Rückseitige Verstärkung von Stahlbetonplatten unter Impaktbeanspruchung

Im Rahmen der beschriebenen Arbeit erfolgt die experimentelle Untersuchung von nachträglich an Stahlbetonplatten aufgetragenen Verstärkungsschichten, die einer Impaktbelastung ausgesetzt werden. Die Grundlage hierfür bilden drei verschieden bewehrte Testserien, welche anhand eines entwickelten Versuchsschemas geprüft werden. Zielstellung ist die Quantifizierung der Leistungsfähigkeit rückseitig applizierter Verstärkungen sowie die Weiterentwicklung einer bereits existierenden Schädigungsbeschreibung und eines analytischen bzw. numerischen Modells

Rückseitige Verstärkung von Stahlbetonplatten unter Impaktbeanspruchung

Im Rahmen der beschriebenen Arbeit erfolgt die experimentelle Untersuchung von nachträglich an Stahlbetonplatten aufgetragenen Verstärkungsschichten, die einer Impaktbelastung ausgesetzt werden. Die Grundlage hierfür bilden drei verschieden bewehrte Testserien, welche anhand eines entwickelten Versuchsschemas geprüft werden. Zielstellung ist die Quantifizierung der Leistungsfähigkeit rückseitig applizierter Verstärkungen sowie die Weiterentwicklung einer bereits existierenden Schädigungsbeschreibung und eines analytischen bzw. numerischen Modells

Rückseitige Verstärkung von Stahlbetonplatten unter Impaktbeanspruchung

Im Rahmen der beschriebenen Arbeit erfolgt die experimentelle Untersuchung von nachträglich an Stahlbetonplatten aufgetragenen Verstärkungsschichten, die einer Impaktbelastung ausgesetzt werden. Die Grundlage hierfür bilden drei verschieden bewehrte Testserien, welche anhand eines entwickelten Versuchsschemas geprüft werden. Zielstellung ist die Quantifizierung der Leistungsfähigkeit rückseitig applizierter Verstärkungen sowie die Weiterentwicklung einer bereits existierenden Schädigungsbeschreibung und eines analytischen bzw. numerischen Modells

Influences on Post-Denitrification in Membrane Bioreactors

Werden Membranbelebungsanlagen (MBR) zur Abwasserreinigung eingesetzt, ergeben sich durch die veränderten Rahmenbedingungen neue Möglichkeiten der Prozessführung. Eine Variante ist die nachgeschaltete Denitrifikation ohne zusätzliche Kohlenstoffdosierung, wel-che in verschiedenen Versuchsanlagen erfolgreich eingesetzt wurde. Noch nicht abschließend geklärt ist die Frage nach der von den Bakterien genutzten Kohlenstoffquelle. Diese Arbeit untersucht Einflüsse auf die Denitrifikation und konzentriert sich besonders auf langsamer abbaubare Substrate. Außerdem wird die Anlagenkonfiguration optimiert. Ein Laborreaktor (MBR) wurde mit biologischer Phosphorelimination und nachgeschalteter Denitrifikation ohne zusätzliche Kohlenstoffdosierung betrieben. Der Zulauf bestand aus ei-nem synthetischen Abwasser, welches insbesondere unterschiedlich gut abbaubare organische Kohlenstoffe enthielt. Batchversuche und mikrobiologische Untersuchungen ergänzen die Ergebnisse der Laboranlage. Die Versuche ergaben eine Abhängigkeit der Denitrifikation von der CSB-Schlamm-belastung, dem CSB:Nges-Zulaufverhältnis und insbesondere dem CSB:oTS-Mischungs-verhältnis am Anlagenzulauf. Letzteres spricht für eine flockengebundene Verarbeitung der Substrate. Dass der alleinige Einsatz von Acetat als Substrat zu höheren Denitrifikationsraten führt, konnte nicht bestätigt werden. Als Ursache wird der schnelle Abbau des Acetats und seiner Metabolite im Aeroben vermutet. Ein Zusammenhang der Phosphorelemination mit der Denitrifikation wurde ebenfalls nicht nachgewiesen, allerdings wird der durch Hydrolysepro-zesse positive Einfluss der anaeroben Zone auf den nachfolgenden Abbau gezeigt. Versuche zur Optimierung der Rezirkulationsströme bestätigten, dass der Betrieb einer nach-geschalteten Denitrifikation mit nur einem Rezirkulationsstrom möglich ist. Diese Konfigura-tion widerspricht jedoch einem geringen Zulauf-Mischungsverhältnis. Der Einsatz muss dem-nach am spezifischen Fall entschieden werden. Mikrobiologische Untersuchungen verschiedener Anlagen konnten keine Abhängigkeit der Populationen von der Abwasserart oder der Verfahrensweise nachweisen.If membrane bioreactors (MBR) are used for sewage treatment, new possibilities of the process technology arise by the changed basic conditions. An alternative is the post-denitrification without an additional carbon source, as it was used in lab scale plants successfully. Not yet clarified is the question of the carbon source used by the bacteria. This work examines the influences on denitrification and focuses particularly on slower biodegradable substrates. In parallel the plant configuration is optimized. A lab reactor (MBR) was operated with biological phosphorus elimination and post denitrification without an additional carbon source. The influent consisted of a synthetic sewage which in particular differently degradable organic carbons contained. Batch tests and microbiological investigations complement the results of the lab scale plant. The trails showed a dependence of the denitrification on the COD sludge load, the relation of COD:Nt and in particular the COD:VSS mixing proportion of the influent. The latter speaks for a flake-bound usage of the substrates. It was not confirmed, that the usage of acetate as single carbon source led to high denitrification rates. It was assumed that the rapid degradation of acetate and its metabolites in the aerobic zone is the reason for this. A connection to the phosphorus elimination could also not be confirmed; however, the positive influence of the anaerobic zone through hydrolysis processes on the subsequent degradation is shown. Attempts to optimize the recirculation configuration confirmed that the operation of a post- denitrification with only one recirculation is possible. Nevertheless, this configuration contradicts a low inflow mixing proportion (COD:VSS). The usage must therefore be decided on the specific case. Microbiological investigations (PCR-DGGE) of various sewage treatment plants could indicate no dependence of the populations on the wastewater composition or the process technology

Study on the Impacts of Peaking Factors on a Water Distribution System in Germany

This paper aims to explore the impacts of peaking factors on a water distribution system designed for a small city in Germany through model-based analysis. As a case study, the water distribution network was modelled by EPANET and then two specific studies were carried out. The first study tested corresponding system-wide influences on water age and energy consumption if the peaking factors used at design stage are inconsistent with ones in real situation. The second study inspected the possible relationship between the choice of peaking factors and budgets by comparing several different pipe configurations of the distribution system, obtained according to variety of peaking factors. Given the analysis results, the first study reveals that average water age will increase if peaking factors estimated at design stage are larger than real values in that specific system, and vice versa. In contrast, energy consumption will increase if peaking factors defined for system design are smaller than ones in real case, and vice versa. According to the second study, it might be possible to amplify peaking factors for design dramatically by a slight increase in the investment on this system. However, further study on budget estimation with more factors and detailed information considered should be carried out

Behaviour of reinforcement in drop tower beam tests

Drop tower tests help to gain understanding about the general behaviour of reinforced concrete members under impact loading and to analyse strains and strain rates occurring within their reinforcement. For this purpose, beam and slab specimens are usually employed. The main advantage of beams compared to slabs is that they are less complex due to the almost two-dimensional instead of three-dimensional wave propagation within them. To investigate the steel strains and strain rates, ten impact tests on beam specimens with various impact energies were performed. The impactor sizes and velocities were varied. The reinforcement bars of the beams were instrumented with semiconductor strain gauges. The measured data suggest that the occurring strains in beam tests are independent of the loading velocity. The same was found for the strain rates. The reason is that higher impact energies mostly influence the concrete damage due to spalling on the impact-facing side which happens after the maximum strains occurred. The strains in the reinforcement bars generally result from the overall deflection because of the impact, the spreading of longitudinal waves in the horizontal direction, and the localized cracking of the concrete due to the formation of a punching cone

Behaviour of reinforcement in drop tower beam tests

Drop tower tests help to gain understanding about the general behaviour of reinforced concrete members under impact loading and to analyse strains and strain rates occurring within their reinforcement. For this purpose, beam and slab specimens are usually employed. The main advantage of beams compared to slabs is that they are less complex due to the almost two-dimensional instead of three-dimensional wave propagation within them. To investigate the steel strains and strain rates, ten impact tests on beam specimens with various impact energies were performed. The impactor sizes and velocities were varied. The reinforcement bars of the beams were instrumented with semiconductor strain gauges. The measured data suggest that the occurring strains in beam tests are independent of the loading velocity. The same was found for the strain rates. The reason is that higher impact energies mostly influence the concrete damage due to spalling on the impact-facing side which happens after the maximum strains occurred. The strains in the reinforcement bars generally result from the overall deflection because of the impact, the spreading of longitudinal waves in the horizontal direction, and the localized cracking of the concrete due to the formation of a punching cone

Reinforced Concrete Plates under Impact Load—Damage Quantification

A large number of impact experiments have been carried out at the Technische Universität Dresden in recent years in several research projects. The focus was on reinforced concrete plates on the one hand and on subsequently strengthened reinforced concrete plates on the other hand. Based on these investigations, two fundamental tasks arose: (1) finding an objective description of the damage of components made of steel reinforced concrete that had previously been subjected to an impact load and (2) quantification of the effect of a subsequently applied strengthening layer. In this paper we will focus on both. At first, the experimental conditions and program as well as the used drop tower facility at the Otto Mohr Laboratory of the Technische Universität Dresden are briefly explained. In the summary presentation of the main test results, the focus is on the observed component damage. Based on the observations, an approach for a damage description is presented. To define global damage, the stiffness of the investigated structural components before and after the impact event is used. At the end of the paper, the potential of the method, but also gaps in knowledge and research needs are discussed

Post-impact evaluation at RC plates with planar tomography and FEM

The project executing agency is the Gesellschaft für Anlagen- und Reaktorsicherheit (GRS) gGmbH, project 1501542

Ballistic limit and damage assessment of hybrid fibre-reinforced cementitious thin composite plates under impact loading

Impact resistance of reinforced concrete (RC) structures can be significantly improved by strengthening RC members with thin composite layers featuring high damage tolerance. Indeed, to limit the well-known vulnerability of cement-based materials against impact loading, the synergistic effects of short fibres and continuous textile meshes as hybrid reinforcement has been proved to be highly beneficial. This paper addresses the characterisation of novel cement-based hybrid composites through accelerated drop-weight impact tests conducted on rectangular plates at different impact energies. Two distinct matrices are assessed, with particular interest in a newly developed limestone calcined clay cement (LC3)-based formulation. Important parameters quantifying energy dissipation capability, load bearing capacity and damage are cross-checked to compute the ballistic limit and estimate the safety-relevant characteristics of the different composites at hand. Although textiles alone can improve the damage tolerance of fine concrete to some extent, the crack-bridging attitude of short, well-dispersed fibres in hybrid composites imparts a certain ductility to the cement-based matrices, allowing a greater portion of the textile to be activated and significantly reducing the amount of matrix spalling under impact