Energy consumption of non-retrofitted institutional building stock inLuxembourg and the potential for a cost-efficient retrofit

in Energy and Buildings (2016), 123(2016), 162-168

The public building stock of a country, consisting of schools, offices, accommodation facilities, single-and multi-family homes, accounts for a high consumption of electrical and heat energy. Therefore ... [more ▼]

The public building stock of a country, consisting of schools, offices, accommodation facilities, single-and multi-family homes, accounts for a high consumption of electrical and heat energy. Therefore, thisstock is often subject to actions with the goal of lowering this energy usage by increasing the efficiencyof those buildings. This is usually done by applying measures to the building envelope like insulationand/or new windows and by using a more efficient HVAC technology. But often, in the initial state, thecurrent energy consumption of such a stock is unknown or only known for single buildings. In this case,the calculation of energy and cost savings is either impossible or not exact. This paper shows a way toquantify and categorize the end-energy for heat use of the public building stock in Luxembourg, whichconsists of a gross area of 1.744 million m2. This analysis was carried out in cooperation with the nationaladministration of public buildings.A certain amount of sample buildings was analyzed and then separated into three groups of low,normal and high end-energy use. The boundaries of these groups were chosen according to literaturevalues, derived from European retrofit projects, which also served as the source for possible renovationcosts. This data was extrapolated to the whole stock. This information serves as a basis for future decisionsconcerning the retrofit of those buildings and makes a calculation of costs possible.As a result, the type of buildings with the highest potential for retrofit measures was identified. Schools,offices and accommodation facilities with a “high” consumption of more than 190 kWh/(m2a) show thehighest economic potential with retrofit costs of 0.04–0.08 D /kWh if their energy consumption is loweredto values of around 90–100 kWh. Other groups of buildings show higher costs of around 0.07–0.19 D /kWh. [less ▲]

Structural health monitoring based on static measurements with temperature compensation

in QUALITY SPECIFICATIONS FOR ROADWAY BRIDGES, STANDARDIZATION AT A EUROPEAN LEVEL (2016)

The paper presents the main results from static tests in a prestressed concrete beam taken out from a real bridge. The tests were achieved during about one month with several scenarios of damage that ... [more ▼]

The paper presents the main results from static tests in a prestressed concrete beam taken out from a real bridge. The tests were achieved during about one month with several scenarios of damage that loaded and unloaded states were monitored for each scenario. Damages in 4 levels were simulated by cutting prestressed tendons. There were 8 transducers distributed along the length’s beam to measure displacements. Deflection lines resulted from the static measurements from every state allow discovering the location of damages. Moreover, the calculation of slope and curvature lines leads also to very interesting issues for damage localization. [less ▲]

Messtechnische Ermittlung der U-Werte von Altbaufassaden im Vergleich mit Typologiewerten für den Gebäudebestand

in Bauphysik (2015)

Die Wirtschaftlichkeit von Renovierungsvorhaben an Altbauten hängt im Wesentlichen von der erwarteten Wertsteigerung, der Miethöhe und den zu erreichenden Energieeinsparungen ab. Um diese Einsparungen zu ... [more ▼]

Die Wirtschaftlichkeit von Renovierungsvorhaben an Altbauten hängt im Wesentlichen von der erwarteten Wertsteigerung, der Miethöhe und den zu erreichenden Energieeinsparungen ab. Um diese Einsparungen zu berechnen, wird ein rechnerischer Vergleich zwischen dem aktuellen Verbrauch und dem Verbrauch nach der Sanierung angestrebt. Zahlreiche Studien zeigen auf, dass der rechnerische Energiebedarf von Gebäuden häufig von dem tatsächlichen Verbrauch abweicht. Dies gilt vor allem für vor 1970 errichtete Altbauten. Ein wichtiger Eingangsparameter der Berechnungsmethodik sind die U-Werte der Aussenwände, welche typischerweise vom Energieexperten vor Ort aus Typologien des Gesetzgebers für die jeweilige Wandkonstruktion ausgewählt werden. In dieser Veröffentlichung werden Mess- und Simulationsergebnisse von verschiedenen Wandtypen präsentiert. Die ermittelten Werte lagen zwischen 0.9 und 1,2 W/(m2K) und somit deutlich unter den in Luxemburg angenommenen Typologiewerten von 1,4 bis 2,1 W/(m2K). Die beschriebenen Abweichungen zwischen Energiebedarfsberechnung und tatsächlichem Energieverbrauch können somit zum Teil auf fehlerhafte Annahmen des ausstellenden Experten vor Ort zurückgeführt werden, welche sich an Typologiewerten orientieren. [less ▲]

Primary energy used in centralized and decentralized ventilation systems measured in field tests in residential buildings

in Proceedings of the 26th AIVC Conference, Effective Ventilation in high performance buildings (2015, September)

Ventilation systems can save heat energy by using heat recovery, but consume electrical energy to power the fans. In practice, the energy efficiency of those systems can be lower than expected, when ... [more ▼]

Ventilation systems can save heat energy by using heat recovery, but consume electrical energy to power the fans. In practice, the energy efficiency of those systems can be lower than expected, when compared to the nominal values provided by the manufacturer. In this paper, results of a comprehensive field tests with 20 centralized and 60 decentralized ventilation systems for residential buildings and the calculation of the primary energy savings of those devices are presented. Factors like volume flow unbalances, shortcuts, temperature change rates and specific fan power have been addressed by tracer gas technology and other means and been used as input factors to calculate the primary energy balance of those devices. Every system showed positive primary energy savings. The mean value for centralized systems was 2.92 Wh/m3 with a high standard deviation of 2.23 Wh/m3, while the decentralized systems showed higher savings of around 4.75 Wh/m3 with a standard deviation of 0.01 to 0.15 Wh/m3. In general, the calculated savings in field tests were significantly lower compared to the case of using nominal values as input parameters. [less ▲]

Biomechanical properties of five different currently used implants for open-wedge high tibial osteotomy

in Journal of Experimental Orthopaedics (2015), 2(14),

Background: As several new tibial osteotomy plates recently appeared on the market, the aim of the present study was to compare mechanical static and fatigue strength of three newly designed plates with ... [more ▼]

Background: As several new tibial osteotomy plates recently appeared on the market, the aim of the present study was to compare mechanical static and fatigue strength of three newly designed plates with gold standard plates for the treatment of medial knee joint osteoarthritis. Methods: Sixteen fourth-generation tibial bone composites underwent a medial open-wedge high tibial osteotomyn(HTO) according to standard techniques, using five TomoFix standard plates, five PEEKPower plates and six iBalance implants. Static compression load to failure and load-controlled cyclic fatigue failure tests were performed. Forces, horizontal and vertical displacements were measured; rotational permanent plastic deformations, maximal displacement ranges in the hysteresis loops of the cyclic loading responses and dynamic stiffness were determined. Results: Static compression load to failure tests revealed that all plates showed sufficient stability up to 2400 N without any signs of opposite cortex fracture, which occurred above this load in all constructs at different load levels. During the fatigue failure tests, screw breakage in the iBalance group and opposite cortex fractures in all constructs occurred only under physiological loading conditions (<2400 N). The highest fatigue strength in terms of maximal load and number of cycles performed prior to failure was observed for the ContourLock group followed by the iBalance implants, the TomoFix standard (std) and small stature (sm) plates. The PEEKPower group showed the lowest fatigue strength. Conclusions: All plates showed sufficient stability under static loading. Compared to the TomoFix and the PEEKPower plates, the ContourLock plate and iBalance implant showed a higher mechanical fatigue strength during cyclic fatigue testing. These data suggest that both mechanical static and fatigue strength increase with a wider proximal T-shaped plate design together with diverging proximal screws as used in the ContourLock plate or a closed-wedge construction as in the iBalance design. Mechanical strength of the bone-implant constructs decreases with a narrow T-shaped proximal end design and converging proximal screws (TomoFix) or a short vertical plate design (PEEKPower Plate). Whenever high mechanical strength is required, a ContourLock or iBalance plate should be selected. [less ▲]

A semi-centralized, valveless and demand controlled ventilation system in comparison to other concepts in field tests

in Building and Environment (2015), 93(21-26),

The idea of adapting the air supply rate to the actual demand in a building is not a new one. In commercial buildings it is already state-of-the-art to establish a demand controlled ventilation, where the ... [more ▼]

The idea of adapting the air supply rate to the actual demand in a building is not a new one. In commercial buildings it is already state-of-the-art to establish a demand controlled ventilation, where the level of air ow is based on sensors or time control. In residential buildings however, mechanical ventilation systems, whether centralized or decentralized, are in most cases operated in a constant modus, providing fresh air regardless if the fresh air is needed or not, even though the technology and the components needed for demand controlled ventilation exist and can be purchased at reasonable prices. In this article, results of eld tests with a semi-centralized demand feedback-controlled ventilation system are shown and compared to outcomes with other demand controlled systems. The semi-centralized prototype includes decentralized fans per ventilation zone, making a room-wise ventilation possible and valves to balance the system hydraulically unnecessary. It is shown that each presented concept of demand controlled ventilation can save energy by decreasing the operational time or the mean airflow rate without compromising air quality. Concepts which make a zone- or even a room-wise control of air ow possible, showed the highest energy saving potential of up to two-thirds compared to a system operating at constant flow rates. In addition to the energy savings due to decreased operational time, the maintenance and lter costs are decreased while the user comfort is increased, as natural ventilation in spring, summer and autumn may easily be added when delta T between inside and outside is small. [less ▲]

Design, Repeatability, and Comparison to Literature Data of a New Noninvasive Device Called "Rotameter" to Measure Rotational Knee Laxity

in International Scholarly Research Notices Orthopedics (2015), Volume 2015, Article ID 439095

The present paper deals with the design, the repeatability, and the comparison to literature data of a new measuring device called “Rotameter” to characterize the rotational knee laxity or the tibia ... [more ▼]

The present paper deals with the design, the repeatability, and the comparison to literature data of a new measuring device called “Rotameter” to characterize the rotational knee laxity or the tibia-femoral rotation (TFR). The initial prototype P1 of the Rotameter is shortly introduced and then modified according to trials carried out on a prosthetic leg and on five healthy volunteers, leading therefore to an improved prototype P2. A comparison of results obtained from P1 and P2 with the same male subject shows the enhancements of P2. Intertester and intratester repeatability of this new device were shown and it was observed that rotational laxities of left and right knees are the same for a healthy subject. Moreover, a literature review showed that measurements with P2 presented lower TFR values than other noninvasive devices.The measured TFR versus torque characteristic was quite similar to other invasive devices, which are more difficult to use and harmful to the patient. Hence, our prototype P2 proved to be an easy-to-use and suitable device for quantifying rotational knee laxity. A forthcoming study will validate the Rotameter thanks to an approach based on computed tomography in order to evaluate its precision. [less ▲]

Fatigue in the Core of Aluminium Honeycomb Panels: Lifetime Prediction compared to Fatigue Tests

in International Journal of Damage Mechanics (2014), 23 no.5

In comparison to their weight, honeycomb composite structures have a high bending stiffness, which makes them very suited for every application where little weight is important, like airplanes, railway ... [more ▼]

In comparison to their weight, honeycomb composite structures have a high bending stiffness, which makes them very suited for every application where little weight is important, like airplanes, railway-cars and vehicles. The sandwich panels consist of two thin and stiff aluminium face sheets , which are bonded to a thick and lightweight aluminium honeycomb core. These structures are subjected to dynamic loading. However, in literature, there are hardly any fatigue properties of the honeycomb core described. The fatigue properties of the core are investigated using the finite element method and experiments. Depending on the load application, the honeycomb core fails either through core indentation or shear failure. For a fatigue prediction, both failure modes have to be investigated. Additionally the physical behavior of the honeycomb core is depending on the orientation of the core. Hence, fatigue tests were conducted in three directions of the core: the stiffest direction, the most compliant direction and the direction with the highest stresses. A three-point bending test setup was built to study the fatigue properties of the honeycomb core. Several fatigue tests were carried out with a load ratio of R=0.1 (maximum load 10 times bigger than minimum load) and the fatigue diagrams being illustrated. Additionally, Food-Cart Roller Tests (wheels of a cart rolling in a circle on a floor panel) were done to dynamically test the panels in every angle. The sandwich structures were modeled with the ANSYS finite element software. The simulations, which were used to determine the stress amplitudes in the specimens, are described in the following pages. In addition, buckling analyses were used to examine core indentation failure. Based on these simulations, failure predictions can be made. The fatigue life of the examined specimens is successfully approximated in this manuscript, with the lifetime analysis being based on the FKM-guideline (error less than 14% in load amplitude). [less ▲]

Some conclusions from the measurements of temperatures and their gradients on eigenfrequencies of bridges

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 ▲]

Prosthesis head

Patent (2014)