13 Zentrale Universitätseinrichtungen
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/14
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Item Open Access Rationalisierung der Bewehrungstechnik - ein unerschöpfliches Forschungsthema oder eine Möglichkeit zur Kostensenkung und Qualitätssteigerung im Stahlbetonbau?(1982) Rehm, Gallus; Eligehausen, Rolf; Neubert, Bernd; Lehmann, RolfVon Flächentragwerken abgesehen, dominiert immer noch die "konventionelle" Bewehrung aus Einzelstäben und Einzelbügeln. Dies ist sowohl im Hinblick auf die Wirtschaftlichkeit als auch auf die Dauerhaftigkeit keineswegs optimal. Daher werden im folgenden am Beispiel stabförmiger Bauteile Maßnahmen zur Verbesserung aufgezeigt und die wirtschaftlichen Vorteile anhand einer praktischen Erprobung erläutert sowie die mögliche Verbesserung der Ausführungsqualität diskutiert.Item Open Access Fire rating of post-installed anchors and rebars(2020) Mahrenholtz, Philipp; Sharma, AkanshuFire safety is a critical performance aspect of construction products, and post-installed anchors and rebars are no exemption in that regard. During their service life, anchors and rebars are subjected to different kinds of load actions, so they have to be qualified and designed for critical safety performance. While the qualification guidelines for static and seismic loading have matured to conclusive requirements over the past two decades, the requirements for determining the resistance to fire are just about to consolidate. This contribution strives to provide clarity on the fire rating of post-installed anchors and rebars. For this, the current status of the regulations, as well as the underlying background, is reviewed after a brief introduction. Typical examples of fire ratings in the field of post-installed anchors and rebars are given, and recent research undertaken to close the last regulative gaps is briefly presented.Item Open Access Residual strength and time to failure of bonded wooden lap joints at high temperatures and superimposed constant loading(2024) Aicher, Simon; Münzer, AaronItem Open Access Investigation of the influence of moisture content on fatigue behaviour of HPC by using DMA and XRCT(2021) Markert, Martin; Katzmann, Josef; Birtel, Veit; Garrecht, Harald; Steeb, HolgerHigh-performance concrete (HPC) is a topic of current research and construction projects, due to its outstanding compressive strength and durability. In particular, its behaviour under high-cycle fatigue loading is the focus of current investigations, to further pave the way to highly challenging long-lasting constructions; e.g., bridges or offshore buildings. In order to investigate the behaviour of HPC with different moisture contents in more detail, a mixture of silica sand and basalt aggregate with a maximum grain size of 8 mm was investigated with three different moisture contents. For this purpose, cyclic compressive fatigue tests at a loading frequency of 10 Hz and different maximum stress levels were performed. The main focus was the moisture influence on the number of cycles to failure and the development of concrete temperature and strain. In a further step, only the mortar matrix was investigated. For this purpose, the mixture was produced without basalt, and the moisture influence was investigated on smaller-sized test specimens using dynamic mechanical analysis (DMA) and X-ray computed tomography (XRCT). It was shown that the moisture content of HPC had a significant influence on the fatigue damage behaviour due to the number of cycles to failure decreasing significantly with increased moisture. In addition, there was also an influence on the temperature development, as well as on the strain development. It was shown that increasing moisture content was associated with an increase in strain development. XRCT scans, in the course of the damage phases, showed an increase in internal cracks, and made their size visible. With the help of DMA as a new research method in the field of concrete research, we were also able to measure damage development related to a decrease in sample stiffness. Both methods, XRCT and DMA, can be listed as nondestructive methods, and thus can complement the known destructive test methods, such as light microscopy.Item Open Access Rationalisierung der Bewehrungstechnik im Stahlbetonbau : vereinfachte Schubbewehrung in Balken. [Teil 1](1978) Rehm, Gallus; Eligehausen, Rolf; Neubert, BerndZur Verminderung der Lohnkosten für das Herstellen und Verlegen der Bewehrung wird eine neuartige Bewehrung für Linientragwerke vorgeschlagen. Als Längsbewehrung dienen gerade Stäbe. Die Schubbewehrung besteht aus einem die Biegezugbewehrung umschließenden Bügelkorb und zusätzlich in den Querschnitt eingestellten leiter- oder korbartigen Elementen, den sog. Schubzulagen, die die Längsbewehrung nicht oder nur teilweise umschließen. In diesem Aufsatz werden die Versuche beschrieben, die zur Ableitung der angegebenen Konstruktionsregeln für Bügel und Schubzulagen dienten.Item Open Access Compressive fatigue investigation on high-strength and ultra-high-strength concrete within the SPP 2020(2022) Basaldella, Marco; Jentsch, Marvin; Oneschkow, Nadja; Markert, Martin; Lohaus, LudgerThe influence of the compressive strength of concrete on fatigue resistance has not been investigated thoroughly and contradictory results can be found in the literature. To date, the focus of concrete fatigue research has been on the determination of the numbers of cycles to failure. Concerning the fatigue behaviour of high-strength concrete (HPC) and, especially, ultra-high-strength concrete (UHPC), which is described by damage indicators such as strain and stiffness development, little knowledge is available, as well as with respect to the underlying damage mechanisms. This lack of knowledge has led to uncertainties concerning the treatment of high-strength and ultra-high-strength concretes in the fatigue design rules. This paper aims to decrease the lack of knowledge concerning the fatigue behaviour of concrete compositions characterised by a very high strength. Within the priority programme SPP 2020, one HPC and one UHPC subjected to monotonically increasing and cyclic loading were investigated comparatively in terms of their numbers of cycles to failure, as well as the damage indicators strain and stiffness. The results show that the UHPC reaches a higher stiffness and a higher ultimate strain and strength than the HPC. The fatigue investigations reveal that the UHPC can resist a higher number of cycles to failure than the HPC and the damage indicators show an improved fatigue behaviour of the UHPC compared to the HPC.Item Open Access Influence and potential of additive manufactured reference geometries for ultrasonic testing(2025) Keuler, Stefan; Jüngert, Anne; Werz, Martin; Weihe, StefanThis study researches and discusses the impact of different manufacturing-induced effects of additive manufacturing (AM), such as anisotropy on sound propagation and attenuation, on the production of test specimens for ultrasonic testing (UT). It was shown that a linear, alternating hatching pattern led to strong anisotropy in sound velocity and attenuation, with a deviation in sound velocity and gain of over 840 m/s and 9 dB, depending on the measuring direction. Furthermore, it was demonstrated that the build direction exhibits distinct acoustic properties. The influence of surface roughness on both the reflector and coupling surfaces was analyzed. It was demonstrated that post-processing of the reflector surface is not necessary, as varying roughness levels did not significantly change the signal amplitude. However, for high frequencies, pre-treatment of the coupling surface can improve sound transmission up to 6 dB at 20 MHz. Finally, the reflection properties of flat bottom holes (FBH) in reference blocks produced by AM and electrical discharge machining (EDM) were compared. The equivalent reflector size (ERS) of the FBH, which refers to the size of an idealized defect with the same ultrasonic reflection behavior as the measured defect, was determined using the distance gain size (DGS) method-a method that uses the relationship between reflector size, scanning depth, and echo amplitude to evaluate defects. The findings suggest that printed FBHs achieve an improved match between the ERS and the actual manufactured reflector size with a deviation of less than 13%, thereby demonstrating the potential for producing standardized test blocks through additive manufacturing.Item Open Access Rationalisierung der Bewehrungstechnik im Stahlbetonbau : vereinfachte Schubbewehrung in Balken. Teil 2(1978) Rehm, Gallus; Eligehausen, Rolf; Neubert, BerndZur Verminderung der Lohnkosten für das Herstellen und Verlegen der Bewehrung wird eine neuartige Bewehrung für Linientragwerke vorgeschlagen. Als Längsbewehrung dienen gerade Stäbe. Die Schubbewehrung besteht aus einem die Biegezugbewehrung umschließenden Bügelkorb und zusätzlich in den Querschnitt eingestellten leiter- oder korbartigen Elementen, den sog. Schubzulagen, die die Längsbewehrung nicht oder nur teilweise umschließen. In diesem Aufsatz werden die Versuche beschrieben, die zur Ableitung der angegebenen Konstruktionsregeln für Bügel und Schubzulagen dienten.Item Open Access Failure behavior of an adaptive concrete beam with integrated fluidic actuators : non-linear three-dimensional finite element analysis(2023) Gambarelli, Serena; Fararoni Platas, Rey Noé; Shankar, Arvinth; Dakova, Spasena; Böhm, Michael; Sawodny, Oliver; Nitzlader, Markus; Blandini, Lucio