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See detailSome conclusions from the measurements of temperatures and their gradients on eigenfrequencies of bridges
Mahowald, Jean UL; Maas, Stefan UL; Nguyen, Viet Ha UL et al

Scientific Conference (2014, June 30)

The ambient air temperature and solar radiation are affecting the soil and asphalts’ stiffness and hence the eigenfrequencies of a bridge. Very often eigenfrequencies are automatically determined by ... [more ▼]

The ambient air temperature and solar radiation are affecting the soil and asphalts’ stiffness and hence the eigenfrequencies of a bridge. Very often eigenfrequencies are automatically determined by special algorithms from structural response data generated by ambient excitation and measured by permanently installed sensors that is sometimes called “output only analysis” or “operating modal analysis”. Additionally the ambient air temperature is registered and finally the eigenfrequencies are analyzed versus the air temperature. The graph is normally a scatter diagram and each point is one measurement. In general the eigenfrequencies decrease with increasing temperature, whereas often linear regression is used to determine the line of best fit. But the slope of this straight line and the width of the scatter around the regression line differ from bridge to bridge. Especially this scatter field around the mean value at a determined temperature complicates the detection of damage, which is also often based on eigenfrequencies’ reduction. Hence the difficulty among others consists in separating damage from environmental effects. [less ▲]

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See detailWie genau sind unsere Energiepässe?
Merzkirch, Alexander UL; Hoos, Thorsten UL; Maas, Stefan UL et al

in Bauphysik (2014), 1(2014), 40-43

Member States of the European Union are obliged to present a calculation method and certificate for the energy performance for buildings according to the guidelines 2002/91/EG und 2010/31/EU. In ... [more ▼]

Member States of the European Union are obliged to present a calculation method and certificate for the energy performance for buildings according to the guidelines 2002/91/EG und 2010/31/EU. In Luxembourg it is obligatory to add the real final energy consumption to the certificate after 3 years. The measured real final energy consumptions and the calculated ones were compared for 125 single-family homes and 105 multi-family homes with 870 dwellings in total. The mean calculated values for single-family homes were 74 % higher, the mean calculated values for multi-family homes 103 % higher than the actual measured data. The older the buildings, the higher the deviations, as the input parameters, which were partly assumed and partly predefined, diverge between calculations and reality. Sensitive parameters of interest are the indoor room temperature, the U-values, the used assessment for thermal bridges and the air exchange rate. [less ▲]

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See detailField Study on the Energy Consumption of School Buildings in Luxembourg
Thewes, Andreas UL; Maas, Stefan UL; Scholzen, Frank UL et al

in Energy & Buildings (2014)

Buildings account for 40 % of total energy consumption and 35 % of the total CO2 emitted in the EU. In consequence, there is an enormous energy saving potential and the European Union requires from all EU ... [more ▼]

Buildings account for 40 % of total energy consumption and 35 % of the total CO2 emitted in the EU. In consequence, there is an enormous energy saving potential and the European Union requires from all EU member states to save energy in this sector. Hence, reducing the energy consumption of buildings represents an essential component of environmental protection efforts. Furthermore, the new European directive 2010/31/EU requires that the member states tighten national standards and draw up national plans to increase the number of “nearly zero-energy buildings”. Well-planned energy-saving strategies presume knowledge of specific characteristics of the current national building stock. Therefore, the implementation of a process to support systematic data collection, classification and analysis of the energy consumption of buildings will become increasingly important during the coming years. In the field study described below we analyzed the energy consumption of 68 school buildings in Luxembourg. A separate collation of electricity and heat energy consumptions allowed to make a detailed analysis of specific energy parameters. Clustered according to energy sources, the new buildings were analyzed from a statistical point of view. We defined the energy relevant parameters such as energy standards, the purpose of use of the buildings or whether they had canteens. [less ▲]

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See detailVOLUME FLOW UNBALANCES AND SHORTCUTS IN DECENTRALIZED AND CENTRALIZED VENTILATION UNITS – FIELD TESTS IN RESIDENTIAL BUILDINGS
Merzkirch, Alexander UL; Maas, Stefan UL; Scholzen, Frank UL et al

Scientific Conference (2014)

Centralized and decentralized mechanical ventilation have become state-of-the-art in modern energy-efficient residential buildings. Calculations for the energy demand of buildings are done with nominal ... [more ▼]

Centralized and decentralized mechanical ventilation have become state-of-the-art in modern energy-efficient residential buildings. Calculations for the energy demand of buildings are done with nominal values of the ventilation units, assuming a proper function of the devices. The used ventilation concepts may be divided into two main categories- centralized and decentralized units and both come with advantages and disadvantages in terms of energy efficiency. In Luxembourg, a comprehensive field test has been performed in order to evaluate and compare their performance in practice. It could be shown that ventilation systems often do not meet the expectations. High unbalances in volume flows, high sensitivity to pressure differences and recirculation were measured in several cases. Only a proper installation and balancing of the systems can ensure an energy efficient function. [less ▲]

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See detailModern damage detection by using static assessment methods for efficient rehabilitation
Scherbaum, Frank; Mahowald, Jean; Waldmann, Danièle UL et al

in Proceedings (2012, September)

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See detailLightweight woodchip concrete in composite constructions
Andreas, May; Waldmann, Danièle UL

in proceedings: p.349-352 (2012, August)

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See detailEvaluation of the bridge Champangshiel by using static assessment methods
Scherbaum, Frank; Mahowald, Jean; Waldmann, Danièle UL

in KIT Scientific Publishing, No. 026a, p. 323-329 (2012, July)

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See detailPilot tests with lightweight woodchip concrete in composite slab constructions
May, Andreas; Waldmann, Danièle UL

in KIT Scientific Publishing (Ed.) No. 073a, p. 323-329 (2012, June)

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See detailWIE VIEL ENERGIE VERBRAUCHEN NEUE UNTERRICHTS- UND BÜROGEBÄUDE IN LUXEMBURG?
Maas, Stefan UL; Scholzen, Frank UL; Thewes, Andreas UL et al

in Cahier Scientifique - Revue Technique Luxembourgeoise (2012)

In Luxemburg hat sich in den vergangenen Jahren der nationale Energieverbrauch ebenfalls verstärkt zum Gebäudesektor hin verändert. Während 1990 noch 71 % des gesamten Energieverbrauches auf den ... [more ▼]

In Luxemburg hat sich in den vergangenen Jahren der nationale Energieverbrauch ebenfalls verstärkt zum Gebäudesektor hin verändert. Während 1990 noch 71 % des gesamten Energieverbrauches auf den Industriesektor zurückzuführen waren und nur 20 % auf die Gebäude, hat sich dies bis zum Jahr 2009 deutlich verändert. Demzufolge entfallen nur noch 30 % auf den Industriesektor, 25 % auf Verkehr (nach Abzug der Treibstoffexporte) und 45 % auf den Verbrauch des Tertiären Sektors3, welcher sowohl die privaten und die öffentlichen Haushalte, als auch Dienstleistungsgebäude beinhaltet. Die Direktive 2010/31/EG2 fordert von den Mitgliedstaaten die nationalen Normen weiterhin zu verschärfen und Pläne zu erstellen, um die Anzahl an Niedrigstenergiegebäuden weiter zu erhöhen. Um die Energieströme in Gebäuden besser zu verstehen, Sparmaßnahmen zu erarbeiten und mögliche Bewertungen über das Energieeinsparpotential für Gebäude durchführen zu können, sind jedoch aussagekräftige Verbrauchsdatenanalysen notwendig, die leider oftmals noch nicht in verlässlicher Qualität vorliegen. In der Direktive wird zudem empfohlen für die Berechnung eine Unterteilung aller Gebäude in angemessene Kategorien vorzunehmen, welche von Einfamilienhäusern (EFH), über Bürogebäude und Unterrichtsgebäude bis hin zu Krankenhäuser, Hotels und Sportanlagen reicht. In einer ersten Studie der Universität Luxemburg4 wurden bereits neuere EFH in Luxemburg hinsichtlich ihres realen Energieverbrauches untersucht und ausgewertet. [less ▲]

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See detailStatic Analysis of new wall system realized by modular concrete blocks
Agaajani, Shahriar; Waldmann, Danièle UL

in proceedings: p.177-180 (2012)

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See detailStabilité de systèmes de murs en blocs de béton emboîtables sans joints en mortier
Agaajani, Shahriar; Waldmann, Danièle UL

Scientific Conference (2012)

Detailed reference viewed: 48 (11 UL)
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See detailStatic and dynamic testing on prestressed concrete slab elements with artificial bond deficiencies
Mahowald, Jean UL; Maas, Stefan UL; Waldmann, Danièle UL et al

in Proceedings of the 4th Bond in Concrete Conference, Vol. 1: General Aspects of Bond (2012)

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See detailDamage Identification and Localisation Using Changes in Modal Parameters for Civil Engineering Structures
Mahowald, Jean UL; Maas, Stefan UL; Waldmann, Danièle UL et al

in Proceedings of the International Conference on Noise and Vibration Engineering (2012)

Detailed reference viewed: 108 (37 UL)
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See detailExperimental and Numerical Investigation on Postcracking Behavior of Steel Fiber Reinforced Concrete
Michels, Julien; Christen, Christen; Waldmann, Danièle UL

in Engineering Fracture Mechanics (2012) (2012)

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See detailDynamic damage identification using linear and nonlinear testing methods on a two-span prestressed concrete bridge
Mahowald, Jean UL; Maas, Stefan UL; Scherbaum, Frank UL 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 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)

Detailed reference viewed: 88 (22 UL)