Axpo Power AG

Baden, Switzerland

Axpo Power AG

Baden, Switzerland
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Mircevska V.,Ss. Cyril and Methodius University of Skopje | Nastev M.,Geological Survey of Canada | Hristovski V.,Ss. Cyril and Methodius University of Skopje | Malla S.,Axpo Power AG | Garevski M.,Ss. Cyril and Methodius University of Skopje
Journal of Computing in Civil Engineering | Year: 2017

This paper presents the theoretical development of a practical numerical method for analysis of complex dam-reservoir interaction problems. The proposed approach takes advantage of the combination of boundary and finite element methods (BEM-FEM) for an independent analysis of two physically distinct dam structure and reservoir-foundation domains. It involves the matrix of hydrodynamic influence (HDI) based on the application of the virtual work principle to the fluid (BEM) domain to calculate the hydrodynamic forces (HDF). Equilibrium between hydrodynamic forces and absolute accelerations is obtained by repetitive solution of the dynamic equation for the FEM domain only until the Euclidean norm of the vector of residual errors at the interface nodes becomes smaller than the prescribed tolerance. The method allows effective consideration of compound wave-field of compressive and dilatational waves and wave-scattering effects for a more realistic evaluation of the interaction phenomenon. A validation procedure is presented through comparisons with analytical and numerical solutions of simple two-dimensional (2D) and three-dimensional (3D) problems. A realistic 3D example of a concrete gravity dam subjected to seismic excitation is given at the end. The method yields fast and accurate results without the necessity of time-consuming iterative computation of dependent variables in both domains. © 2017 American Society of Civil Engineers.

The seismic displacement of a block sliding down an inclined plane is commonly obtained by a double integration of portions of the acceleration time history exceeding the yield acceleration. Although this simple procedure was originally developed by Newmark for a tangential excitation, it is widely used also for horizontal shaking. Strictly speaking, the sliding displacement in this case needs to be modified by a correction factor, a fact that is not very well known and thus often overlooked. The vertical component is usually either ignored or considered by resorting to arbitrary simplifying assumptions. This paper presents an alternative double integration procedure for the calculation of the sliding displacement under the combined action of the horizontal and vertical components. After transforming the excitation to the tangential and normal directions, the procedure is applied to the relative tangential acceleration. Unlike the traditional Newmark approach, the application of the alternative procedure does not require a prior explicit calculation of the yield acceleration, which would not even be a constant when the vertical component is present. The results of a series of case studies performed employing this procedure indicate that the sliding displacement does not necessarily increase when the vertical component is also considered. © 2017 Elsevier Ltd

Karches B.,Johannes Gutenberg University Mainz | Schon J.,Fraunhofer Institute for Solar Energy Systems | Gerstenberg H.,TU Munich | Hampel G.,Johannes Gutenberg University Mainz | And 8 more authors.
Radiochimica Acta | Year: 2017

In a series of crystallization experiments, the directional solidification of silicon was investigated as a low cost path for the production of silicon wafers for solar cells. Instrumental neutron activation analysis was employed to measure the influence of different crystallization parameters on the distribution of 3d-metal impurities of the produced ingots. A theoretical model describing the involved diffusion and segregation processes during the solidification and cooling of the ingots could be verified by the experimental results. By successive etching of the samples after the irradiation, it could be shown that a layer of at least 60 μm of the samples has to be removed to get real bulk concentrations. © 2017 Walter de Gruyter GmbH, Berlin/Boston.

Agency: European Commission | Branch: FP7 | Program: CP | Phase: ENERGY.2013.2.4.1 | Award Amount: 13.30M | Year: 2013

The IMAGE project will develop a reliable science based exploration and assessment method to IMAGE geothermal reservoirs using an interdisciplinary approach based on three general pillars: 1 Understanding the processes and properties that control the spatial distribution of critical exploration parameters at European to local scales. The focus will be on prediction of temperatures, in-situ stresses, fracture permeability and hazards which can be deduced from field analogues, public datasets, predictive models and remote constraints. It provides rock property catalogues for 2 and 3. 2 Improving well-established exploration techniques for imaging and detection beyond the current state of the art and testing of novel geological, geophysical and geochemical methods to provide reliable information on critical subsurface exploration parameters. Methods include a) geophysical techniques such as ambient seismic noise correlation and magnetotellurics with improved noise filtering, b) fibre-optic down-hole logging tools to assess subsurface structure, temperature and physical rock properties, and c) the development of new tracers and geothermometers. 3 Demonstration of the added value of an integrated and multidisciplinary approach for site characterization and well-siting, based on conceptual advances, improved models/parameters and exploration techniques developed in 1 and 2. Further, it provides recommendations for a standardized European protocol for resource assessment and supporting models. The IMAGE consortium comprises the leading European geothermal research institutes and industry partners who will perform testing and validation of the new methods at existing geothermal sites owned by the industry partners, both in high temperature magmatic, including supercritical, and in basement/deep sedimentary systems. Application of the methods as part of exploration in newly developed fields will provide direct transfer from the research to the demonstration stage.

Marcher T.,ILF Consulting Engineers ZT GmbH | John M.,JTC John Tunnel Consult | Hohberg J.-M.,IUB Engineering Ltd. | Fellner D.,Axpo Power AG | And 2 more authors.
Underground - The Way to the Future: Proceedings of the World Tunnel Congress, WTC 2013 | Year: 2013

A 1,000 MW pumped-storage plant is under construction at altitudes between 1,600 and 2,400m in the Glarner Alps of Switzerland, around 90 km south-east of Zurich. The machine and the transformer caverns are situated in Quintner Limestone with an overburden of 400 to 500 m. The 150 m long machine cavern has a height of 53 m and a width of approximately 30 m. The distance between both caverns was increased to 59 m to avoid overlapping plastic zones following the evaluation of geological conditions of the pilot tunnel. During construction it was found that geological conditions are more complex than expected, resulting in displacements varying to a large degree. That was why the design was reviewed by comparing the prognosis with the actual behaviour during excavation of the heading. The rock bolting system with regard to pattern and length was adjusted based on the results of numerical back analyses including sensitivity studies of the rock mass parameters. Additional 3D computations were performed to take account of the numerous intersecting galleries. During excavation of benches, additional rock bolting was provided in specific areas, where deformations continued over some time. © 2013 Taylor & Francis Group.

Kurmann D.,Axpo Power AG | Proske D.,Axpo Power AG | Cervenka J.,Na Hrebenkach 55
Kerntechnik | Year: 2013

Structures can be exposed to seismic loading. For structures of major importance, extreme seismic loadings have to be considered. The proof of safety for such loadings requires sophisticated analysis. This paper introduces an analysis method which of course still includes simplifications, but yields to a far more realistic estimation of the seismic load bearing capacity of reinforced concrete structures compared to common methods. It is based on the development of pushover curves and the application of time-histories for the dynamic model to a representative harmonic oscillator. Dynamic parameters of the oscillator, such as modal mass and damping are computed using a soil-structure-interaction analysis. Based on the pushover-curve nonlinear force-deformation-capacities are applied to the oscillator including hysteresis behaviour characteristics. The oscillator is then exposed to time-histories of several earthquakes. Based on this computation the ductility is computed. The ductility can be scaled based upon the scaling of the time-histories. Since both, the uncertainty of the earthquake by using different timehistories and the uncertainty of the structure by using characteristic and mean material values, are considered, the uncertainty of the structure under seismic loading can be explicitly represented by a fragility. © Carl Hanser Verlag, München.

Proske D.,AXPO Power AG
12th International Conference on Applications of Statistics and Probability in Civil Engineering, ICASP 2015 | Year: 2015

Structures are exposed to an ensemble of natural hazards. Earthquakes and flooding's are the most recognized natural hazards, but structures also have to be safe under extreme weather conditions such wind and hurricanes, heat periods and colds, extreme rainfalls, hail and freezing rain. Some of this hazards are usually not investigated in detail, however based on statistical investigations, hazard curves and representative values of hazards can be defined, if required. They can be applied in probabilistic computations to achieve the probability of failure of the structures. Although major efforts have been undertaken in recent years to estimate the hazards and the representative values, we have to notice, that the validity of the provided natural hazards estimations by means of statistical investigations is limited due to confined sample populations. One of this causes is the recently increased knowledge using data with extreme values from non-instrumental periods, which heavily influences the outcome of the statistics, if considered. Newer statistical methods and the inclusion of historical data can, but need not necessarily improve results under all conditions. This development has also been observed in seismic loading estimation and in flooding hazard prognosis.

Muller U.,Engineering consortium Alpenstrom | Marclay R.,Engineering consortium Alpenstrom | Dunn J.,Engineering consortium Alpenstrom | Hohberg J.M.,Engineering consortium Alpenstrom | Hase M.,Axpo Power AG
Underground - The Way to the Future: Proceedings of the World Tunnel Congress, WTC 2013 | Year: 2013

"Linthal 2015" stands for a couple of records - Switzerland's largest hydro-power plant with Europe's longest concrete dam, a huge construction site at an altitude unique in Europe, and a stunning logistics with two of the largest cableways ever built. The paper describes the design philosophy, the development of the main project - covering the hydraulic system and the underground works - and the steps taken to optimize the layout, the dimensioning and the sequencing of works. Challenges are the ambitious time schedule, the logistics, the concerns for the delicate alpine nature, and last but not least the required high reliability and availability of the power plant. While this paper presents the broad picture of the project, another WTC'13 paper discusses the analysis and construction of the main caverns in more detail. © 2013 Taylor & Francis Group.

Proske D.,Axpo Power AG | Kurmann D.,Axpo Power AG | Cervenka J.,Cervenka Consulting
Beton- und Stahlbetonbau | Year: 2013

Seismology and earthquake engineering have experienced major progress in the last decades. This progress is implemented in current modern codes of practice for the design of new structures. However for existing structures, mainly designed according to former codes of practice, a realistic estimation of the seismic robustness and ultimate load is also necessary. Often in such cases ambitious analyses are carried out. This paper describes the steps of such an analysis for a reinforced concrete structure, which is part of the critical infrastructure. In a first step the nonlinear force-deformation-curve is investigated by a pushover-curve. This curve is applied to an equivalent oscillator. Further dynamic properties of the oscillator are obtained from a soil-structure-interaction analysis. The oscillator is then exposed to various time-acceleration-sequences. This computation yields to a ductility demand. The ductility demand can be related to different earthquake intensities by scaling the time-acceleration-sequences. Finally the investigation was carried out twice, using characteristic and mean material properties. An overall deviation of the structural resistance can be provided by these parallel computations in combination with the deviation of the various time-acceleration-sequences. The results are used to construct a fragility curve and hence the ultimate seismic load bearing capacity. Copyright © 2013 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.

Slabu D.,Axpo Power AG | Zemek M.,Axpo Power AG | Hellwig C.,Axpo Power AG
LWR Fuel Performance Meeting, Top Fuel 2013 | Year: 2013

Axpo has developed a QA system for fuel procurement including manufacturing surveillance. The results - no fabrication-related fuel failures for many years - demonstrate the system efficiency; however the cooperation of the vendors and their willingness for process improvements is crucial for this success. While the best QA system cannot replace a deep technical understanding of the fuel engineering and fabrication, it can make the processes more solid and confident. The here presented system has still some potential for improvement, especially considering the different fuel designs handled. This contribution shall provide inspiration for colleagues of other utilities. An open dialogue on how to practically perform fuel manufacturing surveillance can only be of mutual benefit.

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