coordinates of the electrons spin components makes the governing equation unsolvable for just a few interacted atoms. Some assumptions and theories like Born Oppenheimer and Hartree-Fock mean-field and Hohenberg-Kohn theories are needed to treat with this equation. First, Born Oppenheimer approximation reduces it to the only electronic coordinates. Then Kohn and Sham, based on Hartree-Fock and Hohenberg-Kohn theories, assumed an equivalent fictitious non-interacting electrons system as an electron density functional such that their ground state energies are equal to a set of interacting electrons. Exchange-correlation energy functionals are responsible for satisfying the equivalency between both systems. The exact form of the exchange-correlation functional is not known. However, there are widely used methods to derive functionals like local density approximation (LDA), Generalized gradient approximation (GGA), and hybrid functionals (e.g., B3LYP). In our study, DFT performed using VASP codes within the GGA/PBE approximation, and visualization/post-processing of the results realized via open-source software of VESTA. The extensive DFT calculations are conducted 2D nanomaterials prospects as anode/cathode electrode materials for batteries. Metal-ion batteries' performance strongly depends on the design of novel electrode material. Two-dimensional (2D) materials have developed a remarkable interest in using as an electrode in battery cells due to their excellent properties. Desirable battery energy storage systems (BESS) must satisfy the high energy density, safe operation, and efficient production costs. Batteries have been using in electronic devices and provide a solution to the environmental issues and store the discontinuous energies generated from renewable wind or solar power plants. Therefore, exploring optimal electrode materials can improve storage capacity and charging/discharging rates, leading to the design of advanced batteries. Our results in multiple scales highlight not only the proposed and employed methods' efficiencies but also promising prospect of recently synthesized nanomaterials and their applications as an anode material. In this way, first, a novel approach developed for the modeling of the 1D nanotube as a continuum piezoelectric beam element. The results converged and matched closely with those from experiments and other more complex models. Then mechanical properties of nanosheets estimated and the failure mechanisms results provide a useful guide for further use in prospect applications. Our results indicated a comprehensive and useful vision concerning the mechanical properties of nanosheets with/without defects. Finally, mechanical and electrochemical properties of the several 2D nanomaterials are explored for the first time—their application performance as an anode material illustrates high potentials in manufacturing super-stretchable and ultrahigh-capacity battery energy storage systems (BESS). Our results exhibited better performance in comparison to the available commercial anode materials. KW - Batterie KW - Modellierung KW - Nanostrukturiertes Material KW - Mechanical properties KW - Multi-scale modeling KW - Energiespeichersystem KW - Elektrodenmaterial KW - Elektrode KW - Mechanische Eigenschaft KW - Elektrochemische Eigenschaft KW - Electrochemical properties KW - Battery development KW - Nanomaterial Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20200623-41830 ER - TY - THES A1 - Schuster, Siegbert A1 - Schuster, Karl-Heinz T1 - Hygrothermische Gebäudesimulation – Experimentelle Bestimmung der Randparameter und Sorptionseigenschaften von historischen Räumen N2 - Forscher prognostizieren in den kommenden Jahren eine Klimaerwärmung bis zu 6 ° C. Aus diesem Grund wurde das EU – Forschungsprojekt „ Climate for Culture“ ins Leben gerufen, um Auswirkungen dieses Klimawandels auf denkmalgeschützte, kulturhistorische Gebäude zu untersuchen. Ziel ist es, entsprechende Schutzmaßnahmen in konservatorischer Hinsicht zu erarbeiten. Aufgrund des Zusammenhanges zwischen Temperatur und Luftfeuchte führt diese Klimaerwärmung auch zu einer Änderung des Feuchtehaushaltes im Außenbereich und, bedingt durch einen immer vorhandenen Luftwechsel, schließlich auch im Innenbereich von Gebäuden. Die Fähigkeit eines Gebäudes, durch seine Beschaffenheit auf Feuchteeinflüsse zu reagieren, wird maßgeblich bestimmt durch seine Möglichkeit, in der Gebäudehülle und der vorhandenen Einrichtung anfallende Feuchte zwischenzuspeichern und diese zeitversetzt wieder an die Umgebung abzugeben. Diese Fähigkeit sorptiver Flächen zur Feuchtepufferung konnte bislang nur mit erheblichem Aufwand ermittelt werden. In der vorliegenden Arbeit wird versucht, durch einfachere Methoden mittels hygrothermischer Simulation einen „Zweizahlwert“ zu erhalten, mit dem sich diese Raumkompetenz schnell und nachvollziehbar darstellen lässt. KW - Feuchtepufferung Y1 - 2011 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20131219-20936 ER - TY - THES A1 - Asslan, Milad T1 - An Experimental Study on the Initial Shear Stiffness in Granular Material under Controlled Multi-Phase Laboratory Conditions N2 - The initial shear modulus, Gmax, of soil is an important parameter for a variety of geotechnical design applications. This modulus is typically associated with shear strain levels about 5*10^-3% and below. The critical role of soil stiffness at small-strains in the design and analysis of geotechnical infrastructure is now widely accepted. Gmax is a key parameter in small-strain dynamic analyses such as those to predict soil behavior or soil-structure interaction during earthquake, explosions, machine or traffic vibration where it is necessary to know how the shear modulus degrades from its small-strain value as the level of shear strain increases. Gmax can be equally important for small-strain cyclic situations such as those caused by wind or wave loading and for small-strain static situations as well. Gmax may also be used as an indirect indication of various soil parameters, as it, in many cases, correlates well to other soil properties such as density and sample disturbance. In recent years, a technique using bender elements was developed to investigate the small-strain shear modulus Gmax. The objective of this thesis is to study the initial shear stiffness for various sands with different void ratios, densities, grain size distribution under dry and saturated conditions, then to compare empirical equations to predict Gmax and results from other testing devices with results of bender elements from this study. KW - Soil KW - Shear modulus KW - Shear wave KW - Soil dynamics KW - Bender elements Y1 - 2009 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20120402-15842 ER - TY - INPR A1 - Khosravi, Khabat A1 - Sheikh Khozani, Zohreh A1 - Cooper, James R. T1 - Predicting stable gravel-bed river hydraulic geometry: A test of novel, advanced, hybrid data mining algorithms N2 - Accurate prediction of stable alluvial hydraulic geometry, in which erosion and sedimentation are in equilibrium, is one of the most difficult but critical topics in the field of river engineering. Data mining algorithms have been gaining more attention in this field due to their high performance and flexibility. However, an understanding of the potential for these algorithms to provide fast, cheap, and accurate predictions of hydraulic geometry is lacking. This study provides the first quantification of this potential. Using at-a-station field data, predictions of flow depth, water-surface width and longitudinal water surface slope are made using three standalone data mining techniques -, Instance-based Learning (IBK), KStar, Locally Weighted Learning (LWL) - along with four types of novel hybrid algorithms in which the standalone models are trained with Vote, Attribute Selected Classifier (ASC), Regression by Discretization (RBD), and Cross-validation Parameter Selection (CVPS) algorithms (Vote-IBK, Vote-Kstar, Vote-LWL, ASC-IBK, ASC-Kstar, ASC-LWL, RBD-IBK, RBD-Kstar, RBD-LWL, CVPSIBK, CVPS-Kstar, CVPS-LWL). Through a comparison of their predictive performance and a sensitivity analysis of the driving variables, the results reveal: (1) Shield stress was the most effective parameter in the prediction of all geometry dimensions; (2) hybrid models had a higher prediction power than standalone data mining models, empirical equations and traditional machine learning algorithms; (3) Vote-Kstar model had the highest performance in predicting depth and width, and ASC-Kstar in estimating slope, each providing very good prediction performance. Through these algorithms, the hydraulic geometry of any river can potentially be predicted accurately and with ease using just a few, readily available flow and channel parameters. Thus, the results reveal that these models have great potential for use in stable channel design in data poor catchments, especially in developing nations where technical modelling skills and understanding of the hydraulic and sediment processes occurring in the river system may be lacking. KW - Maschinelles Lernen KW - Künstliche Intelligenz KW - Data Mining KW - Hydraulic geometry KW - Gravel-bed rivers Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20211004-44998 N1 - This is the pre-peer reviewed version of the following article: https://www.sciencedirect.com/science/article/abs/pii/S1364815221002085 ; https://doi.org/10.1016/j.envsoft.2021.105165 VL - 2021 ER - TY - INPR A1 - Steiner, Maria A1 - Bourinet, Jean-Marc A1 - Lahmer, Tom T1 - An adaptive sampling method for global sensitivity analysis based on least-squares support vector regression N2 - In the field of engineering, surrogate models are commonly used for approximating the behavior of a physical phenomenon in order to reduce the computational costs. Generally, a surrogate model is created based on a set of training data, where a typical method for the statistical design is the Latin hypercube sampling (LHS). Even though a space filling distribution of the training data is reached, the sampling process takes no information on the underlying behavior of the physical phenomenon into account and new data cannot be sampled in the same distribution if the approximation quality is not sufficient. Therefore, in this study we present a novel adaptive sampling method based on a specific surrogate model, the least-squares support vector regresson. The adaptive sampling method generates training data based on the uncertainty in local prognosis capabilities of the surrogate model - areas of higher uncertainty require more sample data. The approach offers a cost efficient calculation due to the properties of the least-squares support vector regression. The opportunities of the adaptive sampling method are proven in comparison with the LHS on different analytical examples. Furthermore, the adaptive sampling method is applied to the calculation of global sensitivity values according to Sobol, where it shows faster convergence than the LHS method. With the applications in this paper it is shown that the presented adaptive sampling method improves the estimation of global sensitivity values, hence reducing the overall computational costs visibly. KW - Approximation KW - Sensitivitätsanalyse KW - Abtastung KW - Surrogate models KW - Least-squares support vector regression KW - Adaptive sampling method KW - Global sensitivity analysis KW - Sampling Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20181218-38320 N1 - This is the pre-peer reviewed version of the following article: https://www.sciencedirect.com/science/article/pii/S0951832017311808, which has been published in final form at https://doi.org/10.1016/j.ress.2018.11.015. SP - 1 EP - 33 ER - TY - INPR A1 - Rezakazemi, Mashallah A1 - Mosavi, Amir A1 - Shirazian, Saeed T1 - ANFIS pattern for molecular membranes separation optimization N2 - In this work, molecular separation of aqueous-organic was simulated by using combined soft computing-mechanistic approaches. The considered separation system was a microporous membrane contactor for separation of benzoic acid from water by contacting with an organic phase containing extractor molecules. Indeed, extractive separation is carried out using membrane technology where complex of solute-organic is formed at the interface. The main focus was to develop a simulation methodology for prediction of concentration distribution of solute (benzoic acid) in the feed side of the membrane system, as the removal efficiency of the system is determined by concentration distribution of the solute in the feed channel. The pattern of Adaptive Neuro-Fuzzy Inference System (ANFIS) was optimized by finding the optimum membership function, learning percentage, and a number of rules. The ANFIS was trained using the extracted data from the CFD simulation of the membrane system. The comparisons between the predicted concentration distribution by ANFIS and CFD data revealed that the optimized ANFIS pattern can be used as a predictive tool for simulation of the process. The R2 of higher than 0.99 was obtained for the optimized ANFIS model. The main privilege of the developed methodology is its very low computational time for simulation of the system and can be used as a rigorous simulation tool for understanding and design of membrane-based systems. Highlights are, Molecular separation using microporous membranes. Developing hybrid model based on ANFIS-CFD for the separation process, Optimization of ANFIS structure for prediction of separation process KW - Fluid KW - Simulation KW - Molecular Liquids KW - optimization KW - machine learning KW - Membrane contactors KW - CFD Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20181122-38212 N1 - This is the pre-peer reviewed version of the following article: https://www.sciencedirect.com/science/article/pii/S0167732218345008, which has been published in final form at https://doi.org/10.1016/j.molliq.2018.11.017. VL - 2018 SP - 1 EP - 20 ER - TY - INPR A1 - Kavrakov, Igor A1 - Argentini, Tommaso A1 - Omarini, Simone A1 - Rocchi, Daniele A1 - Morgenthal, Guido T1 - Determination of complex aerodynamic admittance of bridge decks under deterministic gusts using the Vortex Particle Method N2 - Long-span bridges are prone to wind-induced vibrations. Therefore, a reliable representation of the aerodynamic forces acting on a bridge deck is of a major significance for the design of such structures. This paper presents a systematic study of the two-dimensional (2D) fluid-structure interaction of a bridge deck under smooth and turbulent wind conditions. Aerodynamic forces are modeled by two approaches: a computational fluid dynamics (CFD) model and six semi-analytical models. The vortex particle method is utilized for the CFD model and the free-stream turbulence is introduced by seeding vortex particles upstream of the deck with prescribed spectral characteristics. The employed semi-analytical models are based on the quasi-steady and linear unsteady assumptions and aerodynamic coefficients obtained from CFD analyses. The underlying assumptions of the semi-analytical aerodynamic models are used to interpret the results of buffeting forces and aeroelastic response due to a free-stream turbulence in comparison with the CFD model. Extensive discussions are provided to analyze the effect of linear fluid memory and quasi-steady nonlinearity from a CFD perspective. The outcome of the analyses indicates that the fluid memory is a governing effect in the buffeting forces and aeroelastic response, while the effect of the nonlinearity is overestimated by the quasi-steady models. Finally, flutter analyses are performed and the obtained critical velocities are further compared with wind tunnel results, followed by a brief examination of the post-flutter behavior. The results of this study provide a deeper understanding of the extent of which the applied models are able to replicate the physical processes for fluid-structure interaction phenomena in bridge aerodynamics and aeroelasticity. KW - Bridge KW - Aerodynamik KW - Ingenieurwissenschaften KW - Aerodynamic admittance KW - Computational fluid dynamics KW - Vortex particle method KW - Buffeting KW - Long-span bridges Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20200206-40883 N1 - This is the pre-peer reviewed version of the following article: https://www.sciencedirect.com/science/article/pii/S0167610519305719?via%3Dihub, which has been published in final form at https://doi.org/10.1016/j.jweia.2019.103971 ER - TY - INPR A1 - Kavrakov, Igor A1 - Morgenthal, Guido T1 - Aeroelastic analyses of bridges using a Pseudo-3D vortex method and velocity-based synthetic turbulence generation N2 - The accurate representation of aerodynamic forces is essential for a safe, yet reasonable design of long-span bridges subjected to wind effects. In this paper, a novel extension of the Pseudo-three-dimensional Vortex Particle Method (Pseudo-3D VPM) is presented for Computational Fluid Dynamics (CFD) buffeting analysis of line-like structures. This extension entails an introduction of free-stream turbulent fluctuations, based on the velocity-based turbulence generation. The aerodynamic response of a long-span bridge is obtained by subjecting the 3D dynamic representation of the structure to correlated free-stream turbulence in two-dimensional (2D) fluid planes, which are positioned along the bridge deck. The span-wise correlation of the free-stream turbulence between the 2D fluid planes is established based on Taylor's hypothesis of frozen turbulence. Moreover, the application of the laminar Pseudo-3D VPM is extended to a multimode flutter analysis. Finally, the structural response from the Pseudo-3D flutter and buffeting analyses is verified with the response, computed using the semi-analytical linear unsteady model in the time-domain. Meaningful merits of the turbulent Pseudo-3D VPM with respect to the linear unsteady model are the consideration of the 2D aerodynamic nonlinearity, nonlinear fluid memory, vortex shedding and local non-stationary turbulence effects in the aerodynamic forces. The good agreement of the responses for the two models in the 3D analyses demonstrates the applicability of the Pseudo-3D VPM for aeroelastic analyses of line-like structures under turbulent and laminar free-stream conditions. KW - Bridge KW - Aerodynamik KW - Ingenieurwissenschaften KW - Computational Bridge Aerodynamics KW - Buffeting KW - Flutter KW - Long-span Bridges KW - Vortex Particle Method Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20200206-40864 N1 - This is the pre-peer reviewed version of the following article: https://www.sciencedirect.com/science/article/pii/S0141029617322976?via%3Dihub, which has been published in final form at https://doi.org/10.1016/j.engstruct.2018.08.093 ER - TY - INPR A1 - Sheikh Khozani, Zohreh A1 - Kumbhakar, Manotosh T1 - Discussion of “Estimation of one-dimensional velocity distribution by measuring velocity at two points” by Yeganeh and Heidari (2020) N2 - The concept of information entropy together with the principle of maximum entropy to open channel flow is essentially based on some physical consideration of the problem under consideration. This paper is a discussion on Yeganeh and Heidari (2020)’s paper, who proposed a new approach for measuring vertical distribution of streamwise velocity in open channels. The discussers argue that their approach is conceptually incorrect and thus leads to a physically unrealistic situation. In addition, the discussers found some wrong mathematical expressions (which are assumed to be typos) written in the paper, and also point out that the authors did not cite some of the original papers on the topic. KW - Geschwindigkeit KW - Entropie Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20210216-43663 N1 - This is the pre-peer reviewed version of the following article: https://www.sciencedirect.com/science/article/pii/S0955598621000017 ; https://doi.org/10.1016/j.flowmeasinst.2021.101886 ER - TY - INPR A1 - Khosravi, Khabat A1 - Sheikh Khozani, Zohreh A1 - Mao, Luka T1 - A comparison between advanced hybrid machine learning algorithms and empirical equations applied to abutment scour depth prediction N2 - Complex vortex flow patterns around bridge piers, especially during floods, cause scour process that can result in the failure of foundations. Abutment scour is a complex three-dimensional phenomenon that is difficult to predict especially with traditional formulas obtained using empirical approaches such as regressions. This paper presents a test of a standalone Kstar model with five novel hybrid algorithm of bagging (BA-Kstar), dagging (DA-Kstar), random committee (RC-Kstar), random subspace (RS-Kstar), and weighted instance handler wrapper (WIHWKstar) to predict scour depth (ds) for clear water condition. The dataset consists of 99 scour depth data from flume experiments (Dey and Barbhuiya, 2005) using abutment shapes such as vertical, semicircular and 45◦ wing. Four dimensionless parameter of relative flow depth (h/l), excess abutment Froude number (Fe), relative sediment size (d50/l) and relative submergence (d50/h) were considered for the prediction of relative scour depth (ds/l). A portion of the dataset was used for the calibration (70%), and the remaining used for model validation. Pearson correlation coefficients helped deciding relevance of the input parameters combination and finally four different combinations of input parameters were used. The performance of the models was assessed visually and with quantitative metrics. Overall, the best input combination for vertical abutment shape is the combination of Fe, d50/l and h/l, while for semicircular and 45◦ wing the combination of the Fe and d50/l is the most effective input parameter combination. Our results show that incorporating Fe, d50/l and h/l lead to higher performance while involving d50/h reduced the models prediction power for vertical abutment shape and for semicircular and 45◦ wing involving h/l and d50/h lead to more error. The WIHW-Kstar provided the highest performance in scour depth prediction around vertical abutment shape while RC-Kstar model outperform of other models for scour depth prediction around semicircular and 45◦ wing. KW - maschinelles Lernen Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20210311-43889 N1 - This is the pre-peer reviewed version of the following article: https://www.sciencedirect.com/science/article/abs/pii/S0022169421001475?via%3Dihub ; https://doi.org/10.1016/j.jhydrol.2021.126100 ER - TY - THES A1 - Mukherjee, Nilangshu T1 - A numerical comparison of the impact of different climatic conditions in different geographic locations on the construction of an office building N2 - The aim of my research is to observe the variance of energy efficiency of a typical multi-story office building under the exposure of different climatic conditions. Energy efficiency requirements in building codes or energy standards are among the most important single measures for buildings’ energy efficiency. Therefore, this study can be set up for a better understanding of how energy efficiency of a building changes under the effect of adverse to moderate climatic conditions which possess a mentionable effect on the operation of a building. This thesis is structured in three balanced and conceptual steps. Following the aim of the project, the virtual building model is to be analyzed under the effect of seven distinct climatic conditions namely work environment of New Delhi, Mumbai, Berlin, Lisbon, Copenhagen, Dubai and Montreal. Firstly, the task is to do a complete literature research based on the scope of similar researches and studying the problems in detail along with the theoritical background all the concepts which are implemented to get the numerical results. This chapter also comprises a detailed study of the climatic conditions of the above-mentioned cities. Different climatic traits like temperature variations, count of heating and cooling degree days, relative humidity, temperature range and comfort zonal charts for the specified cities are studied in detail. This study helps to understand the effect of these adverse to moderate climates on the operation of the building. On the second step, the virtual building model is prepared on a software platform named Revit Structures. This virtual building model is not necessarily a complete building, but it has the relevant functionalities of a real building. We perform the energy analysis and the heating and cooling analysis on this virtual building model to study the operational outcome of the building under different climatic conditions in detail. By the end of these above two tasks, two scenarios are observed. On one hand, we have a literature research and on the other hand we have the numerical results. Therefore, finally we present a comparative scenario based on the energy efficient performances of the building under such variant climatic conditions. This is followed by the prediction of thermal comfort level inside the building and it based on Fanger’s PMV Model. Understanding the literature and the numerical values in detail helps us to predict the index thermal comfort level inside the building. The conclusion of this master thesis focuses mainly on the scopes of improvement of energy efficiency requirements in energy codes if any, differentiated according to specific locations. The initial aim of my hypothesis which is to study the impacts of climatic variations on the energy efficient performances of a building is fulfilled but as such topics have very deep and broad roots, the scope of further improvements is always predominant. KW - Klima KW - Energieeffizienz KW - Climatic conditions KW - Building performance Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20170811-32700 ER - TY - THES A1 - Küster, Felix Pascal T1 - Helsinki Central N2 - Als zentraler Ort und Eingangstor in die finnische Hauptstadt bietet der Bereich um den Bahnhof, in dem sich das Baufeld befindet zu wenig räumliche Qualitäten und bildet gleichzeitig eine Barriere zwischen dem historischen Stadtkern und dem politischen und kulturellem Zentrum der Stadt. Der historische Bahnhof aus der Epoche des Jugendstils ist momentan eingeschlossen von einer hochfrequentierten Straße im Süden und den flankierenden Stationen des Busbahnhofs an der Ost- und Westseite. Die fußläufigen Verbindungen in die Altstadt sind gestört und das Regierungsviertel mit dem Reichstagsgebäude werden links liegen gelassen. Eine Orientierung als Neuankömmling ist schwer möglich. Darüber hinaus kommt etwa die Hälfte der Züge, vor allem die Regionalzüge nicht in der Bahnhofshalle des Kopfbahnhofes an, weil die Begrenzung durch die Seitenflügel nur eine Erweiterung des Bahnhofs nach Norden hin zuließ. Entstanden ist ein Entwurf der versucht, dem gesamten Bereich um den Bahnhof ein neues Gesicht zu geben und eine Verbesserung auf unterschiedlichen Ebenen zu erreichen. Er bündelt zum einen die verschiedenen Verkehrsströme und stellt eine bisher unterbrochene Querverbindung zwischen den benachbarten Stadtvierteln entlang des Bahnhofsareals her. Zum anderen trägt er dem Erfordernis nach einem städtebaulichen Gegenüber für das Regierungsgebäude Rechnung, welches damit in den Verbund der kulturellen Einrichtungen auf dem Töölönlahti Gelände aufgenommen wird. Darüber hinaus belebt er eine Besonderheit von Helsinki. Zu Beginn des 20. Jahrhunderts bestand die Notwendigkeit den Hafen an das Schienennetz anzubinden. Da der Stadtkern bereits sehr dicht bebaut war, wurde ein Eisenbahnring entlang der Küste, einmal um das Stadtzentrum herum gebaut. Seitdem die Verbindung stillgelegt wurde liegt dieser Ring brach, was nun die große Chance bietet, eine kreuzungsfreien Rad- und Fußweg zu etablieren, der durch den Entwurf eines Mobilityhubs geschlossen würde. In der vorliegenden Broschüre werden die städtebaulichen Rahmenbedingungen, die Analyse der gegenwärtigen Situation und der eigentliche Entwurfsprozess, der zu dieser Lösung führte dokumentiert. KW - Weimar / Bauhaus-Universität Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20120807-16867 ER -