02 Fakultät Bau- und Umweltingenieurwissenschaften
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/3
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Item Open Access Befestigungen mit Verbundankern. [Teil 1](1984) Eligehausen, Rolf; Mallée, Rainer; Rehm, GallusSeit 1975 wurden Verbundankersysteme verschiedener Firmen bauaufsichtlich zugelassen, wobei die Systeme hinsichtlich der Zusammensetzung des Mörtels praktisch identisch sind. Diese Zulassungsbescheide regelten die Verwendung von Einzelankern sowie Ankerpaaren mit Ankern in der aus Lastspannungen erzeugten Druckzone von Beton- und Stahlbetonbauteilen. Die Anwendungsbedingungen wurden u. a. aus den beschriebenen Versuchen abgeleitet und sind ausführlich erläutert. Weitere wichtige Informationen über das Tragverhalten von Verbundankern mit großen Rand- und Achsabständen unter Kurzzeit-, Dauer- und Ermüdungsbelastung sowie bei unterschiedlichen klimatischen Bedingungen (Trocken- oder Naßlagerung) und bei erhöhten Temperaturen sind zu entnehmen. Zwischenzeitlich wurden wesentliche neue Erkenntnisse über das Tragverhalten von Verbundankern bei engen Rand- und Achsabständen sowie von Verankerungen in Rissen gewonnen, die bei der Neufassung der Zulassung berücksichtigt wurden. Diese Neufassung enthält auch wesentliche Vereinfachungen für die Bemessung von Befestigungen mit Verbundankern. In diesem Beitrag wird das Tragverhalten von Verbundankern unter Kurzzeitbelastung beschrieben und es wird auf Langzeiteinflüsse eingegangen. Weiterhin werden die in den Neuzulassungen festgelegten Anwendungsbedingungen erläutert.Item Open Access Design recommendations for concrete pryout capacity of headed steel studs and post-installed anchors(2023) Jebara, Khalil; Sharma, Akanshu; Ožbolt, JoškoCurrent formulas to assess the shear capacity of headed steel stud anchors and post-installed (PI) anchors in case of pryout failure (sometimes known as pull-rear failure) have been derived either based on the indirect-tension resistance model or are fully empirical based on push-out test results. In both cases, the predicted pryout capacity is clearly conservative and underestimates the true pryout capacity of anchorages, especially for stiff anchors with low embedment-to-diameter ratios (hef/d < 4.5). This paper proposes an empirical and a semi-empirical formula to predict the concrete pryout capacity of headed steel studs and PI anchors. They were derived based on an improved indirect-tension model which accounts for the stud diameter and the stud spacing in a group of anchors. Furthermore, a database of 214 monotonic shear tests from the literature, including own tests (push-off and horizontally shear tests), is reevaluated and compared to the provisions of EN1992-4. The scope of this assessment proposal includes single and group of headed steel studs and PI anchors attached to a stiff steel plate as well as shear connectors in composite structures without metal deck embedded in normal-weight concrete.Item Open Access Bidirectional loading history for seismic testing of 3D frame joints(2021) Mahadik, Vinay; Sharma, AkanshuBeam-column-joints (BCJ) in reinforced concrete (RC) frames are known to be critical against seismic actions. Hence, several researchers have conducted related investigations. The loading history used in the experimental investigations must be a sufficiently accurate and conservative representation of seismic loading on the structure and should trigger all possible critical failure mechanisms in the subassembly. Presently, there is significant diversity in the loading histories used for seismic investigation of structural subassemblies. This paper intends to propose an optimum loading history for considering bidirectional (horizontal) seismic action on 3D-RC BCJ subassemblies. To this end, the available loading histories (unidirectional and bidirectional) for simulation of seismic loads on RC joint subassemblies are reviewed in the context of the demands they impose on the joints. Finite element modeling and analyses are used as a tool for investigating the response of 3D-BCJ subassembly under different bidirectional loading states.Item Open Access Verhalten von Beton auf Zug. [Teil 1](1985) Eligehausen, Rolf; Sawade, GottfriedIn Beton- und Stahlbetontragwerken wird die Zugfestigkeit des Betons an vielen Stellen in Anspruch genommen. Die beschriebenen experimentellen Untersuchungen an unbewehrten Zugkörpern, Biegebalken und Kopfbolzenverankerungen und theoretische Überlegungen zeigen, daß zugbeanspruchter Beton nicht spröde versagt, sondern nach Überschreiten der Höchstlast infolge von Bildung diskreter Mikrorisse ein nicht-lineares Last-Verformungsverhalten aufweist. Dieses Ergebnis stimmt mit Untersuchungen anderer Autoren überein.Item Open Access Fracture size effect: review of evidence for concrete structures(1994) Bazant, Zdenek P.; Ozbolt, Josko; Eligehausen, RolfThe paper reviews experimental evidence on the size effect caused by energy release due to fracture growth during brittle failures of concrete structures. The experimental evidence has by now become quite extensive. The size effect is verified for diagonal shear failure and torsional failure of longitudinally reinforced beams without stirrups, punching shear failure of slabs, pull-out failures of deformed bars and of headed anchors, failure of short and slender tied columns, double-punch compression failure and for part of the range also the splitting failure of concrete cylinders in the Brazilian test. Although much of this experimental evidence has been obtained with smaller laboratory specimens and concrete of reduced aggregate size, some significant evidence now also exists for normal-size structures made with normal-size aggregate. There is also extensive and multifaceted theoretical support. A nonlocal finite element code based on the microplane model is shown to be capable of correctly simulating the existing experimental data on the size effect. More experimental data for large structures with normal-size aggregate are needed to strengthen the existing verification and improve the calibration of the theory.Item Open Access Design for and from disassembly with timber elements : strategies based on two case studies from Switzerland(2023) Grüter, Cäsar; Gordon, Matthew; Muster, Marcel; Kastner, Fabian; Grönquist, Philippe; Frangi, Andrea; Langenberg, Silke; Wolf, Catherine deWhen a timber building gets disassembled and its elements either are burned or biodegrade, the carbon stored in the timber structure gets released to the atmosphere as CO2. Reusing timber elements prevents this process from happening and thus delays the global warming caused by greenhouse gas emissions. Even if there is a long historic tradition of timber reuse in Switzerland, currently a low fraction of a timber building’s elements is being reused after its disassembly. In this study, strategies that could facilitate circular use of timber elements are analyzed. The focus lies on the design process, which is investigated from two perspectives: strategies at the start-of-life of buildings to enable new timber element cycles to emerge (design for disassembly, or DforD), and strategies at the end-of-life of buildings to keep existing timber elements cycles closed (design from disassembly, or DfromD). Two case studies of recently completed multi-story timber-hybrid buildings in Switzerland were analyzed from both perspectives. Regarding DforD, a scoring system was developed that assesses single elements according to their disassembly and reuse potential. Regarding DfromD, a building design optimization tool was created that takes dimensional design tolerances of a building as an input and proposes a procurement-optimized and structurally safe arrangement of reused elements, which are taken from an inventory that is based on the two case studies. It was found that connections between reinforced concrete and timber parts play a crucial role in terms of DforD and that building layouts with DfromD elements may vary widely according to the chosen optimization variable. In conclusion, both applications have the potential to scale up the competitiveness of reused elements.Item Open Access Influence on the load‐displacement behaviour of steel‐to‐concrete connections with post‐installed adhesive anchors(2023) Maçi, Nilde; Hofmann, JanDesigning frame structures requires knowing the behaviour of each member of the frame (beam, column, joint, etc.) regarding the axial forces, shear forces, and bending moments. Furthermore, the ductility of the structure under seismic loading is essential in earthquake regions. Nowadays, structural frames are built from different materials such as concrete and steel, to achieve better performance. Therefore, the behaviour of the connections between steel and concrete is essential. The steel‐to‐concrete joints were the focus of the INFASO project, where joint solutions with easy fabrication, quick assembly, applicability in old structures, sufficient ductility, and high loading capacity were developed. They proposed the use of anchor plates with welded studs or post‐installed fasteners such as adhesive anchors to connect the steel and concrete members. This paper focuses on the performance of post‐installed adhesive anchors. During their service life, post‐installed anchors are subjected to monotonic, constant, and seismic loading. Each of these loading approaches is described in the current standards. Seismic and constant loading tests are of importance to the long‐term behaviour of the anchors. Seismic loading tests are carried out using a predefined cycle pattern. According to TR049, seismic tests of category C1 (tension and shear) are performed with 140 load cycles, where the load amplitude decreases after 10, 30, and 100 cycles. On the contrary, C2 category tests increase the amplitude within 75 or 59 cycles, depending on the test. Constant loading tests apply when the anchors are installed in cracked concrete. In contrast to the mentioned patterns, this study observes the behaviour of the adhesive anchors when the amplitude of each cycle is increased by 5 % until the anchor fails. Standard short‐term pull‐out tests are carried out to determine the load increments. Various parameters such as the embedment depth, bond line thickness, hole cleaning, wet concrete, and elevated temperatures are studied. Confined and unconfined tests are performed. Overall, the reference short‐term failure loads are higher than those in the tests with incremental and cyclic loading. The anchors installed with reduced hole cleaning, in wet concrete or subjected to elevated temperatures have a lower failure load compared to the reference series. Two additional bond line thicknesses are used for comparison. The increase in the thickness influenced the failure load differently for confined and unconfined test setups.Item Open Access Tragverhalten von Dübelbefestigungen bei Zugbeanspruchung. Teil 1(1987) Eligehausen, Rolf; Fuchs, Werner; Mayer, BurkhardDie moderne Befestigungstechnik wird in steigendem Maße gezielt bei der Planung und Ausführung von Ingenieurbauwerken eingesetzt. Sie erlaubt die wirtschaftliche Anwendung einfach und zeitsparend montierbarer Dübel, die in nachträglich erstellten Bohrlöchern in Beton- oder Stahlbetonbauteilen verankert werden. In diesem Beitrag werden die unterschiedlichen Systeme von Metalldübeln sowie deren Tragverhalten unter kurzzeitiger Zugbeanspruchung im ungerissenen und gerissenen Beton beschrieben. Das Verhalten von Dübelbefestigungen unter Querzug-, Schrägzug- oder Biegebeanspruchung ist erläutert, ein Vorschlag für die Bemessung enthalten.Item Open Access Bemessung von Befestigungen mit Verbundankern(1985) Eligehausen, Rolf; Mallée, Rainer; Rehm, GallusBefestigungen mit Verbundankern werden seit langem ausgeführt und die Bemessung der Anker wurde erstmals 1975 bauaufsichtlich geregelt. In der Zwischenzeit wurden wesentliche neue Erkenntnisse über das Tragverhalten von Verbundankern mit engen Achs- und Randabständen sowie von Verankerungen in Rissen gewonnen und bei der Neufassung der Zulassung berücksichtigt. In diesem Aufsatz wird das Tragverhalten von Verbundankern im ungerissenen Beton und in Rissen unter Kurzzeitbelastung beschrieben. Weiterhin werden die in den Neuzulassungen festgelegten Anwendungsbedingungen begründet und erläutert.Item Open Access Impact analysis of thermally pre-damaged reinforced concrete frames(2020) Ožbolt, Joško; Lacković, Luka; Ruta, DanielaIn the present study, the influence of thermally induced damage of reinforced concrete (RC) frames on their static and dynamic response is experimentally and numerically investigated. In the experimental test, the RC frame is first pre-damaged through fire exposure and then loaded from the side with the impact of a steel pendulum. To verify the recently developed coupled thermo-mechanical model for concrete, transient 3D FE simulation is carried out. The rate and temperature-dependent microplane model is used as a constitutive law for concrete. It is first shown that the simulation is able to realistically replicate the experimental test. Subsequently, the numerical parametric study is performed where the dynamic and static response of RC frame is simulated for both hot and cold states. It is shown that the pre-damage of RC frame through fire exposure significantly reduces the resistance and changes the response. Finally, it is demonstrated that for the impact load the rate sensitive constitutive law of concrete significantly contributes to the response of RC frame.