Shear tests on external clay unit masonry walls / Monolithische Ziegelaußenwände unter Schubbeanspruchung

Monolithic external walls are commonly made of thermally insulated clay blocks that do not require any additional external thermal insulation such as an external thermally insulated composite system (ETICS). To reduce thermal bridge losses, the support length (a) of the slab on the wall is shorter than the wall thickness (t): a < t. The influence on the shear capacity of the respective masonry walls has not yet been tested and analysed. The paper presents the results of shear tests on monolithic external walls with a reduced support length under static‐cyclic and pseudo‐dynamic loading. The test results will be compared with the shear resistance calculated according to DIN EN 1996 with consideration of the German National Annex and the results according to the relevant Technical Approval.     

A new prefabricated external thermal insulation composite board with ceramic finishing for buildings retrofitting

Given the high energy consumption connected to old buildings and their large environmental impact, there is a strong need for effective solutions for the building envelope retrofitting. Among these solutions, external thermal insulation composite systems (ETICS) have found large application in recent decades. In this paper a new kind of large-size thermal insulation composite boards, prefabricated using porcelain stoneware slab finishing, was developed. Different thermal insulating materials and adhesives, with and without glass fibre mesh, were tested by both current methodologies and purposely designed tests, in order to assess their physical–mechanical properties and durability performance, finally selecting the most suitable materials for the composite board. The strong points of this composite board are mainly: (i) its short placing time and improved execution quality, due to prefabrication; (ii) its high aesthetical value; (iii) its high durability, as the finishing layer is mostly insensible to weathering. The results highlight the good performances of the prefabricated composite board developed in this study (generally higher than current ETICS). The testing procedure followed in this study is also meant to give a contribution to the establishment of methodologies for the selection and durability assessment of materials for the building envelope retrofitting.     

Eignungsprüfungen an Bauteilen und Bausystemen

Suitability tests on building components and systems Xella produces building materials according to European product standards and European technical approvals, respectively. Products of a new type or manufactured with a new raw material undergo an internal release process in which the requirements coming from standards, approvals and supplementary national application documents are proved. In addition, the interaction of the Xella building materials with further products applied on construction site are tested. This includes systems like masonry, external thermal insulation composite systems (ETICS), rendering systems, large‐format reinforced components, structures with fixing elements and much more. The scope of the system tests is determined by the intended application and by Xella internal requirements which, in many points, exceed the sets of rules. This article demonstrates the spectrum of these tests and, using the example of the render and mortar tests, the principle of the internal test guidelines.     

Bewertung des Scherfestigkeitsverhältnisses für Schrauben festgelegter Festigkeitsklassen

The knowledge of the shear capacity of bolts is essential for the design of shear joints. Preloading of joints in steel constructions is in more than 90 % of cases not necessary [1]. In aircraft construction, bearing type fitted joints are very common. In rail vehicle construction these joints are primarily used for risk class G (low) (DIN 25201‐7 [2]). In machine and plant construction, the bearing type joint is not common, but there is a demand that slip resistant joints are designed for an overload against a shearing/ bolt‐bearing‐stress [3]. In the course of earlier investigations on the shear strength ratio, discrepancies for the design according to the various regulations were determined. For this purpose, the authors of this paper carried out over 500 shear tests. The bolts were tested with the nominal diameters ranging from M8 up to M20 with grade 4.6 to 10.9 to determine the shear strength ratio. The focus was on the influences of the single‐/double shear test arrangement as well on the determination of a suitable method for statistical evaluation of the test results. Finally, recommendations are made for the future calculation of the shear resistance.     

Oberflächenenergetische Charakterisierung

Surface Energetic Characterization of Nanoscale Fillers and Elastomers Almost any technically used rubber material is filled with particles in nanometer size, by which the properties of the material can be specific controlled. In modern car tires the used fillers have crucial influence on driving security (wet grip and ice grip), on fuel consumption (rolling resistance) and on the cost‐effectiveness (life time of the tire) [1].The first fillers used in rubber application were carbon blacks; actually in passenger car tires mostly surface modified silica is applied. The implementation of novel filler systems like organophilic modified layered silicates (organo‐clays) or carbon nanotubes is subject of intense research [2,3]. Surface energy and –polarity of the filler surface is a crucial, but often underestimated determining factor. All surface properties of rubber and filler have to be well balanced to get the nanoscale filler particles finely dispersed in the rubber matrix and also to obtain a good adhesion between polymer and filler surface.     

Komplexe zur Herstellung niederenergetischer Oberflächen

Low Surface Energie from Waterborne Nano‐Dispersions of Polymer Complexes Waterborne nano‐dispersions with a supra‐molecular ordering were prepared by using a commercially available polyelectrolyte and a fluorinated surfactant. From this complex, thin coatings on chemically very different surfaces can be prepared at room temperature without using organic solvents. The resulting coatings are smooth, optically invisible and have low surface energies. Critical surface tensions according to Zisman [16] were determined to be in the range from 5.7 to 13.1 mN/m and dispersive surface energies according to the Girifalco‐Good‐Fowkes‐Young equation [17, 18] are in the range from 10.2 to 10.7 mN/m. The low surface energies observed for fluorinated polyelectrolyte surfactant complexes as well as their liquid crystalline‐like structures are caused by the strong segregation tendency of fluorinated and ionic moieties [27].     

Tragfähigkeitstafeln für unbewehrtes Mauerwerk nach DIN EN 1996‐3/NA:2019‐12

Load‐bearing capacity tables for unreinforced masonry according to DIN EN 1996‐3/NA:2019‐12 Practical design aids are important tools in the day‐to‐day business of structural design. The design of primarily vertically loaded masonry walls in usual building construction can be carried out with the help of so‐called load‐bearing capacity tables. A table value is read off exclusively as a function of the geometric conditions, which – multiplied by the masonry compressive strength – results in the load‐bearing capacity of the wall for cold design and in case of fire. By comparing the acting and resisting force, the verification of structural design can be provided in a simple and yet economical form. The bearing capacity tables based on the simplified calculation methods according to DIN EN 1996‐3/NA:2019‐12 [1], [2] and DIN EN 1996‐1‐2/NA:2013‐06 [3], [4] are presented in this paper. Compared to the previous edition of Part 3 of Eurocode 6, the extended scope of application is taken into account, as well as the normative changes to the construction method with partially supported slabs.     

Zur Viskosität von Glasschmelzen und porösen Sintergläsern

Qn the viscosity of glass melts and porous sintered glasses Suspensions of solid phase particles in molten glasses modify their flow behavior and therefore their viscosity. This work deals with the dependence of the effective viscosity (η_eff) of isotropic suspensions on the concentration of the solid phase particles. Independently of the shape of the inclusions the values of the effective viscosities lie between upper [η_eff = η_L (1 ? C_D)^?14 ]and lower bounds [η_eff = η_L (1 ? C_D)^?3], where η_L is the viscosity of the molten glass and C_D is the volume fraction of solid inclusions. The lower bound is also valid for the effective viscosity of suspensions containing spherical inclusions. Pores present in a glass matrix affect its flow behavior and consequently its creep and sintering behavior. The effective viscosity of porous glasses (η_P) as a function of the volume fraction of pores, or porosity (P), also varies between and upper [η_P = η_M (1 ? P)^1.04] and a lower bound [η_P = η_M (1 ? P)¹⁴], where η_M is the viscosity of the nonporous glass matrix. For spherical porosity the equation is: Measured values for the viscosity of different suspensions as reported in the literature as well as own experimental data on two glass-solid systems are compared with the theoretical values predicted by these equations. In a similar way literature data for the viscosity of porous sintered glasses are compared with the respective equations. In all cases a fair agreement between experiment and theory was found in some cases the agreement was excellent. Therefore the presented equations constitute a reliable approach for the prediction of the viscosity of suspensions and porous sintered glasses and since they do not contain fitting parameters, they are of substantial practical relevance (for a comprehensive english treatment of the matter compare Glastechnische Berichte, Proc. Otto-Schott-Colloquium 1994).     

Entwicklung von hybriden Wärmedämmsteinen aus LAC

Die aktuell oftmals diskutierte Notwendigkeit der nachhaltigen Reduktion des Verbrauchs an Heizenergie bzw. der Reduktion des CO2‐Austoßes und die damit immer stärker werdende Forderung nach einem baulichen Wärmeschutz führten an der Universität Luxembourg dazu, ein Projekt auf den Weg zu bringen, welches das Ziel verfolgt, mittels hybrider Mauersteinkonstruktionen die Transmissionswärmeverluste durch die Außenwand weiter zu begrenzen. Mit der Energieeinsparverordnung (EnEV) in Deutschland und dem “règlement grand‐ducal Performance Energétique des b?timents d?habitation” [1] in Luxemburg bestehen neben der Anforderungsgröße des Jahresprimärenergiebedarfs auch über maximal festgesetzte Wärmedurchgangskoeffizienten U Anforderungen an die Transmissionswärmeverluste durch die Gebäudehülle. In Luxemburg beträgt der aktuelle Grenzwert zur Erfüllung des Mindestwärmeschutzes für Außenwände zur Zeit 0,32 W/m2K. Um den aktuellen Stand der Technik auf dem freien Markt festzuhalten, wurde zu Beginn des Projektes mit einer Marktstudie an 12 unterschiedlichen Wärmedämmsteinen aus verschiedenen europäischen Ländern begonnen. Dabei fiel das große Optimierungspotential der klassischen Wärmedämmblöcke aus haufwerksporigem Leichtbeton (LAC) in thermischer und statischer Hinsicht auf. Wie die Marktstudie zeigt, können mit klassischen monolithischen Wärmedämmblöcken (Vbl SW, Hbl) die deklarierten bzw. angestrebten Grenzwerte der Wärmeleitfähigkeit bei gleichzeitiger Einhaltung der Rohdichteklasse und Druckfestigkeit nicht immer gezielt erreicht werden. Es ist daher ratsam, eine Funktionstrennung der statisch und thermisch wirksamen Schichten im Steinquerschnitt vorzunehmen. Ein Weg zur Entwicklung von Mauersteinen mit Funktionstrennung der Trag‐ und Dämmschichten wird in diesem Beitrag aufgezeigt. Development of new heat‐insulating masonry blocks made of LAC. The actual discussion of the necessity of sustainable reduction of primary energy for heating of housing structures and of the reduction of CO2‐emissions led the University of Luxembourg to issue a project aimed to develop hybrid lightweight concrete blocks with high heat‐insulating properties. The progressing Energy Saving Regulation (EnEV) in Germany and the grand‐ducal Regulation in Luxembourg [1] are limiting the annual primary energy consumption for housing structures and office buildings. Supplementary, these regulations are also limiting the heat transfer coefficient U for the transmission of the heat flow through the outer walls. In Luxembourg e.g. the actual U‐value is limited to maximal 0,32 W/m2K. Based on the measured values, the static and thermal properties of the materials themselves (e.g. lightweight concrete with open structure) as well as the whole masonry bricks and blocks, taken from the European free market, were tested and simulated by the finite element method to study their weak spot and to use this experience for the construction of new prototypes. It was revealed that it is suggestive to separate the load bearing from a thermal construction part in the masonry block. The market study showed, that is only possible to reach certainly the declared limit values of the thermal and mechanical properties of the masonry block by separating the load‐bearing from the thermal function of the block.     

Electronic properties of AlVO<Subscript>4</Subscript> for gas sensor applications

The binary oxide AlVO₄ is being proposed as a new gas sensor material. An X-ray investigation, IR spectrum analysis, resistivity and a calculation of the electronic structure of this compound have been carried out in order to determine its structural, absorptive and sensor properties. The fragment [Al₃V₃O₂₃]¹⁸⁻ is the chain chosen to study the electronic properties of AlVO₄ in the framework of the frontier orbital theory and the interaction between molecules has been described by the Molecular Electrostatic Potential (MEP). The vibration analysis and the simulated infrared spectrum (IR) were calculated for the unit [Al₃V₃O₂₃]¹⁸⁻ and a comparative analysis with the experimental spectrum of AlVO₄ is also presented.     

Schallemissionsanalyse an kurzglasfaserverstärkten Thermoplasten: Einfluß der Glasfaserlängenverteilung

Acoustic Emission Analysis on Short Glass Fibre Reinforced Thermoplastics (GRP). – The Influence of Fibre length Distribution In this work a model is developed which relates the length of the glass fibres to the acoustic emission curve. In this model if one assumes that it is possible to strain the matrix infinitely then the emitted acoustic emission due to fibre fracture can be qualitatively analysed. It is also assumed that the mean length of the fibres, as related to their diameter, is considered to be the most important parameter for the probability of a fibre to fracture. This probability B, is 1 for a long thin fibre, and with an ever decreasing fibre length, this value tends towards O. It is possible, with these assumptions, to predict that the acoustic emission curve will have the form ?B exp?B, where ? is the applied strain. This model is supported by experimental results.     

Reaction of Np(VI) with cyclohexanediaminetetraacetic acid in HClO<Subscript>4</Subscript> solutions

The stoichiometry of the reaction of Np(VI) with cis-cyclohexanediaminetetraacetic acid (CHDTA, H4chdta) in 0.05 M HClO₄ solution was studied by spectrophotometry. With Np(VI) in excess, 1 mol of the complexone converts 4 mol of Np(VI) into Np(V). In 0.115–0.98 M HClO₄ solutions (the ionic strength of 1.0 was supported with LiClO₄) containing 3–29 mM CHDTA at 20–45°С, Np(VI) at a concentration of 0.2–3.3 mM is consumed in accordance with the first-order rate law until less than 40% of Np(VI) remains. After that, the reaction decelerates. The reaction rate has first order with respect to [CHDTA] and the order of–1.2 with respect to [H⁺]. The activated complex is formed with the loss of one and two Н⁺ ions. The activation energy is 82.3 ± 3.8 kJ mol^–1.     

Enhanced photoluminescence of CoWO<Subscript>4</Subscript> in CoWO<Subscript>4</Subscript>/PbWO<Subscript>4</Subscript> nanocomposites

CoWO₄/PbWO₄ nanocomposites were successfully synthesized at room temperature (RT) by co-precipitation route without using any templates or surfactants and sintered at 600 °C for good crystallization. The sintered samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy and Zeta potential measurements. UV–Visible diffuse reflectance spectroscopy, photoluminescence (PL) and PL lifetime were studied at RT. The results indicate that the composites have two-phase composition: CoWO₄ and PbWO₄. SEM micrograph and zeta potential measurements reveal particle agglomeration. The intrinsic PL peak emission at 467 nm of CoWO₄ nano sample was enhanced upto four times by optimizing the atomic ratio of Pb/Co concentration. The interconnected interface of CoWO₄/PbWO₄ nanocomposites could have led to increase in number of recombination of electron hole pairs in CoWO₄ and enhanced its intrinsic PL emission intensity. The mechanism of enhanced PL emission for the CoWO₄/PbWO₄ nanocomposites can be attributed to charge transfer between [WO₄]^2? and [WO₆]^6? complexes due to intra particle agglomeration leading to possible interface.     

Nachhaltigkeitsbewertung von Gebäuden

Die Kriterien des nachhaltigen Bauens stellen besondere Anforderungen an die Planung, Errichtung und Nutzung von Gebäuden. Das Hauptaugenmerk liegt gleichermaßen auf umweltbezogenen, wirtschaftlichen und sozialen Aspekten. Das deutsche Zertifizierungssystem für die Nachhaltigkeitsbewertung von Gebäuden wurde im Jahr 2009 vom Bundesministerium für Verkehr, Bau und Stadtentwicklung (BMVBS) eingeführt. Es dient sowohl als Instrument zur Planung und zur Qualitätssicherung der Prozesse Ausführung und Betreiben als auch zur Bewertung von Gebäuden. Im Unterschied zu anderen Zertifizierungssystemen wie LEED (Leadership in Energy and Environmental Design, USA) und BREEAM (Building Research Establishment Environmental Assessment Method, GB) zeichnet sich das Deutsche Gütesiegel dadurch aus, dass alle drei Säulen der Nachhaltigkeit gleichwertig berücksichtigt sind. Das Deutsche Gütesiegel basiert auf den aktuell geltenden Normen und Regelwerken und verbindet so die regulären Planungsanforderungen mit den Kriterien des nachhaltigen Bauens. Diese sind bereits am Beginn der Planungsphase zu berücksichtigen. Gleichzeitig sind Kenntnisse über das Bewertungssystem für die Nachhaltigkeit von Gebäuden erforderlich. Der Sachstandbericht des Deutschen Beton‐ und Bautechnik‐Vereins E.V. gibt einen Überblick über die Nachhaltigkeitskriterien des Deutschen Gütesiegels und deren Bewertung. Die Umsetzung des Zertifizierungssystems wird anhand eines erfolgreich zertifizierten Verwaltungsgebäudes erläutert. Sustainable Building Certification in Germany. Sustainable building involves specific requirements to be met by construction. Its introduction implements a strategy for building works which will gear the design, construction and use of buildings and landholdings to sustainability. The main emphasis is put on ecological, economic and social aspects. In 2009, the German Federal Ministry of Transport, Building, and Urban Development (BMVBS) introduced the German Sustainable Building Certification [1]. It started after two testing phases in cooperation with technical societies and trade associations. The system provides a set of rules to be used as a tool for the planning and evaluation of buildings in a comprehensive perspective on quality. Compared to other international systems like LEED (USA) and BREEAM (UK) the German certification considers both the ecological and economical aspects of the life cycle of buildings [2]. The German system considers actual German rules and construction codes and simplifies the design of a sustainable building. Sustainable planning according to the German system automatically follows both planning as usual and at the same time the sustainable criteria. To fulfill sustainable demands for a designed building sustainable criteria have to be regarded from the beginning of the project [3]. At the same time it is necessary to have the knowledge about the evaluation of sustainable buildings. The guide to good practice of the German Society for Concrete and Construction Technology (DBV) [5] gives a survey on usual and additional knowledge needed for sustainable building. It presents contents and methods to follow and evaluate sustainable criteria. The practice of the system is explained by means of an example: a successful awarded German administration building.     

Excimer laser crystallization of InGaZnO<Subscript>4</Subscript> on SiO<Subscript>2</Subscript> substrate

In this paper, we were able to crystallize InGaZnO₄ (IGZO) by excimer laser on SiO₂ substrate. It was observed that uniform [0001] textured polycrystalline IGZO film has been obtained without any grain boundaries and oxygen vacancies on SiO₂ substrate. This process is very promising in fabricating high quality IGZO thin film transistors (TFT) at low temperature without seed substrate.     

Verfahren zur Bestimmung der Messunsicherheit bei der Härteprüfung. Excel Datei zur Durchführung

Methods for the Determination of Uncertainty for Hardness Testing. EXCEL file for the Determination The determination of uncertainty for hardness testing [1, 2, 3] on the basis of the CRM hardness reference blocks according to GUM [4] are described. The application of an EXCEL based file for this determination of the uncertainty as part of the periodic check is presented.     

Elastizität und mechanische Dämpfung eines unidirektional SiC-kurzfaserverstärkten Alkali-Kalk-Silicatglases

Elasticity and mechanical damping of an unidirectional SiC-short-fibre reinforced alkali-lime-silicate-glass The embedment of short-fibres in inorganic glasses enables as is well know a considerable improvement of the strength as well as the fracture toughness of these materials. Still not investigated is the influence of the fibre-reinforcement on the mechanical damping of the composites. In this paper the dynamic mechanical thermal analysis is presented, which was used to determine mechanical damping and elasticity of not reinforced and unidirectional SiC-short-fibre reinforced AR-glass as a function of temperature and fibre volume fraction. The results show that the composite specimens exhibit - besides a glass-typical temperature dependence of the damping - an additional damping part, which can be attributed to the fibre reinforcement. This damping part is just as the specimen elasticity to a large extent dependent on the fibre volume fraction and is mainly associated with sliding processes in the fibre-matrix-interface under the vibrating stress. Specimens with a fibre volume fraction of 10% and a temperature of 15°C show-in comparison to non-reinforced AR-glass - an about 100% increased damping value connected with a nearly 50% decreased Youngs modulus.     

Untersuchung des Schädigungsablaufes in kohlenstoffaserverstärkten Kunststoffen

Acoustic Emission Investigations on Failure Mechanisms in Carbon Fibre Reinforced Plastics For a reliable application of modern high-strength materials such as carbon fibre reinforced plastics the knowledges of failure mechanisms as well as detailed informations about the influence of defects occuring during the manufacturing process are necessary. To study the damage progression in fibrous composites a non destructive manner, a very sensitive test failure processes in the laminate have only microscopic dimensions. In our investigations the damage progression was studied by means of acoustic emission analysis (AEA) for different types of ply orientated containing several artifical defects, as cut-through fibres, disbonded fibres and porous matrix. In a further step internally pressurized tubes were tested to investigate the applicability of AE-results to real components. Additionally, fractographic investigations improve the interpretation of the acoustic emission data. It is shown, that AEA succeeds in monitoring damages already at a very early state of damage. At increasing loads the different types of defect emit characteristic AE, which is correlated with a void-type dependent damage progression in the laminate. These knowledges of the failure mechanisms and their typical acoustic emission allow a classification of the different types of manufacturing defects concerning their influence. So, especially the porous matrix could be shown to be the most significant failure type as it causes the largest decrease of strength. The onset of AE at porous materials, however, was found at very low load levels, so that this type of defect can be detected properly.     

Oberflächenmodifizierung von Titan zur Verbesserung der Grenzflächenverträglichkeit

Surface Modification of Titanium for Improvement of the Interfacial Biocompatibility We report the CVD‐polymerisation of amino‐functionalized [2,2]‐paracyclophane for polymer coating and functionalization of titanium surfaces. Additionally, the functionalization was carried out by silanization with 3‐aminopropyl‐triethoxysilane. The generated amino‐groups were used for covalent immobilization of bioactive substances to stimulate the adhesion and growth of osteoblasts. As bioactive substances the pentapeptide GRGDS and the growth factor BMP‐2 were chosen. The covalent bonding was achieved by activation with hexamethylene diisocyanate. Each modification step was characterized by X‐ray‐photoelectron‐spectroscopy (XPS), atomic force microscopy (AFM) and contact angle measurements. The covalent bonding of the bioactive substances was proven by radiolabelling and surface‐MALDI‐ToF‐MS. In vitro‐biocompatibility tests with primary, human osteoblasts demonstrated the improved cell adhesion and spreading on the bioactive modified titanium surfaces.