02 Fakultät Bau- und Umweltingenieurwissenschaften
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/3
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Item Open Access Heat transport from atmosphere through the subsurface to drinking‐water supply pipes(2023) Nissler, Elisabeth; Scherrer, Samuel; Class, Holger; Müller, Tanja; Hermannspan, Mark; Osmancevic, Esad; Haslauer, ClausDrinking‐water quality in supply pipe networks can be negatively affected by high temperatures during hot summer months due to detrimental bacteria encountering ideal conditions for growth. Thus, water suppliers are interested in estimating the temperature in their distribution networks. We investigate both experimentally and by numerical simulation the heat and water transport from ground surface into the subsurface, (i.e., above drinking‐water pipes). We consider the meteorological forcing functions by a sophisticated approach to model the boundary conditions for the heat balance at the soil-atmosphere interface. From August to December 2020, soil temperatures and soil moisture were measured dependent on soil type, land‐use cover, and weather data at a pilot site, constructed specifically for this purpose at the University of Stuttgart with polyethylene and cast‐iron pipes installed under typical in situ conditions. We included this interface condition at the atmosphere-subsurface boundary into an integrated non‐isothermal, variably saturated (Richards') the numerical simulator DuMux 3. This allowed, after calibration, to match measured soil temperatures with ±2°C accuracy. The land‐use cover influenced the soil temperature in 1.5 m more than the soil material used for back‐filling the trench above the pipe.Item Open Access Batch studies of phosphonate and phosphate adsorption on granular ferric hydroxide (GFH) with membrane concentrate and its synthetic replicas(2020) Reinhardt, Tobias; Veizaga Campero, Adriana Noelia; Minke, Ralf; Schönberger, Harald; Rott, EduardPhosphonates are widely used as antiscalants for softening processes in drinking water treatment. To prevent eutrophication and accumulation in the sediment, it is desirable to remove them from the membrane concentrate before they are discharged into receiving water bodies. This study describes batch experiments with synthetic solutions and real membrane concentrate, both in the presence of and absence of granular ferric hydroxide (GFH), to better understand the influence of ions on phosphonate and phosphate adsorption. To this end, experiments were conducted with six different phosphonates, using different molar Ca:phosphonate ratios. The calcium already contained in the GFH plays an essential role in the elimination process, as it can be re-dissolved, and, therefore, increase the molar Ca:phosphonate ratio. (Hydrogen-)carbonate ions had a competitive effect on the adsorption of phosphonates and phosphate, whereas the influence of sulfate and nitrate ions was negligible. Up to pH 8, the presence of CaII had a positive effect on adsorption, probably due to the formation of ternary complexes. At pH > 8, increased removal was observed, with either direct precipitation of Ca:phosphonate complexes or the presence of inorganic precipitates of calcium, magnesium, and phosphate serving as adsorbents for the phosphorus compounds. In addition, the presence of (hydrogen-)carbonate ions resulted in precipitation of CaCO3 and/or dolomite, which also acted as adsorbents for the phosphorus compounds.Item Open Access Guidelines for a finite element based design of timber structures and their exemplary application on modelling of beech LVL(2023) Töpler, Janusch; Buchholz, Lea; Lukas, Julian; Kuhlmann, UlrikeDesign verifications of buildings are usually carried out supported by a finite element analysis (FEA), for which, however, there are only a few and almost exclusively non-binding application rules. Within the Cluster of Excellence Integrative Computational Design and Construction for Architecture (IntCDC) at the University of Stuttgart, Guidelines for a Finite Element-Based Design of Timber Structures have been developed. The scope of the guidelines is daily engineering practice, expert engineering applications and product development and certification. Essential parts of the guidelines are design procedures, modelling (including geometrical, material and imperfection modelling), analysis, model verification and validation and design. The content and application of the guidelines are described and illustrated in this paper using two benchmarks. These two benchmarks, which are based on experimental investigations, deal with the elastic material modelling of glulam made of beech laminated veneer lumber (beech LVL) and dowel-type connections for beech LVL members. The experimental basis of the benchmarks is described. With the experiments for the benchmarks, all Poisson’s ratios and the complete elastic material stiffness matrix of beech LVL are determined by means of an optical measuring system. The experimentally determined stiffnesses of the investigated dowel-type connections in beech LVL are compared with normative values. Based on the experiments, a numerical model is developed in RFEM (Dlubal).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 Magnetic resonance imaging of water content and flow processes in natural soils by pulse sequences with ultrashort detection(2021) Haber-Pohlmeier, Sabina; Caterina, David; Blümich, Bernhard; Pohlmeier, AndreasMagnetic resonance imaging is a valuable tool for three-dimensional mapping of soil water processes due to its sensitivity to the substance of interest: water. Since conventional gradient- or spin-echo based pulse sequences do not detect rapidly relaxing fractions of water in natural porous media with transverse relaxation times in the millisecond range, pulse sequences with ultrafast detection open a way out. In this work, we compare a spin-echo multislice pulse sequence with ultrashort (UTE) and zero-TE (ZTE) sequences for their suitability to map water content and its changes in 3D in natural soil materials. Longitudinal and transverse relaxation times were found in the ranges around 80 ms and 1 to 50 ms, respectively, so that the spin echo sequence misses larger fractions of water. In contrast, ZTE and UTE could detect all water, if the excitation and detection bandwidths were set sufficiently broad. More precisely, with ZTE we could map water contents down to 0.1 cm3/cm3. Finally, we employed ZTE to monitor the development of film flow in a natural soil core with high temporal resolution. This opens the route for further quantitative imaging of soil water processes.Item Open Access Update on the revision of Eurocode 3 : evolution by improvement and harmonization(2021) Kuhlmann, Ulrike; Schmidt‐Rasche, Christina; Jörg, Fabian; Pourostad, Vahid; Spiegler, Jennifer; Euler, MathiasThis paper provides an overview of recent work regarding the revision of Eurocode 3 on the European level. Selected scientific and technical issues are described and there is a summary of the activities executed within European Standardization Committee CEN/TC250/SC3 ”Design of Steel Structures“ chaired by Prof. Dr.‐Ing. Ulrike Kuhlmann. This includes the description of current normative developments for the 2nd Generation of Eurocodes, which aim at evolution through improvements and harmonization of the existing codes. In addition, a technical review of selected rules is given for several issues, which support the code revision and reflect well the recent tendencies in steel structures.Item Open Access Impact of combined sewer systems on the quality of urban streams : frequency and duration of elevated micropollutant concentrations(2020) Dittmer, Ulrich; Bachmann-Machnik, Anna; Launay, Marie A.Water quality in urban streams is highly influenced by emissions from WWTP and from sewer systems particularly by overflows from combined systems. During storm events, this causes random fluctuations in discharge and pollutant concentrations over a wide range. The aim of this study is an appraisal of the environmental impact of micropollutant loads emitted from combined sewer systems. For this purpose, high-resolution time series of river concentrations were generated by combining a detailed calibrated model of a sewer system with measured discharge of a small natural river to a virtual urban catchment. This river base flow represents the remains of the natural hydrological system in the urban catchment. River concentrations downstream of the outlets are simulated based on mixing ratios of base flow, WWTP effluent, and CSO discharge. The results show that the standard method of time proportional sampling of rivers does not capture the risk of critical stress on aquatic organisms. The ratio between average and peak concentrations and the duration of elevated concentrations strongly depends on the source and the properties of the particular substance. The design of sampling campaigns and evaluation of data should consider these characteristics and account for their effects.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 Structural member stability verification in the new part 1‐1 of the second generation of Eurocode 3 : part 1: evolution of Eurocodes, background to partial factors, cross‐section classification and structural analysis(2020) Knobloch, Markus; Bureau, Alain; Kuhlmann, Ulrike; da Silva, Luís Simões; Snijder, Hubertus. H.; Taras, Andreas; Bours, Anna‐Lena; Jörg, FabianThis two‐part article gives an overview of the developments of the structural member verification in prEN 1993‐1‐1:2020 “Eurocode 3: Design of steel structures - part 1‐1: General rules and rules for buildings”, one of the second generation of Eurocodes. These developments were undertaken by Working Group 1 (WG1) of Subcommittee CEN/TC250/SC3 and by Project Team 1 (SC3.PT1) responsible for drafting the new version of EN 1993‐1‐1. In the past, WG1 collected many topics needing improvement, and the systematic review conducted every five years also yielded topics needing further development. Based on this, the current version of EN 1993‐1‐1 has been developed into a new draft version prEN 1993‐1‐1:2020 enhancing “ease of use”. The technical content of this new draft was laid down at the end of 2019. Many improvements to design rules have been established with respect to structural analysis, resistance of cross‐sections and stability of members. This two‐part article focuses on member stability design rules and deals with the basis for the calibration of partial factors, the introduction of more economic design rules for semi‐compact sections, methods for structural analysis in relation to the appropriate member stability design rules, new design rules for lateral torsional buckling plus other developments and innovations. This first part of the article primarily serves to explain the general background to the European Commission Mandate M/515 that led to the further evolution of the Eurocodes and to illustrate the developments in prEN1993‐1‐1:2020 that pertain to new material grades, partial factors, cross‐sectional classification and structural analysis. These form the necessary background to the changes to member buckling design rules, which are treated more specifically in the second part.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.