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Organisationseinheit der BAM
Textile-reinforced concrete (TRC) is a material consisting of high-performance concrete (HPC) and tensile reinforcement comprised of carbon roving with epoxy resin matrix. However, the problem of low epoxy resin resistance at higher temperatures persists. In this work, an alternative to the epoxy resin matrix, a non-combustible cement suspension (cement milk) which has proven stability at elevated temperatures, was evaluated. In the first part of the work, microscopic research was carried out to determine the distribution of particle sizes in the cement suspension. Subsequently, five series of plate samples differing in the type of cement and the method of textile reinforcement saturation were designed and prepared. Mechanical experiments (four-point bending tests) were carried out to verify the properties of each sample type. It was found that the highest efficiency of carbon roving saturation was achieved by using finer ground cement (CEM 52.5) and the pressure saturation method. Moreover, this solution also exhibited the best results in the four-point bending test. Finally, the use of CEM 52.5 in the cement matrix appears to be a feasible variant for TRC constructions that could overcome problems with its low temperature resistance.
Emerging infectious diseases (EIDs) have contributed significantly to the current biodiversity crisis, leading to widespread epidemics and population loss. Owing to genetic variation in pathogen virulence, a complete understanding of species decline requires the accurate identification and characterization of EIDs. We explore this issue in the Western honeybee, where increasing mortality of populations in the Northern Hemisphere has caused major concern. Specifically, we investigate the importance of genetic identity of the main suspect in mortality, deformed wing virus (DWV), in driving honeybee loss. Using laboratory experiments and a systematic field survey, we demonstrate that an emerging DWV genotype (DWV-B) is more virulent than the established DWV genotype (DWV-A) and is widespread in the landscape. Furthermore, we show in a simple model that colonies infected with DWV-B collapse sooner than colonies infected with DWV-A. We also identify potential for rapid DWV evolution by revealing extensive genome-wide recombination in vivo. The emergence of DWV-B in naive honeybee populations, including via recombination with DWV-A, could be of significant ecological and economic importance. Our findings emphasize that knowledge of pathogen genetic identity and diversity is critical to understanding drivers of species decline.
The work aims to assess the textile reinforced concrete at elevated temperatures and applications of additional fire protection as well.
Textile-reinforced concrete is currently most frequently used for non-load–bearing structures, but there is a vision for also using it in load–bearing construction elements. In recent years, this construction material has been subjected to detailed examination. Different combinations of materials for potential use in textile-reinforced concrete have been described. These differ in the type of concrete mix and the composition of the textile reinforcement. The aim of this work is to test the application of a specific textile-reinforced concrete, consisting of high-performance concrete, textile reinforcement from carbon fibers and its epoxy resin matrix, at an elevated temperature. The combination of these materials makes it possible to produce subtle load–bearing structures with excellent mechanical properties. The critical issue is the behavior of these structures when exposed to fire. A series of medium-scale fire condition experiments were carried out with a temperature load based on the ISO 834 curve, followed up by mechanical tests. The aim of these experiments was to describe critical areas of textile-reinforced concrete in fire and to propose possible solutions. In an indicative fire experiment, experimental samples displayed massive spall of concrete layers, and interaction between materials was lost due to the low temperature resistance of the epoxy resin. Concurrently, the optimal quantity of polypropylene fibers was experimentally determined. This paper presents an experimental demonstration of the problematic aspects of textile-reinforced concrete and subsequent recommendations for future work with practical application in the design of load–bearing structures.
Emerging infectious diseases (EIDs) pose a risk to human welfare, both directly1 and indirectly, by affecting managed livestock and wildlife that provide valuable resources and ecosystem services, such as the pollination of crops2. Honeybees (Apis mellifera), the prevailing managed insect crop pollinator, suffer from a range of emerging and exotic high-impact pathogens3,4, and population maintenance requires active management by beekeepers to control them. Wild pollinators such as bumblebees (Bombus spp.) are in global decline5,6, one cause of which may be pathogen spillover from managed pollinators like honeybees7,8 or commercial colonies of bumblebees9. Here we use a combination of infection experiments and landscape-scale field data to show that honeybee EIDs are indeed widespread infectious agents within the pollinator assemblage. The prevalence of deformed wing virus (DWV) and the exotic parasite Nosema ceranae in honeybees and bumblebees is linked; as honeybees have higher DWV prevalence, and sympatric bumblebees and honeybees are infected by the same DWV strains, Apis is the likely source of at least one major EID in wild pollinators. Lessons learned from vertebrates10,11 highlight the need for increased pathogen control in managed bee species to maintain wild pollinators, as declines in native pollinators may be caused by interspecies pathogen transmission originating from managed pollinators.
A sting in the spit: widespread cross-infection of multiple RNA viruses across wild and managed bees
(2015)
1.Declining populations of bee pollinators are a cause of concern, with major repercussions for biodiversity loss and food security. RNA viruses associated with honeybees represent a potential threat to other insect pollinators, but the extent of this threat is poorly understood.
2.This study aims to attain a detailed understanding of the current and ongoing risk of emerging infectious disease (EID) transmission between managed and wild pollinator species across a wide range of RNA viruses.
3.Within a structured large-scale national survey across 26 independent sites, we quantify the prevalence and pathogen loads of multiple RNA viruses in co-occurring managed honeybee (Apis mellifera) and wild bumblebee (Bombus spp.) populations. We then construct models that compare virus prevalence between wild and managed pollinators.
4.Multiple RNA viruses associated with honeybees are widespread in sympatric wild bumblebee populations. Virus prevalence in honeybees is a significant predictor of virus prevalence in bumblebees, but we remain cautious in speculating over the principle direction of pathogen transmission. We demonstrate species-specific differences in prevalence, indicating significant variation in disease susceptibility or tolerance. Pathogen loads within individual bumblebees may be high and in the case of at least one RNA virus, prevalence is higher in wild bumblebees than in managed honeybee populations.
5.Our findings indicate widespread transmission of RNA viruses between managed and wild bee pollinators, pointing to an interconnected network of potential disease pressures within and among pollinator species. In the context of the biodiversity crisis, our study emphasizes the importance of targeting a wide range of pathogens and defining host associations when considering potential drivers of population decline.
Ziel des Forschungsvorhabens ist es, ein standardisiertes Prüf- und Bewertungsverfahren zur Bestimmung des Beitrags reaktiver Brandschutzsysteme (RBS) zum Feuerwiderstand von Stahlzuggliedern zu erarbeiten und dieses in ein Entwurfsdokument für eine europäische Prüfnorm zu überführen. Hierzu wurden einerseits bereits vorhandene Erfahrungen und Erkenntnisse genutzt und andererseits mittels Brandversuchen neue Prüfdaten zur Beantwortung bisher offengebliebener Aspekte zum Einfluss der Bauteilorientierung und Profilart erzeugt und ausgewertet. Dadurch wird die prüftechnische Grundlage für eine sichere, zulassungsbasierte Anwendung von reaktiven Brandschutzsystemen auf zugbeanspruchten Stahlbauteilen gelegt und ein einheitliches Sicherheitsniveau etabliert.
Der im Rahmen des Forschungsprojektes entwickelte Normentwurf wurde mit den Fachexperten der zuständigen nationalen und europäischen Normungsgremien diskutiert und abgestimmt. Das erarbeitete Prüf- und Auswertungsverfahren basiert auf der Durchführung von Brandversuchen an mechanisch belasteten Stahlzuggliedern mit RBS. Ergänzend sind unbelastete Brandversuche zur Beurteilung des Einflusses der Bauteilorientierung sowie der Eignung bei Schwelbrandbeanspruchung möglich. Die im Projekt durchgeführten experimentellen Untersuchungen liefern die Grundlage für den im Normenentwurf vorgeschlagenen Prüfaufbau der mechanisch belasteten und unbelasteten Brandversuche. Ferner konnte durch die Untersuchungen gezeigt werden, dass sich unter bestimmten Voraussetzungen die Prüfergebnisse von Stahlzuggliedern mit Kreisvollprofil ohne zusätzliche Brandversuche auf entsprechende Zugglieder mit Rechteckvollprofil übertragen lassen. Darüber hinaus konnte belegt werden, dass die Leistungsfähigkeit eines RBS aufgrund unterschiedlicher Bauteilorientierungen abnehmen kann und daher zwingend beim Anwendungsbereich des RBS zu berücksichtigen ist. Hierzu wird ein Temperaturdifferenz-kriterium vorgeschlagen, bei dessen Einhaltung die Wirksamkeit des RBS bei von der horizontalen Referenzorientierung abweichenden Bauteilneigungen noch gleichwertig gegeben ist. Andernfalls bietet der Normenentwurf die Möglichkeit die reduzierte thermische Schutzwirkung des RBS im Assessment zu berücksichtigen.
Die Ergebnisse aus dem Forschungsvorhaben wurden bereits auf einem wissenschaftlichen Symposium vorgestellt sowie in einer referierten Fachzeitschrift publiziert. Ferner wurden die Informationen zum Forschungsprojekt und dem Normenentwurf im Rahmen eines Anwenderworkshops interessierten Kreisen zugänglich gemacht. Der im Projekt ausgearbeitete Normenentwurf wird dem zuständigen europäischen Normungsgremien, CEN/TC 127/WG 1, zur Verfügung gestellt und dort zur Abstimmung gestellt.