References of "Maas, Stefan 50002241"
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See detailDamage Detection on the Champangshiehl Bridge using Blind Source Separation
Nguyen, Viet Ha UL; Rutten, Christophe; Golinval, Jean-Claude et al

in Proceedings of the Third International Symposium on Life-Cycle Civil Engineering, IALCCE’12 (2012)

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See detailShear Stresses in Honeycomb Sandwich Plates: Analytical Solution, Finite Elemente Method and Experimental Verification
Wahl, Laurent UL; Maas, Stefan UL; Waldmann, Danièle UL et al

in Journal of Sandwich Structures & Materials (2012), 14(4), 449-468

Honeycomb composite structures are used in airplanes, railway cars and vehicles. The sandwich panels consist of two stiff face sheets of aluminium, which are bonded to a very lightweight honeycomb core of ... [more ▼]

Honeycomb composite structures are used in airplanes, railway cars and vehicles. The sandwich panels consist of two stiff face sheets of aluminium, which are bonded to a very lightweight honeycomb core of aluminium. Compared to normal plates, sandwich panels have a very high stiffness and simultaneously a low weight. The core of these structures is mainly subjected to shear stresses. The shear stresses depend strongly on the angle of the load application. The distribution and the level of the shear stresses are investigated using analytical calculations. The load direction which induces highest stresses in the honeycomb core is derived. This direction is not the W-direction, which is the most compliant one. When doing finite element simulations of honeycomb cores, often the core is homogenized in order to reduce the calculation time. In this article, some equations are derived in order to calculate the real shear stresses from the shear stresses of the homogeneous core. The equations are validated by finite element simulations and partially by tests. Three-point bending tests and additionally some Food Cart Roller Tests were conducted in order to test the panels in different angles. [less ▲]

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See detailShear stresses in honeycomb sandwich plates: Analytical solution, finite element method and experimental verification
Wahl, Laurent UL; Maas, Stefan UL; Waldmann, Danièle UL et al

in Journal of Sandwich Structures & Materials (2012), 4

Honeycomb composite structures are used in airplanes, railway cars and vehicles. The sandwich panels consist of two stiff face sheets of aluminium, which are bonded to a very lightweight honeycomb core of ... [more ▼]

Honeycomb composite structures are used in airplanes, railway cars and vehicles. The sandwich panels consist of two stiff face sheets of aluminium, which are bonded to a very lightweight honeycomb core of aluminium. Compared to normal plates, sandwich panels have a very high stiffness and simultaneously a low weight. The core of these structures is mainly subjected to shear stresses. The shear stresses depend strongly on the angle of the load application. The distribution and the level of the shear stresses are investigated using analytical calculations. The load direction which induces highest stresses in the honeycomb core is derived. This direction is not the W-direction, which is the most compliant one. When doing finite element simulations of honeycomb cores, often the core is homogenized in order to reduce the calculation time. In this article, some equations are derived in order to calculate the real shear stresses from the shear stresses of the homogeneous core. The equations are validated by finite element simulations and partially by tests. Three-point bending tests and additionally some Food Cart Roller Tests were conducted in order to test the panels in different angles. [less ▲]

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See detailDamage assessment of concrete structures through dynamic testing methods. Part 2: Bridge tests
Maas, Stefan UL; Zürbes, Arno; Waldmann, Danièle UL et al

in Engineerig Structures (2012), 34

The present paper is split into two parts: in the first part the different dynamic damage indicators are defined and applied to beam and slab structures under laboratory conditions, whereas the present ... [more ▼]

The present paper is split into two parts: in the first part the different dynamic damage indicators are defined and applied to beam and slab structures under laboratory conditions, whereas the present second part deals with experiments carried out on two real post-tensioned bridges. The damage indicators defined in part one are based on swept sine excitation and esveal the drop of the eigenfrequencies, the changes in damping, the varying dependency range of the first eigenfrequency on excitation force amplitude and the occurrence of higher harmonics, which changed the Total Harmonic Distorsion (THD) and a special transfer-function called TF or FRFsmall. In the first part it was proved that the amount of nonlinearities varies with damage and that harmonic excitation is favorable for good test conditions. In the laboratory this can easily be done using an electric or hydraulic shaker, but on real bridges this kind of excitation becomes more complicated due to the higher forces and the necessity to provide counter bearing for any shaker system. That is why two machines were designed and used to excite big structures harmonically, e.g. real bridges in this part. The different indicators are applied to assess the state of two post-tensioned bridges, which had been in good order and condition before artificial damage in multiple steps was caused. It turns out that the decrease in the eigenfrequencies is the most important damage indicator, provided temperature and mass dependant effects can be eliminated. All other indicators may be used as supplements to give correct tendencies, but no strict limits. [less ▲]

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See detailIntegrative analysis of the energy flow in a steel plant and a comprehensive approach to increase the energy efficiency
Tarrés Font, Joana UL; Maas, Stefan UL; Scholzen, Frank UL et al

in Proceedings METEC InSteelCON 2011, Düsseldorf Germany, CCD Congress Center, Düsseldorf, 27.06-01.07. (2011, July)

Steel industry is a highly intensive energy consumer. The energy used by the studied electric steelmaking plant could supply 25,000 households with thermal energy and 100,000 households with electrical ... [more ▼]

Steel industry is a highly intensive energy consumer. The energy used by the studied electric steelmaking plant could supply 25,000 households with thermal energy and 100,000 households with electrical energy. Increasing the energy efficiency of a steel plant will not only have impact in the reduction of greenhouse emissions but also in an increase of the competitiveness of the plant. A Luxembourgish steel plant is studied in detail and several options for energy savings are identified. Promising energy efficiency gains can be achieved by the optimization of the electric arc furnace and the reheating furnaces and by the improvement of the logistics between the continuous casting and the reheating furnace. The possibilities of energy recovery for heating purposes and for the generation of electricity with ORC- (Organic Rankine Cycle) or KALINAtechnologies are studied. In addition there is the opportunity to deliver hot water to a near district-heating system using otherwise lost energy and creating regional synergies. Nevertheless there is a need to develop a comprehensive and integrative approach to find a good overall solution instead of treating each step separately. The University of Luxembourg in collaboration with a Luxembourgish steel plant is developing a methodology to assess the technical, economical and environmental aspects of each solution. The objective is to assist in the decision-making in the company’s energy efficiency strategy and to perform a comparative analysis of the different solutions in order to propose an optimized plant, based on its feasibility due to local restrictions and different energy price scenarios. This ideal plant will be composed of individual elements, which proved their effectiveness in different real plants, so that the approach stays applied [less ▲]

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See detailInfluence of environmental changes on modal characteristics
Waldmann, Danièle UL; Bungard, Volker UL; Mahowald, Jean UL et al

in Federation for Structural Concrete (fib) (2011)

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See detailFatigue in Aluminium Honeycomb-core Plates
Wahl, Laurent UL; Zürbes, Arno UL; Maas, Stefan UL et al

in Benchmark: The International Magazine for Engineering Designers & Analysts (2011), (January), 26-32

Honeycomb composite lightweight structures made of aluminium or aramid fibres are used in airplanes, railway carriages and automobiles. These structures are subjected to dynamic loading but hardly any ... [more ▼]

Honeycomb composite lightweight structures made of aluminium or aramid fibres are used in airplanes, railway carriages and automobiles. These structures are subjected to dynamic loading but hardly any fatigue properties of the honeycomb core exist in current literature. Hence here a theoretical and experimental approach is presented. [less ▲]

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See detailEntwicklung von hybriden Wärmedämmsteinen aus LAC
Leufgens, Nadine UL; Waldmann, Danièle UL; Maas, Stefan UL et al

in Mauerwerk (2010), 14(1), 10-18

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See detailDynamic simulations to develop a natural ventilation concept for an office building
Thewes, Andreas UL; Maas, Stefan UL; Scholzen, Frank UL et al

in 8th International Conference on System Simulation in Buildings (2010)

The Sustainability Group of the University of Luxembourg defined for their new buildings a maximum thermal end-energy of 14 kWh/(m3a) and an electricity consumption for HVAC and lighting below 6 kWh/(m3a ... [more ▼]

The Sustainability Group of the University of Luxembourg defined for their new buildings a maximum thermal end-energy of 14 kWh/(m3a) and an electricity consumption for HVAC and lighting below 6 kWh/(m3a). Therefore it was necessary to avoid active cooling loads and mechanical ventilation in the offices and small lecture rooms. The well insulated and air-tight façade, including special outside shading elements which were designed as a grid over the complete building envelope, was an essential given architectural element of the building. Therefore further external shading devices were not applicable. The only possibility to have an influence on solar gains was to optimize the window size, the glazing type and potentially an internal shading device. Furthermore, to prevent the risk of overheating during the summer period, it was necessary to reduce the internal gains from lighting and IT-equipment. Hence detailed dynamic simulations using TRNSYS and TRNFLOW were done to evaluate the thermal comfort without air-conditioning and mechanical ventilation. The effects of optimizations like a state-of-the-art lighting control system or a window-based night ventilation, as well as the influence of the effective thermal inertia of the building were analyzed. The assumed natural ventilation rates were calculated by combining TRNFLOW and TRNSYS simulations and by the software LESOCOOL. [less ▲]

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See detailThermal comfort of a new university building in Luxembourg with passive cooling
Thewes, Andreas UL; Maas, Stefan UL; Scholzen, Frank UL et al

in Thermal comfort of a new university building in Luxembourg with passive cooling (2010)

The new Luxembourgish university buildings should comply with a low energy standard, which was defined for typical offices and smaller lecture rooms by a thermal end-energy lower than 14 kWh/m3a and an ... [more ▼]

The new Luxembourgish university buildings should comply with a low energy standard, which was defined for typical offices and smaller lecture rooms by a thermal end-energy lower than 14 kWh/m3a and an electricity use for HVAC and lighting of max. 6 kWh/m3a. Consequently it was necessary to find ways to avoid the need for mechanical ventilation and air-conditioning. The heat consumption was minimized by an air-tight and well insulated building envelope. A difficulty was posed by special outside façade elements which were set-up as a grid over the complete outer surface as an architectural element. To prevent the risk of overheating during summer, it is necessary to reduce the solar gains by optimizing the window sizes and the glazing types, as well as through the installation of movable indoor shading elements. Nevertheless enough daylight should enter the rooms to limit the consumption of electricity for artificial lighting. Hence detailed dynamic simulations were performed using TRNSYS and TRNFLOW to ensure thermal comfort without active cooling. The effective electricity consumption of a newly installed state-of-the-art lighting system, including presence detectors and daylight controllers for dimming, was measured in a test installation to determine the internal loads by lighting. Radiation and illuminance measurements were performed on sample elements of the façade grid. The results were used to verify the daylight simulations and to analyze the benefits of daylight controllers. Several iterative steps were taken to gradually improve the building by introducing different modifications, e.g. reduction of the window sizes, installation of a lighting control system, improving the night ventilation and effective use of the thermal inertia of the building. [less ▲]

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See detailAmbient Vibration and Forced Excitation Tests of a Composite Bridge: Environmental influences and nonlinear effects on the dynamic properties
Bungard, Volker UL; Mahowald, Jean UL; Waldmann, Danièle UL et al

in Proceedings of the International Conference on Noise and Vibration Engineering, ISMA (2010)

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See detailComparison of linear and nonlinear static and dynamic behaviour of prestressed and non-prestressed concrete slab elements
Mahowald, Jean UL; Bungard, Volker UL; Maas, Stefan UL et al

in Proceedings of the International Conference of Noise and Vibration Engineering (2010)

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See detailAcoustics During the Vibratory Pile Driving of Sheet Piles: Measurement Conditions and Key Parameters of the Noise Generation
Hanus, Vincent UL; Zürbes, Arno; Maas, Stefan UL et al

in Acta Acustica United with Acustica (2010), 96(1-1),

This paper studies the sound generation during the vibratory pile driving of double sheet piles for different crosssections with the aims to give guidelines how to make high-quality acoustic measurements ... [more ▼]

This paper studies the sound generation during the vibratory pile driving of double sheet piles for different crosssections with the aims to give guidelines how to make high-quality acoustic measurements and to find the keyparameters in this noise generation. These objectives are reached by studying the assumed hypotheses when performing the acoustic measurements and by using a beamforming system; details about the vibratory pile driving are also given to obtain reproducible and representative measurements. The experiment results confirm some previouslypresented hypotheses and show two key parameters involved in the sound generation: the space between the welds of the common interlock of a double sheet pile and the wall height above the soil of a neighbouring wall. [less ▲]

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See detailMechanical material properties of polymethylmethacrylate (PMMA) für medical applications
Thielen, Thomas UL; Maas, Stefan UL; Zürbes, Arno UL et al

in Materials Testing (2009), 51(4), 203-209

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See detailComparison of static behaviour and nonlinear vibration characteristic of gradually damaged prestressed concrete slabs and reinforced concrete beams
Bungard, Volker UL; Waltering, Markus UL; Waldmann, Danièle UL et al

in Proceedings of the International Conference on Experimental Vibration Analysis for Civil Engineering Structures (2009)

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See detailMarket study of improved heat-insulating masonry bricks.
Waldmann, Danièle UL; Leufgens, Nadine UL; Maas, Stefan UL et al

in Concrete 21st Century Superhero (2009)

Detailed reference viewed: 54 (5 UL)