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See detailDamage assessment of concrete structures through dynamic testing methods. Part 1 - Laboartory Test
Maas, Stefan UL; Zürbes, Arno; Waldmann, Danièle UL et al

in Journal of Engineering Structures (2012), 34

The present paper is split into two parts: Part 1 is about laboratory tests whereas the second part deals with experiments on real bridges. This article aims at summarizing several experimental dynamic ... [more ▼]

The present paper is split into two parts: Part 1 is about laboratory tests whereas the second part deals with experiments on real bridges. This article aims at summarizing several experimental dynamic testing methods with different damage indicators to evaluate the state of prestressed as well as of passively reinforced concrete structures. First the differences between prestressed and passively reinforced concrete are repeated for static behavior, before the transition to dynamics is made. As it will be proved in the following that the amount of nonlinearities increases with damage, harmonic excitation is favorable to realize good testing conditions. It is applied to visualize variations in linear as well as in non-linear structural characteristics, which are subsequently used as damage indicators, e.g. the drop of the eigenfrequencies, the changes in damping and modeshapes, the occurrence of higher harmonics and a varying dependency of the eigenfrequency on excitation force amplitude. These different indicators will be used on passively reinforced beam elements and industrially produced prestressed slabs in the first part and on two real post-tensioned bridges in the second part. All these structures were in good order and condition before artificial damage was applied in multiple steps and the sensitivity of each damage indicator was analyzed. [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 detailNouveaux systèmes de murs isolants en béton
Agaajani, Shariar; Waldmann, Danièle UL

in RF2B 2011 – 12ème édition des Journées scientifiques du Regroupement francophone pour la recherche et la formation sur le béton (2011)

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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 detailSteel fibres as only reinforcement for flat slab construction
Julien, Michels; Waldmann, Danièle UL; Maas, Stefan et al

in Construction and Building Materials (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 detailInfluence of environmental conditions for the rheological properties of SCC
Weisheit, Sandro UL; Waldmann, Danièle UL; Greger, Manfred UL

in Professeur D. SC. A. Kamal H. Khayat (Ed.) CD-Proceedings, Paper ID: MS-096 (2010, September 28)

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See detailStudy of the vibrating stationary state of a sheet pile during a vibratory pile driving
Hanus, Vincent; Zürbes, Arno; Maas, Stefan et al

in Proceedings of ISMA 2010 - International Conference on Noise and Vibration Engineering (2010, September 20)

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See detailDetermination of the rheological characteristics of Self-Compacting Concrete at different temperatures
Waldmann, Danièle UL; Weisheit, Sandro UL

in Abstract book of 3rd Congress of the International Federation for Structural Concrete (fib) (2010)

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See detailDesign model for sfrc flat slabs with openings in the column area
Michels, Julien UL; Waldmann, Danièle UL

in Abstract book of 3rd Congress of the International Federation for Structural Concrete (fib) (2010)

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See detailStatische und dynamische Zustandsbewertung von Stahlbetonbauteilen
Bungard, Volker UL; Waldmann, Danièle UL

in Abstract book of 51. Forschungskolloquium des Deutschen Ausschusses für Stahlbetonbau (2010)

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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 detailUntersuchungen zur Oberflächenqualität von Selbstverdichtendem Beton
Weisheit; Waldmann, Danièle UL; Greger, Manfred UL

Scientific Conference (2010)

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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 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 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 ▲]

Detailed reference viewed: 173 (8 UL)