References of "Maas, Stefan 50002241"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailPrimary energy used in centralized and decentralized ventilation systems measured in field tests in residential buildings
Merzkirch, Alexander UL; Maas, Stefan UL; Scholzen, Frank UL et al

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 ▲]

Detailed reference viewed: 157 (25 UL)
Full Text
Peer Reviewed
See detailDesign rules for autofrettage of an aluminium valve body
Sellen, Stephan UL; Maas, Stefan UL; Andreas, Thomas et al

in Fatigue & Fracture of Engineering Materials & Structures (2015)

The following paper is intended to improve the fatigue behaviour of a complex aluminium valve geometry under high internal cyclic pres sure loading. The autofrettage process helps to increase the f atigue ... [more ▼]

The following paper is intended to improve the fatigue behaviour of a complex aluminium valve geometry under high internal cyclic pres sure loading. The autofrettage process helps to increase the f atigue durability and a simple, but efficient design method for this proces s is deployed. Based o n non-linear material’s behaviour, fin ite eleme nt simulations of t he crack-free geometry help to determine the minimum and maximum autofrettage pressure to be used, without iterative crack simulations , which would require higher computational effort. Material tests under inverse plastifications were performed in order to determine the correct material model. The derived design method was validated with simplified specimens subjected to different autofrettage pressure levels and su bsequent cyclic fatigue tests. [less ▲]

Detailed reference viewed: 180 (23 UL)
Full Text
Peer Reviewed
See detailBiomechanical properties of five different currently used implants for open-wedge high tibial osteotomy
Diffo Kaze, Arnaud UL; Maas, Stefan UL; Waldmann, Danièle UL et al

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 ▲]

Detailed reference viewed: 197 (34 UL)
Full Text
Peer Reviewed
See detailImproved design of threaded connections by autofrettage in aluminium compounds for cyclic high pressure loading: design calculations and experimental verification
Sellen, Stephan; Maas, Stefan UL; Andreas, Thomas et al

in Fatigue & Fracture of Engineering Materials & Structures (2015)

Threaded connections in an aluminium valve body under high internal swelling pressure are investigated. A static straining process called autofrettage leads to an improved fatigue behaviour of the ... [more ▼]

Threaded connections in an aluminium valve body under high internal swelling pressure are investigated. A static straining process called autofrettage leads to an improved fatigue behaviour of the aluminium component, while normally the threaded connections are unloaded during this autofrettage. But by unloading the thread during autofrettage the first loaded thread flank became the weakest point of this valve component. This effect is analyzed with non-linear finite element simulations, FKM guideline for fatigue assessment and by experimental testing. The analytical and experimental parts match very well and it can be shown that a well-designed autofrettage without unloading the threaded connection is helpful for the aluminium thread and extends its fatigue lifetime, as compressive residual stresses and an equalized stress distribution over the thread flanks can be generated. Finally different materials were chosen for the plug or screw and this effect for cyclic loading is shortly analyzed. [less ▲]

Detailed reference viewed: 154 (14 UL)
Full Text
Peer Reviewed
See detailA semi-centralized, valveless and demand controlled ventilation system in comparison to other concepts in field tests
Merzkirch, Alexander UL; Maas, Stefan UL; Scholzen, Frank UL et al

in Building & 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 ▲]

Detailed reference viewed: 149 (30 UL)
Full Text
Peer Reviewed
See detailDesign, Repeatability, and Comparison to Literature Data of a New Noninvasive Device Called "Rotameter" to Measure Rotational Knee Laxity
Neumann, Simon UL; Maas, Stefan UL; Waldmann, Danièle UL et al

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 ▲]

Detailed reference viewed: 171 (38 UL)
Full Text
Peer Reviewed
See detailUse of a Computed Tomography Based Approach to Validate Noninvasive Devices to Measure Rotational Knee Laxity
Neumann, Simon UL; Maas, Stefan UL; Waldmann, Danièle UL et al

in International Scholarly Research Notices (2015)

The purpose of this study is to validate a noninvasive rotational knee laxity measuring device called “Rotameter P2” with an approach based on Computed Tomography (CT). This CT-approach using X-rays is ... [more ▼]

The purpose of this study is to validate a noninvasive rotational knee laxity measuring device called “Rotameter P2” with an approach based on Computed Tomography (CT). This CT-approach using X-rays is hence invasive and can be regarded as a precise reference method that may also be applied to similar devices. An error due to imperfect femur fixation was observed but can be neglected for small torques. The most significant estimation error is due to the unavoidable soft tissues rotation and hence flexibility in the measurement chain. The error increases with the applied torque.The assessment showed that the rotational knee angle measured with the Rotameter is still overestimated because of thigh and femur displacement, soft tissues deformation, and measurement artefacts adding up to a maximum of 285% error at +15Nm for the Internal Rotation of female volunteers. This may be questioned if such noninvasive devices for measuring the Tibia-Femoral Rotation (TFR) can help diagnosing knee pathologies and investigate ligament reconstructive surgery. [less ▲]

Detailed reference viewed: 141 (31 UL)
Full Text
Peer Reviewed
See detailFatigue in the Core of Aluminium Honeycomb Panels: Lifetime Prediction compared to Fatigue Tests
Wahl, Laurent UL; Maas, Stefan UL; Waldmann, Danièle UL et al

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 ▲]

Detailed reference viewed: 191 (23 UL)
Full Text
Peer Reviewed
See detailA signal processing method to remove environmental effects for damage detection in bridge structures
Nguyen, Viet Ha UL; Mahowald, Jean UL; Maas, Stefan UL et al

Poster (2014, July)

This paper consists in damage diagnosis for several real bridges in Luxembourg. Before, different analysis methods were applied to the data measured from these structures showing interesting results ... [more ▼]

This paper consists in damage diagnosis for several real bridges in Luxembourg. Before, different analysis methods were applied to the data measured from these structures showing interesting results. However, some difficulties are faced, especially due to environmental influences (temperature and soil-behaviour variations) which overlaid the structural changes caused by damage or confuse damage levels. These environmental effects are investigated in detail and removed in this work through Principal Component Analysis. Damage index is based on outlier analysis [less ▲]

Detailed reference viewed: 157 (31 UL)
Full Text
Peer Reviewed
See detailDamage detection in bridge structures including environmental effects
Nguyen, Viet Ha UL; Mahowald, Jean UL; Golinval, Jean-Claude et al

in the Ninth International Conference on Structural Dynamics EURODYN 2014 (2014, July)

Damage identification for two real big bridges in Luxembourg is carried out in this paper. Vibration responses were captured from different types of excitation such as measurable and adjustable harmonic ... [more ▼]

Damage identification for two real big bridges in Luxembourg is carried out in this paper. Vibration responses were captured from different types of excitation such as measurable and adjustable harmonic swept sine excitation and hammer impact. Before, different analysis methods were applied to the data measured from these structures showing interesting results. However, some difficulties are faced, especially due to environmental influences (temperature and soil-behaviour variations) overlaid to the structural changes caused by damage. These environmental effects are investigated in detail in this work. First, the modal parameters are identified from the response data by means of Wavelet Transform. In the next step, they are stochastically collected and processed through Principal Component Analysis. Damage index is based on outlier analysis. [less ▲]

Detailed reference viewed: 122 (30 UL)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 186 (31 UL)
Full Text
Peer Reviewed
See detailUse Of Time- And Frequency-Domain Approaches For Damage Detection In Civil Engineering Structures
Nguyen, Viet Ha UL; Mahowald, Jean UL; Maas, Stefan UL et al

in Shock and Vibration (2014), 2014

The aim of this paper is to apply both time- and frequency-domain-based approaches on real-life civil engineering structures and to assess their capability for damage detection. The methodology is based ... [more ▼]

The aim of this paper is to apply both time- and frequency-domain-based approaches on real-life civil engineering structures and to assess their capability for damage detection. The methodology is based on Principal Component Analysis. The first structure is the Champangshiehl Bridge located in Luxembourg. Several damage levels were intentionally created by cutting a growing number of prestressed tendons and vibration data were acquired by the University of Luxembourg for each damaged state. The second example consists in reinforced and prestressed concrete panels. Successive damages were introduced in the panels by loading heavy weights and by cutting steel wires. The illustrations show different consequences in damage identification by the considered techniques [less ▲]

Detailed reference viewed: 123 (12 UL)
Full Text
See detailProsthesis head
Kelm, Jens; Maas, Stefan UL; Collé, Claude UL

Patent (2014)

Detailed reference viewed: 291 (69 UL)
Full Text
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 ▲]

Detailed reference viewed: 457 (83 UL)
Full Text
See detailProceedings of IMAC XXXII Dynamics of Coupled Structures
Nguyen, Viet Ha UL; Mahowald, Jean UL; Golinval, Jean-Claude et al

in Firkret, Necati Catbas (Ed.) Damage Detection in Civil Engineering Structure Considering Temperature Effect (2014, February)

This paper concerns damage identification of a bridge located in Luxembourg. Vibration responses were captured from measurable and adjustable harmonic swept sine excitation and hammer impact. Different ... [more ▼]

This paper concerns damage identification of a bridge located in Luxembourg. Vibration responses were captured from measurable and adjustable harmonic swept sine excitation and hammer impact. Different analysis methods were applied to the data measured from the structure showing interesting results. However, some difficulties arise, especially due to environmental influences (temperature and soil-behaviour variations) which overlay the structural changes caused by damage. These environmental effects are investigated in detail in this work. First, the modal parameters are identified from the response data. In the next step, they are statistically collected and processed through Principal Component Analysis (PCA) and Kernel PCA. Damage indexes are based on outlier analysis. [less ▲]

Detailed reference viewed: 90 (8 UL)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 384 (57 UL)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 81 (16 UL)
Full Text
Peer Reviewed
See detailSimulated and experimental results on heat recovery from hot steel beams in a cooling bed applying modified solar absorbers
Tarrés Font, Joana UL; Maas, Stefan UL; Scholzen, Frank UL et al

in Journal of Cleaner Production (2014), (68), 261-271

In recent years, the steel industry has undertaken efforts to increase energy efficiency by reducing energy consumption and recover otherwise lost heat. About 60% of the energy consumed in a steel plant ... [more ▼]

In recent years, the steel industry has undertaken efforts to increase energy efficiency by reducing energy consumption and recover otherwise lost heat. About 60% of the energy consumed in a steel plant is lost in cooling beds where the hot steel beams are cooled down by natural convection and radiation. In this paper, the potential of heat recovery by radiation in a cooling bed was determined. Firstly, numerical simulations of the heat flux were done and validated with experimental measures. Secondly, a pilot test to recover the heat with modified solar absorbers was installed at the side of the cooling bed. The standard solar panels were painted with high absorption paint in the wavelength range of the hot beams. The results showed that up to 1 kW/m2 could be recovered with a temperature of 70°C at the side of the cooling bed, with a thermal efficiency of approximately 40%. As the experimental results were promising, further research is suggested to find an adequate selective coating and glazing. This would maximize the absorption at the wavelength range of the hot beams and minimize the emissivity at operational temperature of the absorber (100°C). Additionally, it would be of interest to find the optimum position for the absorbers in the cooling bed, which maximizes the heat recovery and does not interfere in the production process. [less ▲]

Detailed reference viewed: 180 (6 UL)
See detailMeasured and perceived indoor comfort versus energy efficiency and users‟ control in Luxembourg‟s new school buildings
Brensing, Jessica UL; Schweizer-Ries, Petra; Thewes, Andreas UL et al

Scientific Conference (2013, September)

Room climate can be evident for job productivity and individual ́s health. Its realisation is often of high relevance for the building ́s energy consumption e.g. air conditioning vs. natural ventilation ... [more ▼]

Room climate can be evident for job productivity and individual ́s health. Its realisation is often of high relevance for the building ́s energy consumption e.g. air conditioning vs. natural ventilation. New school buildings in Luxembourg differ significantly regarding to energy consumption, heating, air-conditioning technology and technical control as well as interaction means given to the user. Several studies have shown that personal control plays an important role for the satisfaction with the room climate. Central research question was, how the technological control has to be designed that energy is used efficiently and users are still satisfied with the room climate. In this study technical features to control the room climate e.g. features for ventilation, opening windows and heating systems were summarized to an overall control factor to be compared with perceived control by the users. Physical room climate and its users ́ satisfaction level were measuredas well as the buildings ́ individual energy consumption levels were taken into account. 342 Teachers were asked by a standardised questionnaire during winter 2010/2011 in 31 new school buildings in Luxembourg, in 17 schools technical devices for air temperature, quality and humidity were installed. The results show a strong correlation between perceived control and room climate satisfaction as well as a significant correlation between the technical control factor and perceived control. Further results will be examined. [less ▲]

Detailed reference viewed: 121 (19 UL)
Full Text
See detailDETECTION AND LOCALISATION OF DAMAGE ON INDUSTRIALLY PRODUCED CONCRETE SLABS THROUGH TIME- AND FREQUENCY-DOMAIN APPROACHES
Nguyen, Viet Ha UL; Mahowald, Jean UL; Golinval, Jean-Claude et al

in Carrera, E.; Miglioretti, F; Petrolo, M. (Eds.) 6th ECCOMAS Thematic Conference on Smart Structures and Materials (SMART2013), Torino 24-26 June 2013 (2013, June)

The objective of this work is to address the problem of damage detection in civil engineering structures using non-destructive techniques and dynamic measurements. To this purpose, time- or frequency ... [more ▼]

The objective of this work is to address the problem of damage detection in civil engineering structures using non-destructive techniques and dynamic measurements. To this purpose, time- or frequency-domain methods are used for the diagnostics. It consists in practical output-only techniques as Stochastic Subspace Identification (SSI) for modal identification or Enhanced Principal Component Analysis (EPCA) for detecting the presence of damage. The use of the Hankel matrix instead of the observation matrix improves effectively the robustness of these methods. Damage localization is based on Frequency Response Functions (FRFs) and sensitivity analysis of PCA results. The efficiency of the above-mentioned methods has been demonstrated in earlier studies mainly on numerical examples and small-scale laboratory experiments. It was also tested successfully on industrial examples to perform machine condition monitoring using a reduced set of sensors. In this work, the investigation is performed on precast prestressed and non-prestressed concrete slabs. Successive damages were artificially introduced in the slabs by loading heavy weights and by cutting steel wires, which induced cracks in the structure. The examples show the consequences of the considered techniques for damage identification. The results that are very different between prestressed and non-prestressed slabs may be used as input for the condition control of this kind of structures. [less ▲]

Detailed reference viewed: 83 (15 UL)