Composites are being increasingly used for industrial applications and combine the advantageous properties of two or more constituents. The urge to reduce material to a minimum and the trend towards ...lightweight glass structures require further developments in high performance and fully transparent composite structures for the building industry. Novel innovative glass–plastic-composite panels combining a lightweight polymer polymethylmethacrylate (PMMA) interlayer core and cover layers of thin glass are currently under development. The panels exhibit high structural load-bearing performance, are durable and fully transparent with a low self-weight. These properties make the composite panels suitable for slender and lightweight glass constructions and reveal new design possibilities for the building industry. However, the material properties of the modified PMMA polymer interlayer core for precise design considerations are lacking. Furthermore, the material behaviour of thermoplastic polymers changes over time, ages due to environmental influences and is temperature-dependent. This significantly affects the composite load-bearing behaviour and defines the limits of application for the composite panels in the building industry. In order to facilitate during the development process and to build a design basis for the composite panels, material model parameters and simulation methods are required. Hence, an extensive test programme was conducted to investigate the material properties of the PMMA interlayer core by means of dynamic mechanical thermal analysis as well as uniaxial tensile and creep tests. The dataset and subsequent implementation into finite element software allowed for realistic simulations of the glass–plastic-composite panels and an extension of experimental results. Numerical simulations were performed with the commercial finite element programme ANSYS Workbench 19.3. Additionally, four-point bending tests were performed on composite test specimens with a different build-up and conventional glass panels to validate the material model and finite element simulations. These investigations and adopted material properties formed the basis for a numerical parametric study to evaluate the influence of stiffness, the load-bearing and lightweight performance in different build-ups. All the results are evaluated in detail and discussed in comparison with conventional monolithic and laminated glass panels. The dataset and material model parameters can be applied to further developments and design of lightweight glass–plastic-composite panels for structural applications in the building industry.
Since façade-integrated photovoltaic (PV) modules heat up greatly, which reduces the efficiency of the PV, façade panels with PV and phase change materials (PCM) were developed. PCMs absorb a ...significant amount of thermal energy during the phase transition from solid to liquid, while maintaining a specific melting temperature. This cools down the PV and increases the electrical yield. Numerical studies on PV-PCM warm façades without rear-ventilation have so far been missing. Therefore, a thermal and an electrical simulation model for PV-PCM warm façades were developed and validated. They were then used to analyse the yield increase of two PCM-types and -quantities in PV warm façades facing east, south, and west in Athens, Potsdam, and Helsinki. An annual yield increase of 1.2% to 8.5% for monocrystalline PV modules was determined. The maximum monthly yield increase is 8.0% in Helsinki, 11.4% in Potsdam, and 11.3% in Athens. The study shows that a case-specific selection of the appropriate type and quantity of PCM is necessary. Using the models, a design tool for PV-PCM warm façades will be developed. It will be validated with real monitoring data from PV-PCM façade test rigs at the Technische Universität Dresden and the National Technical University of Athens
Guaranteeing high indoor air quality and high degree of usersatisfaction at the same time is one of the challenges when improving the energy efficiency, namely the energy consumption, of a building. ...Current non-residential buildings mainly use mechanical ventilation systems to ensure high air quality. Natural ventilation can be an alternative regarding to lower maintenance costs and the psychological feeling of fresh air. Present natural ventilated buildings pose the risk of higher energy demand and less indoor air quality due to user's behaviour. Controlled natural ventilation based on indoor CO
2
concentration and room air temperature is needed. However, the energy efficiency of a control strategy highly depends on climate zone and control parameters. This paper aims to explore the impact of different control strategies on the energy efficiency of an operable louver window. The analyses are done for yearly results and then for each month individual to clarify the effect of monthly varying control strategies. For the analysis EnergyPlus as a building energy simulation tool and for the natural ventilation in specific the EnergyPlus Design Flow Rate method is used. In the simulation four window opening strategies based on CO
2
concentration and one simple intake/exhaust mechanical ventilation system were tested in Mediterranean, subtropical and moderate climate zone. The highest impact on energy efficiency and thermal comfort was seen at the cold months in the moderate climate. Long window opening strategies cannot be implemented because of a high thermal discomfort. In the hot months in the Mediterranean and subtropical climate an impact of ventilation strategies are seen as well. Only at moderate conditions no major differences in the natural ventilation strategies were observed. When comparing the natural ventilation conditions to mechanical ventilation major differences were found. In almost all climate conditions natural ventilation outperformed the mechanical ventilation. Only in winter months in the moderate climate mechanical ventilation outperforms natural ventilation.
The desire of builders and architects of maximum transparency and homogeneous surfaces in glass façades and glass structures extends to interior all-glass applications such as glass partitions or ...all-glass doors. In conventional glass systems the interconnections are performed by eye-catching fittings and clamping details that reduce the transparency and disturb the aesthetics. Novel glass–plastic-composite panels show a significantly reduced self-weight by composition of a polymer polymethylmethacrylate (PMMA) interlayer core and cover layers of thin glass. The innovative composites show high structural performance with optical properties of conventional glass. The panels allow for a direct connection into the thick PMMA interlayer core with the supporting structure or other panels. Such an integrated connection design reduces stress concentrations and allows for the development of small and unobtrusive fittings. Different integrated connections for the glass–plastic-composite panels have been designed and investigated. This article presents an experimental study on different connections, such as mechanically fastened and adhesively integrated, tested under tensile loading. Based on video analyses, crack progressions and failure mechanisms are evaluated and discussed in detail. The tests investigate temperature effects as well as the influence of the interlayer core thickness and glass type of the cover layers in varying build-ups. The comprehensive evaluation includes a description of the mechanical load-bearing behaviour in form of load versus displacement graphs as well as an investigation of crack progression and failure mechanisms for the final assessment. The results from this experimental study elucidate the structural characteristics of integrated connections in glass–plastic-composite panels under tensile loading and represent a basis for the ongoing development of real application fittings.
Untersuchungen zur Kantenfestigkeit von Gläsern zeigen, dass diese in Abhängigkeit des Herstellers und der Kantenbearbeitungsart nach DIN 1249‐11 stark variiert. Insbesondere der Bearbeitungsprozess ...des Schleifens weist eine Vielzahl von Parametern auf, welche die resultierende Oberflächenbeschaffenheit der Glaskante beeinflussen, allerdings noch unzureichend untersucht sind. Eine objektive Erfassung der Oberflächenbeschaffenheit über Kennwerte der Rauheit könnte helfen, Prozessparameter bewertbar zu machen und eine Korrelation zwischen dem Bearbeitungsprozess und der Kantenfestigkeit zu schaffen. Im Rahmen einer ersten Vorstudie wurden Rauheitskennwerte geschliffener und polierter Kantenoberflächen von drei Herstellern mittels konfokalem Laserscanning‐Mikroskop ermittelt und hinsichtlich ihrer Eignung zur Bewertung der Bearbeitungsprozesse geprüft.
Roughness examination of processed glass edges under a confocal laser scanning microscope. Findings on the edge strength show that, it varies depending on the manufacturer and the type of edge finishing. In particular the grinding process has a large number of parameters that influence the surface quality of the glass edge, which have not yet been fully investigated. The determination of objective roughness parameters could help to evaluate the grinding processes and further correlate the surface quality with the edge strength. Within the scope of a preliminary study, roughness parameters were calculated for ground and polished glass edges of three manufacturers using a confocal laser scanning microscope. Finally the method was tested regarding to its suitability for a determination of characteristic roughness parameters that could be used to evaluate the grinding processes.
Das Gebäude‐Energie‐Gesetz (GEG) regelt in Deutschland die Grenzwerte für den Energiebedarf von Neubauten und Sanierungen mit dem Ziel, bis zum Jahr 2050 einen nahezu klimaneutralen Gebäudebestand zu ...erreichen. Anforderungswerte für die Wärmedurchgangskoeffizienten, die Wärmebrücken und die Luftdichtheit sind im GEG explizit angegeben, für die Planung der Belüftung wurden jedoch keine expliziten Regelungen getroffen. Ein geplantes Belüftungssystem ist erlaubt, sofern der resultierende Primärenergiebedarf des Gebäudes den Anforderungen entspricht. Eine natürliche Lüftung wird in den vereinfachten Nachweisen des Monatsbilanzverfahrens dabei meist als energetisch nachteilig angesehen, führt sie zwingendermaßen zu Lüftungswärmeverlusten. Mechanische Lüftungssysteme können dahingegen mit Anrechnung ihrer Wärmerückgewinnung vorteilig angesetzt werden. Die natürliche Lüftung hat jedoch, ist sie als kontrollierte elektrisch betriebene Fensteröffnung ausgeführt, das Potenzial einer Energieeffizienzsteigerung mit hoher Nutzerbehaglichkeit. In einer Simulation über EnergyPlus wurden für einen Büroraum Öffnungs‐ und Schließsignale einer CO2‐geregelten natürlichen Fensterlüftung verglichen. Eine Regelung, die bei 900 ppm CO2‐Konzentration öffnet und bei 800 ppm schließt, stellte die energieeffizienteste und thermisch behaglichste Regelung dar. Für diese Regelung wurden die realen Öffnungsdauern an einem experimentellen Büroraum ausgewertet. Es ergaben sich in Abhängigkeit des Windes und der Temperaturdifferenz zwischen Innen und Außen Öffnungsdauern von 3 bis 5 Minuten.
Energy‐efficient controlled natural ventilation in non‐residential buildings – Experimental investigation of opening durations
In Germany, the Building Energy Act (GEG) regulates the limit values for the energy requirements of new buildings and renovations with the aim of achieving an almost climate‐neutral building stock by 2050. Requirements for heat transfer coefficients, thermal bridges and air tightness are explicitly stated in the GEG, but no explicit regulations have been made for the planning of ventilation. A planned ventilation system is permitted as long as the resulting primary energy demand of the building meets the requirements. In the simplified verifications of the monthly balance procedure, natural ventilation is usually considered to be disadvantageous in terms of energy, as it leads to ventilation heat losses. Mechanical ventilation systems, on the other hand, can be considered advantageous because of their heat recovery. Natural ventilation, however, has the potential to increase energy efficiency with high user comfort if it is designed as a controlled electrically operated window opening. In a simulation with EnergyPlus, opening and closing signals of a CO2‐controlled natural window ventilation were compared for an office room. A window that opens at 900 ppm CO2 concentration and closes at 800 ppm represented the most energy‐efficient and thermally comfortable control. For this control, the real opening times were evaluated for an experimentally office room. Depending on the wind and the temperature difference between inside and outside, opening times of 3 to 5 minutes were obtained.
Abstract
Das Gebäude‐Energie‐Gesetz (GEG) regelt in Deutschland die Grenzwerte für den Energiebedarf von Neubauten und Sanierungen mit dem Ziel, bis zum Jahr 2050 einen nahezu klimaneutralen ...Gebäudebestand zu erreichen. Anforderungswerte für die Wärmedurchgangskoeffizienten, die Wärmebrücken und die Luftdichtheit sind im GEG explizit angegeben, für die Planung der Belüftung wurden jedoch keine expliziten Regelungen getroffen. Ein geplantes Belüftungssystem ist erlaubt, sofern der resultierende Primärenergiebedarf des Gebäudes den Anforderungen entspricht. Eine natürliche Lüftung wird in den vereinfachten Nachweisen des Monatsbilanzverfahrens dabei meist als energetisch nachteilig angesehen, führt sie zwingendermaßen zu Lüftungswärmeverlusten. Mechanische Lüftungssysteme können dahingegen mit Anrechnung ihrer Wärmerückgewinnung vorteilig angesetzt werden. Die natürliche Lüftung hat jedoch, ist sie als kontrollierte elektrisch betriebene Fensteröffnung ausgeführt, das Potenzial einer Energieeffizienzsteigerung mit hoher Nutzerbehaglichkeit. In einer Simulation über
EnergyPlus
wurden für einen Büroraum Öffnungs‐ und Schließsignale einer CO
2
‐geregelten natürlichen Fensterlüftung verglichen. Eine Regelung, die bei 900 ppm CO
2
‐Konzentration öffnet und bei 800 ppm schließt, stellte die energieeffizienteste und thermisch behaglichste Regelung dar. Für diese Regelung wurden die realen Öffnungsdauern an einem experimentellen Büroraum ausgewertet. Es ergaben sich in Abhängigkeit des Windes und der Temperaturdifferenz zwischen Innen und Außen Öffnungsdauern von 3 bis 5 Minuten.
Abstract
Energy‐efficient controlled natural ventilation in non‐residential buildings – Experimental investigation of opening durations
In Germany, the Building Energy Act (GEG) regulates the limit values for the energy requirements of new buildings and renovations with the aim of achieving an almost climate‐neutral building stock by 2050. Requirements for heat transfer coefficients, thermal bridges and air tightness are explicitly stated in the GEG, but no explicit regulations have been made for the planning of ventilation. A planned ventilation system is permitted as long as the resulting primary energy demand of the building meets the requirements. In the simplified verifications of the monthly balance procedure, natural ventilation is usually considered to be disadvantageous in terms of energy, as it leads to ventilation heat losses. Mechanical ventilation systems, on the other hand, can be considered advantageous because of their heat recovery. Natural ventilation, however, has the potential to increase energy efficiency with high user comfort if it is designed as a controlled electrically operated window opening. In a simulation with
EnergyPlus
, opening and closing signals of a CO
2
‐controlled natural window ventilation were compared for an office room. A window that opens at 900 ppm CO
2
concentration and closes at 800 ppm represented the most energy‐efficient and thermally comfortable control. For this control, the real opening times were evaluated for an experimentally office room. Depending on the wind and the temperature difference between inside and outside, opening times of 3 to 5 minutes were obtained.
Post-Tensioned Glass Beams for a 9 m Spannglass Bridge Engelmann, Michael; Weller, Bernhard
Structural engineering international : journal of the International Association for Bridge and Structural Engineering (IABSE),
20/5/1/, Volume:
26, Issue:
2
Journal Article
Peer reviewed
Glass beams may be reinforced to allow for a fail-safe behaviour and to avoid brittle and total collapse. This approach from reinforced concrete design is applied to glass and extended by ...post-tensioning the reinforcement by using Spannglass beams. A high-grade steel cable relieves the brittle material from unbeneficial tensile stress and accommodates permanent dead-load deflection. A structural concept was evolved that led to the development of Spannglass beams, which were tested for a span of 2 m. This concept was extended to larger spans in order to consider size effects and to provide this option to a broader field of application. To verify this, a 9 m pedestrian glass bridge with post-tensioned reinforcement was designed and tested experimentally. Three full-size glass specimens were utilised with adhesive connectors and two reinforcement designs. A post-tensioning concept was finalised and put into practice. Finally, four-point bending tests were performed to yield the maximum loads. This paper explains the experimental design, presents the results and provides conclusions of how to design workable structural glass beams with post-tensioned reinforcement. The paper also presents the design process and the construction of a 9 m Spannglass Bridge used by pedestrians at Glasstec 2014 in Düsseldorf, Germany.
Das Bauen mit Glas eröffnet den Planern faszinierende gestalterische Möglichkeiten. Schon lange dient es als lichtdurchlässiger Raumabschluss, kann aber deutlich mehr: Glas sichert gegen Absturz, ...schützt vor Explosionen, wehrt bewaffnete Angriffe ab, bildet begehbare Flächen in Dächern, Treppen und Emporen und übernimmt sogar Systemlasten innerhalb eines Tragwerks. In Kombination mit zahlreichen Veredelungsmethoden sowie verschiedenen Materialien und Beschichtungen erfüllt Glas auch hohe bauphysikalische Anforderungen. Dieser Band liefert kompakt, übersichtlich und anschaulich einen über die Grundlagen hinausreichenden Überblick über den materialgerechten konstruktiven Einsatz dieses ambivalenten Baustoffs. Die Grenzen des Entwerfens setzen die Physik und das Gesetz: Dieses Buch geht daher auch auf die Kennwerte der Basis- und Veredelungsprodukte sowie auf die baurechtlichen Regelungen ein. Eine Auswahl hervorragender ausgeführter Projekte rundet den theoretischen Teil ab.
Nowadays, post-tensioning of glass beams in the style of prestressed concrete is a promising option for advanced architecture but lacks in vital knowledge. Previous research has shown that ...prestressing creates fail-safe and even ductile structural glass beams. However, long-term effects, namely losses of prestress in post-tensioned glass beams, have not been investigated yet.
This paper introduces a general design concept and suggests an analytic model to estimate losses. As glass is known not to show considerable creeping deformation over time, the model focuses on the contribution by plastic parts of structural glass elements. The results include a proposal to use creep coefficients for the interlayer in laminated glass as well as the blocking materials used in contact structures. This approach is advantageous due to its ability to be applied with arbitrary material models, thus broadening the application to a variety of interlayer foils and advanced glass contact materials.
A comprehensive experimental investigation was carried out to test the hypothesis using 28 specimens in a variety of tendon diameters and cables forces as well as reference specimens. The tests make it possible to describe losses analytically using regression functions. Moreover, the investigation revealed additional effects that need to be included in a model for life-time prediction. The given results show the time-dependent effects on novel precompressed glass beams for the first time and build a basis for future structural options in facade design and glass roofs.
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