02 Fakultät Bau- und Umweltingenieurwissenschaften
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/3
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Item Open Access A novel transformation model for deployable scissor-hinge structures(2010) Akgün, Yenal; Sobek, Werner (Prof. Dr.-Ing. Dr.-Ing. E.h.)Primary objective of this dissertation is to propose a novel analytical design and implementation framework for deployable scissor-hinge structures which can offer a wide range of form flexibility. When the current research on this subject is investigated, it can be observed that most of the deployable and transformable structures in the literature have predefined open and closed body forms; and transformations occur between these two forms by using one of the various transformation types such as sliding, deploying, and folding. During these transformation processes, although some parts of these structures do move, rotate or slide, the general shape of the structure remains stable. Thus, these examples are insufficient to constitute real form flexibility. To alleviate this deficiency found in the literature, this dissertation proposes a novel transformable scissor-hinge structure which can transform between rectilinear geometries and double curved forms. The key point of this novel structure is the modified scissor-like element (M-SLE). With the development of this element, it becomes possible to transform the geometry of the whole system without changing the span length. In the dissertation, dimensional properties, transformation capabilities, geometric, kinematic and static analysis of this novel element and the whole proposed scissor-hinge structure are thoroughly examined and discussed. During the research, simulation and modeling have been used as the main research methods. The proposed scissor-hinge structure has been developed by preparing computer simulations, producing prototypes and investigating the behavior of the structures in these media by several kinematic and structural analyses.Item Open Access Performance-oriented design and assessment of naturally ventilated buildings(2021) Sakiyama, Nayara R. M.; Garrecht, Harald (Prof.)A high-performance building must fulfill comfort and energy efficiency requirements. Possible solutions include passive strategies, such as improving the building envelope and taking advantage of natural light and ventilation. Natural ventilation (NV), for instance, can provide both thermal comfort and energy savings. However, its performance relies on building design and interaction with the local environmental characteristics. In this study, Natural Ventilation Potential (NVP) was analyzed under two approaches: a general evaluation using meteorological data and a specific investigation through building simulation, using an experimental house as a reference case located in a temperate climate with warm summer. Although there are many parameters and metrics applied in assessing NVP, predicting building air change rates (ACH) and airflows is a challenge for designers seeking to deal with this passive strategy. Among the methods available for this task, Computational Fluid Dynamics (CFD) appears as the most compelling, in ascending use. However, CFD simulations have high computational costs, besides requiring a range of settings and skills that inhibit its wide application. Therefore, a pragmatic CFD framework to promote wind-driven assessments through 3D parametric modeling platforms was proposed as an attractive alternative to enable the tool application. The approach addresses all simulation steps: geometry and weather definition, model set-up, control, results edition, and visualization. Besides, it explores alternatives to display and compute ACH and parametrically generates horizontal planes across the spaces to calculate surface average air velocities. Usually, network models throughout Building Energy Simulation (BES) are the most employed NV investigations approach, especially in annual analysis. Nevertheless, as the wind is a significant driving force for ventilation, wind pressure coefficients (Cp) represent a critical boundary condition when assessing building airflows, influencing BES models’ results. The Cp values come from either a primary source that includes CFD simulations or a secondary one where the primary is considered the most reliable. In this sense, a performance metric was proposed, namely the Natural Ventilation Effectiveness (NVE). It verifies when outdoor airflows can maintain indoor temperatures within a comfortable range. The metric uses BES results, and within this context, the impact of five different Cp sources on its outputs was investigated. Three secondary sources and surface-averaged Cp values calculated with CFD for both the whole façade and windows were considered. The differences between the CFD Cp values are minor when wind direction is normal to the surface, with more significant discrepancies for the openings close to roof eaves. Although there was considerable variance among the Cp sources, its effect on the NVE was relatively small. Additionally, when designing high-performance buildings for cold climates, efficient insulating systems are encouraged since they help reduce heat losses through the building envelope, thus promoting building energy savings. Still, climate exposure deteriorates material properties, compromising a building’s energy performance over its lifetime. Therefore, this aging impact on the hygrothermal performance of an aerogel-based insulating system was investigated through a large-scale test, U-Value measurements, and heat and moisture transfer (HMT) models, calibrated with the experimental data. A low thermal conductivity degradation was measured after the tests, showing that its effectiveness is not harshly compromised throughout its life-cycle. Finally, this research performed parametric modeling and optimization to minimize annual building energy demand and maximize NVE. The workflow was divided into i) model setting, ii) sensitivity analyses (SA), and iii) multi-objective optimization (MOO), with a straightforward process implemented through a parametric platform. Input variables dimension was firstly reduced with SA, and the last step ran with a model-based optimization algorithm (RBFOpt). MOO results showed a remarkable potential for NV and heating energy savings. The design solutions could be employed in similar typologies and climates, and the adopted framework configures a practical and replicable approach for design approaches aiming to develop high-performance buildings through MOO.Item Open Access Branding im Industriebau am Beispiel der Automobilfertigung : eine gebäudetypologische Betrachtung(2009) Schönbeck, Dewi; Sobek, Werner (Prof. Dr.-Ing.)In der Automobilbranche nimmt das so genannte Branding zur Schaffung einer unverwechselbaren Markenidentität einen immer höheren Stellenwert ein. Dabei stellt auch die Architektur eines Unternehmens ein Medium zur Vermittlung von Markenwerten dar, das ein dreidimensionales, räumlich erfahrbares Markenerlebnis bietet. Gerade beim Lifestyle-Produkt Auto tritt die ursprüngliche Transportfunktion mehr und mehr in den Hintergrund. Vielmehr will der Kunde damit auch Lebensphantasien, sinnliche Werte und Sozialprestige einkaufen. Umso mehr kann deshalb die Unternehmensarchitektur dieses diffuse Kundenverlangen mit im eigentlichen Sinne begreifbaren Werten ästhetisch umsetzen und damit zu einer innigeren Kundenbindung entscheidend beitragen. Längst haben die Automobilhersteller die Architektur als Medium zur Vermittlung ihrer Markenwerte entdeckt. Beispiele wie der BMW "Vierzylinder" in München, die Autostadt Wolfsburg, das Mercedes-Benz Museum in Stuttgart sowie zahlreiche spektakuläre Mikroarchitekturen im Messebau zeigen, dass das Markenerlebnis durch Architekturerfahrung im Wettbewerb um den Kunden unverzichtbar geworden ist. Der bewusste Einsatz von Markenarchitektur im Industriebau ist jedoch nach wie vor eher ungewöhnlich und nur an vereinzelten Bauten realisiert worden. Pilotprojekte wie die Gläserne Manufaktur in Dresden oder der Zentralbau des BMW Werks in Leipzig geben eine Tendenz zu einer vollkommen neuartigen Gebäudeform im Industriebau vor. Die Automobilfabrik ist bei diesen Projektbeispielen nicht mehr als reine Produktionsstätte zu sehen, in der Mensch und Maschine möglichst effizient zusammenarbeiten, sondern bezieht den Kunden emotional in den Produktionsprozess mit ein. Diese Entwicklung hat zur Konsequenz, dass die Fabrik in Zukunft nicht mehr nur als reine Produktionsstätte fungiert, sondern gleichzeitig als Kunden-Erlebniszentrum gestaltet werden kann. Durch die theoretische Analyse der veränderten architektonischen Anforderungen sowie der Untersuchung von realisierten Beispielen wird in dieser Arbeit eine neuartige, funktionshybride Gebäudetypologie definiert und entsprechende Planungskriterien abgeleitet.Item Open Access Performance evaluation and strengthening of deficient beam-column sub-assemblages under cyclic loading(2009) Sasmal, Saptarshi; Novák, Balthasar (Prof. Dr.-Ing. )Evidence from the previous earthquakes has posed a serious question on the performance of reinforced concrete (RC) structures, both existing and newly built, under seismic loading. In the present study, exterior beam-column sub-assemblage which is proved to be one of the most critical components of an RC structure has been chosen for investigation. European Codes and Indian Standards of practice for seismic design have been considered for designing and detailing the sub-assemblages of a most regular and conventional RC structure. Different specimens represented the existing condition of buildings designed according to the available knowledge and prevailing guidelines at different times. The experimental investigations under repeated cyclic loading have shown that "GLD" specimen can hardly withstand any reverse loading due to insufficient reinforcement, inadequate bonding and poor detailing. Among the "NonDuctile" specimens, Indian Standard based specimen exhibited better performance (strength deterioration, stiffness degradation and energy dissipation) over the Eurocode based specimen, even though in both cases energy dissipation was mainly through the damage in joint region which is extremely unwanted. The strength hierarchy of all the specimens has been developed based on the results obtained from experimental and analytical studies for identification and quantification of required improvements of deficient sub-assemblages towards "Ductile" ones. After the experimental investigations, severely damaged specimens were further studied for adequate retrofitting to ensure their re-usability in post-earthquake scenario. An effective, simple and economical retrofitting scheme has been proposed here by judiciously using GFRP in members beyond the joint and steel plate in the joint region holding by through-through bolts. Surface treatment and epoxy injection were carried out to re-install concrete integrity and bond. From the experimental investigation, it has have noted that the retrofitted "NonDuctile" and "Ductile" specimens could be able to regain, if not better, their original seismic performance. Deformation capacity of the retrofitted "NonDuctile" specimen was also considerably increased with respect to undamaged ones. Further, in both retrofitted specimens, strength deterioration with increase in displacement demand was extremely low. Thus, the retrofitting schemes as proposed in this study could effectively be implemented for damaged "NonDuctile" or "Ductile" sub-assemblages for their further usage. Three different schemes have been proposed in this study for upgradation of poorly designed "GLD" structures which are present in massive quantity throughout the world. The schemes have been developed by using hybrid FRP-steel plate system. Using the analytical formulation, a detailed study has been carried out on improvement of strength and ductility due to application of external reinforcement and confinement. CFRP fabric and CFRP laminate were used for flexural strengthening, GFRP wrap was used for confinement of beam and column sections and steel plate-bolt system was adopted for confinement and shear strength enhancement of the joint. From the cyclic load test as adopted for original "GLD" specimen, it has been observed that the seismic performance of the upgraded specimens can be considerably improved by using these schemes. For example, double the energy dissipation was achieved at same drift ratio and final energy dissipation was 5 times more than that obtained from original "GLD" specimen. Most importantly, the plastic hinge shifted in the beam away the joint and in last upgraded specimen where only D-region upgradation was carried out, it could even form a spread plastic hinge in the beam, which ensures large and consistent dissipation of energy with increase in drift demand. Finally, non-linear Finite Element analysis using software ATENA has been carried out on "GLD", "NonDuctile" and upgraded specimens. Material and geometrical models have suitably been incorporated in the numerical analyses. The results obtained from numerical analyses are in good agreement with that from experimental investigations. A comparative study on energy dissipation obtained from both numerical and experimental studies has been carried out and correlated for practical use. Influence of axial load in column has also been explored. Further, a parametric study has also been conducted to investigate the effects of amount of bending FRP, number of wrapping layers, bond behaviour and role of individual upgradation components on the overall performance of the upgraded specimens which would offer the scope for any further modifications on the proposed schemes. The study as a whole would provide the promising aspects on strengthening of deficient structural components and encourage for further research.Item Open Access Behavior of concrete structures subjected to static and dynamic loading after fire exposure(2021) Lacković, Luka; Ožbolt, Joško (Prof. Dr.-Ing. habil.)The resistance of concrete structures exposed to extreme loading conditions such as explosion, impact, industrial accidents, tsunami, earthquake or their combination represents one of the major topics in research today. Such loading conditions are characterized with high loading rates often acting in conjunction with fire exposure. Especially vulnerable are the structures located in the seismically active areas with high level of urbanization and proximity to HAZMAT landfills, which additionally exacerbate fire conflagrations. The behavior of concrete changes significantly when exposed to elevated temperatures resulting in the decrease of its mechanical properties. Reinforced concrete (RC), when exposed to high temperature culminates in a simultaneous thermal behavior of its two constituents, steel and concrete, that should be considered in the analysis. It is also known that the resistance, crack pattern and failure mode in concrete are strongly influenced by the loading rate. The dynamic response of RC structures previously exposed to fire changes significantly when compared to initially undamaged RC structures. The main objective of the present work is to further improve the existing rate sensitive thermo-mechanical model for concrete through the following: (i) the implementation of the experimentally obtained thermal dependence of concrete fracture energy in the thermo-mechanical model, (ii) the calculation of concrete thermally dependent mechanical properties by means of nonlocal (average) temperature and (iii) to perform parametric study on fastening elements and RC frames in order to investigate the interaction between the thermally induced damage and mechanical behavior of structures. The experimental investigations in the present work indicated that the concrete fracture energy has a declining tendency with the temperature increase, measured on small and mid-sized concrete beams. This is implemented in the thermo-mechanical model and it is indicated that the decrease of fracture energy has a relatively mild influence on reaction values in terms of loading rate. However, its effect on the fracture patterns and reaction-time histories can be considered as more significant. The influence of the nonlocal temperature is validated against the experimental results carried out on RC frames which had been thermally pre-damaged and subsequently loaded with impact. Currently there are almost no models that can realistically predict the structural behavior at this level of complexity. Furthermore, a parametric study is carried out to show the influence of preloading of single-headed stud anchor and anchor group with two and four studs, on the residual concrete edge failure capacity after fire exposure. The anchors are exposed to fire and loaded in shear, perpendicular to the free edge of the concrete member up to failure, in both hot and cold state (after cooling). The influence of different geometry configurations and initial conditions such as the edge distance, embedment depth, anchor diameter and duration of fire on the load-bearing behavior of anchors is investigated. It is demonstrated that the preloading has a strong negative influence on the residual load-bearing capacity of the concrete. Finally, the numerical parametric study is performed to investigate the influence of fire duration and the loading rate on the resistance of RC frames. The response of the RC structures strongly depends on whether it was loaded in hot or residual (cold) state, i.e. after being naturally cooled down to ambient temperature. Furthermore, an extensive numerical investigation on the influence of post-earthquake fire on the residual capacity of RC frames with and without ductile detailing is conducted. The numerical investigation encompassed the validation of the thermo-mechanical model in terms of temperature distributions, thermal deflections and load-bearing capacity against the test data and subsequent parametric analysis with different levels of fire exposure ranging from 15 to 120 min.Item Open Access Zero-waste sand formworks for lightweight concrete structures(2025) Kovaleva, Daria; Sobek, Werner (Prof. Dr. Dr. E.h. Dr. h.c.)To address the growing urgent need to reduce resource consumption, embodied energy, and waste in construction, this thesis presents a new method for the zero-waste production of lightweight concrete structures using water-soluble sand formwork. The application of lightweight construction principles allows the creation of efficient and expressive structures with minimal material consumption and, consequently, an ecological footprint. Due to its ability to take any conceivable shape, concrete provides architects and engineers with virtually unlimited design freedom and is ideal for putting these principles into practice. However, despite the wide availability of design solutions known since the middle of the 20th century, lightweight concrete structures are still not widely used due to the lack of adequate sustainable production methods. This often involves formwork manufacturing, which is still labor-intensive and wasteful and accounts for over two-thirds of the production budget. Digital production methods, such as additive and subtractive manufacturing, enable highly precise creation of geometrically complex objects. However, their broader application in formwork production is limited by their narrow specialization in the types of geometry produced, the generation of waste during processing, and the use of toxic and non-recyclable formwork materials. Therefore, the emergence of a flexible and environmentally friendly formwork method suitable for producing geometrically complex structures is necessary for the broader application of lightweight construction with concrete. Offering a comprehensive approach to the above-described problem, this thesis proposes a novel zero-waste technology to produce lightweight concrete structures using additive manufacturing of a specially developed water-soluble sand and binder mixture. The powder-bed-based 3D printing of granular materials gives the greatest freedom in terms of geometric complexity, while the water-soluble nature of the formwork material mix allows it to be fully recycled after casting and reused in further production cycles. Following the overall goal of promoting lightweight concrete construction, this technology also has an inverse effect on designing lightweight structures. It makes it possible to realize structural morphologies that would be inefficient or even impossible to produce with conventional formwork methods. The water solubility of the formwork material allows the creation of structures with geometrically complex external shapes and internal configurations. This enables not only improved structural performance but also the integration of other functional elements, such as MEP systems, acoustic and thermal insulation. The work on the thesis includes the conceptualization of a closed-loop production cycle, the creation of an automated manufacturing process based on 3D printing of sand molds with a specially developed material mix, and the development of necessary accompanying CAD-CAM tools. The proposed technology is validated in the production of formworks for lightweight concrete structures of various scales, from small-scale prototypes to architectural demonstrator.